,illustration3 ,,the ,,most ,,important ,,tool ,,in ,,the ,,building ,,of ,,model ,,aeroplanes4 ,illustration by permission from ,,messrs4 ,a4 ,,gallenkamp ,,co',s4 ,,chemical ,,catalogue4 ,,the ,,theory ,,and ,,practice ,,of ,,model ,,aeroplaning ,,by ,v4,e4 ,,johnson1 ,m4,a4 ,,author ,,of ',,the ,,best ,,shape ,,for ,,an ,,airship1' ',,soaring ,,flight1' ',,how ,,to ,,advance ,,the ,,science ,,of ,,aeronautics1' ',,how ,,to ,,build ,a ,,model ,,aeroplane1' ,,etc4 ,model ,aeroplaning is an ,art in itself ,illustration ,london ,e4 ,f4,n4 ,,spon1 ,,ltd41 #eg ,,haymarket ,new ,york ,,spon ,,chamberlain1 #abc ,,liberty ,,street #aiaj ,,preface ,the object of this little book is not to describe how to construct some particular kind of aeroplane2 this has been done elsewhere3 but to narrate in plain language the general practice and principles of model aeroplaning4 ,there is a science of model aeroplaning--just as there is a science of model yachting and model steam and electric traction1 and an endeavour is made in the following pages to do in some measure for model aeroplanes what has already been done for model yachts and locomotives4 ,to achieve the best results1 theory and practice must go hand in hand4 ,from a series of carefully conducted experiments empirical formul can be obtained which1 combined later with mathematical induction and deduction1 may lead1 not only to a more accurate and generalized law than that contained in the empirical formula1 but to valuable deductions of a totally new type1 embodying some general law hitherto quite unknown by experimentalists1 which in its turn may serve as a foundation or stepping stone for suggesting other experiments and empirical formul which may be of especial importance1 to be treated in their turn like their predecessor4 ,by especial importance1 ,i mean not only to model1 but ,aeroplaning generally4 ,as to the value of experiments on or with models with respect to full-sized machines1 fifteen years ago ,i held the opinion that they were a very doubtful factor4 ,i have since considerably modified that view1 and now consider that experiments with models--if properly carried out1 and given due1 not undue1 weight--both can and will be of as much use to the science of ,aeronautics as they have already proved themselves to be in that of marine engineering4 ,the subject of model propellers and motors has been somewhat fully dealt with1 as but little has been published 7in book form1 at any rate7 on these all-important departments4 ,on similar grounds the reasons why and how a model aeroplane flies have been practically omitted1 because these have been dealt with more or less in every book on heavier-than-air machines4 ,great care has been exercised in the selection of matter1 and in the various facts stated herein2 in most cases ,i have personally verified them2 great pains have also been exercised to exclude not only misleading1 but also doubtful matter4 ,i have no personal axe to grind whatever1 nor am ,i connected either directly or indirectly with any firm of aeroplane builders1 model or otherwise4 ,the statements contained in these pages are absolutely free from bias of any kind1 and for them ,i am prepared to accept full responsibility4 ,i have to thank ,messrs4 ,a4,w4 ,,gamage 7,holborn7 for the use of various model parts for testing purposes1 and also for the use of various electros from their modern ,aviation ,catalogue2 also ,messrs4 ,t4,w4,k4 ,,clarke ,,co41 of ,kingston-on-,thames4 ,for the further use of electros1 and for permission to reproduce illustrations which have previously appeared in their papers1 ,i must express my acknowledgment and thanks to the publishers of the ,model ,engineer1 ,flight1 and the ,aero4 ,corrections and suggestions of any kind will be gratefully received1 and duly acknowledged4 ,v4,e4 ,,johnson4 ,,contents ,,introduction4 ,,page #a-e4 ,the two classes of models--,first requisite of a model aeroplane4 #f4 ,an art in itself4 #g4 ,the leading principle #a ,,chapter ,i4 ,,the ,,question ,,of ,,weight4 #a-b4 ,its primary importance both in rubber and power-driven models--,professor ,langley's experiences4 #c4 ,theoretical aspect of the question4 #d4 ,means whereby more weight can be carried--,how to obtain maximum strength with minimum weight4 #e4 ,heavy models versus light ones #d ,,chapter ,,ii4 ,,the ,,question ,,of ,,resistance4 #a4 ,the chief function of a model in the medium in which it travels4 #b4 ,resistance considered as load percentage4 #c4 ,how made up4 #d4 ,the shape of minimum resistance4 #e4 ,the case of rubber-driven models4 #f4 ,the aerofoil surface--,shape and material as affecting this question4 #g4 ,skin friction--,its coefficient4 #h4 ,experimental proofs of its existence and importance #g ,,chapter ,,iii4 ,,the ,,question ,,of ,,balance4 #a4 automatic stability essential in a flying model4 #b4 theoretical researches on this question4 #c-f4 a brief summary of the chief conclusions arrived at--remarks on and deductions from the same--conditions for automatic stability4 #g4 theory and practice--stringfellow--pnaud--tatin--th e question of fins--clarke's models--some further considerations4 #h4 longitudinal stability4 #i4 transverse stability4 #aj4 the dihedral angle4 #aa4 different forms of the latter4 #ab4 the upturned tip4 #ac4 the most efficient section #ac ,,chapter ,,iv4 ,,the ,,motive ,,power4 ,,section ,i4--,,rubber ,,motors4 #a4 ,some experiments with rubber cord4 #b4 ,its extension under various weights4 #c4 ,the laws of elongation 7stretching7--,permanent set4 #d4 ,effects of elongation on its volume4 #e4 ,stretched-twisted rubber cord--,torque experiments with rubber strands of varying length and number4 #f4 ,results plotted as graphs--,deductions--,various relations--,how to obtain the most efficient results--,relations between the torque and the number of strands1 and between the length of the strands and their number4 #g4 ,analogy between rubber and spring motors--,where it fails to hold4 #h4 ,some further practical deductions4 #i4 ,the number of revolutions that can be given to rubber motors4 #aj4 ,the maximum number of turns4 #aa4 ,lubricants for rubber4 #ab4 ,action of copper upon rubber4 #ab;,a4 ,action of water1 etc4 #ab;,b4 ,how to preserve rubber4 #ac4 ,to test rubber4 #ad4 ,the shape of the section4 #ae4 ,size of section4 #af4 ,geared rubber motors4 #ag4 ,the only system worth consideration--,its practical difficulties4 #ah4 ,its advantages #bd ,,section ,,ii4--,,other ,,forms ,,of ,,motors4 #ah;,a4 ,spring motors2 their inferiority to rubber4 #ah;,b4 ,the most efficient form of spring motor4 #ah;,c4 ,compressed air motors--,a fascinating form of motor1 on paper4 #ah;,d4 ,the pneumatic drill--,application to a model aeroplane--,length of possible flight4 #ah;,e4 ,the pressure in motor-car tyres4 #ai4 ,hargraves' compressed air models--,the best results compared with rubber motors4 #bj4 ,the effect of heating the air in its passage from the reservoir to the motor--,the great gain in efficiency thereby attained--,liquid air--,practical drawbacks to the compressed-air motor4 #ba4 ,reducing valves--,lowest working pressure4 #bb4 ,the inferiority of this motor compared with the steam engine4 #bb;,a4 ,tatin's air-compressed motor4 #bc4 ,steam engine--,steam engine model--,professor ,langley's models--,his experiment with various forms of motive power--,conclusions arrived at4 #bd4 ,his steam engine models--,difficulties and failures--and final success--,the boiler the great difficulty--,his model described4 #be4 ,the use of spirit or some very volatile hydrocarbon in the place of water4 #bf4 ,steam turbines4 #bg4 ,relation between difficulty in construction and the size of the model4 #bh4 ,experiments in ,france4 #bi4 ,petrol motors4--,but few successful models4 #cj4 ,limit to size4 #ca4 ,stanger's successful model described and illustrated4 #cb4 ,one-cylinder petrol motors4 #cc4 ,electric motors #ci ,,chapter ,v4 ,,propellers ,,or ,,screws4 #a4 ,the position of the propeller4 #b4 ,the number of blades4 #c4 ,fan versus propeller4 #d4 ,the function of a propeller4 #e4 ,the pitch4 #f4 ,slip4 #g4 ,thrust4 #h4 ,pitch coefficient 7or ratio74 #i4 ,diameter4 #aj4 ,theoretical pitch4 #aa4 ,uniform pitch4 #ab4 ,how to ascertain the pitch of a propeller4 #ac4 ,hollow-faced blades4 #ad4 ,blade area4 #ae4 ,rate of rotation4 #af4 ,shrouding4 #ag4 ,general design4 #ah4 ,the shape of the blades4 #ai4 ,their general contour--,propeller design--,how to design a propeller4 #bj4 ,experiments with propellers--,havilland's design for experiments--,the author experiments on dynamic thrust and model propellers generally4 #ba4 ,fabric-covered screws4 #bb4 ,experiments with twin propellers4 #bc4 ,the ,fleming ,williams propeller4 #bd4 ,built-up v4 twisted wooden propellers #eb ,,chapter ,,vi4 ,,the ,,question ,,of ,,sustentation4 ,,the ,,centre ,,of ,,pressure4 #a4 ,the centre of pressure--,automatic stability4 #b4 ,oscillations4 #c4 ,arched surfaces and movements of the centre of pressure--,reversal4 #d4 ,the centre of gravity and the centre of pressure4 #e4 ,camber4 #f4 ,dipping front edge--,camber--,the angle of incidence and camber--,attitude of the ,wright machine4 #g4 ,the most efficient form of camber4 #h4 ,the instability of a deeply cambered surface4 #i4 ,aspect ratio4 #aj4 ,constant or varying camber4 #aa4 ,centre of pressure on arched surfaces #gh ,,chapter ,,vii4 ,,materials ,,for ,,aeroplane ,,construction4 #a4 ,the choice strictly limited4 #b4 ,bamboo4 #c4 ,ash--spruce-- whitewood--poplar4 #d4 ,steel4 #e4 ,umbrella section steel4 #f4 ,steel wire4 #g4 ,silk4 #h4 ,aluminium and magnalium4 #i4 ,alloys4 #aj4 ,sheet ebonite--,vulcanized fibre--,sheet celluloid--,mica #hf ,,chapter ,,viii4 ,,hints ,,on ,,the ,,building ,,of ,,model ,,aeroplanes4 #a4 ,the chief difficulty to overcome4 #b4 ,general design--,the principle of continuity4 #c4 ,simple monoplane4 #d4 ,importance of soldering4 #e4 ,things to avoid4 #f4 ,aerofoil of metal--wood--or fabric4 #g4 ,shape of aerofoil4 #h4 ,how to camber an aerocurve without ribs4 #i4 ,flexible joints4 #aj4 ,single surfaces4 #aa4 ,the rod or tube carrying the rubber motor4 #ab4 ,position of the rubber4 #ac4 ,the position of the centre of pressure4 #ad4 ,elevators and tails4 #ae4 ,skids versus wheels--,materials for skids4 #af4 ,shock absorbers1 how to attach--,relation between the gap and the chord #ic ,,chapter ,,ix4 ,,the ,,steering ,,of ,,the ,,model4 #a4 ,a problem of great difficulty--,effects of propeller torque4 #b4 ,how obviated4 #c4 ,the two-propeller solution--,the reason why it is only a partial success4 #d4 ,the speed solution4 #e4 ,vertical fins4 #f4 ,balancing tips or ailerons4 #g4 ,weighting4 #h4 ,by means of transversely canting the elevator4 #i4 ,the necessity for some form of keel #aje ,,chapter ,x4 ,,the ,,launching ,,of ,,the ,,model4 #a4 ,the direction in which to launch them4 #b4 ,the velocity--wooden aerofoils and fabric-covered aerofoils--,poynter's launching apparatus4 #c4 ,the launching of very light models4 #d4 ,large size and power-driven models4 #e4 ,models designed to rise from the ground--,paulhan's prize model4 #f4 ,the setting of the elevator4 #g4 ,the most suitable propeller for this form of model4 #h4 ,professor ,kress' method of launching4 #i4 ,how to launch a twin screw model4 #aj4 ,a prior revolution of the propellers4 #aa4 ,the best angle at which to launch a model #aji ,,chapter ,,xi4 ,,helicopter ,,models4 #a4 ,models quite easy to make4 #b4 ,sir ,george ,cayley's helicopter model4 #c4 ,phillips' successful power-driven model4 #d4 ,toy helicopters4 #e4 ,incorrect and correct way of arranging the propellers4 #f4 ,fabric covered screws4 #g4 ,a design to obviate weight4 #h4 ,the question of a fin or keel4 #aac ,,chapter ,,xii4 ,,experimental ,,records #aaf ,,chapter ,,xiii4 ,,model ,,flying ,,competitions4 #a4 ,a few general details concerning such4 #b4 ,aero ,models ,association's classification1 etc4 #c4 ,various points to be kept in mind when competing #aai ,,chapter ,,xiv4 ,,useful ,,notes1 ,,tables1 ,,formul1 ,,etc4 #a4 ,comparative velocities4 #b4 ,conversions4 #c4 ,areas of various shaped surfaces4 #d4 ,french and ,english measures4 #e4 ,useful data4 #f4 ,table of equivalent inclinations4 #g4 ,table of skin friction4 #h4 ,table ,i4 7metals74 #i4 ,table ,,ii4 7wind pressures74 #aj4 ,wind pressure on various shaped bodies4 #aa4 ,table ,,iii4 7lift and drift7 on a cambered surface4 #ab4 ,table ,,iv4 7lift and drift7--,on a plane aerofoil--,deductions4 #ac4 ,table ,v4 7timber74 #ad4 ,formula connecting weight lifted and velocity4 #ae4 ,formula connecting models of similar design but different weights4 #af4 ,formula connecting power and speed4 #ag4 ,propeller thrust4 #ah4 ,to determine experimentally the static thrust of a propeller4 #ai4 ,horse-power and the number of revolutions4 #bj4 ,to compare one model with another4 #ba4 ,work done by a clockwork spring motor4 #bb4 ,to ascertain the horse-power of a rubber motor4 #bc4 ,foot-pounds of energy in a given weight of rubber--,experimental determination of4 #bd4 ,theoretical length of flight4 #be4 ,to test different motors4 #bf4 ,efficiency of a model4 #bg4 ,efficiency of design4 #bh4 ,naphtha engines4 #bi4 ,horse-power and weight of model petrol motors4 #cj4 ,formula for rating the same4 #cj;,a4 ,relation between static thrust of propeller and total weight of model4 #ca4 ,how to find the height of an inaccessible object 7kite1 balloon1 etc474 #cb4 ,formula for ,i4,h4,p4 of model steam engines #abe ,,appendix ,a4 ,some models which have won medals at open competitions #adc ,,glossary ,,of ,,terms ,,used ,,in ,,model ,,aeroplaning4 ,aeroplane4 ,a motor-driven flying machine which relies upon surfaces for its support in the air4 ,monoplane 7single74 ,an aeroplane with one pair of outstretched wings4 ,aerofoil4 ,these outstretched wings are often called aerofoil surfaces4 ,one pair of wings forming one aerofoil surface4 ,monoplane 7double74 ,an aeroplane with two aerofoils1 one behind the other or two main planes1 tandem-wise4 ,biplane4 ,an aeroplane with two aerofoils1 one below the other1 or having two main planes superposed4 ,triplane4 ,an aeroplane having three such aerofoils or three such main planes4 ,multiplane4 ,any such machine having more than three of the above4 ,glider4 ,a motorless aeroplane4 ,helicopter4 ,a flying machine in which propellers are employed to raise the machine in the air by their own unaided efforts4 ,dihedral ,angle4 ,a dihedral angle is an angle made by two surfaces that do not lie in the same plane1 i4e4 when the aerofoils are arranged ,v-shaped4 ,it is better1 however1 to somewhat extend this definition1 and not to consider it as necessary that the two surfaces do actually meet1 but would do so if produced thus in figure4 ,,ba and ,,cd are still dihedrals1 sometimes termed upturned tips4 ,illustration3 ,dihedrals4 ,span is the distance from tip to tip of the main supporting surface measured transversely 7across7 the line of flight4 ,camber 7a slight arching or convexity upwards74 ,this term denotes that the aerofoil has such a curved transverse section4 ,chord is the distance between the entering 7or leading7 edge of the main supporting surface 7aerofoil7 and the trailing edge of the same2 also defined as the fore and aft dimension of the main planes measured in a straight line between the leading and trailing edges4 span ,aspect ,ratio is ----- chord ,gap is the vertical distance between one aerofoil and the one which is immediately above it4 7,the gap is usually made equal to the chord74 ,angle of ,incidence4 ,the angle of incidence is the angle made by the chord with the line of flight4 ,illustration3 ,,ab chord4 ,,ab cambered surface4 ,,sp line of flight4 ,,asp alpha ,l of incidence4 ,width4 ,the width of an aerofoil is the distance from the front to the rear edge1 allowing for camber4 ,length4 ,this term is usually applied to the machine as a whole1 from the front leading edge of elevator 7or supports7 to tip of tail4 ,arched4 ,this term is usually applied to aerofoil surfaces which dip downwards like the wings of a bird4 ,the curve in this case being at right angles to camber4 ,a surface can1 of course1 be both cambered and arched4 ,propeller4 ,a device for propelling or pushing an aeroplane forward or for raising it vertically 7lifting screw74 ,tractor ,screw4 ,a device for pulling the machine 7used when the propeller is placed in the front of the machine74 ,keel4 ,a vertical plane or planes 7usually termed fins7 arranged longitudinally for the purposes of stability and steering4 ,tail4 ,the plane1 or group of planes1 at the rear end of an aeroplane for the purpose chiefly of giving longitudinal stability4 ,in such cases the tail is normally 7approx47 horizontal1 but not unfrequently vertical tail-pieces are fitted as well for steering 7transversely7 to the right or left1 or the entire tail may be twisted for the purpose of transverse stability 7vide ,elevator74 ,such appendages are being used less and less with the idea of giving actual support4 ,rudder is the term used for the vertical plane1 or planes1 which are used to steer the aeroplane sideways4 ,warping4 ,the flexing or bending of an aerofoil out of its normal shape4 ,the rear edges near the tips of the aerofoil being dipped or tilted respectively1 in order to create a temporary difference in their inclinations to the line of flight4 ,performed in conjunction with rudder movements1 to counteract the excessive action of the latter4 ,ailerons 7also called righting-tips1 balancing-planes1 etc474 ,small aeroplanes in the vicinity of the tips of the main aerofoil for the purpose of assisting in the maintenance of equilibrium or for steering purposes either with or without the assistance of the rudder4 ,elevator4 ,the plane1 or planes1 in front of the main aerofoil used for the purpose of keeping the aeroplane on an even keel1 or which cause 7by being tilted or dipped7 the aeroplane to rise or fall 7vide ,tail74 ,,model ,,aeroplaning ,,introduction4 #a4 ,model ,aeroplanes are primarily divided into two classes3 first1 models intended before all else to be ones that shall fly2 secondly1 models1 using the word in its proper sense of full-sized machines4 ,herein model aeroplanes differ from model yachts and model locomotives4 ,an extremely small model locomotive built to scale will still work1 just as a very small yacht built to scale will sail2 but when you try to build a scale model of an ,antoinette monoplane1 including engine1 it cannot be made to fly unless the scale be a very large one4 ,if1 for instance1 you endeavoured to make a #a_/aj scale model1 your model petrol motor would be compelled to have eight cylinders1 each #jeb bore1 and your magneto of such size as easily to pass through a ring half an inch in diameter4 ,such a model could not possibly work4#a ,note4--,readers will find in the ,model ,engineer of ,june #af1 #aiaj1 some really very fine working drawings of a prize-winning ,antoinette monoplane model4 #b4 ,again1 although the motor constitutes the chief1 it is by no means the sole difficulty in scale model aeroplane building4 ,to reproduce to scale at scale weight1 or indeed anything approaching it1 all the necessary--in the case of a full-sized machine--framework is not possible in a less than #a_/e scale4 #c4 ,special difficulties occur in the case of any prototype taken4 ,for instance1 in the case of model ,blriots it is extremely difficult to get the centre of gravity sufficiently forward4 #d4 ,scale models of actual flying machines that will fly mean models at least #aj or #ab feet across1 and every other dimension in like proportion2 and it must always be carefully borne in mind that the smaller the scale the greater the difficulties1 but not in the same proportion--it would not be twice as difficult to build a -in4 scale model as a -in41 but four1 five or six times as difficult4 #e4 ,now1 the first requirement of a model aeroplane1 or flying machine1 is that it shall ,,fly4 ,as will be seen later on--unless the machine be of large size1 #aj feet and more spread--the only motor at our disposal is the motor of twisted rubber strands1 and this to be efficient requires to be long1 and is of practically uniform weight throughout2 this alone alters the entire distribution of weight on the machine and makes3 #f4 ,model ,aeroplaning an ,art in itself1 and as such we propose to consider it in the following pages4 ,we have said that the first requisite of a model aeroplane is that it shall fly1 but there is no necessity1 nor is it indeed always to be desired1 that this should be its only one1 unless it be built with the express purpose of obtaining a record length of flight4 ,for ordinary flights and scientific study what is required is a machine in which minute detail is of secondary importance1 but which does along its main lines approximate to the real thing4 #g4 ,simplicity should be the first thing aimed at--simplicity means efficiency1 it means it in full-sized machines1 still more does it mean it in models--and this very question of simplicity brings us to that most important question of all1 namely1 the question of weight4 ,,footnote3 #a ,the smallest working steam engine that the writer has ever heard of has a net weight of #d grains4 ,one hundred such engines would be required to weigh one ounce4 ,the bore being #jjc in41 and stroke #a_/cb of an inch1 r4p4m4 #fjjj per min41 h4p4 developed #a_/dhijjj 7,model ,engineer1 ,july #g1 #aiaj74 ,when working it hums like a bee4 ,,chapter ,i4 ,,the ,,question ,,of ,,weight4 #a4 ,the following is an extract from a letter that appeared in the correspondence columns of ,the ,aero4#b ,to give you some idea how slight a thing will make a model behave badly1 ,i fitted a skid to protect the propeller underneath the aeroplane1 and the result in retarding flight could be seen very quickly1 although the weight of the skid was almost nil4#c ,to all model makers who wish to make a success ,i would say1 strip all that useless and heavy chassis off1 cut down the 'good1 honest stick' that you have for a backbone to half its thickness1 stay it with wire if it bends under the strain of the rubber1 put light silk on the planes1 and use an aluminium#d propeller4 ,the result will surpass all expectations4 #b4 ,the above refers1 of course1 to a rubber-motor driven model4 ,let us turn to a steam-driven prototype4 ,i take the best known example of all1 ,professor ,langley's famous model4 ,here is what the professor has to say on the question#e3-- ,every bit of the machinery had to be constructed with scientific accuracy4 ,it had to be tested again and again4 ,the difficulty of getting the machine light enough was such that every part of it had to be remade several times4 ,it would be in full working order when something would give way1 and this part would have to be strengthened4 ,this caused additional weight1 and necessitated cutting off so much weight from some other part of the machinery4 ,at times the difficulty seemed almost heartbreaking2 but ,i went on1 piece by piece and atom by atom1 until ,i at last succeeded in getting all the parts of the right strength and proportion4 ,how to obtain the maximum strength with the minimum of weight is one of the1 if not the most1 difficult problems which the student has to solve4 #c4 ,the theoretical reason why weight is such an all-important item in model aeroplaning1 much more so than in the case of full-size machines1 is that1 generally speaking1 such models do not fly fast enough to possess a high weight carrying capacity4 ,if you increase the area of the supporting surface you increase also the resistance1 and thereby diminish the speed1 and are no better off than before4 ,the only way to increase the weight carrying capacity of a model is to increase its speed4 ,this point will be recurred to later on4 ,one of ,mr4 ,t4,w4,k4 ,clarke's well-known models1 surface area #a sq4 ft41 weight #a lb41 is stated to have made a flight of #cjj yards carrying #f oz4 of lead4 ,this works out approximately at #ba oz4 per sq4 ft4 ,the velocity 7speed7 is not stated1 but some earlier models by the same designer1 weight #a lb41 supporting area #a sq4 ft41 i4e41 at rate of #af oz4 per sq4 ft41 travelled at a rate of #cg ft4 per second1 or #be miles an hour4 ,the velocity of the former1 therefore1 would certainly not be less than #cj miles an hour4 #d4 ,generally speaking1 however1 models do not travel at anything like this velocity1 or carry anything like this weight per sq4 ft4 ,an average assumption of #ac to #ae miles an hour does nor err on the minimum side4 ,some very light fabric covered models have a speed of less than even #aj miles an hour4 ,such1 of course1 cannot be termed efficient models1 and carry only about #c oz4 per sq4 ft4 ,between these two types--these two extremes--somewhere lies the ,ideal ,model4 ,the maximum of strength with the minimum of weight can be obtained only3-- #a4 ,by a knowledge of materials4 #b4 ,of how to combine those materials in a most efficient and skilful manner4 #c4 ,by a constant use of the balance or a pair of scales1 and noting 7in writing7 the weight and result of every trial and every experiment in the alteration and change of material used4 ,,weigh ,,everything4 #e4 ,the reader must not be misled by what has been said1 and think that a model must not weigh anything if it is to fly well4 ,a heavy model will fly much better against the wind than a light one1 provided that the former will fly4 ,to do this it must fly fast4 ,to do this again it must be well powered1 and offer the minimum of resistance to the medium through which it moves4 ,this means its aerofoil 7supporting7 surfaces must be of polished wood or metal4 ,this point brings us to the question of ,resistance1 which we will now consider4 ,,footnotes3 #b ,aero1 ,may #c1 #aiaj4 #c ,part of this retardation was1 of course1 increased resistance4 #d ,personally ,i do not recommend aluminium4--,v4,e4,j4 #e ,aeronautical ,journal1 ,january #ahig1 p4 #g4 ,,chapter ,,ii4 ,,the ,,question ,,of ,,resistance4 #a4 ,it is1 or should be1 the function of an aeroplane--model or otherwise--to pass through the medium in which it travels in such a manner as to leave that medium in as motionless a state as possible1 since all motion of the surrounding air represents so much power wasted4 ,every part of the machine should be so constructed as to move through the air with the minimum of disturbance and resistance4 #b4 ,the resistance1 considered as a percentage of the load itself1 that has to be overcome in moving a load from one place to another1 is1 according to ,mr4 ,f4,w4 ,lanchester1 #ab per cent4 in the case of a flying machine1 and #ja per cent4 in the case of a cargo boat1 and of a solid tyre motor car #c per cent41 a locomotive #a per cent4 ,four times at least the resistance in the case of aerial locomotion has to be overcome to that obtained from ordinary locomotion on land4 ,the above refer1 of course1 to full-sized machines2 for a model the resistance is probably nearer #ad or #ae per cent4 #c4 ,this resistance is made up of-- #a4 ,aerodynamic resistance4 #b4 ,head resistance4 #c4 ,skin-friction 7surface resistance74 ,the first results from the necessity of air supporting the model during flight4 ,the second is the resistance offered by the framework1 wires1 edges of aerofoils1 etc4 ,the third1 skin-friction or surface resistance1 is very small at low velocities1 but increases as the square of the velocity4 ,to reduce the resistance which it sets up1 all surfaces used should be as smooth as possible4 ,to reduce the second1 contours of ichthyoid1 or fish-like1 form should be used1 so that the resultant stream-line flow of the medium shall keep in touch with the surface of the body4 #d4 ,as long ago as #ahid a series of experiments were made by the writer#f to solve the following problem3 given a certain length and breadth1 to find the shape which will offer the least resistance4 ,the experiments were made with a whirling table #dj ft4 in diameter1 which could be rotated so that the extremity of the arm rotated up to a speed of #de miles an hour4 ,the method of experimenting was as follows3 ,the bodies 7diam4 #d in47 were balanced against one another at the extremity of the arm1 being so balanced that their motions forward and backward were parallel4 ,provision was made for accurately balancing the parallel scales on which the bodies were suspended without altering the resistance offered by the apparatus to the air4 ,two experiments at least 7to avoid error7 were made in each case1 the bodies being reversed in the second experiment1 the top one being put at the bottom1 and vice versa4 ,the conclusions arrived at were3-- ,for minimum 7head7 resistance a body should have-- #a4 ,its greatest diameter two-fifths of its entire length from its head4 #b4 ,its breadth and its depth in the proportion of four to three4 #c4 ,its length at least from five to nine times its greatest breadth 7nine being better than five74 #d4 ,a very tapering form of stern1 the actual stern only being of just sufficient size to allow of the propeller shaft passing through4 ,in the case of twin propellers some slight modification of the stern would be necessary4 #e4 ,every portion of the body in contact with the fluid to be made as smooth as possible4 #f4 ,a body of such shape gives at most only one-twentieth the resistance offered by a flat disk of similar maximum sectional area4 ,results since fully confirmed4 ,illustration3 ,,fig4 #a4--,,shape ,,of ,,least ,,resistance4 ,the design in ,fig4 #b is interesting1 not only because of its probable origin1 but because of the shape of the body and arrangement of the propellers2 no rudder is shown1 and the long steel vertical mast extending both upwards and downwards through the centre would render it suitable only for landing on water4 #e4 ,in the case of a rubber-driven model1 there is no containing body part1 so to speak1 a long thin stick1 or tubular construction if preferred1 being all that is necessary4 ,the long skein of elastic1 vibrating as well as untwisting as it travels with the machine through the air1 offers some appreciable resistance1 and several experimenters have enclosed it in a light tube made of very thin veneer wood rolled and glued1 or paper even may be used2 such tubes can be made very light1 and possess considerable rigidity1 especially longitudinally4 ,if the model be a biplane1 then all the upright struts between the two aerofoils should be given a shape1 a vertical section of which is shown in ,fig4 #c4 #f4 ,in considering this question of resistance1 the substance of which the aerofoil surface is made plays a very important part1 as well as whether that surface be plane or curved4 ,for some reason not altogether easy to determine1 fabric-covered planes offer considerably more resistance than wooden or metal ones4 ,that they should offer more resistance is what common sense would lead one to expect1 but hardly to the extent met with in actual practice4 ,illustration3 ,,fig4 #b4--;,,design ,,for ,,an ,,aeroplane ,,model 7,,power ,,driven74 ,this design is attributed to ,professor ,langley4 ,built up fabric-covered aeroplanes#g gain in lightness1 but lose in resistance4 ,in the case of curved surfaces this difference is considerably more2 one reason1 undoubtedly1 is that in a built up model surface there is nearly always a tendency to make this curvature excessive1 and much more than it should be4 ,having called attention to this under the head of resistance1 we will leave it now to recur to it later when considering the aerofoil proper4 ,illustration3 ,,fig4 #c4--;,,horizontal ,,section ,,of ,,vertical ,,strut 7,,enlarged47 #g4 ,allusion has been made in this chapter to skin friction1 but no value given for its coefficient4#h ,lanchester's value for planes from to #a sq4 ft4 in area1 moving about #bj to #cj ft4 per second1 is #jjji to #jjae4 ,professor ,zahm 7,washington7 gives #jjjbf lb4 per sq4 ft4 at #be ft4 per second1 and at #cg ft4 per second1 #jjje1 and the formula f #jjjjjjgghl#icv#ahe f being the average friction in lb4 per sq4 in41 l the length in feet1 and v the velocity in ft4 per second4 ,he also experimented with various kinds of surfaces1 some rough1 some smooth1 etc4 ,his conclusion is3--,all even surfaces have approximately the same coefficient of skin friction4 ,uneven surfaces have a greater coefficient4 ,all formul on skin friction must at present be accepted with reserve4 #h4 ,the following three experiments1 however1 clearly prove its existence1 and that it has considerable effect3-- #a4 ,a light1 hollow celluloid ball1 supported on a stream of air projected upwards from a jet1 rotates in one direction or the other as the jet is inclined to the left or to the right4 7,f4,w4 ,lanchester47 #b4 ,when a golf ball 7which is rough7 is hit so as to have considerable underspin1 its range is increased from #ace to #ahj yards1 due entirely to the greater frictional resistance to the air on that side on which the whirl and the progressive motion combine4 7,prof4 ,tait47 #c4 ,by means of a 7weak7 bow a golf ball can be made to move point blank to a mark #cj yards off1 provided the string be so adjusted as to give a good underspin2 adjust the string to the centre of the ball1 instead of catching it below1 and the drop will be about #h ft4 7,prof4 ,tait47 ,,footnotes3 #f ,vide ,invention1 ,feb4 #ae1 #bb1 and #bi1 #ahif4 #g ,really aerofoils1 since we are considering only the supporting surface4 #h ,i4e41 to express it as a decimal fraction of the resistance1 encountered by the same plane when moving face instead of edge on4 ,,chapter ,,iii4 ,,the ,,question ,,of ,,balance4 #a4 ,it is perfectly obvious for successful flight that any model flying machine 7in the absence of a pilot7 must possess a high degree of automatic stability4 ,the model must be so constructed as to be naturally stable1 in the medium through which it is proposed to drive it4 ,the last remark is of the greatest importance1 as we shall see4 #b4 ,in connexion with this same question of automatic stability1 the question must be considered from the theoretical as well as from the practical side1 and the labours and researches of such men as ,professors ,brian and ,chatley1 ,f4,w4 ,lanchester1 ,captain ,ferber1 ,mouillard and others must receive due weight4 ,their work cannot yet be fully assessed1 but already results have been arrived at far more important than are generally supposed4 ,the following are a few of the results arrived at from theoretical considerations2 they cannot be too widely known4 7,a7 ,surfaces concave on the under side are not stable unless some form of balancing device 7such as a tail1 etc47 is used4 7,b7 ,if an aeroplane is in equilibrium and moving uniformly1 it is necessary for stability that it shall tend towards a condition of equilibrium4 7,c7 ,in the case of oscillations it is absolutely necessary for stability that these oscillations shall decrease in amplitude1 in other words1 be damped out4 7,d7 ,in aeroplanes in which the dihedral angle is excessive or the centre of gravity very low down1 a dangerous pitching motion is quite likely to be set up4 ,analogy in shipbuilding--an increase in the metacentre height while increasing the stability in a statical sense causes the ship to do the same4 7,e7 ,the propeller shaft should pass through the centre of gravity of the machine4 7,f7 ,the front planes should be at a greater angle of inclination than the rear ones4 7,g7 ,the longitudinal stability of an aeroplane grows much less when the aeroplane commences to rise1 a monoplane becoming unstable when the angle of ascent is greater than the inclination of the main aerofoil to the horizon4 7,h7 ,head resistance increases stability4 7,i7 ,three planes are more stable than two4 ,elevator--main aerofoil--horizontal rudder behind4 7,j7 ,when an aeroplane is gliding 7downwards7 stability is greater than in horizontal flight4 7,k7 ,a large moment of inertia is inimical 7opposed7 to stability4 7,m7 ,aeroplanes 7naturally7 stable up to a certain velocity 7speed7 may become unstable when moving beyond that speed4 ,possible explanation4 ,the motion of the air over the edges of the aerofoil becomes turbulent1 and the form of the stream lines suddenly changes4 ,aeroplane also probably becomes deformed4 7,n7 ,in a balanced glider for stability a separate surface at a negative angle to the line of flight is essential4 ,compare ,f4 7,o7 ,a keel surface should be situated well above and behind the centre of gravity4 7,p7 ,an aeroplane is a conservative system1 and stability is greatest when the kinetic energy is a maximum4 ,illustration1 the pendulum4 #c4 ,referring to ,a4 ,models with a plane or flat surface are not unstable1 and will fly well without a tail2 such a machine is called a simple monoplane4 ,illustration3 ,,fig4 #d4--,,one ,,of ,,mr4 ,,burge ,,webb',s ,,simple ,,monoplanes4 ,showing balance weight ,a 7movable71 and also his winding-up gear--a very handy device4 #d4 ,referring to ,d4 ,many model builders make this mistake1 i4e41 the mistake of getting as low a centre of gravity as possible under the quite erroneous idea that they are thereby increasing the stability of the machine4 ,theoretically the centre of gravity should be the centre of head resistance1 as also the centre of pressure4 ,in practice some prefer to put the centre of gravity in models slightly above the centre of head resistance1 the reason being that1 generally speaking1 wind gusts have a lifting action on the machine4 ,it must be carefully borne in mind1 however1 that if the centre of wind pressure on the aerofoil surface and the centre of gravity do not coincide1 no matter at what point propulsive action be applied1 it can be proved by quite elementary mechanics that such an arrangement1 known as acentric1 produces a couple tending to upset the machine4 ,this action is the probable cause of many failures4 ,illustration3 ,,fig4 #e4--,,the ,,stringfellow ,,model ,,monoplane ,,of #ahdh4 #e4 ,referring to ,e4 ,if the propulsive action does not pass through the centre of gravity the system again becomes acentric4 ,even supposing condition ,d fulfilled1 and we arrive at the following most important result1 viz41 that for stability3-- ,,the ,,centres ,,of ,,gravity1 ,,of ,,pressure1 ,,of ,,head ,,resistance1 ,,should ,,be ,,coincident1 ,,and ,,the ,,propulsive ,,action ,,of ,,the ,,propeller ,,pass ,,through ,,this ,,same ,,point4 ,illustration3 ,,fig4 #f4--,,the ,,stringfellow ,,model ,,triplane ,,of #ahfh4 #f4 ,referring to ,f and ,n--the problem of longitudinal stability4 ,there is one absolutely essential feature not mentioned in ,f or ,n1 and that is for automatic longitudinal stability the two surfaces1 the aerofoil proper and the balancer 7elevator or tail1 or both71 must be separated by some considerable distance1 a distance not less than four times the width of the main aerofoil4#i ,more is better4 ,illustration3 ,,fig4 #g4 ,p,,naud #ahga #g4 ,with one exception 7,pnaud7 early experimenters with model aeroplanes had not grasped this all-important fact1 and their models would not fly1 only make a series of jumps1 because they failed to balance longitudinally4 ,in ,stringfellow's and ,tatin's models the main aerofoil and balancer 7tail7 are practically contiguous4 ,pnaud in his rubber-motored models appears to have fully realised this 7vide ,fig4 #g71 and also the necessity for using long strands of rubber4 ,some of his models flew #aej ft41 and showed considerable stability4 ,illustration3 ,,fig4 #h4--,,tatin',s ,,aeroplane 7#ahgi74 ,surface #jg sq4 metres1 total weight #age kilogrammes1 velocity of sustentation #h metres a second4 ,motor1 compressed air 7for description see #bc1 ch4 iv74 ,revolved round and round a track tethered to a post at the centre4 ,in one of its jumps it cleared the head of a spectator4 ,with three surfaces one would set the elevator at a slight plus angle1 main aerofoil horizontal 7neither positive nor negative71 and the tail at a corresponding negative angle to the positive one of the elevator4 ,referring to ,o4#aj ,one would naturally be inclined to put a keel surface--or1 in other words1 vertical fins--beneath the centre of gravity1 but ,d shows us this may have the opposite effect to what we might expect4 ,in full-sized machines1 those in which the distance between the main aerofoil and balancers is considerable 7like the ,farman7 show considerable automatic longitudinal stability1 and those in which it is short 7like the ,wright7 are purposely made so with the idea of doing away with it1 and rendering the machine quicker and more sensitive to personal control4 ,in the case of the ,stringfellow and ,tatin models we have the extreme case--practically the bird entirely volitional and personal--which is the opposite in every way to what we desire on a model under no personal or volitional control at all4 ,illustration3 ,,fig4 #i4--;,,clark',s ,,model ,,flyer4 ,main aerofoil set at a slight negative angle4 ,dihedral angles on both aerofoils4 ,the theoretical conditions stated in ,f and ,n are fully borne out in practice4 ,and since a curved aerofoil even when set at a slight negative angle has still considerable powers of sustentation1 it is possible to give the main aerofoil a slight negative angle and the elevator a slight positive one4 ,this fact is of the greatest importance1 since it enables us to counteract the effect of the travel of the centre of pressure4#aa ,illustration3 ,,fig4 #aj4--,,large ,,model ,,monoplane4 ,designed and constructed by the author1 with vertical fin 7no dihedral angle74 ,with a larger and more efficient propeller than the one here shown some excellent flights were obtained4 ,constructed of bamboo and nainsook4 ,stayed with steel wire4 #h4 ,referring to ,i4 ,this1 again1 is of primary importance in longitudinal stability4 ,the ,farman machine has three such planes--elevator1 main aerofoil1 tail the ,wright originally had not1 but is now being fitted with a tail1 and experiments on the ,short-,wright biplane have quite proved its stabilising efficiency4 ,the three plane 7triple monoplane7 in the case of models has been tried1 but possesses no advantage so far over the double monoplane type4 ,the writer has made many experiments with vertical fins1 and has found the machine very stable1 even when the fin or vertical keel is placed some distance above the centre of gravity4 #i4 ,the question of transverse 7side to side7 stability at once brings us to the question of the dihedral angle1 practically similar in its action to a flat plane with vertical fins4 ,illustration3 ,,fig4 #aa4--,,sir ,,george ,,cayley',s ,,flying ,,machine4 ,eight feathers1 two corks1 a thin rod1 a piece of whalebone1 and a piece of thread4 #aj4 ,the setting up of the front surface at an angle to the rear1 or the setting of these at corresponding compensatory angles already dealt with1 is nothing more nor less than the principle of the dihedral angle for longitudinal stability4 ,illustration3 ,,fig4 #ab4--,,various ,,forms ,,of ,,dihedrals4 ,as early as the commencement of last century ,sir ,george ,cayley 7a man more than a hundred years ahead of his times7 was the first to point out that two planes at a dihedral angle constitute a basis of stability4 ,for1 on the machine heeling over1 the side which is required to rise gains resistance by its new position1 and that which is required to sink loses it4 #aa4 ,the dihedral angle principle may take many forms4 ,as in ,fig4 #ab a is a monoplane1 the rest biplanes4 ,the angles and curves are somewhat exaggerated4 ,it is quite a mistake to make the angle excessive1 the lift being thereby diminished4 ,a few degrees should suffice4 ,whilst it is evident enough that transverse stability is promoted by making the sustaining surface trough-shaped1 it is not so evident what form of cross section is the most efficient for sustentation and equilibrium combined4 ,illustration3 ,,fig4 #ac4 ,it is evident that the righting moment of a unit of surface of an aeroplane is greater at the outer edge than elsewhere1 owing to the greater lever arm4 #ab4 ,the upturned tip dihedral certainly appears to have the advantage4 ,the outer edges of the aerofoil then should be turned upward for the purpose of transverse stability1 while the inner surface should remain flat or concave for greater support4 #ac4 ,the exact most favourable outline of transverse section for stability1 steadiness and buoyancy has not yet been found2 but the writer has found the section given in ,fig4 #ac1 a very efficient one4 ,,footnotes3 #i ,if the width be not uniform the mean width should be taken4 #aj ,this refers1 of course1 to transverse stability4 #aa ,see ch4 vi4 ,,chapter ,,iv4 ,,the ,,motive ,,power4 ,,section ,i4--,,rubber ,,motors4 #a4 ,some forty years have elapsed since ,pnaud first used elastic 7rubber7 for model aeroplanes1 and during that time no better substitute 7in spite of innumerable experiments7 has been found4 ,nor for the smaller and lighter class of models is there any likelihood of rubber being displaced4 ,such being the case1 a brief account of some experiments on this substance as a motive power for the same may not be without interest4 ,the word elastic 7in science7 denotes3 the tendency which a body has when distorted to return to its original shape4 ,glass and ivory 7within certain limits7 are two of the most elastic bodies known4 ,but the limits within which most bodies can be distorted 7twisted or stretched1 or both7 without either fracture or a ,,large permanent alteration of shape is very small4 ,not so rubber--it far surpasses in this respect even steel springs4 #b4 ,let us take a piece of elastic 7rubber7 cord1 and stretch it with known weights and observe carefully what happens4 ,we shall find that1 first of all3 the extension is proportional to the weight suspended--but soon we have an increasing increase of extension4 ,in one experiment made by the writer1 when the weights were removed the rubber cord remained #a_/h of an inch longer1 and at the end of an hour recovered itself to the extent of #a_/af1 remaining finally permanently #a_/af of an inch longer4 ,length of elastic cord used in this experiment #h-a_/h inches1 #c_/af of an inch thick4 ,suspended weights1 #a oz4 up to #fd oz4 ,extension from inch up to #bd-e_/h inches4 ,graph drawn in ,fig4 #ad1 ,no4 ,b absciss extension in eighths of an inch1 ordinates weights in ounces4 ,so long as the graph is a straight line it shows the extension is proportional to the suspended weight2 afterwards in excess4 ,illustration3 ,,fig4 #ad4--,,weight ,,and ,,extension4 ,b1 rubber #c_/af in4 thick2 ,c1 #b_/af in4 thick2 ,d1 #a_/af in4 thick4 ,a1 theoretical line if extension were proportional to weight4 ,in this experiment we have been able to stretch 7distort7 a piece of rubber to more than three times its original length1 and afterwards it finally returns to almost its original length3 not only so1 a piece of rubber cord can be stretched to eight or nine times its original length without fracture4 ,herein lies its supreme advantage over steel or other springs4 ,weight for weight more energy can be got or more work be done by stretched 7or twisted1 or1 to speak more correctly1 by stretched-twisted7 rubber cord than from any form of steel spring4#ab ,it is true it is stretched--twisted--far beyond what is called the elastic limit1 and its efficiency falls off1 but with care not nearly so quickly as is commonly supposed1 but in spite of this and other drawbacks its advantages far more than counterbalance these4 #c4 ,experimenting with cords of varying thickness we find that3 the extension is inversely proportional to the thickness4 ,if we leave a weight hanging on a piece of rubber cord 7stretched1 of course1 beyond its elastic limit7 we find that3 the cord continues to elongate as long as the weight is left on4 ,for example3 a #a lb4 weight hung on a piece of rubber cord1 #h-a_/h inches long and #a_/h of an inch thick1 stretched it--at first--#f inches2 after two minutes this had increased to #f-e_/h 7#c_/h of an inch more74 ,one hour later #a_/h of an inch more1 and sixteen hours later #a_/h of an inch more1 i4e4 a sixteen hours' hang produced an additional extension of of an inch4 ,on a thinner cord 7half the thickness7 same weight produced an additional extension 7after #ad hours7 of #aj-c_/h in4 ,n4,b4--,an elastic cord or spring balance should never have a weight left permanently on it--or be subjected to a distorting force for a longer time than necessary1 or it will take a permanent set1 and not return to even approximately its original length or form4 ,in a rubber cord the extension is directly proportional to the length as well as inversely proportional to the thickness and to the weight suspended--true only within the limits of elasticity4 ,illustration3 ,,fig4 #ae4--;,,extension ,,and ,,increase ,,in ,,volume4 #d4 ,when a ,rubber ,cord is stretched there is an ,increase of ,volume4--,on stretching a piece of rubber cord to twice its original 7natural7 length1 we should perhaps expect to find that the string would only be half as thick1 as would be the case if the volume remained the same4 ,performing the experiment1 and measuring the cord as accurately as possible with a micrometer1 measuring to the one-thousandth of an inch1 we at once perceive that this is not the case1 being about two-thirds of its former volume4 #e4 ,in the case of rubber cord used for a motive power on model aeroplanes1 the rubber is both twisted and stretched1 but chiefly the latter4 ,thirty-six strands of rubber1 weight about #ef grammes1 at #aej turns give a torque of #d oz4 on a #e-;in4 arm1 but an end thrust1 or end pull1 of about #c lb4 7,ball bearings1 or some such device1 can be used to obviate this end thrust when desirable47 ,a series of experiments undertaken by the writer on the torque produced by twisted rubber strands1 varying in number1 length1 etc41 and afterwards carefully plotted out in graph form1 have led to some very interesting and instructive results4 ,ball bearings were used1 and the torque1 measured in eighths of an ounce1 was taken 7in each case7 from an arm #e in4 in length4 ,the following are the principal results arrived at4 ,for graphs1 see ,fig4 #af4 #f4 ,a4 ,increasing the number of 7rubber7 strands by one-half 7length and thickness of rubber remaining constant7 increases the torque 7unwinding tendency7 twofold1 i4e41 doubles the motive power4 ,b4 ,doubling the number of strands increases the torque more than three times--about #c-a_/c times1 #c times up to #ajj turns1 #c times from #ajj to #bej turns4 ,c4 ,trebling the number of strands increases the torque at least seven times4 ,the increased size of the coils1 and thereby increased extension1 explains this result4 ,as we increase the number of strands1 the number of twists or turns that can be given it becomes less4 ,d4 ,doubling the number of strands 7length1 etc41 remaining constant7 diminishes the number of turns by one-third to one-half4 7,in few strands one-third1 in #cj and over one-half47 ,illustration3 ,,fig4 #af4--,,torque ,,graphs ,,of ,,rubber ,,motors4 ,absciss ,turns4 ,ordinates ,torque measured in #a_/af of an oz4 ,length of arm1 #e in4 ,a4 #ch strands of new rubber1 #b ft4 #f in4 long2 #eh grammes weight4 ,b4 #cf strands1 #b ft4 #f in4 long2 end thrust at #aej turns1 #c lb4 ,c4 #cb strands1 #b ft4 #f in4 long4 ,d4 #bd ,e4 #ah weight #bh grammes4 ,f4 #ab #a ft4 #c in4 long ,g4 #ab #b ft4 #f in4 long4 ,e4 ,if we halve the length of the rubber strands1 keeping the number of strands the same1 the torque is but slightly increased for the first #ajj turns2 at #bdj turns it is double4 ,but the greater number of turns--in ratio of about #b3a--that can be given the longer strand much more than compensates for this4 ,f4 ,no arrangement of the strands1 per se1 gets more energy 7more motive power7 out of them than any other1 but there are special reasons for making the strands-- ,g4 ,as long and as few in number as possible4 #a4 ,more turns can be given it4 #b4 ,it gives a far more even torque4 ,twelve strands #b ft4 #f in4 long give practically a line of small constant angle4 ,thirty-six strands same length a much steeper angle1 with considerable variations4 ,a very good result1 which the writer has verified in practice1 paying due regard to both propeller and motor1 is to make-- ,h4 ,the length of the rubber strands twice#ac in feet the number of the strands in inches1#ad e4g41 if the number of strands is #ab their length should be #b ft41 if #ah1 #c ft41 and so on4 #g4 ,experiments with #cb to #ch strands #b ft4 #f in4 long give a torque curve almost precisely similar to that obtained from experiments made with flat spiral steel springs1 similar to those used in watches and clocks2 and1 as we know1 the torque given by such springs is very uneven1 and has to be equalised by use of a fusee1 or some such device4 ,in the case of such springs it must not be forgotten that the turning moment 7unwinding tendency7 is ,,not proportional to the amount of winding up1 this being true only in the balance springs of watches1 etc41 where both ends of the spring are rigidly fastened4 ,in the case of ,,spring ,,motors4#ae ,i4 ,the turning moment 7unwinding tendency7 is proportional to the difference between the angle of winding and yielding1 proportional to the moment of inertia of its section1 i4e41 to the breadth and the cube of its thickness1 also proportional to the modulus of elasticity of the substance used1 and inversely proportional to the length of the strip4 #h4 ,referring back to ,a1 ,b1 ,c1 there are one or two practical deductions which should be carefully noted4 ,supposing we have a model with one propeller and #cf strands of elastic4 ,if we decide to fit it with twin screws1 then1 other reasons apart1 we shall require two sets of strands of more than #ah in number each to have the same motive power 7#bg if the same torque be required74#af ,this is an important point1 and one not to be lost sight of when thinking of using two propellers4 ,experiments on-- #i4 ,the ,number of ,revolutions 7turns7 that can be given to ,rubber ,motors led to interesting results1 e4g41 the number of turns to produce a double knot in the cord from end to end were1 in the case of rubber1 one yard long3-- ,no4 of ,strands4 ,no4 of ,turns4 ,no4 of ,strands4 ,no4 of ,turns4 #d #ddj #af #bjj #h #caj #bh #agj #ab #bej ,it will be at once noticed that the greater the number of rubber strands used in a given length1 the fewer turns will it stand in proportion4 ,for instance1 #h strands double knot at #caj1 and #d at #ddj 7and not at #fbj71 #af at #bjj1 and #h at #caj 7and not #djj71 and so on4 ,the reason1 of course1 is the more the strands the greater the distance they have to travel round themselves4 #aj4 ,the ,maximum ,number of ,turns4--,as to the maximum number of permissible turns1 rubber has rupture stress of #ccj lb4 per sq4 in41 but a very high permissible stress1 as much as #hj per cent4 ,the resilience 7power of recovery after distortion7 in tension of rubber is in considerable excess of any other substance1 silk being the only other substance which at all approaches it in this respect1 the ratio being about #aa 3 #i4 ,the resilience of steel spiral spring is very slight in comparison4 ,a rubber motor in which the double knot is not exceeded by more than #ajj turns 7rubber one yard in length7 should last a good time4 ,when trying for a record flight1 using new elastic1 as many as even #ejj or #fjj or even more turns have been given in the case of #cb-cf strands a yard in length2 but such a severe strain soon spoils the rubber4 #aa4 ,on the ,use of ,lubricants4--,one of the drawbacks to rubber is that if it be excessively strained it soon begins to break up4 ,one of the chief causes of this is that the strands stick together--they should always be carefully separated1 if necessary1 after a flight--and an undue strain is thereby cast on certain parts4 ,apart also from this the various strands are not subject to the same tension4 ,it has been suggested that if some means could be devised to prevent this1 and allow the strands to slip over one another1 a considerable increase of power might result4 ,it must1 however1 be carefully borne in mind that anything of an oily or greasy nature has an injurious effect on the rubber1 and must be avoided at all costs4 ,benzol1 petroleum1 ether1 volatile oils1 turpentine1 chloroform1 naphtha1 vaseline1 soap1 and all kinds of oil must be carefully avoided1 as they soften the rubber1 and reduce it more or less to the consistence of a sticky mass4 ,the only oil which is said to have no action on rubber1 or practically none1 is castor oil2 all the same1 ,i do not advise its use as a lubricant4 ,there are three only which we need consider3-- #a4 ,soda and water4 #b4 ,french chalk4 #c4 ,pure redistilled glycerine4 ,the first is perfectly satisfactory when freshly applied1 but soon dries up and evaporates4 ,the second falls off2 and unless the chalk be of the softest kind1 free from all grit and hard particles1 it will soon do more harm than good4 ,the third1 glycerine1 is for ordinary purposes by far the best1 and has a beneficial rather than a deleterious effect on the rubber2 but it must be pure4 ,the redistilled kind1 free from all traces of arsenic1 grease1 etc41 is the only kind permissible4 ,it does not evaporate1 and a few drops1 comparatively speaking1 will lubricate fifty or sixty yards of rubber4 ,being of a sticky or tacky nature it naturally gathers up dust and particles of dirt in course of time4 ,to prevent these grinding into the rubber1 wash it from time to time in warm soda1 and warm and apply fresh glycerine when required4 ,glycerine1 unlike vaseline 7a product of petroleum71 is not a grease2 it is formed from fats by a process known as saponification1 or treatment of the oil with caustic alkali1 which decomposes the compound1 forming an alkaline stearate 7soap71 and liberating the glycerine which remains in solution when the soap is separated by throwing in common salt4 ,in order to obtain pure glycerine1 the fat can be decomposed by lead oxide1 the glycerine remaining in solution1 and the lead soap or plaster being precipitated4 ,by using glycerine as a lubricant the number of turns that can be given a rubber motor is greatly increased1 and the coils slip over one another freely and easily1 and prevent the throwing of undue strain on some particular portion1 and absolutely prevent the strands from sticking together4 #ab4 ,the ,action of ,copper upon ,rubber4--,copper1 whether in the form of the metal1 the oxides1 or the soluble salts1 has a marked injurious action upon rubber4 ,in the case of metallic copper this action has been attributed to oxidation induced by the dissolved oxygen in the copper4 ,in working drawings for model aeroplanes ,i have noticed designs in which the hooks on which the rubber strands were to be stretched were made of copper4 ,in no case should the strands be placed upon bare metal4 ,i always cover mine with a piece of valve tubing1 which can easily be renewed from time to time4 #ab;,a4 ,the ,action of ,water1 etc41 on ,rubber4--,rubber is quite insoluble in water2 but it must not be forgotten that it will absorb about #be per cent4 into its pores after soaking for some time4 ,ether1 chloroform1 carbon-tetrachloride1 turpentine1 carbon bi-sulphide1 petroleum spirit1 benzene and its homologues found in coal-tar naphtha1 dissolve rubber readily4 ,alcohol is absorbed by rubber1 but is not a solvent of it4 #ab;,b4 ,how to ,preserve ,rubber4--,in the first place1 in order that it shall be possible to preserve and keep rubber in the best condition of efficiency1 it is absolutely essential that the rubber shall be1 when obtained1 fresh and of the best kind4 ,only the best ,para rubber should be bought2 to obtain it fresh it should be got in as large quantities as possible direct from a manufacturer or reliable rubber shop4 ,the composition of the best ,para rubber is as follows3--,carbon1 #hgdf per cent42 hydrogen1 #abjj per cent42 oxygen and ash1 #jed per cent4 ,in order to increase its elasticity the pure rubber has to be vulcanised before being made into the sheet some sixty or eighty yards in length1 from which the rubber threads are cut2 after vulcanization the substance consists of rubber plus about #c per cent4 of sulphur4 ,now1 unfortunately1 the presence of the sulphur makes the rubber more prone to atmospheric oxidation4 ,vulcanized rubber1 compared to pure rubber1 has then but a limited life4 ,it is to this process of oxidation that the more or less rapid deterioration of rubber is due4 ,to preserve rubber it should be kept from the sun's rays1 or1 indeed1 any actinic rays1 in a cool1 airy place1 and subjected to as even a temperature as possible4 ,great extremes of temperature have a very injurious effect on rubber1 and it should be washed from time to time in warm soda water4 ,it should be subjected to no tension or compression4 ,deteriorated rubber is absolutely useless for model aeroplanes4 #ac4 ,to ,test ,rubber4--,good elastic thread composed of pure ,para rubber and sulphur should1 if properly made1 stretch to seven times its length1 and then return to its original length4 ,it should also possess a stretching limit at least ten times its original length4 ,as already stated1 the threads or strands are cut from sheets2 these threads can now be cut fifty to the inch4 ,for rubber motors a very great deal so far as length of life depends on the accuracy and skill with which the strands are cut4 ,when examined under a microscope 7not too powerful7 the strands having the least ragged edge1 i4e41 the best cut1 are to be preferred4 #ad4 ,the ,section--,strip or ,ribbon versus ,square4--,in section the square and not the ribbon or strip should be used4 ,the edge of the strip ,i have always found more ragged under the microscope than the square4 ,i have also found it less efficient4 ,theoretically no doubt a round section would be best1 but none such 7in small sizes7 is on the market4 ,models have been fitted with a tubular section1 but such should on no account be used4 #ae4 ,size of the ,section4--,one-sixteenth or one-twelfth is the best size for ordinary models2 personally1 ,i prefer the thinner4 ,if more than a certain number of strands are required to provide the necessary power1 a larger size should be used4 ,it is not easy to say what this number is1 but fifty may probably be taken as an outside limit4 ,remember the size increases by area section2 twice the sectional height and breadth means four times the rubber4 #af4 ,geared ,rubber ,motors4--,it is quite a mistake to suppose that any advantage can be obtained by using a four to one gearing1 say2 all that you do obtain is one-fourth of the power minus the increased friction1 minus the added weight4 ,this presumes1 of course1 you make no alteration in your rubber strands4 ,gearing such as this means short rubber strands1 and such are not to be desired2 in any case1 there is the difficulty of increased friction and added weight to overcome4 ,it is true by splitting up your rubber motor into two sets of strands instead of one you can obtain more turns1 but1 as we have seen1 you must increase the number of strands to get the same thrust1 and you have this to counteract any advantage you gain as well as added weight and friction4 #ag4 ,the writer has tried endless experiments with all kinds of geared rubber motors1 and the only one worth a moment's consideration is the following1 viz41 one in which two gear wheels--same size1 weight1 and number of teeth--are made use of1 the propeller being attached to the axle of one of them1 and the same number of strands are used on each axle4 ,the success or non-success of this motor depends entirely on the method used in its construction4 ,at first sight it may appear that no great skill is required in the construction of such a simple piece of apparatus4 ,no greater mistake could be made4 ,it is absolutely necessary that the friction and weight be reduced to a minimum1 and the strength be a maximum4 ,the torque of the rubber strands on so short an arm is very great4 ,ordinary light brass cogwheels will not stand the strain4 ,a4 ,the cogwheels should be of steel#ag and accurately cut of diameter sufficient to separate the two strands the requisite distance1 but no more4 ,b4 ,the weight must be a minimum4 ,this is best attained by using solid wheels1 and lightening by drilling and turning4 ,c4 ,the friction must be a minimum4 ,use the lightest ball bearings obtainable 7these weigh only #jc gramme71 adjust the wheels so that they run with the greatest freedom1 but see that the teeth overlap sufficiently to stand the strain and slight variations in direction without fear of slipping4 ,shallow teeth are useless4 ,d4 ,use vaseline on the cogs to make them run as easily as possible4 ,illustration3 ,,fig4 #ag4--;,,geared ,,rubber ,,motor4 ,designed and constructed by the writer4 ,for description of the model1 etc41 see ,appendix4 ,e4 ,the material of the containing framework must be of maximum strength and minimum lightness4 ,construct it of minimum size1 box shaped1 use the thinnest tin 7really tinned sheet-iron7 procurable1 and lighten by drilling holes1 not too large1 all over it4 ,do not use aluminium or magnalium4 ,steel1 could it be procured thin enough1 would be better still4 ,f4 ,use steel pianoforte wire for the spindles1 and hooks for the rubber strands1 using as thin wire as will stand the strain4 ,unless these directions are carefully carried out no advantage will be gained--the writer speaks from experience4 ,the requisite number of rubber strands to give the best result must be determined by experiment4 #ah4 ,one advantage in using such a motor as this is that the two equal strands untwisting in opposite directions have a decided steadying effect on the model1 similar almost to the case in which two propellers are used4 ,the best model flights that the writer has achieved have been obtained with a motor of this description4#ah ,in the case of twin screws two such gearings can be used1 and the rubber split up into four strands4 ,the containing framework in this case can be simply light pieces of tubing let into the wooden framework1 or very light iron pieces fastened thereto4 ,do not attempt to split up the rubber into more than two strands to each propeller4 ,,section ,,ii4--,,other ,,forms ,,of ,,motors4 #ah;,a4 ,spring ,motors4--,this question has already been dealt with more or less whilst dealing with rubber motors1 and the superiority of the latter over the former pointed out4 ,rubber has a much greater superiority over steel or other springs1 because in stretch-twisted rubber far more energy can be stored up weight for weight4 ,one pound weight of elastic can be made to store up some #cbj ft4-lb4 of energy1 and steel only some #fe lb4 ,and in addition to this there is the question of gearing1 involving extra weight and friction2 that is1 if flat steel springs similar to those used in clockwork mechanism be made use of1 as is generally the case4 ,the only instance in which such springs are of use is for the purpose of studying the effects of different distributions of weight on the model1 and its effect on the balance of the machine2 but effects such as this can be brought about without a change of motor4 #ah;,b4 ,a more efficient form of spring motor1 doing away with gearing troubles1 is to use a long spiral spring 7as long as the rubber strands7 made of medium-sized piano wire1 similar in principle to those used in some roller-blinds1 but longer and of thinner steel4 ,the writer has experimented with such1 as well as scores of other forms of spring motors1 but none can compare with rubber4 ,the long spiral form of steel spring is1 however1 much the best4 #ah;,c4 ,compressed ,air ,motors4--,this is a very fascinating form of motor1 on paper1 and appears at first sight the ideal form4 ,it is so easy to write3 ,its weight is negligible1 and it can be provided free of cost2 all that is necessary is to work a bicycle pump for as many minutes as the motor is desired to run4 ,this stored-up energy can be contained in a mere tube1 of aluminium or magnalium1 forming the central rib of the machine1 and the engine mechanism necessary for conveying this stored-up energy to the revolving propeller need weigh only a few ounces4 ,another writer recommends a pressure of #cjj lb4 #ah;,d4 ,a pneumatic drill generally works at about #hj lb4 pressure1 and when developing #a horse-power1 uses about #ee cubic ft4 of free air per minute4 ,now if we apply this to a model aeroplane of average size1 taking a reservoir #c ft4 long by #a in4 internal diameter1 made of magnalium1 say--steel would1 of course1 be much better--the weight of which would certainly not be less than #d oz41 we find that at #hj lb4 pressure such a motor would use #ee_/;,horse ,power 7,h4,p47 cub4 ft4 per minute4 ,now #hj lb4 is about #e atmospheres1 and the cubical contents of the above motor some #fc cub4 in4 ,the time during which such a model would fly depends on the ,h4,p4 necessary for flight2 but a fair allowance gives a flight of from #aj to #cj sec4 ,i take #hj lb4 pressure as a fair practical limit4 #ah;,e4 ,the pressure in a motor-car tyre runs from #dj to #hj lb41 usually about #gj lb4 ,now #bfj strokes are required with an ordinary inflator to obtain so low a pressure as #gj lb41 and it is no easy job1 as those who have done it know4 #ai4 ,prior to #ahic ,mr4 ,hargraves 7of cellular kite fame7 studied the question of compressed-air motors for model flying machines4 ,his motor was described as a marvel of simplicity and lightness1 its cylinder was made like a common tin can1 the cylinder covers cut from sheet tin and pressed to shape1 the piston and junk rings of ebonite4 ,one of his receivers was #bc-c_/h in4 long1 and #ee in4 diameter1 of aluminium plate #jb in4 thick1 #c_/h in4 by #a_/h in4 riveting strips were insufficient to make tight joints2 it weighed #bf oz41 and at #hj lb4 water pressure one of the ends blew out1 the fracture occurring at the bend of the flange1 and not along the line of rivets4 ,the receiver which was successful being apparently a tin-iron one2 steel tubing was not to be had at that date in ,sydney4 ,with a receiver of this character1 and the engine referred to above1 a flight of #cdc ft4 was obtained1 this flight being the best4 7,the models constructed by him were not on the aeroplane1 but ornithoptere1 or wing-flapping principle47 ,the time of flight was #bc seconds1 with #ed double vibrations of the engines4 ,the efficiency of this motor was estimated to be #bi per cent4 #bj4 ,by using compressed air1 and heating it in its passage to the cylinder1 far greater efficiency can be obtained4 ,steel cylinders can be obtained containing air under the enormous pressure of #abj atmospheres4#ai ,this is practically liquid air4 ,a #bj-;ft4 cylinder weighs empty #bc lb4 ,the smaller the cylinder the less the proportionate pressure that it will stand2 and supposing a small steel cylinder1 produced of suitable form and weight1 and capable of withstanding with safety a pressure of from #cjj to #fjj lb4 per sq4 in41 or from #bj to #dj atmospheres4 ,the most economical way of working would be to admit the air from the reservoir directly to the motor cylinders2 but this would mean a very great range in the initial working pressure1 entailing not-to-be-thought-of weight in the form of multi-cylinder compound engines1 variable expansion gear1 etc4 #ba4 ,this means relinquishing the advantages of the high initial pressure1 and the passing of the air through a reducing valve1 whereby a constant pressure1 say1 of #ij to #aej1 according to circumstances1 could be maintained4 ,by a variation in the ratio of expansion the air could be worked down to1 say1 #cj lb4 ,the initial loss entailed by the use of a reducing valve may be in a great measure restored by heating the air before using it in the motor cylinders2 by heating it to a temperature of only #cbj;,f41 by means of a suitable burner1 the volume of air is increased by one half1 the consumption being reduced in the same proportion2 the consumption of air used in this way being #bd lb4 per indicated horse-power per hour4 ,but this means extra weight in the form of fuel and burners1 and what we gain in one way we lose in another4 ,it is1 of course1 desirable that the motor should work at as low a pressure as possible1 since as the store of air is used up the pressure in the reservoir falls1 until it reaches a limit below which it cannot usefully be employed4 ,the air then remaining is dead and useless1 adding only to the weight of the aeroplane4 #bb4 ,from calculations made by the writer the entire weight of a compressed-air model motor plant would be at least one-third the weight of the aeroplane1 and on a small scale probably one-half1 and cannot therefore hold comparison with the steam engine discussed in the next paragraph4 ,in concluding these remarks on compressed-air motors1 ,i do not wish to dissuade anyone from trying this form of motor2 but they must not embark on experiments with the idea that anything useful or anything superior to results obtained with infinitely less expense by means of rubber can be brought to pass with a bicycle pump1 a bit of magnalium tube1 and #fj lb4 pressure4 #bb;,a4 ,in ,tatin's air-compressed motor the reservoir weighed #gjj grammes1 and had a capacity of #h litres4 ,it was tested to withstand a pressure of #bj atmospheres1 but was worked only up to seven4 ,the little engine attached thereto weighed #cjj grammes1 and developed a motive power of #b kilogram-metres per second 7see ch4 iii474 #bc4 ,steam-,driven ,motors4--,several successful steam-engined model aeroplanes have been constructed1 the most famous being those of ,professor ,langley4 ,having constructed over #cj modifications of rubber-driven models1 and experimented with compressed air1 carbonic-acid gas1 electricity1 and other methods of obtaining energy1 he finally settled upon the steam engine 7the petrol motor was not available at that time1 #ahic74 ,after many months' work it was found that the weight could not be reduced below #dj lb41 whilst the engine would only develop ,h4,p41 and finally the model was condemned4 ,a second apparatus to be worked by compressed air was tried1 but the power proved insufficient4 ,then came another with a carbonic-acid gas engine4 ,then others with various applications of electricity and gas1 etc41 but the steam engine was found most suitable2 yet it seemed to become more and more doubtful whether it could ever be made sufficiently light1 and whether the desired end could be attained at all4 ,the chief obstacle proved not to be with the engines1 which were made surprisingly light after sufficient experiment4 ,the great difficulty was to make a boiler of almost no weight which would give steam enough4 #bd4 ,at last a satisfactory boiler and engine were produced4 ,the engine was of #a to #a ,h4,p41 total weight 7including moving parts7 #bf oz4 ,the cylinders1 two in number1 had each a diameter of #a in41 and piston stroke #b in4 ,the boiler1 with its firegrate1 weighed a little over #e lb4 ,it consisted of a continuous helix of copper tubing1 #c_/h in4 external diameter1 the diameter of the coil being #c in4 altogether4 ,through the centre of this was driven the blast from an lopile1 a modification of the naphtha blow-torch used by plumbers1 the flame of which is about #bjjj ,f4#bj ,the pressure of steam issuing into the engines varied from #ajj to #aej lb4 per sq4 in42 #d lb4 weight of water and about #aj oz4 of naphtha could be carried4 ,the boiler evaporated #a lb4 of water per minute4 ,the twin propellers1 #ci in4 in diam41 pitch #a1 revolved from #hjj to #ajjj a minute4 ,the entire aeroplane was #ae ft4 in length1 the aerofoils from tip to tip about #ad ft41 and the total weight slightly less than #cj lb41 of which one-fourth was contained in the machinery4 ,its flight was a little over half a mile in length1 and of #a minutes' duration4 ,another model flew for about three-quarters of a mile1 at a rate of about #cj miles an hour4 ,it will be noted that engine1 generator1 etc41 work out at about #g lb4 per ,h4,p4 ,considerable advance has been made in the construction of light and powerful model steam engines since ,langley's time1 chiefly in connexion with model hydroplanes1 and a pressure of from #ejj to #fjj lb4 per sq4 in4 has been employed2 the steam turbine has been brought to a high state of perfection1 and it is now possible to make a model ,de ,laval turbine of considerable power weighing almost next to nothing1#ba the real trouble1 in fact the only one1 being the steam generator4 ,an economization of weight means a waste of steam1 of which models can easily spend their only weight in five minutes4 #be4 ,one way to economize without increased weight in the shape of a condenser is to use spirit 7methylated spirit1 for instance7 for both fuel and boiler1 and cause the exhaust from the engines to be ejected on to the burning spirit1 where it itself serves as fuel4 ,by using spirit1 or some very volatile hydrocarbon1 instead of water1 we have a further advantage from the fact that such vaporize at a much lower temperature than water4 #bf4 ,when experimenting with an engine of the turbine type we must use a propeller of small diameter and pitch1 owing to the very high velocity at which such engines run4 ,anyone1 however1 who is not an expert on such matters would do well to leave such motors alone1 as the very highest technical skill1 combined with many preliminary disappointments and trials1 are sure to be encountered before success is attained4 #bg4 ,and the smaller the model the more difficult the problem--halve your aeroplane1 and your difficulties increase anything from fourfold to tenfold4 ,the boiler would in any case be of the flash type of either copper or steel tubing 7the former for safety71 with a magnalium container for the spirit1 and a working pressure of from #aej to #bjj lb4 per sq4 in4 ,anything less than this would not be worth consideration4 #bh4 ,some ten months after ,professor ,langley's successful model flights 7#ahif71 experiments were made in ,france at ,carquenez1 near ,toulon4 ,the total weight of the model aeroplane in this case was #gj lb42 the engine power a little more than #a ,h4,p4 ,twin screws were used--one in front and one behind4 ,the maximum velocity obtained was #dj miles per hour2 but the length of run only #aed yards1 and duration of flight only a few seconds4 ,this result compares very poorly with ,langley's distance 7of best flight71 nearly one mile1 duration #a min4 #de sec4 ,the maximum velocity was greater--#cj to #dj miles per hour4 ,the total breadth of this large model was rather more than #f metres1 and the surface a little more than #h sq4 metres4 #bi4 ,petrol ,motors4--,here it would appear at first thought is the true solution of the problem of the model aeroplane motor4 ,such a motor has solved the problem of aerial locomotion1 as the steam engine solved that of terrestrial and marine travel1 both full sized and model2 and if in the case of full sized machines1 then why not models4 ,illustration3 ,,fig4 #ah4--,,mr4 ,,stanger',s ,,model ,,in ,,full ,,flight4 ,illustration3 ,,fig4 #ai4--,,mr4 ,,stanger',s ,,petrol-,,driven ,,model ,,aeroplane4 7,illustrations by permission from electros supplied by the ,aero47 #cj4 ,the exact size of the smallest working model steam engine that has been made ,i do not know1#bb but it is or could be surprisingly small2 not so the petrol motor--not one1 that is1 that would work4 ,the number of petrol motor-driven model aeroplanes that have actually flown is very small4 ,personally ,i only know of one1 viz41 ,mr4 ,d4 ,stanger's1 exhibited at the aero exhibition at the ,agricultural ,hall in #aijh4 ,illustration3 ,,fig4 #bj4--,,mr4 ,,stanger',s ,,model ,,petrol ,,engine4 ,illustration3 ,,fig4 #ba4--,,mr4 ,,stanger',s ,,model ,,petrol ,,engine4 ,in ,fig4 #ba the motor is in position on the aeroplane4 ,note small carburettor4 ,in ,fig4 #bj an idea of the size of engine may be gathered by comparing it with the ordinary sparking-plug seen by the side1 whilst to the left of this is one of the special plugs used on this motor4 7,illustrations by permission from electros supplied by the ,aero47 #ca4 ,the following are the chief particulars of this interesting machine3--,the engine is a four-cylinder one1 and weighs 7complete with double carburetter and petrol tank7 #e lb41 and develops #a ,h4,p4 at #acjj revolutions per minute4 ,illustration3 ,,fig4 #bb4--,,one-,,cylinder ,,petrol ,,motor4 7,electro from ,messrs4 ,a4,w4 ,gamage's ,aviation ,catalogue47 ,the propeller1 #bi in4 in diam4 and #cf in4 in pitch1 gives a static thrust of about #g lb4 ,the machine has a spread of #h ft4 #b in41 and is #f ft4 #aj in4 in length4 ,total weight #ba lb4 ,rises from the ground when a speed of about #af miles an hour is attained4 ,a clockwork arrangement automatically stops the engine4 ,the engine air-cooled4 ,the cylinder of steel1 cast-iron heads1 aluminium crank-case1 double float feed carburetter1 ignition by single coil and distributor4 ,the aeroplane being #g ft4 #f in4 long1 and having a span #h ft4 #cb4 ,one-cylinder ,petrol ,motors4--,so far as the writer is aware no success has as yet attended the use of a single-cylinder petrol motor on a model aeroplane4 ,undoubtedly the vibration is excessive2 but this should not be an insuperable difficulty4 ,it is true it is heavier in proportion than a two-cylinder one1 and not so efficient2 and so far has not proved successful4 ,the question of vibration on a model aeroplane is one of considerable importance4 ,a badly balanced propeller even will seriously interfere with and often greatly curtail the length of flight4 #cc4 ,electric ,motors4--,no attempt should on any account be made to use electric motors for model aeroplanes4 ,they are altogether too heavy1 apart even from the accumulator or source of electric energy1 for the power derivable from them4 ,to take an extreme case1 and supposing we use a #b-oz4 electric motor capable of driving a propeller giving a static thrust of #c oz41#bc on weighing one of the smallest size accumulators without case1 etc41 ,i find its weight is #d oz4 ,one would1 of course1 be of no use2 at least three would be required1 and they would require practically short circuiting to give sufficient amperage 7running them down1 that is1 in some #aj to #ae seconds74 ,total weight1 #a lb4 nearly4 ,now from a pound weight of rubber one could obtain a thrust of pounds1 not ounces4 ,for scale models not intended for actual flight1 of course1 electric motors have their uses4 ,,footnotes3 #ab ,also there is no necessity for gearing4 #ac ,in his latest models the writer uses strands even three times and not twice as long1 viz4 fourteen strands #dc in4 long4 #ad ,this refers to #a_/af in4 square sectioned rubber4 #ae ,of uniform breadth and thickness4 #af ,in practice ,i find not quite so high a proportion as this is always necessary4 #ag ,steel pinion wire is very suitable4 #ah ,see ,appendix4 #ai ,as high a pressure as #bej atmospheres has been used4 #bj ,there was a special pump keeping the water circulating rapidly through the boiler1 the intense heat converting some of it into steam as it flowed4 ,the making of this boiler alone consumed months of work2 the entire machine taking a year to construct1 with the best mechanical help available4 #ba ,model ,steam ,turbines4 ,model ,engineer ,series1 ,no4 #ac1 price #f;d4 #bb ,see ,introduction1 note to #a4 #bc ,the voltage1 etc41 is not stated4 ,,chapter ,v4 ,,propellers ,,or ,,screws4 #a4 ,the design and construction of propellers1 more especially the former1 is without doubt one of the most difficult parts of model aeroplaning4 ,with elastic or spring driven models the problem is more complicated than for models driven by petrol or some vaporized form of liquid fuel2 and less reliable information is to hand4 ,the problem of weight1 unfortunately1 is of primary importance4 ,we will deal with these points in due course2 to begin with let us take3-- ,,the ,,position ,,of ,,the ,,propeller4 ,in model aeroplanes the propeller is usually situated either in front or in the rear of the model2 in the former case it is called a ,,tractor ,,screw1 i4e41 it pulls instead of pushes4 ,as to the merits of the two systems with respect to the tractor1 there is1 we know1 in the case of models moving through water a distinct advantage in placing the propeller behind1 and using a pushing or propulsive action1 on account of the frictional wake created behind the boat1 and which causes the water to flow after the vessel1 but at a lesser velocity4 ,in placing the propeller behind1 we place it in such a position as to act upon and make use of this phenomenon1 the effect of the propeller being to bring this following wake to rest4 ,theoretically a boat1 model or otherwise1 can be propelled with less horse-power than it can be towed4 ,but with respect to aeroplanes1 apart altogether from the difference of medium1 there is at present a very considerable difference of form1 an aeroplane1 model or otherwise1 bearing at present but little resemblance to the hull of a boat4 ,undoubtedly there is a frictional wake in the case of aeroplanes1 possibly quite as much in proportion as in the case of a boat1 allowing for difference of medium4 ,admitting1 then1 that this wake does exist1 it follows that a propulsive screw is better than a tractor4 ,in a matter of this kind constructional considerations1 or ease of launching1 and ability to land without damage1 must be given due weight4 ,in the case of model aeroplanes constructional details incline the balance neither one way nor the other2 but ease in launching and ability to land without damage weigh the balance down most decidedly in favour of a driving or propulsive screw4 ,in the case of full-sized monoplanes constructional details had most to do with the use of tractors2 but monoplanes are now being built with propulsive screws4#bd ,in the case of models1 not models of full-sized machines1 but actual model flyers1 the writer considers propulsive screws much the best4#be ,in no case should the propeller be placed in the centre of the model1 or in such a position as to shorten the strands of the elastic motor1 if good flights are desired4 ,in the case of petrol or similar driven models the position of the propeller can be safely copied from actual well-recognised and successful full-sized machines4 #b4 ,the ,number of ,blades4--,theoretically the number of blades does not enter into consideration4 ,the mass of air dealt with by the propeller is represented by a cylinder of indefinite length1 whose diameter is the same as that of the screw1 and the rate at which this cylinder is projected to the rear depends theoretically upon the pitch and revolutions 7per minute1 say7 of the propeller and not the number of blades4 ,theoretically one blade 7helix incomplete7 would be sufficient1 but such a screw would not balance1 and balance is of primary importance2 the minimum number of blades which can be used is therefore two4 ,in marine models three blades are considered best1 as giving a better balance4 ,in the case of their aerial prototypes the question of weight has again to be considered1 and two blades is practically the invariable custom4#bf ,here1 again1 constructional considerations again come to the fore1 and in the case of wooden propellers one of two blades is of far more easy construction than one of three4 ,by increasing the number of blades the thrust is1 of course1 more evenly distributed over a larger area1 but the weight is considerably increased1 and in models a greater advantage is gained by keeping down the weight than might follow from the use of more blades4 #c4 ,fan versus ,propeller4--,it must always be most carefully borne in mind that a fan 7ventilating7 and a propeller are not the same thing4 ,because many blades are found in practice to be efficient in the case of the former1 it is quite wrong to assume that the same conclusion holds in the case of the latter4 ,by increasing the number of blades the skin friction due to the resistance that has to be overcome in rotating the propeller through the air is added to4 ,moreover a fan is stationary1 whilst a propeller is constantly advancing as well as rotating through the air4 ,the action of a fan blower is to move a small quantity of air at a high velocity2 whereas the action of a propeller is1 or should be1 to move a large quantity of air at a small velocity1 for the function of a screw is to create thrust4 ,operating on a yielding fluid medium this thrust will evidently be in proportion to the mass of fluid moved1 and also to the velocity at which it is put in motion4 ,but the power consumed in putting this mass of fluid in motion is proportional to the mass and to the square of the velocity at which it moves4 ,from this it follows1 as stated above1 that in order to obtain a given thrust with the least loss of power1 the mass of fluid acted on should be as large as possible1 and the velocity imparted to it as little as possible4 ,a fan requires to be so designed as to create a thrust when stationary 7static thrust71 and a propeller whilst moving through the air 7dynamic thrust74 #d4 ,the ,function of a ,propeller is to produce dynamic thrust2 and the great advantage of the use of a propeller as a thrusting or propulsive agent is that its surface is always active4 ,it has no dead points1 and its motion is continuous and not reciprocating1 and it requires no special machinery or moving parts in its construction and operation4 #e4 ,the ,pitch of a propeller or screw is the linear distance a screw moves1 backwards or forwards1 in one complete revolution4 ,this distance is purely a theoretical one4 ,when1 for instance1 a screw is said to have a pitch of #a ft41 or #ab in41 it means that the model would advance #a ft4 through the air for each revolution of the screw1 provided that the propeller blade were mounted in solid guides1 like a nut on a bolt with one thread per foot4 ,in a yielding fluid such as water or air it does not practically advance this distance1 and hence occurs what is known as-- #f4 ,slip1 which may be defined as the distance which ought to be traversed1 but which is lost through imperfections in the propelling mechanism2 or it may be considered as power which should have been used in driving the model forward4 ,in the case of a locomotive running on dry rails nothing is lost in slip1 there being none4 ,in the case of a steamer moored and her engines set going1 or of an aeroplane held back prior to starting1 all the power is used in slip1 i4e4 in putting the fluid in motion1 and none is used in propulsion4 ,supposing the propeller on our model has a pitch of #a ft41 and we give the elastic motor #ajj turns1 theoretically the model should travel #ajj ft4 in calm air before the propeller is run down2 no propeller yet designed will do this4 ,supposing the actual length #gg ft41 #bc per cent4 has been lost in slip4 ,for this to be actually correct the propeller must stop at the precise instant when the machine comes to ground4 ,taking slip into account1 then-- ,the speed of the model in feet per minute pitch 7in feet7 revolutions per minute -- slip 7feet per minute74 ,this slip wants to be made small--just how small is not yet known4 ,if made too small then the propeller will not be so efficient1 or1 at any rate1 such is the conclusion come to in marine propulsion1 where it is found for the most economical results to be obtained that the slip should be from #aj to #bj per cent4 ,in the case of aerial propellers a slip of #be per cent4 is quite good1 #dj per cent4 bad2 and there are certain reasons for assuming that possibly about #ae per cent4 may be the best4 #g4 ,it is true that slip represents energy lost2 but some slip is essential1 because without slip there could be no thrust1 this same thrust being derived from the reaction of the volume of air driven backwards4 ,the thrust is equal to-- ,weight of mass of air acted on per second slip velocity in feet per second4 ,in the case of an aeroplane advancing through the air it might be thought that the thrust would be less4 ,sir ,hiram ,maxim found1 however1 as the result of his experiments that the thrust with a propeller travelling through the air at a velocity of #dj miles an hour was the same as when stationary1 the r4p4m4 remaining constant throughout4 ,the explanation is that when travelling the propeller is continually advancing on to undisturbed air1 the slip velocity is reduced1 but the undisturbed air is equivalent to acting upon a greater mass of air4 #h4 ,pitch ,coefficient or ,pitch ,ratio4--,if we divide the pitch of a screw by its diameter we obtain what is known as pitch coefficient or ratio4 ,the mean value of eighteen pitch coefficients of well-known full-sized machines works out at #jfb1 which1 as it so happens1 is exactly the same as the case of the ,farman machine propeller considered alone1 this ratio varying from #jd to #ab2 in the case of the ,wright's machine it is 7probably7 #a4 ,the efficiency of their propeller is admitted on all hands4 ,their propeller is1 of course1 a slow-speed propeller1 #dej r4p4m4 ,the one on the ,blriot monoplane 7,blriot ,,xi47 pitch ratio #jd1 r4p4m4 #acej4 ,in marine propulsion the pitch ratio is generally #ac for a slow-speed propeller1 decreasing to #ji for a high-speed one4 ,in the case of rubber-driven model aeroplanes the pitch ratio is often carried much higher1 even to over #c4 ,mr4 ,t4,w4,k4 ,clarke recommends a pitch angle of #de1 or less1 at the tips1 and a pitch ratio of #c-a_/g 7with an angle of #de74 ,within limits the higher the pitch ratio the better the efficiency4 ,the higher the pitch ratio the slower may be the rate of revolution4 ,now in a rubber motor we do not want the rubber to untwist 7run out7 too quickly2 with too fine a pitch the propeller races1 or does something remarkably like it4 ,it certainly revolves with an abnormally high percentage of slip4 ,and for efficiency it is certainly desirable to push this ratio to its limit2 but there is also the question of the #i4 ,diameter4--,the diameter 7says ,mr4 ,t4,w4,k4 ,clarke7 should be equal to one-quarter the span of the machine4 ,if we increase the diameter we shall decrease the pitch ratio4 ,from experiments which the writer has made he prefers a lower pitch ratio and increased diameter1 viz4 a pitch ratio of #ae1 and a diameter of one-third to even one-half the span1 or even more4#bg ,certainly not less than one-third4 ,some model makers indulge in a large pitch ratio1 angle1 diameter1 and blade area as well1 but such a course is not to be recommended4 #aj4 ,theoretical ,pitch4--,theoretically the pitch 7from boss to tip7 should at all points be the same2 the boss or centre of the blade at right angles to the plane of rotation1 and the angle decreasing as one approaches the tips4 ,this is obvious when one considers that the whole blade has to move forward the same amount4 ,in the diagrams ,figs4 #bc and #bd the tip ,a of the propeller travels a distance #b pi ,r every revolution4 ,at a point ,d on the blade1 distant r from the centre1 the distance is #b pi r4 ,in both instances the two points must advance a distance equal to the pitch1 i4e4 the distance represented by ,p ,o4 ,illustration3 ,,fig4 #bc4 ,illustration3 ,,fig4 #bd4 ,a ,o #b pi ,r2 ,d ,o #b pi r4 ,a will move along ,a ,p1 ,b along ,b ,p1 and so on4 ,the angles at the points ,a1 ,b1 ,c 444 7,fig4 #bd71 showing the angles at which the corresponding parts of the blade at ,a1 ,b1 ,c 444 in ,fig4 #bc must be set in order that a uniform pitch may be obtained4 #aa4 ,if the pitch be not uniform then there will be some portions of the blade which will drag through the air instead of affording useful thrust1 and others which will be doing more than they ought1 putting air in motion which had better be left quiet4 ,this uniform total pitch for all parts of the propeller is 7as already stated7 a decreasing rate of pitch from the centre to the edge4 ,with a total pitch of #e ft41 and a radius of #d ft41 and an angle at the circumference of #f1 then the angle of pitch at a point midway between centre and circumference should be #ab1 in order that the total pitch may be the same at all parts4 #ab4 ,to ,ascertain the ,pitch of a ,propeller4--,take any point on one of the blades1 and carefully measure the inclination of the blade at that point to the plane of rotation4 ,if the angle so formed be about #ai 7#aide71bh i4e41 #a in #c1 and the point #e in4 from the centre1 then every revolution this point will travel a distance #b pi r #b #bb_/g #e #cacd4 ,now since the inclination is #a in #c1bi the propeller will travel forward theoretically one-third of this distance1 or #cadc_/c #ajdh #aj in4 approx4 ,similarly any other case may be dealt with4 ,if the propeller have a uniform constant angle instead of a uniform pitch1 then the pitch may be calculated at a point about one-third the length of the blade from the tip4 #ac4 ,hollow-,faced ,blades4#cj--;,it must always be carefully borne in mind that a propeller is nothing more nor less than a particular form of aeroplane specially designed to travel a helical path4 ,it should1 therefore1 be hollow faced and partake of the stream line form1 a condition not fulfilled if the face of the blade be flat--such a surface cutting into the air with considerable shock1 and by no means creating as little undesirable motion in the surrounding medium as possible4 ,it must not be forgotten that a curved face blade has of necessity an increasing pitch from the cutting to the trailing edge 7considering1 of course1 any particular section74 ,in such a case the pitch is the mean effective pitch4 #ad4 ,blade ,area4--,we have already referred to the fact that the function of a propeller is to produce dynamic thrust--to drive the aeroplane forward by driving the air backwards4 ,at the same time it is most desirable for efficiency that the air should be set in motion as little as possible1 this being so much power wasted2 to obtain the greatest reaction or thrust the greatest possible volume of air should be accelerated to the smallest velocity4 ,in marine engineering in slow-speed propellers 7where cavitation#ca does not come in7 narrow blades are usually used4 ,in high-speed marine propellers 7where cavitation is liable to occur7 the projected area of the blades is sometimes as much as #jf of the total disk area4 ,in the case of aerial propellers1 where cavitation does not occur1 or not unless the velocity be a very high one 7#aejj or more a minute71 narrow blades are the best4 ,experiments in marine propulsion also show that the thrust depends more on the disk area than on the width of the blades4 ,all the facts tend to show that for efficiency the blades of the propeller should be narrow1 in order that the air may not be acted on for too long a time1 and so put too much in motion1 and the blades be so separated that one blade does not disturb the molecules of air upon which the next following one must act4 ,both in the case of marine and aerial propellers multiplicity of blades 7i4e4 increased blade area7 tends to inefficiency of action1 apart altogether from the question of weight and constructional difficulties4 ,the question of increasing pitch in the case of hollow-faced blades1 considered in the last paragraph1 has a very important bearing on the point we are considering4 ,to make a wide blade under such circumstances would be to soon obtain an excessive angle4 ,in the case of a flat blade the same result holds1 because the air has by the contact of its molecules with the initial minimum width been already accelerated up to its final velocity1 and further area is not only wasted1 but inimical to good flights1 being our old bugbear weight in excess4 ,requisite strength and stiffness1 of course1 set a limit on the final narrowness of the blades1 apart from other considerations4 #ae4 ,the velocity with which the propeller is rotated has also an important bearing on this point2 but a higher speed than #ijj r4p4m4 does not appear desirable1 and even #gjj or less is generally preferable4#cb ,in case of twin-screw propellers1 with an angle at the tips of #dj to #de1 as low a velocity of #ejj or even less would be still better4#cc #af4 ,shrouding4--,no improvement whatever is obtained by the use of any kind of shrouding or ring round the propeller tips1 or by corrugating the surface of the propeller1 or by using cylindrical or cone-shaped propeller chamber or any kind of air guide either before or after the propeller2 allow it to revolve in as free an air-feed as possible1 the air does not fly off under centrifugal force1 but is powerfully sucked inwards in a well-designed propeller4 ,illustration3 ,,fig4 #be4 ,a ,,tube ,,of ,,air4 ,illustration3 ,,fig4 #bf4 ,a ,,cylinder ,,of ,,air4 #ag4 ,general ,design4--,the propeller should be so constructed as to act upon a tube and not a cylinder of air4 ,many flying toys 7especially the ,french ones7 are constructed with propellers of the cylinder type4 ,ease of manufacture and the contention that those portions of the blades adjacent to the boss do little work1 and a slight saving in weight1 are arguments that can be urged in their favour4 ,but all the central cut away part offers resistance in the line of travel1 instead of exerting its proportionate propulsive power1 and their efficiency is affected by such a practice4 #ah4 ,a good ,shape for the blades#cd is rectangular with rounded corners2 the radius of the circle for rounding off the corners may be taken as about one-quarter of the width of the blade4 ,the shape is not truly rectangular1 for the width of this rectangular at 7near7 the boss should be one-half the width at the tip4 ,the thickness should diminish uniformly from the boss to the tip4 7,in models the thickness should be as little as is consistent with strength to keep down the weight74 ,the pitch uniform and large4 ,illustration3 ,,fig4 #bg4--,o ,t #a_/c ,o ,p4 #ai4 ,the ,blades1 two in number1 and hollow faced--the maximum concavity being one-third the distance from the entering to the trailing edge2 the ratio of ,a ,t to ,o ,p 7the width7 being #jjdh or #a 3 #ba1 these latter considerations being founded on the analogy between a propeller and the aerofoil surface4 7,if the thickness be varied from the entering to the trailing edge the greatest thickness should be towards the former47 ,the convex surface of the propeller must be taken into account1 in fact1 it is no less important than the concave1 and the entire surface must be given a true stream line form4 ,illustration3 ,,fig4 #bh4 ,illustration3 ,,fig4 #bi4 ,if the entering and trailing edge be not both straight1 but one be curved as in ,fig4 #bh1 then the straight edge must be made the trailing edge4 ,and if both be curved as in ,fig4 #bi1 then the concave edge must be the trailing edge4 #ai4 ,propeller ,design4--,to design a propeller1 proceed as follows4 ,suppose the diameter #ad in4 and the pitch three times the diameter1 i4e4 #eb in4 7,see ,fig4 #cj47 ,take one-quarter scale1 say4 ,draw a centre line ,a ,b of convenient length1 set of half the pitch #eb in4 -- scale #e in4 ,c - ,d4 ,draw lines through ,c and ,d at right angles to ,c ,d4 ,with a radius equal to half the diameter 7i4e4 in this case #a in47 of the propeller1 describe a semicircle ,e ,b ,f and complete the parallelogram ,f ,h ,g ,e4 ,divide the semicircle into a number of equal parts2 twelve is a convenient number to take1 then each division subtends an angle of #ae at the centre ,d4 ,divide one of the sides ,e ,g into the same number of equal parts 7twelve7 as shown4 ,through these points draw lines parallel to ,f ,e or ,h ,g4 ,and through the twelve points of division on the semicircle draw lines parallel to ,f ,h or ,e ,g as shown4 ,the line drawn through the successive intersections of these lines is the path of the tip of the blade through half a revolution1 viz4 the line ,h ,s ,o ,t ,e4 ,s ,o ,t ,x gives the angle at the tip of the blades #dd4 ,let the shape of the blade be rectangular with rounded corners1 and let the breadth at the tip be twice that at the boss4 ,then the area 7neglecting the rounded off corners7 is #aj sq4 in4 ,illustration3 ,,fig4 #cj4--,,propeller ,,design4 ,one quarter scale4 ,diameter #ad in4 ,pitch #eb in4 ,angle at tip #dd4 ,the area being that of a rectangle #g in4 #a in4 #g sq4 in4 plus area of two triangles1 base in41 height #g in4 ,now area of triangle half base height4 ,therefore area of both triangles in4 #g in4 #c sq4 in4 ,now the area of the disc swept out by the propeller is pi_/#d 7diam47 7pi #bb_/g7 ,illustration3 ,,fig4 #ca4--,,propeller ,,design4 ,scale one-eighth for ,a ,b and ,b ,c2 but sections of blade are full-sized4 ,and if d ,a r the disc area ratio we have 7d ,a r7 pi_/#d 7#ad7 area of blade #aj1 whence d ,a r #jjg about4 ,illustration3 ,,fig4 #cb4 ,illustration3 ,,fig4 #cc4 ,in ,fig4 #ca set off ,a ,b equal to the pitch of the propeller 7#db in471 one-eighth scale4 ,set off ,b ,c at right angles to ,a ,b and equal to pi diameter #bb_/g #ad #dd in4 to scale #e in4 ,divide ,b ,c into a convenient number of equal parts in the figure2 five only are taken1 ,d1 ,e1 ,f1 ,g1 ,h2 join ,a ,d1 ,a ,e1 ,a ,f1 ,a ,g1 ,a ,h and produce them2 mark off distances ,p ,o1 ,s ,r1 ,y ,t 444 equal to the width of the blade at these points 7,h ,p ,h ,o2 ,g ,s ,g ,r 4447 and sketch in the sections of blade as desired4 ,in the figure the greatest concavity of the blade is supposed to be one-third the distances ,p ,o1 ,s ,r 444 from ,,ps4444 ,the concavity is somewhat exaggerated4 ,the angles ,a ,h ,b1 ,a ,g ,b1 ,a ,f ,b 444 represent the pitch angle at the points ,h1 ,g1 ,f 444 of the blade4 ,similarly any other design may be dealt with2 in a propeller of #ad in4 diameter the diameter of the boss should not be more than #aj_/af in4 #bj4 ,experiments with ,propellers4--,the propeller design shown in ,figs4 #cb and #cc1 due to ,mr4 ,g4 de ,havilland1#ce is one very suitable for experimental purposes4 ,a single tube passing through a ,t-shaped boss forms the arms4 ,on the back of the metal blade are riveted four metallic clips2 these clips being tightened round the arm by countersunk screws in the face of the blade4 ,the tube and clips1 etc41 are all contained with the back covering of the blade1 as shown in ,fig4 #ce1 if desired1 the blade then practically resembling a wooden propeller4 ,the construction1 it will be noticed1 allows of the blade being set at any angle1 constant or otherwise2 also the pitch can be constant or variable as desired1 and any shape of propeller can be fitted4 ,the advantage of being able to twist the blade 7within limits7 on the axis is one not to be underestimated in experimental work4 ,illustration3 ,,fig4 #cd4--,,the ,,author',s ,,propeller ,,testing ,,apparatus4 ,with a view to ascertain some practical and reliable data with respect to the dynamic1 or actual thrust given when moving through free air at the velocity of actual travel1 the author experimented with the apparatus illustrated in ,figs4 #cd and #ce1 which is so simple and obvious as to require scarcely any explanation4 ,the wires were of steel1 length not quite #aej ft41 fitted with wire strainers for equalising tension1 and absolutely free from kinks4 ,as shown most plainly in ,fig4 #ce1 there were two parallel wires sufficiently far apart for the action of one propeller not to affect the other4 ,calling these two wires ,a and ,b1 and two propellers x and y1 then x is first tried on ,a and y on ,b4 ,results carefully noted4 ,illustration3 ,,fig4 #ce4--,,propeller ,,testing4 ,showing distance separating the two wires4 ,then x is tried on ,b and y on ,a1 and the results again carefully noted4 ,if the results confirm one another1 the power used in both cases being the same1 well and good2 if not1 adjustments1 etc41 are made in the apparatus until satisfactory results are obtained4 ,this was done when the propellers raced one against the other4 ,at other times one wire only was made use of1 and the time and distance traversed was noted in each case4 ,propellers were driven through smoke1 and with silk threads tied to a light framework slightly larger than their disc area circumference4 ,results of great interest were arrived at4 ,these results have been assumed in much that has been said in the foregoing paragraphs4 ,illustration3 ,,fig4 #cf4--,,one ,,group ,,of ,,propellers ,,tested ,,by ,,the ,,author4 ,briefly put1 these results showed3-- #a4 ,the inefficiency of a propeller of the fan blower or of the static thrust type4 #b4 ,the advantage of using propellers having hollow-faced blades and large diameter4 #c4 ,that diameter was more useful than blade area1 i4e4 given a certain quantity 7weight7 of wood1 make a long thin blade and not a shorter one of more blade area--blade area1 i4e41 as proportionate to its corresponding disc area4 #d4 ,that the propeller surface should be of true stream-line form4 #e4 ,that it should act on a cylinder and not tubes of air4 #f4 ,that a correctly designed and proportioned propeller was just as efficacious in a small size of #i in4 to #bh in4 as a full-sized propeller on a full-sized machine4 ,illustration3 ,,fig4 #cg4--;,,an ,,efficient ,,propeller1 ,,but ,,rather ,,heavy4 ,ball bearings1 old and new4 ,note difference in sizes and weights4 ,propeller1 #ad in4 diam42 weight #cf grammes4 ,a propeller of the static-thrust type was1 of course1 first off1 sometimes #aj ft4 or #ab ft4 ahead1 or even more2 but the correctly designed propeller gradually gathered up speed and acceleration1 just as the other fell off and lost it1 and finally the dynamic finished along its corresponding wire far ahead of the static1 sometimes twice as far1 sometimes six times4 ,freak propellers were simply not in it4 ,illustration3 ,,fig4 #ch4--,,venna ,,propeller4 ,a #bj per cent4 more efficient propeller than that shown in ,fig4 #da2 #ad per cent4 lighter2 #f per cent4 better in dynamic thrust--#ad in4 diam42 weight #ca grammes4 ,metal propellers of constant angle1 as well as wooden ones of uniform 7constant7 pitch1 were tested2 the former gave good results1 but not so good as the latter4 ,the best angle of pitch 7at the tip7 was found to be from #bj to #cj4 ,in all cases when the slip was as low as #be per cent41 or even somewhat less1 nearly #bj per cent41 a distinct back current of air was given out by the screw4 ,this slip stream1 as it is caused1 is absolutely necessary for efficiency4 #ba4 ,fabric-covered screws did not give very efficient results2 the only point in their use on model aeroplanes is their extreme lightness4 ,two such propellers of #f in4 diameter can be made to weigh less than #a_/e oz4 the pair2 but wooden propellers 7built-up principle7 have been made #e in4 diameter and #a_/ab oz4 in weight4 #bb4 ,further experiments were made with twin screws mounted on model aeroplanes4 ,in one case two propellers1 both turning in the same direction1 were mounted 7without any compensatory adjustment for torque7 on a model1 total weight #a lb4 ,diameter of each propeller #ad in42 angle of blade at tip #be4 ,the result was several good flights--the model 7see ,fig4 #di;c7 was slightly unsteady across the wind1 that was all4 ,in another experiment two propellers of same diameter1 pitch1 etc41 but of shape similar to those shown in ,figs4 #bh and #bi1 were tried as twin propellers on the same machine4 ,the rubber motors were of equal weight and strength4 ,the model described circled to the right or left according to the position of the curved-shaped propeller1 whether on the left or right hand1 thereby showing its superiority in dynamic thrust4 ,various alterations were made1 but always with the same result4 ,these experiments have since been confirmed1 and there seems no doubt that the double-curved shaped blade is superior4 7,see ,fig4 #ci47 #bc4 ,the ,fleming-,williams ,propeller4--,a chapter on propellers would scarcely be complete without a reference to the propeller used on a machine claiming a record of over a quarter of a mile4 ,this form of propeller1 shown in the group in ,fig4 #cf 7top right hand71 was found by the writer to be extremely deficient in dynamic thrust1 giving the worst result of any shown there4 ,illustration3 ,,fig4 #ci4--;,,curved ,,double ,,propeller4 ,the most efficient type yet tested by the writer1 when the blade is made hollow-faced4 ,when given to the writer to test it was flat-faced on one side4 ,illustration3 ,,fig4 #dj4--,,the ,,fleming-,,williams ,,model4 ,it possesses large blade area1 large pitch angle--more than #de at the tip--and large diameter4 ,these do not combine to propeller efficiency or to efficient dynamic thrust2 but they do1 of course1 combine to give the propeller a very slow rotational velocity4 ,provided they give sufficient thrust to cause the model to move through the air at a velocity capable of sustaining it1 a long flight may result1 not really owing to true efficiency on the part of the propellers1#cf but owing to the check placed on their revolutions per minute by their abnormal pitch angle1 etc4 ,the amount of rubber used is very great for a #aj oz4 model1 namely1 #cd strands of #a_/af in4 square rubber to each propeller1 i4e4 #fh strands in all4 ,illustration3 ,,fig4 #da4--,,the ,,same ,,in ,,flight4 7,reproduced by permission from ,the ,aero47 ,on the score of efficiency1 when it is desired to make a limited number of turns give the longest flight 7which is the problem one always has to face when using a rubber motor7 it is better to make use of an abnormal diameter1 say1 more than half the span1 and using a tip pitch angle of #be1 than to make use of an abnormal tip pitch #de and more1 and large blade area4 ,in a large pitch angle so much energy is wasted1 not in dynamic thrust1 but in transverse upsetting torque4 ,on no propeller out of dozens and dozens that ,i have tested have ,i ever found a tip-pitch of more than #ce give a good dynamic thrust2 and for length of flight velocity due to dynamic thrust must be given due weight1 as well as the duration of running down of the rubber motor4 #bd4 ,of built up or carved out and twisted wooden propellers1 the former give the better result2 the latter have an advantage1 however1 in sometimes weighing less4 ,,footnotes3 #bd ,note4--,since the above was written some really remarkable flights have been obtained with a #a oz4 model having two screws1 one in front and the other behind4 ,equally good flights have also been obtained with the two propellers behind1 one revolving in the immediate rear of the other4 ,flying1 of course1 with the wind1 weight is of paramount importance in these little models1 and in both these cases the single stick can be made use of4 ,see also ch4 iv41 #bh4 #be ,see also ch4 viii41 #e4 #bf ,save in case of some models with fabric-covered propellers4 ,some dirigibles are now being fitted with four-bladed wooden screws4 #bg ,vide ,appendix4 #bh ,vide ,equivalent ,inclinations--,table of4 #bi ,one in #c or #jccc is the sine of the angle2 similarly if the angle were #cj the sine would be #je or 1 and the theoretical distance travelled one-half4 #cj ,flat-,faced ,blades4--,if the blade be not hollow-faced--and we consider the screw as an inclined plane and apply the ,duchemin formula to it--the velocity remaining the same1 the angle of maximum thrust is #ce4 ,experiments made with such screws confirm this4 #ca ,cavitation is when the high speed of the screw causes it to carry round a certain amount of the medium with it1 so that the blades strike no undisturbed1 or solid1 air at all1 with a proportionate decrease in thrust4 #cb ,in the ,wright machine r4p4m4 #dej2 in ,blriot ,,xi4 r4p4m4 #acej4 #cc ,such propellers1 however1 require a considerable amount of rubber4 #cd ,but see also #bb4 #ce ,flight1 ,march #aj1 #aiaj4 7,illustration reproduced by permission47 #cf ,according to the author's views on the subject4 ,,chapter ,,vi4 ,,the ,,question ,,of ,,sustentation ,,the ,,centre ,,of ,,pressure4 #a4 ,passing on now to the study of an aeroplane actually in the air1 there are two forces acting on it1 the upward lift due to the air 7i4e4 to the movement of the aeroplane supposed to be continually advancing on to fresh1 undisturbed virgin air71 and the force due to the weight acting vertically downwards4 ,we can consider the resultant of all the upward sustaining forces as acting at a single point--that point is called the ,centre of ,pressure4 ,suppose ,a ,b a vertical section of a flat aerofoil1 inclined at a small angle a to the horizon ,c1 the point of application of the resultant upward 'lift1' ,d the point through which the weight acts vertically downwards4 ,omitting for the moment the action of propulsion1 if these two forces balance there will be equilibrium2 but to do this they must pass through the same point1 but as the angle of inclination varies1 so does the centre of pressure1 and some means must be employed whereby if ,c and ,d coincide at a certain angle the aeroplane will come back to the correct angle of balance if the latter be altered4 ,in a model the means must be automatic4 ,automatic stability depends for its action upon the movement of the centre of pressure when the angle of incidence varies4 ,when the angle of incidence increases the centre of pressure moves backwards towards the rear of the aerofoil1 and vice versa4 ,let us take the case when steady flight is in progress and ,c and ,d are coincident1 suppose the velocity of the wind suddenly to increase--increased lifting effect is at once the result1 and the fore part of the machine rises1 i4e4 the angle of incidence increases and the centre of pressure moves back to some point in the rear of ,c ,d4 ,the weight is now clearly trying to pull the nose of the aeroplane down1 and the lift tending to raise the tail4 ,the result being an alteration of the angle of incidence1 or angle of attack as it is called1 until it resumes its original position of equilibrium4 ,a drop in the wind causes exactly an opposite effect4 ,illustration3 ,,fig4 #db4 #b4 ,the danger lies in oscillations being set up in the line of flight due to changes in the position of the centre of pressure4 ,hence the device of an elevator or horizontal tail for the purpose of damping out such oscillations4 #c4 ,but the aerofoil surface is not flat1 owing to the increased lift given by arched surfaces1 and a much more complicated set of phenomena then takes place1 the centre of pressure moving forward until a certain critical angle of incidence is reached1 and after this a reversal takes place1 the centre of pressure then actually moving backwards4 ,the problem then consists in ascertaining the most efficient aerocurve to give the greatest lift with the least drift1 and1 having found it1 to investigate again experimentally the movements of the centre of pressure at varying angles1 and especially to determine at what angle 7about7 this reversal takes place4 ,illustration3 ,,fig4 #dc4 #d4 ,natural automatic stability 7the only one possible so far as models are concerned7 necessitates permanent or a permanently recurring coincidence 7to coin a phrase7 of the centre of gravity and the centre of pressure3 the former is1 of course1 totally unaffected by the vagaries of the latter1 any shifting of which produces a couple tending to destroy equilibrium4 #e4 ,as to the best form of camber 7for full sized machine7 possibly more is known on this point than on any other in the whole of aeronautics4 ,in ,figs4 #dd and #de are given two very efficient forms of cambered surfaces for models4 ,illustration3 ,,fig4 #dd4--;,,an ,,efficient ,,form ,,of ,,camber4 ,b ,d ,maximum ,altitude4 ,a ,c ,chord4 ,ratio of ,b ,d3 ,a ,c 33 #a3ag4 ,a ,d #a_/c of ,a ,c4 ,illustration3 ,,fig4 #de4--;,,another ,,efficient ,,form4 ,ratio of ,b ,d to ,a ,c #a to #ag4 ,,ad rather more than of ,a ,c4 ,the next question1 after having decided the question of aerocurve1 or curvature of the planes1 is at what angle to set the cambered surface to the line of flight4 ,this brings us to the question of the-- #f4 ,dipping ,front ,edge4--,the leading or front edge is not tangential to the line of flight1 but to a relative upward wind4 ,it is what is known as the cyclic up-current1 which exists in the neighbourhood of the entering edge4 ,now1 as we have stated before1 it is of paramount importance that the aerofoil should receive the air with as little shock as possible1 and since this up-current does really exist to do this1 it must travel through the air with a dipping front edge4 ,the relative wind 7the only one with which we are concerned7 is thereby met tangentially1 and as it moves onward through the air the cambered surface 7or aerocurve7 gradually transforms this upward trend into a downward wake1 and since by ,newton's law1 ,action and reaction are equal and opposite1 we have an equal and opposite upward reaction4 ,we now know that the top 7or convex side7 of the cambered surface is practically almost as important as the underneath or concave side in bringing this result about4 ,the exact amount of dipping edge1 and the exact angle at which the chord of the aerocurve1 or cambered surface1 should be set to the line of flight--whether at a positive angle1 at no angle1 or at a negative angle--is one best determined by experiment on the model in question4 ,illustration3 ,,fig4 #df4 ,but if at any angle1 that angle either way should be a very small one4 ,if you wish to be very scientific you can give the underside of the front edge a negative angle of #e to #g for about one-eighth of the total length of the section1 after that a positive angle1 gradually increasing until you finally finish up at the trailing edge with one of #d4 ,also1 the form of cambered surface should be a paraboloid--not arc or arc of circles4 ,the writer does not recommend such an angle1 but prefers an attitude similar to that adopted in the ,wright machine1 as in ,fig4 #dg4 #g4 ,apart from the attitude of the aerocurve3 the greatest depth of the camber should be at one-third of the length of the section from the front edge1 and the total depth measured from the top surface to the chord at this point should not be more than one-seventeenth of the length of section4 #h4 ,it is the greatest mistake in model aeroplanes to make the camber otherwise than very slight 7in the case of surfaced aerofoils the resistance is much increased71 and aerofoils with anything but a very slight arch are liable to be very unstable1 for the aerocurve has always a decided tendency to follow its own curve4 ,illustration3 ,,fig4 #dg4--;,,attitude ,,of ,,wright ,,machine4 ,the nature of the aerocurve1 its area1 the angle of inclination of its chord to the line of flight1 its altitude1 etc41 are not the only important matters one must consider in the case of the aerofoil1 we must also consider-- #i4 ,its ,aspect ,ratio1 i4e4 the ratio of the span 7length7 of the aerofoil to the chord--usually expressed by span_/chord4 ,in the ,farman machine this ratio is #ed2 ,blriot1 #dc2 ,short1 #f to #ge2 ,roe triplane1 #ge2 a ,clark flyer1 #if4 ,now the higher the aspect ratio the greater should be the efficiency4 ,air escaping by the sides represents loss1 and the length of the sides should be kept short4 ,a broader aerofoil means a steeper angle of inclination1 less stability1 unnecessary waste of power1 and is totally unsuited for a model--to say nothing of a full-sized machine4 ,in models this aspect ratio may with advantage be given a higher value than in full-sized machines1 where it is well known a practical safe constructional limit is reached long before theory suggests the limit4 ,the difficulty consists in constructing models having a very high aspect ratio1 and yet possessing sufficient strength and lightness for successful flight4 ,it is in such a case as this where the skill and ingenuity of the designer and builder come in4 ,it is this very question of aspect ratio which has given us the monoplane1 the biplane1 and the triplane4 ,a biplane has a higher aspect ratio than a monoplane1 and a triplane 7see above7 a higher ratio still4 ,it will be noticed the ,clark model given has a considerably higher aspect ratio1 viz4 #if4 ,and even this can be exceeded4 ,an aspect ratio of #aj3a or even #ab3a should be used if possible4#cg #aj4 ,constant or ,varying ,camber4--,some model makers vary the camber of their aerofoils1 making them almost flat in some parts1 with considerable camber in others2 the tendency in some cases being to flatten the central portions of the aerofoil1 and with increasing camber towards the tips4 ,in others the opposite is done4 ,the writer has made a number of experiments on this subject1 but cannot say he has arrived at any very decisive results1 save that the camber should in all cases be 7as stated before7 very slight1 and so far as his experiments do show anything1 they incline towards the further flattening of the camber in the end portions of the aerofoil4 ,it must not be forgotten that a flat-surfaced aerofoil1 constructed as it is of more or less elastic materials1 assumes a natural camber1 more or less1 when driven horizontally through the air4 ,reference has been made to a reversal of the-- #aa4 ,centre of ,pressure on ,arched ,surfaces4--,wilbur ,wright in his explanation of this reversal says3 ,this phenomenon is due to the fact that at small angles the wind strikes the forward part of the aerofoil surface on the upper side instead of the lower1 and thus this part altogether ceases to lift1 instead of being the most effective part of all4 ,the whole question hangs on the value of the critical angle at which this reversal takes place2 some experiments made by ,mr4 ,m4,b4 ,sellers in #aijf 7published in ,flight1 ,may #ad1 #aiaj7 place this angle between #af and #bj4 ,this angle is much above that used in model aeroplanes1 as well as in actual full-sized machines4 ,but the equilibrium of the model might be upset1 not by a change of attitude on its part1 but on that of the wind1 or both combined4 ,by giving 7as already advised7 the aerofoil a high aspect ratio we limit the travel of the centre of pressure1 for a high aspect ratio means1 as we have seen1 a short chord2 and this is an additional reason for making the aspect ratio as high as practically possible4 ,the question is1 is the critical angle really as high as ,mr4 ,seller's experiments would show4 ,further experiments are much needed4 ,,footnotes3 #cg ,nevertheless some models with a very low aspect ratio make good flyers1 owing to their extreme lightness4 ,,chapter ,,vii4 ,,materials ,,for ,,aeroplane ,,construction4 #a4 ,the choice of materials for model aeroplane construction is more or less limited1 if the best results are to be obtained4 ,the lightness absolutely essential to success necessitates--in addition to skilful building and best disposition of the materials--materials of no undue weight relative to their strength1 of great elasticity1 and especially of great resilience 7capacity to absorb shock without injury74 #b4 ,bamboo4--,bamboo has per pound weight a greater resilience than any other suitable substance 7silk and rubber are obviously useless as parts of the framework of an aeroplane74 ,on full-sized machines the difficulty of making sufficiently strong connections and a liability to split1 in the larger sizes1 are sufficient reasons for its not being made more use of2 but it makes an almost ideal material for model construction4 ,the best part to use 7split out from the centrepiece7 is the strip of tough wood immediately below the hard glazed surface4 ,for struts1 spars1 and ribs it can be used in this manner1 and for the long strut supporting the rubber motor an entire tube piece should be used of the requisite strength required2 for an ordinary rubber motor 7one yard long71 #cj to #ej strands1 this should be a piece #c_/h in4 in diameter1 and weight about #e_/h oz4 per ft4 ,bamboo may be bent by either the dry heat from a spirit lamp or stove1 or it may be steamed1 the latter for preference1 as there is no danger of scorching the fibres on the inside of the bend4 ,when bent 7as in the case of other woods7 it should be bound on to a former having a somewhat greater curvature than the curve required1 because when cool and dry it will be sure to go back slightly4 ,it must be left on the former till quite dry4 ,when bending the tube entire1 and not split portions thereof1 it should be immersed in very hot1 or even boiling1 water for some time before steaming4 ,the really successful bending of the tube en bloc requires considerable patience and care4 ,bamboo is inclined to split at the ends1 and some care is required in making joints4 ,the ribs can be attached to the spars by lashing them to thin ,t strips of light metal1 such as aluminium4 ,thin thread1 or silk1 is preferable to very thin wire for lashing purpose1 as the latter gives too much1 and cuts into the fibres of the wood as well4 #c4 ,ash1 ,spruce1 ,whitewood are woods that are also much used by model makers4 ,many prefer the last named owing to its uniform freedom from knots and ease with which it can be worked4 ,it is stated #ae per cent4 additional strength can be imparted by using hot size and allowing it to soak into the wood at an increase only of #cg per cent4 of weight4 ,it is less than half the weight of bamboo1 but has a transverse rupture of only #g1ijj lb4 per sq4 in4 compared to #bb1ejj in the case of bamboo tubing 7thickness one-eighth diameter7 and a resilience per lb4 weight of slightly more than one half4 ,some model makers advocate the use of poplar owing to its extreme lightness 7about the same as whitewood71 but its strength is less in the ratio of about #d3c2 its resilience is very slightly more4 ,it must be remembered that wood of the same kind can differ much as to its strength1 etc41 owing to what part of the tree it may have been cut from1 the manner in which it may have been seasoned1 etc4 ,for model aeroplanes all wood used should have been at least a year in seasoning1 and should be so treated when in the structure that it cannot absorb moisture4 ,if we take the resilience of ash as #a1 then 7according to ,haswell7 relative resilience of beech is #jhf1 and spruce #jfd4 ,the strongest of woods has a weight when well seasoned of about #dj lb4 per cub4 ft4 and a tenacity of about #aj1jjj lb4 per sq4 in4 ,illustration3 ,,fig4 #dg;,a4--,,aeroplane ,,alma4 ,a very effective ,french ,toy ,monoplane4 #d4 ,steel4--,ash has a transverse rupture of #ad1cjj lb4 per sq4 in41 steel tubing 7thickness #a_/cj its diameter7 #ajj1jjj lb4 per sq4 in4 ,ash weighs per cub4 ft4 #dg lb41 steel #dij4 ,steel being more than ten times as heavy as ash--but a transverse rupture stress seven times as high4 ,bamboo in tube form1 thickness one-third of diameter1 has a transverse rupture of #bb1ejj lb4 per sq4 in41 and a weight of #ee lb4 per cub4 ft4 ,steel then is nine times as heavy as bamboo--and has a transverse rupture stress #dd times as great4 ,in comparing these three substances it must be carefully borne in mind that lightness and strength are not the only things that have to be provided for in model aeroplane building2 there is the question of resistance--we must offer as small a cross-section to moving through the air as possible4 ,now while ash or bamboo and certain other timbers may carry a higher load per unit of weight than steel1 they will present about three to three and a half times the cross-section1 and this produces a serious obstacle1 while otherwise meeting certain requirements that are most desirable4 ,steel tubing of sufficiently small bore is not1 so far as the writer knows1 yet on the market in ,england4 ,in ,france very thin steel tubes are made of round1 oval1 hexagon1 etc41 shape1 and of accurate thickness throughout1 the price being about #ahs4 a lb4 ,although suitable steel tubing is not yet procurable under ordinary circumstances1 umbrella steel is4 #e4 ,umbrella ,section ,steel is a section #e_/cb in4 by #a_/h in4 deep1 #f ft4 long weighing #ba oz41 and a section #c_/cb in4 across the base by #a_/h in4 deep1 #f ft4 long weighing #aie oz4 ,it is often stated that umbrella ribs are too heavy--but this entirely depends on the length you make use of1 in lengths of #be in4 for small aerofoils made from such lengths it is so2 but in lengths of #dh in4 7two such lengths joined together7 the writer has used it with great success2 often making use of it now in his larger models2 the particular size used by him weighs #ac grammes1 to a length of #be in4 ,he has never had one of these aerofoils break or become kinked--thin piano wire is used to stay them and also for spars when employed--the front and ends of the aerofoil are of umbrella steel1 the trailing edge of steel wire1 comparatively thin1 kept taut by steel wire stays4 #f4 ,steel ,wire4--,tensile strength about #cjj1jjj lb4 per sq4 in4 ,for the aerofoil framework of small models and for all purposes of staying1 or where a very strong and light tension is required1 this substance is invaluable4 ,also for framework of light fabric covered propellers as well as for skids and shock absorber--also for hooks to hold the rubber motor strands1 etc4 ,no model is complete without it in some form or another4 #g4 ,silk4--,this again is a sine qua non4 ,silk is the strongest of all organic substances for certain parts of aeroplane construction4 ,it has1 in its best form1 a specific gravity of #ac1 and is three times as strong as linen1 and twice as strong in the thread as hemp4 ,its finest fibres have a section of from #jjjaj to #jjjae in diameter4 ,it will sustain about #ce1jjj lb4 per sq4 in4 of its cross section2 and its suspended fibre should carry about #aej1jjj ft4 of its own material4 ,this is six times the same figure for aluminium1 and equals about #ge1jjj lb4 steel tenacity1 and #ej more than is obtained with steel in the form of watch springs or wire4 ,for aerofoil surface no substance can compare with it4 ,but it must be used in the form of an oiled or specially treated silk4 ,several such are on the market4 ,hart's fabric and radium silk are perhaps the best known4 ,silk weighs #fb lb4 per cub4 ft41 steel has1 we have seen1 #dij lb41 thus paying due regard to this and to its very high tensile strength it is superior to even steel wire stays4 #h4 ,aluminium and ,magnalium4--,two substances about which a great deal has been heard in connection with model aeroplaning2 but the writer does not recommend their use save in the case of fittings for scale models1 not actual flyers1 unless especially light ones meant to fly with the wind4 ,neither can compare with steel4 ,steel1 it is true1 is three times as heavy as aluminium1 but it has four or five times its strength2 and whereas aluminium and magnalium may with safety be given a permissible breaking strength of #fj per cent4 and #hj per cent4 respectively1 steel can easily be given #hj per cent4 ,being also less in section1 resistance to air travel is again less as in the case of wood4 ,in fact1 steel scores all round4 ,weight of magnalium 3 weight of aluminium 33 #h3i4 #i4 ,alloys4--,during recent years scores1 hundreds1 possibly thousands of different alloys have been tried and experimented on1 but steel still easily holds its own4 ,it is no use a substance being lighter than another volume for volume1 it must be lighter and stronger weight for weight1 to be superior for aeronautical purpose1 and if the difference be but slight1 question of bulk may decide it as offering less resistance4 #aj4 ,sheet ,ebonite4--,this substance is sometimes useful for experiments with small propellers1 for it can be bent and moulded in hot water1 and when cold sets and keeps its shape4 ,vulcanized fibre can be used for same purpose4 ,sheet celluloid can be used in the same way1 but in time it becomes brittle and shrinks4 ,mica should be avoided4 ,jointless cane in various sizes is a very useful material--the main aerofoil can be built of it1 and it is useful for skids1 and might be made more use of than it is4#ch ,three ply wood1 from #a_/ej in4 in thickness1 is now on the market4 ,four or five ply wood can also be obtained4 ,to those desiring to build models having wooden aerofoils such woods offer the advantage of great strength and extreme lightness4 ,referring to ,table ,v4 7,timber7 at the end of the book1 apparently the most suitable wood is ,lombardy poplar2 but its light weight means increased bulk1 i4e4 additional air resistance4 ,honduras mahogany is really a better all-round wood1 and beech is not far behind4 ,resilience is an important factor4 ,ash heads the list2 but mahogany's factor is also good1 and in other respects superior4 ,lombardy poplar ought to be a very good wood for propellers1 owing to its lightness and the ease with which it can be worked4 ,hollow reeds1 and even porcupine quills1 have been pressed into the service of the model maker1 and owing to their great strength and extreme lightness1 more especially the latter1 are not without their uses4 ,,footnotes3 #ch ,the chief advantage of cane--its want of stiffness1 or facility in bending--is for some parts of the machine its chief disadvantage1 where stiffness with resilience is most required4 ,,chapter ,,viii4 ,,hints ,,on ,,the ,,building ,,of ,,model ,,aeroplanes4 #a4 ,the chief difficulty in the designing and building of model aeroplanes is to successfully combat the conflicting interests contained therein4 ,weight gives stability1 but requires extra supporting surface or a higher speed1 i4e4 more power1 i4e4 more weight4 ,inefficiency in one part has a terrible manner of repeating itself2 for instance1 suppose the aerofoil surface inefficient--badly designed--this means more resistance2 more resistance means more power1 i4e4 weight1 i4e4 more surface1 and so on ad infinitum4 ,it is because of circumstances like the above that it is so difficult to design really good and efficient flying models2 the actual building of them is not so difficult1 but few tools are required1 none that are expensive or difficult to use4 ,in the making of any particular model there are special points that require special attention2 but there are certain general rules and features which if not adhered to and carefully carried out1 or as carefully avoided1 will cause endless trouble and failure4 #b4 ,in constructing a model aeroplane1 or1 indeed1 any piece of aerial apparatus1 it is very important not to interrupt the continuity of any rib1 tube1 spar1 etc41 by drilling holes or making too thinned down holding places2 if such be done1 additional strength by binding 7with thread1 not wire71 or by slipping a small piece of slightly larger tube over the other1 must be imparted to the apparatus4 #c4 ,begin by making a simple monoplane1 and afterwards as you gain skill and experience proceed to construct more elaborate and scientific models4 #d4 ,learn to solder--if you do not know how to--it is absolutely essential4 #e4 ,do not construct models 7intended for actual flight7 with a tractor screw-main plane in front and tail 7behind74 ,avoid them as you would the plague4 ,allusion has already been made in the ,introduction to the difficulty of getting the centre of gravity sufficiently forward in the case of ,blriot models2 again with the main aerofoil in front1 it is this aerofoil and not the balancing elevator1 or tail1 that first encounters the upsetting gust1 and the effect of such a gust acting first on the larger surface is often more than the balancer can rectify in time to avert disaster4 ,the proper place for the propeller is behind1 in the wake of the machine4 ,if the screw be in front the backwash from it strikes the machine and has a decidedly retarding action4 ,it is often contended that it drives the air at an increased velocity under 7and over7 the main aerofoil1 and so gives a greater lifting effect4 ,but for proper lifting effect which it can turn without effort into air columns of proper stream line form what the aerofoil requires is undisturbed air--not propeller backwash4 ,the rear of the model is the proper place for the propeller1 in the centre of greatest air disturbance2 in such a position it will recover a portion of the energy lost in imparting a forward movement to the air1 caused by the resistance1 the model generally running in such air--the slip of the screw is reduced to a corresponding degree--may even vanish altogether1 and what is known as negative slip occur4 #f4 ,wooden or metal aerofoils are more efficient than fabric covered ones4 ,but they are only satisfactory in the smaller sizes1 owing1 for one thing1 to the smash with which they come to the ground4 ,this being due to the high speed necessary to sustain their weight4 ,for larger-sized models fabric covered aerofoils should be used4 #g4 ,as to the shape of such1 only three need be considered--the 7a7 rectangular1 7b7 the elongated ellipse1 7c7 the chamfered rear edge4 ,illustration3 ,,fig4 #dh4--7;a71 7b71 7c74 #h4 ,the stretching of the fabric on the aerofoil framework requires considerable care1 especially when using silk4 ,it is quite possible1 even in models of #c ft4 to #d ft4 spread1 to do without ribs1 and still obtain a fairly correct aerocurve1 if the material be stretched on in a certain way4 ,it consists in getting a correct longitudinal and transverse tension4 ,we will illustrate it by a simple case4 ,take a piece of thickish steel pianoforte wire1 say1 #ah in4 long1 bend it round into a circle1 allowing in4 to #a in4 to overlap1 tin and solder1 bind this with soft very thin iron wire1 and again solder 7always use as little solder as possible74 ,now stitch on to this a piece of nainsook or silk1 deforming the circle as you do so until it has the accompanying elliptical shape4 ,the result is one of double curvature2 the transverse curve 7dihedral angle7 can be regulated by cross threads or wires going from ,a to ,b and ,c to ,d4 ,illustration3 ,,fig4 #di4 ,illustration3 ,,fig4 #di;,a4--,,mr4 ,t4,w4,k4 ,,clarke',s #a ,,oz4 ,,model4 ,the longitudinal curve on the camber can be regulated by the original tension given to it1 and by the manner of its fixing to the main framework4 ,suitable wire projections or loops should be bound to it by wire1 and these fastened to the main framework by binding with thin rubber cord1 a very useful method of fastening1 since it acts as an excellent shock absorber1 and gives when required1 and yet possesses quite sufficient practical rigidity4 #i4 ,flexible joints are an advantage in a biplane2 these can be made by fixing wire hooks and eyes to the ends of the struts1 and holding them in position by binding with silk or thread4 ,rigidity is obtained by use of steel wire stays or thin silk cord4 ,illustration3 ,,fig4 #di;,b4--,,mr4 ,t4,w4,k4 ,,clarke',s #a ,,oz4 ,,model4 ,showing the position of ,c4 of ,g41 or point of support4 #aj4 ,owing to the extra weight and difficulties of construction on so small a scale it is not desirable to use double surface aerofoils except on large size power-driven models4 #aa4 ,it is a good plan not to have the rod or tube carrying the rubber motor connected with the outrigger carrying the elevator1 because the torque of the rubber tends to twist the carrying framework1 and interferes with the proper and correct action of the elevator4 ,if it be so connected the rod must be stayed with piano wire1 both longitudinally 7to overcome the pull which we know is very great71 and also laterally1 to overcome the torque4 ,illustration3 ,,fig4 #di;,c4--,a ,,large ,,model ,,aeroplane4 ,shown without rubber or propellers4 ,designed and constructed by the writer4 ,as a test it was fitted with two #ad in4 propellers revolving in the same direction1 and made some excellent flights under these conditions1 rolling slightly across the wind1 but otherwise keeping quite steady4 ,total weight1 #a lb42 length1 #f ft42 span of main aerofoil1 #e ft4 ,constructed of bamboo1 cane1 and steel wire4 ,front skids steel wire4 ,back skids cane4 ,aerofoil covering nainsook4 #ab4 ,some builders place the rubber motor above the rod1 or bow frame carrying the aerofoils1 etc41 the idea being that the pull of the rubber distorts the frame in such a manner as to lift the elevator1 and so cause the machine to rise rapidly in the air4 ,this it does2 but the model naturally drops badly at the finish and spoils the effect4 ,it is not a principle that should be copied4 ,illustration3 ,,fig4 #di;,d4--,a ,,very ,,light ,,weight ,,model4 ,constructed by the author4 ,provided with twin propellers of a modified ,fleming-,williams type4 ,this machine flew well when provided with an abnormal amount of rubber1 owing to the poor dynamic thrust given by the propellers4 #ac4 ,in the ,clarke models with the small front plane1 the centre of pressure is slightly in front of the main plane4 ,the balancing point of most models is generally slightly in front1 or just within the front edge of the main aerofoil4 ,the best plan is to adjust the rod carrying the rubber motor and propeller until the best balance is obtained1 then hang up the machine to ascertain the centre of gravity1 and you will have 7approximately7 the centre of pressure4 ,illustration3 ,,fig4 #di;,e4--,,useful ,,fittings ,,for ,,models4 #a4 ,rubber tyred wheels4 #b4 ,ball-bearing steel axle shafts4 #c4 ,brass wire strainers with steel screws2 breaking strain #bjj lb4 #d4 ,magnalium tubing4 #e4 ,steel eyebolt4 #f4 ,aluminium ,t joint4 #g4 ,aluminium ,l piece4 #h4 ,brass brazed fittings4 #i4 ,ball-bearing thrust4 #aj4 ,flat aluminium ,l piece4 7,the above illustrations taken 7by permission7 from ,messrs4 ,gamage's catalogue on ,model ,aviation47 #ad4 ,the elevator 7or tail7 should be of the non-lifting type--in other words1 the entire weight should be carried by the main aerofoil or aerofoils2 the elevator being used simply as a balancer4#ci ,if the machine be so constructed that part of the weight be carried by the elevator1 then either it must be large 7in proportion7 or set up at a large angle to carry it4 ,both mean considerably more resistance--which is to be avoided4 ,in practice this means the propeller being some little distance in rear of the main supporting surface4 ,illustration3 ,,fig4 #di;,f4--,,useful ,,fittings ,,for ,,models4 #aa4 ,aluminium ball thrust and racket4 #ab4 ,ball-bearing propeller1 thrust1 and stay4 7,the above illustrations taken 7by permission7 from ,messrs4 ,gamage's catalogue on ,model ,aviation47 #ae4 ,in actual flying models skids should be used and not wheels2 the latter to be of any real use must be of large diameter1 and the weight is prohibitive4 ,skids can be constructed of cane1 imitation whalebone1 steel watch or clock-spring1 steel pianoforte wire4 ,steel mainsprings are better than imitation whalebone1 but steel pianoforte wire best of all4 ,for larger sized models bamboo is also suitable1 as also ash or strong cane4 #af4 ,apart from or in conjunction with skids we have what are termed shock absorbers to lessen the shock on landing--the same substances can be used--steel wire in the form of a loop is very effectual2 whalebone and steel springs have a knack of snapping4 ,these shock absorbers should be so attached as to give all ways for a part side and part front landing as well as a direct front landing4 ,for this purpose they should be lashed to the main frame by thin indiarubber cord4 #ag4 ,in the case of a biplane model the gap must not be less than the chord--preferably greater4 ,in a double monoplane 7of the ,langley type7 there is considerable interference1 i4e4 the rear plane is moving in air already acted on by the front one1 and therefore moving in a downward direction4 ,this means decreased efficiency4 ,it can be overcome1 more or less1 by varying the dihedral angle at which the two planes are set2 but cannot be got rid of altogether1 or by placing them far apart4 ,in biplanes not possessing a dihedral angle--the propeller can be placed slightly to one side--in order to neutralise the torque of the propeller--the best portion should be found by experiment--unless the pitch be very large2 with a well designed propeller this is not by any means essential4 ,if the propeller revolve clockwise1 place it towards the right hand of the machine1 and vice versa4 #ah4 ,in designing a model to fly the longest possible distance the monoplane type should be chosen1 and when desiring to build one that shall remain the longest time in the air the biplane or triplane type should be adopted4#dj ,for the longest possible flight twin propellers revolving in opposite directions#da are essential4 ,to take a concrete case--one of the writer's models weighed complete with a single propeller #h oz4 ,it was then altered and fitted with two propellers 7same diameter and weight72 this complete with double rubber weighed #aj oz4 ,the advantage double the power4 ,weight increased only #bj per cent41 resistance about #aj per cent41 total #cj per cent4 ,gain #gj per cent4 ,or if the method of gearing advocated 7see ,geared ,motors7 be adopted then we shall have four bunches of rubber instead of two1 and can thereby obtain so many more turns4#db ,the length of the strands should be such as to render possible at least a thousand turns4 ,the propellers should be of large diameter and pitch 7not less than #ce at the tips71 of curved shape1 as advocated in #bb ch4 v42 the aerofoil surface of as high an aspect ratio as possible1 and but slight camber if any2 this is a very difficult question1 the question of camber1 and the writer feels bound to admit he has obtained as long flights with surfaces practically flat1 but which do1 of course1 camber slightly in a suitable wind1 as with stiffer cambered surfaces4 ,wind cambered surfaces are1 however1 totally unsuitable in gusty weather1 when the wind has frequently a downward trend1 which has the effect of cambering the surface the wrong way about1 and placing the machine flat on the ground4 ,oiled or specially prepared silk of the lightest kind should be used for surfacing the aerofoils4 ,some form of keel1 or fin1 is essential to assist in keeping the machine in a straight course1 combined with a rudder and universally jointed elevator4 ,the manner of winding up the propellers has already been referred to 7see chap4 iii41 #i74 ,a winder is essential4 ,another form of aerofoil is one of wood 7as in ,clarke's flyers7 or metal1 such a machine relying more on the swiftness of its flight than on its duration4 ,in this the gearing would possibly not be so advantageous--but experiment alone could decide4 ,the weight of the machine would require to be an absolute minimum1 and everything not absolutely essential omitted4 ,it is quite possible to build a twin-screw model on one central stick alone2 but the isosceles triangular form of framework1 with two propellers at the base corners1 and the rubber motors running along the two sides and terminating at the vertex1 is preferred by most model makers4 ,it entails1 of course1 extra weight4 ,a light form of skid1 made of steel pianoforte wire1 should be used4 ,as to the weight and size of the model1 the now famous one-ouncers have made some long flights of over #cjj yards#dc2 but the machine claiming the record1 half a mile1#dd weighs about #aj oz4 ,and apart from this latter consideration altogether the writer is inclined to think that from #e oz4 to #aj oz4 is likely to prove the most suitable4 ,it is not too large to experiment with without difficulty1 nor is it so small as to require the skill of a jeweller almost to build the necessary mechanism4 ,the propeller speed has already been discussed 7see ch4 v41 #ae74 ,the model will1 of course1 be flown with the wind4 ,the total length of the model should be at least twice the span of the main aerofoil4 ,,footnotes3 #ci ,this is a good plan--not a rule4 ,good flying models can1 of course1 be made in which this does not hold4 #dj ,this is in theory only3 in practice the monoplane holds both records4 #da ,the best position for the propellers appears to be one in front and one behind1 when extreme lightness is the chief thing desired4 #db ,because the number of strands of rubber in each bunch will be much less4 #dc ,mr4 ,burge ,webb claims a record of #ejj yards for one of his4 #dd ,flying1 of course1 with the wind4 ,note4--,in the ,model ,engineer of ,july #g1 #aiaj1 will be found an interesting account 7with illustrations7 of ,mr4 ,w4,g4 ,aston's #a oz4 model1 which has remained in the air for over a minute4 ,,chapter ,,ix4 ,,the ,,steering ,,of ,,the ,,model4 #a4 ,of all the various sections of model aeroplaning that which is the least satisfactory is the above4 ,the torque of the propeller naturally exerts a twisting or tilting effect upon the model as a whole1 the effect of which is to cause it to fly in 7roughly speaking7 a circular course1 the direction depending on whether the pitch of the screw be a right or left handed one4 ,there are various devices by which the torque may be 7approximately7 got rid of4 #b4 ,in the case of a monoplane1 by not placing the rod carrying the rubber motor in the exact centre of the main aerofoil1 but slightly to one side1 the exact position to be determined by experiment4 ,in a biplane the same result is obtained by keeping the rod in the centre1 but placing the bracket carrying the bearing in which the propeller shaft runs at right angles horizontally to the rod to obtain the same effect4 #c4 ,the most obvious solution of the problem is to use two equal propellers 7as in the ,wright biplane7 of equal and opposite pitch1 driven by two rubber motors of equal strength4 ,theoretically this idea is perfect4 ,in practice it is not so4 ,it is quite possible1 of course1 to use two rubber motors of an equal number of strands 7equality should be first tested by weighing74 ,it should be possible to obtain two propellers of equal and opposite pitch1 etc41 and it is also possible to give the rubber motors the same number of turns4 ,in practice one is always wound up before the other4 ,this is the first mistake4 ,they should be wound up at the same time1 using a double winder made for the purpose4 ,the fact that this is not done is quite sufficient to give an unequal torsion4 ,the friction in both cases must also be exactly equal4 ,both propellers must be released at exactly the same instant4 ,supposing all these conditions fulfilled 7in practice they never are71 supposing also the propellers connected by gearing 7prohibitive on account of the weight71 and the air quite calm 7which it never is71 then the machine should and undoubtedly would fly straight4 ,for steering purposes by winding up one propeller many more times than the other1 the aeroplane can generally speaking be steered to the right or left2 but from what ,i have both seen and tried twin-screw model aeroplanes are not the success they are often made out to be1 and they are much more troublesome to deal with1 in spite of what some say to the contrary4 ,the solution of the problem of steering by the use of two propellers is only partially satisfactory and reliable1 in fact1 it is no solution at all4#de ,the torque of the propeller and consequent tilting of the aeroplane is not the only cause at work diverting the machine from its course4 #d4 ,as it progresses through the air it is constantly meeting air currents of varying velocity and direction1 all tending to make the model deviate more or less from its course2 the best way1 in fact1 the only way1 to successfully overcome such is by means of speed1 by giving the aeroplane a high velocity1 not of ten or twelve to fifteen miles an hour1 as is usual in built up fabric-covered aerofoils1 but a velocity of twenty to thirty miles an hour1 attainable only in models 7petrol or steam driven7 or by means of wooden or metal aerofoils4 #e4 ,amongst devices used for horizontal steering are vertical ,,fins4 ,these should be placed in the rear above the centre of gravity4 ,they should not be large1 and can be made of fabric tightly stretched over a wire frame1 or of a piece of sheet magnalium or aluminium1 turning on a pivot at the front edge1 adjustment being made by simply twisting the fin round to the desired angle4 ,as to the size1 think of rudder and the size of a boat1 but allow for the difference of medium4 ,the frame carrying the pivot and fin should be made to slide along the rod or backbone of the model in order to find the most efficient position4 #f4 ,steering may also be attempted by means of little balancing tips1 or ailerons1 fixed to or near the main aerofoil1 and pivoted 7either centrally or otherwise7 in such a manner that they can be rotated one in one direction 7tilted7 and the other in the other 7dipped71 so as to raise one side and depress the other4 #g4 ,the model can also be steered by giving it a cant to one side by weighting the tip of the aerofoil on that side on which it is desired it should turn1 but this method is both clumsy and weighty4 #h4 ,another way is by means of the elevator2 and this method1 since it entails no additional surfaces entailing extra resistance and weight1 is perhaps the most satisfactory of all4 ,it is necessary that the elevator be mounted on some kind of universal joint1 in order that it may not only be tipped or dipped1 but also canted sideways for horizontal steering4 #i4 ,a vertical fin in the rear1 or something in the nature of a keel1 i4e4 a vertical fin running down the backbone of the machine1 greatly assists this movement4 ,if the model be of the tractor screw and tail 7,blriot7 type1 then the above remarks re elevator apply mutatis mutandis to the tail4 #aj4 ,it is of the most vital importance that the propeller torque should be1 as far as possible1 correctly balanced4 ,this can be tested by balancing the model transversely on a knife edge1 winding up the propeller1 and allowing it to run down1 and adjusting matters until the torque and compensatory apparatus balance4 ,as the torque varies the mean should be used4 ,in the case of twin propellers1 suspend the model by its centre of gravity1 wind up the propellers1 and when running down if the model is drawn forward without rotation the thrust is equal2 if not adjustment must be made till it does4 ,the easiest way to do this may be by placing one propeller1 the one giving the greater thrust1 slightly nearer the centre4 ,in the case of two propellers rotating in opposite directions 7by suitable gearing7 on the common centre of two axes1 one of the axes being1 of course1 hollow1 and turning on the other--the rear propeller working in air already driven back by the other will require a coarser pitch or larger diameter to be equally efficient4 ,,footnote3 #de ,these remarks apply to rubber driven motors4 ,in the case of two-power driven propellers in which the power was automatically adjusted1 say1 by a gyroscope as in the case of a torpedo--and the speed of each propeller varied accordingly--the machine could1 of course1 be easily steered by such means2 but the model to carry such power and appliances would certainly weigh from #dj lb4 to #fj lb4 ,,chapter ,x4 ,,the ,,launching ,,of ,,the ,,model4 #a4 ,generally speaking1 the model should be launched into the air against the wind4 #b4 ,it should 7theoretically7 be launched into the air with a velocity equal to that with which it flies4 ,if it launch with a velocity in excess of that it becomes at once unstable and has to settle down before assuming its normal line of flight4 ,if the velocity be insufficient1 it may be unable to pick up its requisite velocity in time to prevent its falling to the ground4 ,models with wooden aerofoils and a high aspect ratio designed for swift flying1 such as the well-known ,clarke flyers1 require to be practically hurled into the air4 ,other fabric-covered models capable of sustentation at a velocity of #h to #aj miles an hour1 may just be released4 #c4 ,light featherweight models designed for long flights when travelling with the wind should be launched with it4 ,they will not advance into it--if there be anything of a breeze--but1 if well designed1 just hover1 finally sinking to earth on an even keel4 ,many ingenious pieces of apparatus have been designed to mechanically launch the model into the air4 ,fig4 #ej is an illustration of a very simple but effective one4 #d4 ,for large size power-driven models1 unless provided with a chassis and wheels to enable them to run along and rise from the ground under their own power1 the launching is a problem of considerable difficulty4 #e4 ,in the case of rubber-driven models desired to run along and rise from the ground under their own power1 this rising must be accomplished quickly and in a short space4 ,a model requiring a #ej ft4 run is useless1 as the motor would be practically run out by that time4 ,ten or twelve feet is the limit2 now1 in order to rise quickly the machine must be light and carry considerable surface1 or1 in other words1 its velocity of sustentation must be a low one4 ,illustration3 ,,fig4 #ej4--,,mr4 ,,poynter',s ,,launching ,,apparatus4 7,reproduced by permission from the ,model ,engineer47 #f4 ,it will not do to tip up the elevator to a large angle to make it rise quickly1 because when once off the ground the angle of the elevator is wrong for actual flight and the model will probably turn a somersault and land on its back4 ,i have often seen this happen4 ,if the elevator be set at an increased angle to get it to rise quickly1 then what is required is a little mechanical device which sets the elevator at its proper flight angle when it leaves the ground4 ,such a device does not present any great mechanical difficulties2 and ,i leave it to the mechanical ingenuity of my readers to devise a simple little device which shall maintain the elevator at a comparatively large angle while the model is on the ground1 but allowing of this angle being reduced when free flight is commenced4 #g4 ,the propeller most suitable to get the machine off the ground is one giving considerable statical thrust4 ,a small propeller of fine pitch quickly starts a machine1 but is not1 of course1 so efficient when the model is in actual flight4 ,a rubber motor is not at all well adapted for the purpose just discussed4 #h4 ,professor ,kress uses a polished plank 7down which the models slip on cane skids7 to launch his models4 #i4 ,when launching a twin-screw model the model should be held by each propeller1 or to speak more correctly1 the two brackets holding the bearings in which the propeller shafts run should be held one in each hand in such a way1 of course1 as to prevent the propellers from revolving4 ,hold the machine vertically downwards1 or1 if too large for this1 allow the nose to rest slightly on the ground2 raise 7or swing7 the machine up into the air until a little more than horizontal position is attained1 and boldly push the machine into the air 7moving forward if necessary7 and release both brackets and screws simultaneously4#df #aj4 ,in launching a model some prefer to allow the propellers to revolve for a few moments 7a second1 say7 before actually launching1 contending that this gives a steadier initial flight4 ,this is undoubtedly the case1 see note on page #aaa4 #aa4 ,in any case1 unless trying for a height prize1 do not point the nose of the machine right up into the air with the idea that you will thereby obtain a better flight4 ,launch it horizontally1 or at a very small angle of inclination4 ,when requiring a model to run along a field or a lawn and rise therefrom this is much facilitated by using a little strip of smooth oilcloth on which it can run4 ,remember that swift flying wooden and metal models require a high initial velocity1 particularly if of large size and weight4 ,if thrown steadily and at the proper angle they can scarcely be overthrown4 ,,footnote3 #df ,another and better way--supposing the model constructed with a central rod1 or some suitable holdfast 7this should be situated at the centre of gravity of the machine7 by which it can be held in one hand--is to hold the machine with both hands above the head1 the right hand grasping it ready to launch it1 and the left holding the two propellers4 ,release the propellers and allow them a brief interval 7about half a second7 to start4 ,then launch boldly into the air4 ,the writer has easily launched #a lb4 models by this means1 even in a high wind4 ,never launch a model by one hand only4 ,,chapter ,,xi4 ,,helicopter ,,models4 #a4 ,there is no difficulty whatever about making successful model helicopters1 whatever there may be about full-sized machines4 #b4 ,the earliest flying models were helicopters4 ,as early as #agif ,sir ,george ,cayley constructed a perfectly successful helicopter model 7see ch4 iii472 it should be noticed the screws were superimposed and rotated in opposite directions4 #c4 ,in #ahdb a ,mr4 ,phillips constructed a successful power-driven model helicopter4 ,the model was made entirely of metal1 and when complete and charged weighed #b lb4 ,it consisted of a boiler or steam generator and four fans supported between eight arms4 ,the fans had an inclination to the horizon of #bj1 and through the arms the steam rushed on the principle of ,hero's engines 7,barker's ,mill ,principle probably74 ,by the escape of steam from the arms the fans were caused to revolve with immense energy1 so much so that the model rose to an immense altitude and flew across two fields before it alighted4 ,the motive power employed was obtained from the combustion of charcoal1 nitre and gypsum1 as used in the original fire annihilator2 the products of combustion mixing with water in the boiler and forming gas-charged steam1 which was delivered at high pressure from the extremities of the eight arms4#dg ,this model and its flight 7fully authenticated7 is full of interest and should not be lost sight of1 as in all probability being the first model actuated by steam which actually flew4 ,the helicopter is but a particular phase of the aeroplane4 #d4 ,the simplest form of helicopter is that in which the torque of the propeller is resisted by a vertical loose fabric plane1 so designed as itself to form a propeller1 rotating in the opposite direction4 ,these little toys can be bought at any good toy shop from about #f;d4 to #as4 ,supposing we desire to construct a helicopter of a more ambitious and scientific character1 possessing a vertically rotating propeller or propellers for horizontal propulsion1 as well as horizontally rotating propellers for lifting purposes4 ,illustration3 ,,fig4 #ea4--;,,incorrect ,,way ,,of ,,arranging ,,screws4 #e4 ,there is one essential point that must be carefully attended to1 and that is1 that the horizontal propulsive thrust must be in the same plane as the vertical lift1 or the only effect will be to cause our model to turn somersaults4 ,i speak from experience4 ,when the horizontally revolving propellers are driven in a horizontal direction their lifting powers will be materially increased1 as they will 7like an ordinary aeroplane7 be advancing on to fresh undisturbed air4 #f4 ,i have not for ordinary purposes advocated very light weight wire framework fabric-covered screws1 but in a case like this where the thrust from the propeller has to be more than the total weight of the machine1 these might possibly be used with advantage4 #g4 ,instead of using two long vertical rods as well as one long horizontal one for the rubber strands1 we might dispense with the two vertical ones altogether and use light gearing to turn the torque action through a right angle for the lifting screws1 and use three separate horizontal rubber strands for the three propellers on a suitable light horizontal framework4 ,such should result in a considerable saving of weight4 ,illustration3 ,,fig4 #eb4--;,,correct ,,manner4 ,a1 ,b1 ,c ,screws4 #h4 ,the model would require something in the nature of a vertical fin or keel to give the sense of direction4 ,four propellers1 two for lift and two for drift1 would undoubtedly be a better arrangement4 ,,footnote3 #dg ,report on ,first ,exhibition of ,aeronautical ,society of ,great ,britain1 held at ,crystal ,palace1 ,june #ahfh4 ,,chapter ,,xii4 ,,experimental ,,records4 ,a model flying machine being a scientific invention and not a toy1 every devotee to the science should make it his or her business to keep1 as far as they are able1 accurate and scientific records4 ,for by such means as this1 and the making known of the same1 can a science of model aeroplaning be finally evolved4 ,the following experimental entry forms1 left purposely blank to be filled in by the reader1 are intended as suggestions only1 and can1 of course1 be varied at the reader's discretion4 ,when you have obtained carefully established data1 do not keep them to yourself1 send them along to one of the aeronautical journals4 ,do not think them valueless2 if carefully arranged they cannot be that1 and may be very valuable4 ,,experimental ,,data4 ,,form ,i4 ,column ,headings3 ,a3 ,model ,b3 ,weight ,c3 ,area of ,supporting ,surface ,d3 ,aspect ,ratio ,e3 ,average ,length of ,flight in ,feet ,f3 ,maximum ,flight ,g3 ,time of ,flight1 ,a4 average ,h3 ,m4 maximum ,i3 ,kind and ,direction of ,wind ,j3 ,camber ,k3 ,angle of ,inclination of ,main ,aerofoil to ,line of ,flight ---------------------------------------- --------------- ,a ,b ,c ,d ,e ,f ,g ,h ,i ,j ,k ---------------------------------------- --------------- ,a ,m #a #b #c #d #e #f #g #h #i #aj #aa #ab ---------------------------------------- --------------- ,,form ,i4--continued4 ,column ,headings3 ,a3 ,model ,b3 ,weight of 7,rubber7 ,motor ,c3 ,kind of ,rubber1 ,flat1 ,square or ,round ,d3 ,lenght in ,inches and ,number of ,strands ,e3 ,number of ,turns ,f3 ,condition at ,end of ,flight ,g3 ,number of ,propellers 7,no47 and ,diameter 7,diam47 ,h3 ,number of ,blades ,i3 ,disc ,area 7,disc,a47 and ,pitch 7,pitch7 ,j3 ,percentage of ,slip ,k3 ,thrust ,l3 ,torque in ,inche-,ounces ---------------------------------------- ----------- ,a ,b ,c ,d ,e ,f ,g ,h ,i ,j ,k ,l ---------------------------------------- ----------- #a #b #c #d #e #f #g #h #i #aj #aa #ab ---------------------------------------- ----------- ,,chapter ,,xiii4 ,,model ,,flying ,,competitions4 #a4 ,from time to time flying competitions are arranged for model aeroplanes4 ,sometimes these competitions are entirely open1 but more generally they are arranged by local clubs with both closed and open events4 ,no two programmes are probably exactly alike1 but the following may be taken as fairly representative3-- #a4 ,longest flight measured in a straight line 7sometimes both with and against the wind74#dh #b4 ,stability 7both longitudinal and transverse74 #c4 ,longest glide when launched from a given height without power1 but with motor and propeller attached4 #d4 ,steering4 #e4 ,greatest height4 #f4 ,the best all-round model1 including1 in addition to the above1 excellence in building4 ,generally so many points or marks are given for each test1 and the model whose aggregate of points makes the largest total wins the prize2 or more than one prize may be offered-- ,one for the longest flight4 ,one for the swiftest flight over a measured distance4 ,one for the greatest height4 ,one for stability and steering4 ,and one for the best all-round model4 ,the models are divided into classes3-- #b4 ,aero ,models ,association's ,classification1 etc4 ,a4 ,models of #a sq4 ft4 surface and under4 ,b4 #b sq4 ft4 ,c4 #d sq4 ft4 ,d4 #h sq4 ft4 ,e4 over #h sq4 ft4 ,all surfaces1 whether vertical1 horizontal1 or otherwise1 to be calculated together for the above classification4 ,all round efficiency--marks or points as percentages3-- ,distance #dj per cent4 ,stability #ce ,directional control #ae ,gliding angle #aj #di ,two prizes3-- ,one for length of flight4 ,one for all-round efficiency 7marked as above74 ,every competitor to be allowed three trials in each competition1 the best only to count4 ,all flights to be measured in a straight line from the starting to the landing point4 ,repairs may be made during the competition at the direction of the judges4#ej ,there are one or two other points where flights are not made with and against the wind4 ,the competitors are usually requested to start their models from within a given circle of 7say7 six feet diameter1 and fly them in any direction they please4 ,gliding angle means that the model is allowed to fall from a height 7say7 of #bj ft4 ,illustration3 ,,fig4 #ec4--,,model ,,designed ,,and ,,constructed ,,by ,,the ,,author ,,for ,,greatest ,,height4 ,a very lightly built model with a very low aspect ratio1 and screw giving a very powerful dynamic thrust1 and carrying rather a large amount of rubber4 ,climbs in left-handed spirals4 ,directional control1 that the model is launched in some specified direction1 and must pass as near as possible over some indicated point4 ,the models are practically always launched by hand4 #c4 ,those who desire to win prizes at such competitions would do well to keep the following points well in mind4 #a4 ,the distance is always measured in a straight line4 ,it is absolutely essential that your model should be capable of flying 7approximately7 straight4 ,to see1 as ,i have done1 model after model fly quite #aej to #bjj yards and finish within #ej yards of the starting-point 7credited flight #ej yards7 is useless1 and a severe strain on one's temper and patience4 ,illustration3 ,,fig4 #ed4--,,the ,,gamage ,,challenge ,,cup4 ,open ,competition for longest flight4 ,crystal ,palace1 ,july #bg4 ,won by ,mr4 ,e4,w4 ,twining4 ,illustration3 ,,fig4 #ee4--,,medal ,,won ,,by ,,the ,,author ,,in ,,the ,,same ,,competition4 #b4 ,always enter more than one model1 there nearly always is an entrance fee2 never mind the extra shilling or so4 ,go in to win4 #c4 ,it is not necessary that these models should be replicas of one another4 ,on some days a light fabric-covered model might stand the best chance2 on another day1 a swift flying wooden or metal aerofoil4 ,against the wind the latter have an immense advantage2 also if the day be a gusty one4#ea #d4 ,always make it a point of arriving early on the ground1 so that you can make some trial flights beforehand4 ,every ground has its local peculiarities of air currents1 etc4 #e4 ,always be ready in time1 or you may be disqualified4 ,if you are flying a twin-screw model use a special winder1 so that both propellers are wound up at the same time1 and take a competent friend with you as assistant4 #f4 ,for all-round efficiency nothing but a good all-round model1 which can be absolutely relied on to make a dozen 7approximately7 equivalent flights1 is any good4 #g4 ,in an open distance competition1 unless you have a model which you can rely on to make a minimum flight of #bjj yards1 do not enter unless you know for certain that none of the crack flyers will be present4 #h4 ,do not neglect the smallest detail likely to lead to success2 be prepared with spare parts1 extra rubber1 one or two handy tools1 wire1 thread1 etc4 ,before a lecture1 that prince of experimentalists1 ,faraday1 was always careful to see that the stoppers of all the bottles were loose1 so that there should be no delay or mishap4 #i4 ,if the rating of the model be by weight 7#a oz41 #b oz41 #d oz41 etc47 and not area1 use a model weighing from #aj oz4 to a pound4 #aj4 ,if there is a greatest height prize1 a helicopter model should win it4#eb 7,the writer has attained an altitude of between three and four hundred feet with such47 ,the altitude was arrived at by observation1 not guesswork4 #aa4 ,it is most important that your model should be able to land without damage1 and1 as far as possible1 on an even keel2 do not omit some form of skid or shock-absorber with the idea of saving weight1 more especially if your model be a biplane1 or the number of flights may be restricted to the number one4 #ab4 ,since the best gliding angle and flying angle are not the same1 being1 say1 #g in the former case and #a-c1 say1 in the latter1 an adjustable angle might in some cases be advantageous4 #ac4 ,never turn up at a competition with a model only just finished and practically untested which you have flown only on the morning of the competition1 using old rubber and winding to #ejj turns2 result1 a flight of #bej yards1 say4 ,arrived on the competition ground you put on new rubber and wind to #gej turns1 and expect a flight of a quarter of a mile at least2 result #gj yards1 measured in a straight line from the starting-point4 #ad4 ,directional control is the most difficult problem to overcome with any degree of success under all adverse conditions1 and #ae per cent41 in the writer's opinion1 is far too low a percentage2 by directional ,i include flying in a straight line2 personally ,i would mark for all-round efficiency3 7,a7 distance and stability1 #ej per cent42 7,b7 directional control1 #cj per cent42 7,c7 duration of flight1 #bj per cent4 ,in ,a the competitor would launch his model in any direction2 in ,b as directed by the judges4 ,no separate flights required for ,c4 ,,footnotes3 #dh ,the better way1 undoubtedly1 is to allow the competitor to choose his direction1 the starting circle only to be fixed4 #di ,or #aj per cent4 for duration of flight4 #ej ,in another competition1 held under the rules and regulations of the ,kite and ,model ,aeroplane ,association for the best all-round model1 open to the world1 for machines not under #b sq4 ft4 of surface1 the tests 7#ej marks for each7 were3--,a4 ,longest flight in a straight line4 ,b4 ,circular flight to the right4 ,c4 ,circular flight to the left4 ,d4 ,stability and landing after a flight4 ,e4 ,excellence in building of the model4 #ea ,on the assumption that the model will fly straight4 #eb ,if permitted to enter2 if not see ,fig4 #ec4 ,,chapter ,,xiv4 ,,useful ,,notes1 ,,tables1 ,,formul1 ,,etc4 #a4 ,,comparative ,,velocities4 ,miles per hr4 ,feet per sec4 ,metres per sec4 #aj #adg #ddgj #ae #bb #fgje #bj #bid #hidj #be #cfg #aaagf #cj #dd #acdaa #ce #eac #aefdf #b4 ,a metre #cicgjgi inches4 ,in order to convert3-- ,metres into inches multiply by #cicg feet #cbh yards #aji miles #jjjjfbad ,miles per hour into ft4 per min4 multiply by #hhj min4 sec4 #hhj hr4 into kilometres per hr4 #afjic metres per sec4 #jddgjb ,pounds into grammes multiply by #deceic kilogrammes #jdecf #h4 ,total surface of a cylinder circumference of base height #b area of base4 ,area of a circle square of diameter #jghed4 ,area of a circle square of rad4 #cadaei4 ,area of an ellipse product of axes #jghed4 ,circumference of a circle diameter #cadaei4 ,solidity of a cylinder height area of base4 ,area of a circular ring sum of diameters difference of diameters #jghed4 ,for the area of a sector of a circle the rule is3--,as #cfj 3 number of degrees in the angle of the sector 33 area of the sector 3 area of circle4 ,to find the area of a segment less than a semicircle3--,find the area of the sector which has the same arc1 and subtract the area of the triangle formed by the radii and the chord4 ,the areas of corresponding figures are as the squares of corresponding lengths4 #d4 #a mile #afji kilometres4 #a kilometre #ajic yards4 #a oz4 #bhce grammes4 #a lb4 #decei #a lb4 #jdec kilogrammes4 #bh lb4 #abg #aab lb4 #ejh #bbdj lb4 #ajaf #a kilogram #bbjdf lb4 #a gram #jjjbb lb4 #a sq4 in4 #fde sq4 millimetres4 #a sq4 ft4 #jjibi sq4 metres4 #a sq4 yard #jhcf #a sq4 metre #ajgfd sq4 ft4 #e4 ,one atmosphere #adg lb4 per sq4 in4 #baaf lb4 per sq4 ft4 #gfj millimetres of mercury4 ,a column of water #bc ft4 high corresponds to a pressure of #a lb4 per sq4 in4 #a ,h4,p4 #cc1jjj ft4-lb4 per min4 #gdf watts4 ,volts amperes watts4 pi #cadaf4 g #cbahb ft4 per sec4 at ,london4 #f4 ,,table ,,of ,,equivalent ,,inclinations4 ,rise4 ,angle in ,degs4 #a in #cj #aia #a #be #bbi #a #bj #bhg #a #ah #cah #a #af #ceh #a #ad #dji #a #ab #dgh #a #aj #egc #a #i #fch #a #h #gah #a #g #hbb #a #f #if #a #e #aaec #a #d #addh #a #c #aide #a #b #cjjj #a square root#b #dejj #g4 ,,table ,,of ,,skin ,,friction4 ,per sq4 ft4 for various speeds and surface lengths4 ---------------------------------------- ---------------------------- ,velocity of ,wind #a ft4 ,plane #b ft4 ,plane #d ft4 ,plane #h ft4 ,plane ---------------------------------------- ---------------------------- #aj #jjaab #jjaje #jjaja #jjjifg #ae #jjbcg #jjbbf #jjbae #jjbje #bj #jjdjb #jjchd #jjcfe #jjcdi #be #jjfjf #jjegi #jjeea #jjebg #cj #jjhej #jjhaj #jjggb #jjgcf #ce #jaacj #jajh #jajc #jjih ---------------------------------------- ---------------------------- ,this table is based on ,dr4 ,zahm's experiments and the equation f #jjjjjjgghl-#jjgv#ahe ,where f skin friction per sq4 ft42 l length of surface2 v velocity in feet per second4 ,in a biplane model the head resistance is probably from twelve to fourteen times the skin friction2 in a racing monoplane from six to eight times4 #h4 ,,table ,i4--7,,metals74 ---------------------------------------- ---------------- ,material ,specific ,elasticity ,e,a ,tenacity ,gravity per sq4 in4 ---------------------------------------- ---------------- ,magnesium #agd #bb1jjj- #cb1jjj ,magnalium,b #bd-beg #ajb ,aluminium- ,copper,c #bhb #ed1ggc ,aluminium #bf #aaa #bf1ece ,iron #gg 7about7 #bi #ed1jjj ,steel #gh 7about7 #cb #ajj1jjj ,brass #gh-hd #ae #ag1ejj ,copper #hh #cf #cc1jjj ,mild ,steel #gh #cj #fj1jjj ---------------------------------------- ---------------- ,a ,e in millions of lb4 per sq4 in4 ,b ,magnalium is an alloy of magnesium and aluminium4 ,c ,aluminium #id per cent41 copper #f per cent4 7the best percentage71 a #f per cent4 alloy thereby doubles the tenacity of pure aluminium with but #e per cent4 increase of density4 ---------------------------------------- ---------------- #i4 ,,table ,,ii4--,,wind ,,pressures4 p kv4 k coefficient 7mean value taken7 #jjc 7miles per hour7 #jjjaf ft4 per second4 p pressure in lb4 per sq4 ft4 v velocity of wind4 ,miles per hr4 ,ft4 per sec4 ,lb4 per sq4 ft4 #aj #adg #jcjj #ab #agf #jdcb #ad #bje #jehh #af #bce #jgfh #ah #bfd #jigb #bj #bice #abjj #be #cfg #ahge #cj #dci #bgjj #ce #eac #cfge #aj4 ,representing normal pressure on a plane surface by #a2 pressure on a rod 7round section7 is #jf2 on a symmetrical elliptic cross section 7axes #b3a7 is #jb 7approx474 ,similar shape1 but axes #f3a1 and edges sharpened 7see ch4 ii41 #e71 is only #jje1 or #a_/bj1 and for the body of minimum resistance 7see ch4 ii41 #d7 about #a_/bd4 #aa4 ,,table ,,iii4--,,lift ,,and ,,drift4 ,on a well shaped aerocurve or correctly designed cambered surface4 ,aspect ratio #de4 ,inclination4 ,ratio ,lift to ,drift4 #j #ai3a #bhg #ae3a #ceh #af3a #dji #ad3a #dgh #ab3a #egc #if3a #gah #gi3a ,wind velocity #dj miles per hour4 7,the above deduced from some experiments of ,sir ,hiram ,maxim47 ,at a velocity of #cj miles an hour a good aerocurve should lift #ba oz4 to #bd oz4 per sq4 ft4 #ab4 ,,table ,,iv4--,,lift ,,and ,,drift4 ,on a plane aerofoil4 ,n ,p7#b sin alpha_/#a sin alpha7 ,inclination4 ,ratio ,lift to ,drift4 #a #ehc3a #b #bib3a #c #aic3a #d #adc3a #e #aad3a #f #ie3a #g #hj3a #h #gj3a #i #fc3a #aj #eg3a ,p #bkd ,,av sin alpha4 ,a useful formula for a single plane surface4 ,p pressure supporting the plane in pounds per square foot1 k a constant #jjjc in miles per hour1 d the density of the air4 ,a the area of the plane1 ,v relative velocity of translation through the air1 and alpha the angle of flight4 ,transposing we have ,,av ,p_/7#bkd sin alpha7 ,if ,p and alpha are constants2 then ,,av a constant or area is inversely as velocity squared4 ,increase of velocity meaning diminished supporting surface 7and so far as supporting surface goes71 diminished resistance and skin friction4 ,it must be remembered1 however1 that while the work of sustentation diminishes with the speed1 the work of penetration varies as the cube of the speed4 #ac4 ,,table ,v4--,,timber4 ,column ,headings3 ,a4 ,material ,b4 ,specific ,gravity ,c4 ,weight per ,cub4 ,ft4 in ,lb4 ,d4 ,strength per ,sq4 ,in4 in ,lb4 ,e4 ,ultimate ,breaking ,load 7,lb47 span #a' x #a x #a ,f4 ,relative ,resilience in ,bending ,g4 ,modulus of ,elasticity in millions of ,lb4 per ,sq4 ,in4 for ,bending ,h4 ,relative ,value4 ,bending ,strength compared with ,weight ---------------------------------------- --------------------- ,a ,b ,c ,d ,e ,f ,g ,h ---------------------------------------- --------------------- ,ash #gi #dc-eb #ad1jjj-ag1jjj #fbb #dfi #aee #acj ,bamboo #be;,a #fcjjec #cjg #cbj ,beech #fi #dc #aj1jjj-ab1jjj #hej #afe #aih ,birch #ga #de #ae1jjj #eej #cbh #abb ,box #abh #hj #bj1jjj-bc1jjj #hae #ajb ,cork #bd #ae ,fir 7,norway ,spruce7 #ea #cb #i1jjj-aa1jjj #dej #cja #agj #adj ,american ,hickory #di #aa1jjj #hjj #cdg #bdj #afc ,honduras ,mahogany #ef #ce #bj1jjj #gej #cdj #afj #bad ,maple #fh #dd #aj1fjj #gej #agj ,american ,white ,pine #db #be #aa1hjj #dej #bcg #aci #ahj ,lombardy ,poplar #bd #g1jjj #eej #bhi #jggbbi ,american ,yellow ,poplar #dd #aj1jjj #cfc #adj ,satinwood #if #fj #a1jcc #agb ,spruce #ej #ca #ab1djj #dej #ade ,tubular ,ash1 t #a_/h d #dg #cej #aee ---------------------------------------- --------------------- t thickness3 d diameter4 ,a ,given elsewhere as #ee and #bb1ejj 7t #a_/c;d71 evidently regarded as solid4 #ad4--;,formula connecting the ,weight ,lifted in ,pounds per ,square ,foot and the ,velocity4--,the empirical formula ,w 7,v,c7_/g ,where ,w weight lifted in lb4 per sq4 ft4 ,v velocity in ft4 per sec4 ,c a constant #jjbe4 g #cbb1 or #cb approx4 may be used for a thoroughly efficient model4 ,this gives 7approximately7 #a lb4 per sq4 ft4 lift at #be miles an hour4 #ba oz4 #cj #f oz4 #ae #d oz4 #ab #bg oz4 #aj ,remember the results work out in feet per second4 ,to convert 7approximately7 into miles per hour multiply by #b_/c4 #ae4 ,formula connecting ,models of ,similar ,design1 but ,different ,weights4 ,d proportional to square root,w4 or in models of similar design the distances flown are proportional to the square roots of the weights4 7,derived from data obtained from ,clarke's flyers47 ,for models from #a oz4 to #bd-cj oz4 the formula appears to hold very well4 ,for heavier models it appears to give the heavier model rather too great a distance4 ,since this was deduced a #a oz4 ,clarke model of somewhat similar design but longer rubber motor has flown #gej ft4 at least2 it is true the design is not1 strictly speaking1 similar1 but not too much reliance must be placed on the above4 ,the record for a #a oz4 model to date is over #cjj yards 7with the wind1 of course71 say #gej ft4 in calm air4 #af4 ,power and ,speed4--,the following formula1 given by ,mr4 ,l4 ,blin ,desbleds1 between these is-- ,w_/,w#j 7#cv#j7_/7dv7 7v_/v#j74 ,where v#j speed of minimum power ,w#j work done at speed v#j4 ,w work done at speed v4 ,making v #bv#j1 i4e4 doubling the speed of minimum power1 and substituting1 we have finally ,w 7#b-c_/h7,w#j i4e4 the speed of an aeroplane can be doubled by using a power #b-c_/h times as great as the original one4 ,the speed of minimum power being the speed at which the aeroplane must travel for the minimum expenditure of power4 #ag4 ,the thrust of the propeller has evidently to balance the ,aerodynamic resistance ,r ,the head resistance 7including skin friction7 ,s ,now according to ,renard's theorem1 the power absorbed by ,r ,s is a minimum when ,s ,r_/#c4 ,having built a model1 then1 in which the total resistance 7#d_/c7,r4 ,this is the thrust which the propeller should be designed to give4 ,now supposing the propeller's efficiency to be #hj per cent41 then ,p--the minimum propulsion power 7#d_/c7,r #ajj_/hj #ajj_/ge v4 ,where #be per cent4 is the slip of the screw1 v the velocity of the aeroplane4 #ah4 ,to determine experimentally the ,static ,thrust of a ,propeller4--,useful for models intended to raise themselves from the ground under their own power1 and for helicopters4 ,the easiest way to do this is as follows3 ,mount the propeller on the shaft of an electric motor1 of sufficient power to give the propeller #ajjj to #aejj revolutions per minute2 a suitable accumulator or other source of electric energy will be required1 a speedometer or speed counter1 also a voltmeter and ammeter4 ,place the motor in a pair of scales or on a suitable spring balance 7the former is preferable71 the axis of the motor vertical1 with the propeller attached4 ,rotate the propeller so that the air current is driven upwards4 ,when the correct speed 7as indicated by the speed counter7 has been attained1 notice the difference in the readings if a spring balance be used1 or1 if a pair of scales1 place weights in the scale pan until the downward thrust of the propeller is exactly balanced4 ,this gives you the thrust in ounces or pounds4 ,note carefully the voltage and amperage1 supposing it is #h volts and #aj amperes #hj watts4 ,remove the propeller and note the volts and amperes consumed to run the motor alone1 i4e4 to excite itself1 and overcome friction and air resistance2 suppose this to be #h volts and #b amperes #af2 the increased load when the propeller is on is therefore #hj - #af #fd watts4 ,all this increased power is not1 however1 expended on the propeller4 ,the lost power in the motor increases as ,c,r4 ,r resistance of armature and ,c current4 ,if we deduct #aj per cent4 for this then the propeller is actually driven by #ef watts4 ,now #gdf watts #a h4p4 therefore #ef_/gdf #a_/ac h4p4 approx4 at the observed number of revolutions per minute4 #ai4 ,n4,b4--,the h4p4 required to drive a propeller varies as the cube of the revolutions4 ,proof4--,double the speed of the screw1 then it strikes the air twice as hard2 it also strikes twice as much air1 and the motor has to go twice as fast to do it4 #bj4 ,to compare one model with another the formula ,weight velocity 7in ft4 per sec47_/horse-power is sometimes useful4 #ba4 ,a ,horse-power is #cc1jjj lb4 raised one foot in one minute1 or #eej lb4 one foot in one second4 ,a clockwork spring raised #a lb4 through #d ft4 in #c seconds4 ,what is its h4p48 #a lb4 through #d ft4 in #c seconds is #a lb4 #ij ft4 #a minute4 therefore ,work done is #ij ft4-lb4 #ij_/ccjjj #jjjbgbg h4p4 ,the weight of the spring was #f oz4 7this is taken from an actual experiment71 i4e4 this motor develops power at the rate of #jjjbgbg h4p4 for #c seconds only4 #bb4 ,to ,ascertain the ,h4,p4 of a ,rubber ,motor4 ,supposing a propeller wound up to #bej turns to run down in #ae seconds1 i4e4 at a mean speed of #abjj revolutions per minute or #bj per second4 ,suppose the mean thrust to be #b oz41 and let the pitch of the propeller be #a foot4 ,then the number of foot-pounds of energy developed 7#b oz4 #abjj revols4 #a ft4 7pitch77 _/ #af oz4 #aej ft4-lb4 per minute4 ,but the rubber motor runs down in #ae seconds4 therefore ,energy really developed is 7#aej #ae7 _/ #fj #cge ft4-lb4 ,the motor develops power at rate of #aej_/ccjjj #jjjdede h4p41 but for #ae seconds only4 #bc4 ,foot-pounds of ,energy in a ,given ,weight of ,rubber 7experimental determination of74 ,length of rubber #cf yds4 ,weight #b-g_/af oz4 ,number of turns #bjj4 #ab oz4 were raised #ai ft4 in #e seconds4 i4e4 lb4 was raised #ai #ab ft4 in #a minute4 i4e4 #a lb4 was raised #ai #c #c ft4 in #a minute4 #aga ft4 in #a minute4 i4e4 #aga ft4-lb4 of energy per minute4 ,but actual time was #e seconds4 therefore ,actual energy developed by #b-g_/af oz4 of rubber of #cf yards1 i4e4 #cf strands #a yard each at #bjj turns is #aga_/ab ft4-lb4 #ad ft4-lb4 ,this allows nothing for friction or turning the axle on which the cord was wound4 ,ball bearings were used2 but the rubber was not new and twenty turns were still unwound at the end of the experiment4 ,now allowing for friction1 etc4 being the same as on an actual model1 we can take of a ft4-lb4 for the unwound amount and estimate the total energy as #ae ft4-lb4 as a minimum4 ,the energy actually developed being at the rate of #jjjee h4p41 or #a_/bjj of a h4p4 if supposed uniform4 #bd4 ,the actual energy derivable from #a lb4 weight of rubber is stated to be #cjj ft4-lb4 ,on this basis #b-g_/af oz4 should be capable of giving #deg ft4-lb4 of energy1 i4e4 three times the amount given above4 ,now the motor-rubber not lubricated was only given #bjj turns--lubricated #djj could have been given it1 #fjj probably before rupture--and the energy then derivable would certainly have been approximating to #de ft4-lb41 i4e4 #cfbe4 ,now on the basis of #cjj ft4-lb4 per lb4 a weight of oz4 7the amount of rubber carried in one-ouncers7 gives #i ft4-lb4 of energy4 ,now assuming the gliding angle 7including weight of propellers7 to be #a in #h2 a perfectly efficient model should be capable of flying eight times as great a distance in a horizontal direction as the energy in the rubber motor would lift it vertically4 ,now #i ft4-lb4 of energy will lift #a oz4 #aed ft4 ,therefore theoretically it will drive it a distance 7in yards7 of 7#h #aed7_/c #dajf yards4 ,now the greatest distance that a #a oz4 model has flown in perfectly calm air 7which never exists7 is not known4 ,flying with the wind #ejj yards is claimed4 ,admitting this what allowance shall we make for the wind2 supposing we deduct half this1 viz4 #bej yards4 ,then1 on this assumption1 the efficiency of this one ouncer works out 7in perfectly still air7 at #fa per cent4 ,the gliding angle assumption of #a in #h is rather a high one1 possibly too high2 all the writer desires to show is the method of working out4 ,mr4 ,t4,w4,k4 ,clarke informs me that in his one-ouncers the gliding angle is about #a in #e4 #be4 ,to ,test ,different ,motors or ,different ,powers of the ,same ,kind of ,motor4--,test them on the same machine1 and do not use different motors or different powers on different machines4 #bf4 ,efficiency of a ,model4--,the efficiency of a model depends on the weight carried per h4p4 #bg4 ,efficiency of ,design4--,the efficiency of some particular design depends on the amount of supporting surface necessary at a given speed4 #bh4 ,naphtha ,engines1 that is1 engines made on the principle of the steam engine1 but which use a light spirit of petrol or similar agent in their generator instead of water with the same amount of heat1 will develop twice as much energy as in the case of the ordinary steam engine4 #bi4,petrol ,motors4 ,horse-power4 ,no4 of ,cylinders4 ,weight4 ,single #d lb4 to #f #a ,double #i #cj4 ,the ,horse-power of ,model ,petrol ,motors4--,formula for rating of the above4 7,r4,p4,m4 revolutions per minute47 ,h4,p4 77,bore7 stroke no4 of cylinders ,r4,p4,m47_/#ab1jjj ,if the right-hand side of the equation gives a less h4p4 than that stated for some particular motor1 then it follows that the h4p4 of the motor has been over-estimated4 ,illustration3 ,,fig4 #ef4 #cj;,a4 ,relation between ,static ,thrust of ,propeller and ,total ,weight of ,model4--,the thrust should be approx4 of the weight4 #ca4 ,how to find the ,height of an ,inaccessible ,object by ,means of ,three ,observations taken on the ,ground 7supposed flat7 in the same ,straight ,line4--,let ,a1 ,c1 ,b be the angular elevations of the object ,d1 as seen from these points1 taken in the same straight line4 ,let the distances ,b ,c1 ,c ,a and ,a ,b be a1 b1 c respectively4 ,and let required height ,p ,d h2 then by trigonometry we have 7see ,fig4 #ef7 h abc_/7a cot,a - c cot,c b cot,b74 #cb4 ,formula for calculating the ,i4,h4,p4 7indicated horse-power7 of a single-cylinder double-acting steam-engine4 ,indicated h4p4 means the h4p4 actually exerted by the steam in the cylinder without taking into account engine friction4 ,brake h4p4 or effective h4p4 is the actual h4p4 delivered by the crank shaft of the engine4 ,i4,h4,p4 7#b ,s ,r ,a ,p7_/#cc1jjj4 ,where ,s stroke in feet4 ,r revolutions per minute4 ,a area of piston in inches4 ,p mean pressure in lb4 exerted per sq4 in4 on the piston4 ,the only difficulty is the mean effective pressure2 this can be found approximately by the following rule and accompanying table4 ,,table ,,vi4 ---------------------------------------- ---------------- ,cut-off ,constant ,cut-off ,constant ,cut-off ,constant ---------------------------------------- ---------------- #a_/f #eff #c_/h #gga #b_/c #iag #a_/e #fjc #d #ghi #g #ibf #a_/d #fei #a_/b #hdg #c_/d #icg #c #gjh #f #hie #h #idd #a_/c #gdc #e_/h #ijd #g_/h #iea ---------------------------------------- ---------------- ,rule4--,add #adg to gauge pressure of boiler1 this giving 'absolute steam pressure1' multiply this sum by the number opposite the fraction representing the point of cut-off in the cylinder in accompanying table4 ,subtract #ag from the product and multiply the remainder by #ji4 ,the result will be very nearly the ,m4,e4,p4 7,r4,m4 de ,vignier47 ,,footnote3 #ec ,given elsewhere as #ee and #bb1ejj 7t #a_/c d71 evidently regarded as solid4 ,,appendix ,a4 ,,some ,,models ,,which ,,have ,,won ,,medals ,,at ,,open ,,competitions4 ,illustration3 ,,fig4 #eg4--,,the ,g4,p4,b4 ,,smith ,,model4 ,the model shown in ,fig4 #eg has won more competition medals than any other4 ,it is a thoroughly well designed#ed and well constructed model4 ,originally a very slow flyer1 the design has been simplified1 and although by no means a fast flyer1 its speed has been much accelerated4 ,originally a one-propeller machine1 it has latterly been fitted with twin propellers1 with the idea of obtaining more directional control2 but in the writer's opinion1 speaking from personal observation1 with but little1 if any1 success4 ,the steering of the model is effected by canting the elevator4 ,originally the machine had ailerons for the purpose1 but these were removed owing1 ,i understand1 to their retarding the speed of the machine4 ,in every competition in which this machine has been entered it has always gained very high marks for stability4 ,illustration3 ,,fig4 #eh4--,,the ,,gordon-,,jones ,,dihedral ,,biplane4 ,up to the time of writing it has not been provided with anything in the nature of fins or rudder4 ,fig4 #eh is a biplane very much after the type of the model just alluded to1 but the one straight and one curved aerofoil surfaces are here replaced by two parallel aerofoils set on a dihedral angle4 ,the large size of the propeller should be noted2 with this the writer is in complete agreement4 ,he has not unfortunately seen this model in actual flight4 ,the scientifically designed and beautifully made models illustrated in ,fig4 #ei are so well known that any remarks on them appear superfluous4 ,their efficiency1 so far as their supporting area goes1 is of the highest1 as much as #ba oz4 per square foot having been carried4 ,illustration3 ,,fig4 #ei4--,,messrs4 ,t4,w4,k4 ,,clarke ,,and ,,co4',s ,,model ,,flyers4 ,for illustrations1 etc41 of the ,fleming-,williams model1 see ch4 v41 #bc4 7,fig4 #fj47 ,this is another well-constructed and efficient model1 the shape and character of the aerofoil surfaces much resembling those of the ,french toy monoplane ,,al-,,ma 7see #d1 ch4 vii471 but they are supported and held in position by quite a different method1 a neat little device enabling the front plane to become partly detached on collision with any obstacle4 ,the model is provided with a keel 7below the centre of gravity71 and rudder for steering2 in fact1 this machine especially claims certainty of directional control4 ,the writer has seen a number of flights by this model1 but it experiences1 like other models1 the greatest difficulty in keeping straight if the conditions be adverse4 ,the model which will do this is1 in his opinion1 yet to be evolved4 ,the small size of the propellers is1 of course1 in total disagreement with the author's ideas4 ,all the same1 the model is in many respects an excellent one1 and has flown over #cjj yards at the time of writing4 ,illustration3 ,,fig4 #fj4--,,the ,,ding ,,sayers ,,monoplane4 ,more than a year ago the author made a number of models with triangular-shaped aerofoils1 using umbrella ribs for the leading edge and steel piano wire for the trailing1 but has latterly used aerofoils of the elongated ellipse shape4 ,fig4 #fa is an illustration of one of the author's latest models which won a ,bronze ,medal at the ,long ,distance ,open ,competition1 held at the ,crystal ,palace on ,july #bg1 #aiaj1 the largest and most keenly contested competition held up to that date4 ,the best and straightest flight against the wind was made by this model4 ,on the morning of the competition a flight of about #cbj yards 7measured in a straight line7 was made on ,mitcham ,common1 the model being launched against the wind so as to gain altitude1 and then flying away with the breeze behind the writer4 ,duration of flight #ej seconds4 ,the following are the chief particulars of the model3--,weight1 #g oz4 ,area of supporting surface1 #a-a_/c sq4 ft4 ,total length1 #d ft4 ,span of main aerofoil1 #be in4 ,aspect ratio1 #d 3 #a4 ,diameter of propeller1 #ad in4 ,two strand geared rubber motor1 carrying altogether #bh strands of #a_/af square rubber cord #dc in4 long4 ,the propeller was originally a ,venna1 but with the weight reduced by one-third1 and considerable alteration made in its central contours4 ,the front skid of steel pianoforte wire1 the rear of jointless cane wire tipped2 the rear skid was a necessity in order to protect the delicate gearing mechanism1 the weight of which was reduced to a minimum4 ,illustration3 ,,fig4 #fa4--,,the ,,author',s ,,grasshopper ,,model4 ,the very large diameter of the propeller should be noted1 being #ef per cent4 of the span4 ,the fin1 high above the centre of gravity1 was so placed for transverse stability and direction4 ,at the rear of the fin was a rudder4 ,the small amount of rubber carried 7for a long distance machine7 should also be noted1 especially when allowing for friction in gearing1 etc4 ,the central rod was a penny bamboo cane1 the large aerofoil of jointless cane and ,hart's fabric1 and the front aerofoil of steel wire surfaced with the same material4 ,,london3 ,,printed ,,by ,,william ,,clowes ,,and ,,sons1 ,,limited1 ,,great ,,windmill ,,street1 ,w41 ,,and ,,duke ,,street1 ,,stamford ,,street1 ,s4,e4 ,,footnote3 #ed ,the design is patented4 ,october1 #aiaj ,a ,,short ,,list ,,of ,,scientific ,,books ,,published ,,and ,,sold ,,by ,e4 ,f4,n4 ,,spon1 ,limited1 #eg ,haymarket1 ,london1 ,s4,w4 ,,sole ,,english ,,agents for the ,books of-- ,,myron ,c4 ,,clark1 ,,new ,,york ,,the ,,business ,,code ,,company1 ,,chicago ,,spon ,,chamberlain1 ,,new ,,york ,,page ,,aeronautics #b ,,agriculture #b ,,architecture #c ,,artillery #e ,,bridges ,,and ,,roofs #e ,,building #c ,,cement ,,and ,,concrete #g ,,civil ,,engineering #h ,,dictionaries #aa ,,domestic ,,economy #ab ,,drawing #ac ,,electrical ,,engineering #ad ,,foreign ,,exchange #ai ,,gas ,,and ,,oil ,,engines #bj ,,gas ,,lighting #bj ,,historical2 ,,biographical #ba ,,horology #bb ,,hydraulics #bb ,,industrial ,,chemistry #bd ,,irrigation #bg ,,logarithm ,,tables #bh ,,manufactures #bd ,,marine ,,engineering #bh ,,materials #cj ,,mathematics #ca ,,mechanical ,,engineering #cc ,,metallurgy #cf ,,metric ,,tables #ch ,,mineralogy ,,and ,,mining #ch ,,municipal ,,engineering #de ,,naval ,,architecture #bh ,,organisation #dj ,,physics #da ,,price ,,books #db ,,railway ,,engineering #dc ,,sanitation #de ,,structural ,,design #de ,,telegraph ,,codes #dg ,,warming2 ,,ventilation #dg ,,water ,,supply #dh ,,workshop ,,practice #di ,,useful ,,tables #eb ,,miscellaneous #ec ,full particulars post free on application4 ,all books are bound in cloth unless otherwise stated4 ,,note3 ,the ,prices in this ,catalogue apply to books sold in the ,united ,kingdom only4 ,,aeronautics ,the ,atmosphere3 its characteristics and dynamics4 ,by ,f4,j4,b4 ,,cordeiro4 ,with #ce illus4 #abi pp4 medium #hvo4 7,new ,york1 #aiaj7 net #aj #f ,theory and ,practice of ,model ,aeroplaning4 ,by ,v4,e4 ,,johnson4 #fa illus4 #aej pp4 crown #hvo4 7#aiaj7 net #c #f ,how to ,build a #bj-;ft4 ,biplane ,glider4 ,by ,a4,p4 ,,morgan4 #ca illus4 #fj pp4 crown #hvo1 limp4 7,s4 ,c4 ,,series1 ,,no4 #ad47 7,new ,york1 #aiji7 net #a #f ,flight-,velocity4 ,by ,a4 ,,samuelson4 #d plates1 #db pp4 #hvo1 sewed4 7#aijf7 net #b #j ,resistance of ,air and the ,question of ,flying4 ,by ,a4 ,,samuelson4 #bc illus4 #cf pp4 #hvo1 sewed4 7#aije7 net #b #j ,,agriculture4 ,hemp4 ,a ,practical ,treatise on the ,culture for ,seed and ,fibre4 ,by ,s4,s4 ,,boyce4 #ac illus4 #aab pp4 crown #hvo4 7,new ,york1 #aijj7 net #b #j ,the ,fertilisation of ,tea4 ,by ,g4,a4 ,,cowie4 ,with #ag illus4 #fh pp4 crown #hvo1 sewed4 7#aijh7 net #b #f ,farm ,drainage4 ,by ,h4,f4 ,,french4 #ajj illus4 #bhd pp4 crown #hvo4 7,new ,york1 #aijd7 net #d #f ,talks on ,manures4 ,by ,j4 ,,harris4 ,new edition1 #cff pp4 crown #hvo4 7,new ,york1 #ahic7 net #f #f ,coffee1 its ,culture and ,commerce in all ,countries4 ,by ,c4,g4,w4 ,,lock4 #aa plates1 #bgd pp4 crown #hvo4 7#ahhh7 #ab #f ,sugar1 a ,handbook for ,planters and ,refiners4 ,by the late ,j4,a4 ,r4 ,,newlands and ,b4,e4,r4 ,,newlands4 #bcf illus4 #hgf pp4 demy #hvo4 7,london1 #aiji7 net #a #e #j ,hops1 their ,cultivation1 ,commerce and ,uses4 ,by ,p4,l4 ,,simmonds4 #adc pp4 crown #hvo4 7#ahgg7 #d #f ,the ,future of ,cocoa-,planting4 ,by ,h4 ,,hamel ,,smith4 ,with illustrations1 #ie pp4 crown #hvo1 sewed4 7#aijh7 net #a #j ,estate ,fences1 their ,choice1 ,construction and ,cost4 ,by ,a4 ,,vernon4 ,re-issue1 #aej illus4 #dbj pp4 #hvo4 7#aiji7 net #h #f ,,architecture ,,and ,,building4 ,the ,hydropathic ,establishment and its ,baths4 ,by ,r4,o4 ,,allsop4 #h plates1 #ajg pp4 demy #hvo4 7#ahia7 #e #j ,the ,turkish ,bath1 its ,design and ,construction4 ,by ,r4,o4 ,,allsop4 #bg illus4 #aeb pp4 demy #hvo4 7#ahij7 #f #j ,public ,abattoirs1 their ,planning1 ,design and ,equipment4 ,by ,r4,s4 ,,ayling4 #cc plates1 #ajj pp4 demy #dto4 7#aijh7 net #h #f ,the ,builder's ,clerk4 ,by ,t4 ,,bales4 ,second edition1 #ib pp4 fcap4 #hvo4 7#aijd7 #a #f ,glossary of ,technical ,terms used in ,architecture and the ,building ,trades4 ,by ,g4,j4 ,,burns4 #acf pp4 crown #hvo4 7#ahie7 #c #f ,chimney ,design and ,theory4 ,by ,w4,w4 ,,christie4 ,second edition1 #ed illus4 #bjj pp4 crown #hvo4 7,new ,york1 #aijb7 net #ab #f ,approximate ,estimates4 ,by ,t4,e4 ,,coleman4 ,third edition1 #dha pp4 oblong #cbmo1 leather4 7#aijg7 net #e #j ,stable ,sanitation and ,construction4 ,by ,t4,e4 ,,coleman4 #ahc illus4 #bbf pp4 crown #hvo4 7#ahig7 net #f #j ,architectural ,examples in ,brick1 ,stone1 ,wood and ,iron4 ,by ,w4 ,,fullerton4 ,third edition1 #bde plates1 #bed pp4 demy #dto4 7#aijh7 net #ae #j ,bricklaying ,system4 ,by ,f4,b4 ,,gilbreth4 ,fully illustrated1 #cba pp4 #hvo4 7,new ,york1 #aiji7 net #ab #f ,field ,system4 ,by ,f4,b4 ,,gilbreth4 #aid pp4 #abmo leather4 7,new ,york1 #aijh7 net #ab #f ,the ,building ,trades ,pocket ,book4 ,compiled by ,r4 ,,hall4 #abmo4 ,with interchangeable diary net #a #f ,ditto ditto1 in leather net #b #f ,the ,clerk of ,works' ,vade ,mecum4 ,by ,g4,g4 ,,hoskins4 ,seventh edition1 #eb pp4 fcap4 #hvo4 7#aija7 #a #f ,a ,handbook of ,formul1 ,tables1 and ,memoranda1 for ,architectural ,surveyors and others engaged in ,building4 ,by ,j4,t4 ,,hurst4 ,fifteenth edition1 #eab pp4 royal #cbmo1 roan4 7#aije7 net #e #j ,quantity ,surveying1 for the ,use of ,surveyors1 ,architects1 ,engineers and ,builders4 ,by ,j4 ,,leaning4 ,fifth edition1 #icf pp4 demy #hvo4 7#aijd7 net #a #e #j ,obstruction to ,light4 ,a ,graphic ,method of determining ,problems of ,ancient ,lights4 ,by ,h4,b4 ,,molesworth4 #i folding plates1 #dto4 7#aijb7 net #f #j ,suburban ,houses4 ,a series of practical plans4 ,by ,j4,h4 ,,pearson4 #df plates and #ab pp4 text1 crown #dto4 7#aije7 net #g #f ,solid ,bitumens1 their ,physical and ,chemical ,properties and ,chemical ,analysis4 ,by ,s4,f4 ,,peckham4 #bc illus4 #cbd pp4 #hvo4 7,new ,york1 #aiji7 net #a #a #j ,roman ,architecture1 ,sculpture and ,ornament4 ,by ,g4,b4 ,,piranesi4 #bjj plates1 reproduced in facsimile from the original4 #b vols4 ,imperial folio1 in wrappers4 7#aijj7 net #b #b #j ,the ,seven ,periods of ,english ,architecture1 defined and illustrated4 ,by ,e4 ,,sharpe4 ,third edition1 #bj steel plates1 royal #hvo4 7#ahhh7 #ab #f ,our ,factories1 ,workshops and ,warehouses1 their ,sanitary and ,fire-,resisting ,arrangements4 ,by ,b4,h4 ,,thwaite4 #ahc illus4 #bhb pp4 crown #hvo4 7#ahhb7 #i #j ,elementary ,principles of ,carpentry4 ,by ,t4 ,,tredgold and ,j4,t4 ,,hurst4 ,eleventh edition1 #dh plates1 #eag pp4 crown #hvo4 7#aijd7 #ab #f ,practical ,stair ,building and ,handrailing4 ,by ,w4,h4 ,,wood4 #cb plates1 #ia pp4 crown #dto4 7#ahid7 #aj #f ,spons' ,architects' and ,builders' ,pocket ,price-,book1 ,memoranda1 ,tables and ,prices4 ,edited by ,,clyde ,,young4 ,revised by ,,stanford ,m4 ,,brooks4 ,illustrated1 #eeb pp4 #afmo1 leather cloth 7size #f in4 by #c in4 by in4 thick74 ,issued annually net #c #j ,heating ,engineers' ,quantities4 ,by ,w4,l4 ,,white and ,g4,m4 ,,white4 #d plates1 #cc pp4 folio4 7#aiaj7 net #aj #f ,,artillery4 ,guns and ,gun ,making ,material4 ,by ,g4 ,,ede4 ,crown #hvo4 7#ahhi7 #f #j ,treatise on ,application of ,wire to ,construction of ,ordnance4 ,by ,j4,a4 ,,longridge4 #ahj pp4 #hvo4 7#ahhd7 #a #e #j ,the ,progress of ,artillery3 ,naval ,guns4 ,by ,j4,a4 ,,longridge4 #hvo1 sewed4 7#ahif7 #b #j ,the ,field ,gun of the ,future4 ,by ,j4,a4 ,,longridge4 #hvo1 sewed4 7#ahib7 #b #f ,,bridges1 ,,arches1 ,,roofs1 ,,and ,,structural ,,design4 ,strains in ,ironwork4 ,by ,,henry ,,adams4 ,fourth edition1 #h plates1 #fe pp4 crown #hvo4 7#aijd7 #e #j ,the ,practical ,designing of ,structural ,ironwork4 ,by ,,henry ,,adams4 #ac plates1 #aid pp4 #hvo4 7#ahid7 #h #f ,designing ,ironwork4 ,by ,,henry ,,adams4 ,second series4 #hvo1 sewed4 ,part ,i4 ,a ,steel ,box ,girder4 7#ahid7 net #j #i ,,ii4 ,built-up ,steel ,stanchions4 7#aija7 net #a #c ,,iii4 ,cisterns and ,tanks4 7#aijb7 net #a #j ,,iv4 ,a ,fireproof ,floor4 7#aijc7 net #a #j ,a ,practical ,treatise on ,segmental and ,elliptical ,oblique or ,skew ,arches4 ,by ,g4,j4 ,,bell4 ,second edition1 #ag plates1 #abe pp4 royal #hvo4 7#aijf7 net #a #a #j ,economics of ,construction in relation to ,framed ,structures4 ,by ,r4,h4 ,bow4 ,third thousand1 #af plates1 #hh pp4 #hvo4 7#ahgc7 #e #j ,theory of ,voussoir ,arches4 ,by ,prof4 ,w4 ,,cain4 ,third edition1 #bja pp4 #ahmo1 boards4 7,new ,york1 #aije7 net #b #j ,new ,formul for the ,loads and ,deflections of ,solid ,beams and ,girders4 ,by ,w4 ,,donaldson4 ,second edition1 #hvo4 7#ahgb7 #d #f ,plate ,girder ,railway ,bridges4 ,by ,m4 ,,fitzmaurice4 #d plates1 #ajd pp4 #hvo4 7#ahie7 #f #j ,pocket ,book of ,calculations in ,stresses4 ,by ,e4,m4 ,,george4 #ff illus4 #adj pp4 royal #cbmo1 half roan4 7#ahie7 #c #f ,strains on ,braced ,iron ,arches and ,arched ,iron ,bridges4 ,by ,a4,s4 ,,heaford4 #ci pp4 #hvo4 7#ahhc7 #f #j ,tables for ,roof ,framing4 ,by ,g4,d4 ,,inskip4 ,second edition1 #dea pp4 #hvo1 leather4 7,new ,york1 #aije7 net #ab #f ,stresses in ,girder and ,roof ,frames1 for both dead and live loads1 by simple ,multiplication1 etc4 ,by ,f4,r4 ,,johnson4 #bh plates1 #bae pp4 crown #hvo4 7#ahid7 #f #j ,a ,graphical ,method for ,swing ,bridges4 ,by ,b4,f4 ,,la ,,rue4 #d plates1 #ajd pp4 #ahmo1 boards4 7,new ,york1 #ahib7 net #b #j ,notes on ,cylinder ,bridge ,piers and the ,well ,system of ,foundations4 ,by ,j4 ,,newman4 #add pp4 #hvo4 7#ahic7 #f #j ,a ,new ,method of ,graphic ,statics applied in the ,construction of ,wrought ,iron ,girders4 ,by ,e4 ,,olander4 #af plates1 small folio4 7#ahhg7 #aj #f ,reference ,book for ,statical ,calculations4 ,by ,f4 ,,ruff4 ,with diagrams1 #adj pp4 crown #hvo4 7#aijf7 net #e #j ,the ,strength and ,proportion of ,riveted ,joints4 ,by ,b4,b4 ,,stoney4 #hg pp4 #hvo4 7#ahhe7 #e #j ,the ,anatomy of ,bridgework4 ,by ,w4,h4 ,,thorpe4 #ajc illus4 #aij pp4 crown #hvo4 7#aijf7 net #f #j ,,cement ,,and ,,concrete4 ,portland ,cement3 its ,manufacture1 ,testing and ,use4 ,by ,d4,b4 ,,butler4 ,second edition1 #ig illus4 #cif pp4 demy #hvo4 7#aije7 net #af #j ,theory of ,steel-,concrete ,arches and of ,vaulted ,structures4 ,by ,w4 ,,cain4 ,fourth edition1 #bg illus4 #bab pp4 #ahmo1 boards4 7,new ,york1 #aijf7 net #b #j ,cement ,users' and ,buyers' ,guide4 ,by ,,calcare4 #aae pp4 #cbmo1 cloth4 7#aija7 net #a #f ,diagrams for ,designing ,reinforced ,concrete ,structures4 ,by ,g4,f4 ,,dodge4 #ca illus4 #ajd pp4 oblong folio4 7,new ,york1 #aiaj7 net #ag #j ,cements1 ,mortars1 and ,concretes2 their ,physical properties4 ,by ,m4,s4 ,,falk4 #gh illus4 #agf pp4 #hvo4 7,new ,york1 #aijd7 net #aj #f ,concrete ,construction1 ,methods and ,cost4 ,by ,h4,p4 ,,gillette and ,c4,s4 ,,hill4 #caj illus4 #fij pp4 #hvo4 7,new ,york1 #aijh7 net #a #a #j ,engineers' ,pocket-,book of ,reinforced ,concrete4 ,by ,e4,l4 ,,heidenreich4 #afd illus4 #cfd pp4 crown #hvo1 leather1 gilt edges4 7,new ,york1 #aiji7 net #ab #f ,concrete ,inspection4 ,by ,c4,s4 ,,hill4 ,illustrated1 #agi pp4 #abmo4 7,new ,york1 #aiji7 net #d #f ,reinforced ,concrete4 ,by ,e4 ,,mcculloch4 #bh illus4 #abh pp4 crown #hvo4 7,new ,york1 #aijh7 net #f #f ,concrete and ,reinforced ,concrete4 ,by ,h4,a4 ,,reid4 #gae illus4 #hhd pp4 royal #hvo4 7,new ,york1 #aijg7 net #ba #j ,theory and ,design of ,reinforced ,concrete ,arches4 ,by ,a4 ,,reuterdahl4 #da illus4 #abf pp4 #hvo4 7,new ,york1 #aijh7 net #h #f ,practical ,cement ,testing4 ,by ,w4,p4 ,,taylor4 ,with #adb illus4 #cbi pp4 demy #hvo4 7,new ,york1 #aijf7 net #ab #f ,concrete ,bridges and ,culverts4 ,by ,h4,g4 ,,tyrrell4 #ff illus4 #bea pp4 crown #hvo1 leather net #ab #f ,,civil ,,engineering4 ,,canals1 ,,surveying4 7,see also ,,irrigation and ,,water ,,supply47 ,practical ,hints to ,young ,engineers ,employed on ,indian ,railways4 ,by ,a4,w4,c4 ,,addis4 ,with #ad illus4 #aed pp4 #abmo4 7#aiaj7 net #c #f ,levelling1 ,barometric1 ,trigonometric and ,spirit4 ,by ,i4,o4 ,,baker4 ,second edition1 #ae illus4 #ade pp4 #ahmo1 boards4 7,new ,york1 #aijc7 44 net #b #j ,notes on ,instruments best suited for ,engineering ,field ,work in ,india and the ,colonies4 ,by ,w4,g4 ,,bligh4 #fe illus4 #bah pp4 #hvo4 7#ahii7 #g #f ,the ,sextant and other ,reflecting ,mathematical ,instruments4 ,by ,f4,r4 ,,brainard4 #cc illus4 #abj pp4 #ahmo1 boards4 7,new ,york1 #ahia7 net #b #j ,practical ,designing of ,retaining ,walls4 ,by ,prof4 ,w4 ,,cain4 ,fifth edition1 #ad illus4 #agb pp4 #ahmo1 boards4 7,new ,york1 #aijh7 net #b #j ,the ,maintenance of ,macadamised ,roads4 ,by ,t4 ,,codrington4 ,second edition1 #ahf pp4 #hvo4 7#ahib7 #g #f ,retaining ,walls in ,theory and ,practice4 ,by ,t4,e4 ,,coleman4 #ajd illus4 #afj pp4 crown #hvo4 7#aiji7 net #e #j ,the ,barometrical ,determination of ,heights4 ,by ,f4,j4,b4 ,,cordeiro4 ,crown #hvo1 limp leather4 7,new ,york1 #ahih7 net #d #f ,on ,curved ,masonry ,dams4 ,by ,w4,b4 ,,coventry4 #hvo1 sewed4 7#ahid7 #b #j ,a ,practical ,method of ,determining the ,profile of a ,masonry ,dam4 ,by ,w4,b4 ,,coventry4 #hvo1 sewed4 7#ahid7 #b #f ,the ,stresses on ,masonry ,dams 7oblique sections74 ,by ,w4,b4 ,,coventry4 #hvo1 sewed4 7#ahid7 #b #j ,tables for facilitating the ,calculation of ,earthworks4 ,by ,d4 ,,cunningham4 #abj pp4 royal #hvo #aj #f ,handbook of ,cost ,data for ,contractors and ,engineers4 ,by ,h4,p4 ,,gillette4 #ahed pp4 crown #hvo1 leather1 gilt edges4 7,new ,york1 #aiaj7 net #a #a #j ,rock ,excavation1 ,methods and ,cost4 ,by ,h4,p4 ,,gillette4 #ef illus4 #cgf pp4 crown #hvo4 7,new ,york1 #aijd7 net #ab #f ,high ,masonry ,dams4 ,by ,e4,s4 ,,gould4 ,with illus4 #hh pp4 #ahmo1 boards4 7,new ,york1 #ahig7 net #b #j ,grace's ,tables for ,curves1 with hints to young engineers4 #h figures1 #dc pp4 oblong #hvo4 7#aijh7 net #e #j ,grace's ,earthwork ,tables4 #cf double-page tables1 #dto4 7#aijg7 net #ab #f ,railway ,tunnelling in ,heavy ,ground4 ,by ,c4 ,,gripper4 #c plates1 #ff pp4 royal #hvo4 7#ahgi7 #g #f ,levelling and its ,general ,application4 ,by ,t4 ,,holloway4 ,second edition1 #ec illus4 #adg pp4 #hvo4 7#ahie7 #e #j ,waterways and ,water ,transport in different ,countries4 ,by ,j4,s4 ,,jeans4 #ee illus4 #ebj pp4 #hvo4 7#ahij7 net #i #j ,table of ,barometrical ,heights to #bj1jjj ,feet4 ,by ,w4,h4 ,,mackesy1 with some practical suggestions by ,sir ,guildford ,molesworth4 #a plate1 #bd pp4 royal #cbmo4 7#ahhb7 #c #j ,aid ,book to ,engineering ,enterprise4 ,by ,e4 ,,matheson4 ,third edition1 illustrated1 #iaf pp4 medium #hvo1 buckram4 7#ahih7 #a #d #j ,a ,treatise on ,surveying4 ,by ,r4,e4 ,,middleton and ,o4 ,,chadwick4 ,second edition1 royal #hvo4 ,part ,i4 #aa plates1 #bif pp4 7#aijd7 #aj #f ,,ii4 ,fully illustrated1 #ccd pp4 7#aijf7 #aj #f ,a ,pocket ,book of ,useful ,formul and ,memoranda1 for ,civil and ,mechanical ,engineers4 ,by ,sir ,g4,l4 ,,molesworth and ,h4,b4 ,,molesworth4 ,with an ,electrical ,supplement by ,w4,h4 ,,molesworth4 ,twenty-sixth edition1 #gfj illus4 #ija pp4 royal #cbmo1 ,french morocco1 gilt edges4 7#aijh7 net #e #j ,the ,pocket ,books of ,sir ,g4,l4 ,molesworth and ,j4,t4 ,hurst1 printed on ,india paper and bound in one vol4 ,royal #cbmo1 russia1 gilt edges4 net #aj #f ,metallic ,structures3 ,corrosion and ,fouling and their ,prevention4 ,by ,j4 ,,newman4 ,illustrated1 #che pp4 crown #hvo4 7#ahif7 #i #j ,scamping ,tricks and ,odd ,knowledge occasionally practised upon ,public ,works4 ,by ,j4 ,,newman4 ,new impression1 #abi pp4 crown #hvo4 7#aijh7 net #b #j ,earthwork ,slips and ,subsidences on ,public ,works4 ,by ,j4 ,,newman4 #bdj pp4 crown #hvo4 7#ahij7 #g #f ,co-ordinate ,geometry as applied to ,land ,surveying4 ,by ,w4 ,,pilkington4 #e illus4 #dd pp4 #abmo4 7#aiji7 net #a #f ,diagrams for the ,graphic ,calculation of ,earthwork ,quantities4 ,by ,a4,h4 ,,roberts4 ,ten cards1 fcap4 in cloth case net #aj #f ,pioneering4 ,by ,f4 ,,shelford1 illustrated4 #hh pp4 crown #hvo4 7#aiji7 net #c #j ,topographical ,surveying4 ,by ,g4,j4 ,,specht4 ,second edition1 #b plates and #bh illus4 #baj pp4 #ahmo1 boards4 7,new ,york1 #ahih7 net #b #j ,spons' ,dictionary of ,engineering1 ,civil1 ,mechanical1 ,military and ,naval4 #aj1jjj illus4 #dcjj pp4 super royal #hvo4 7#ahgd1 ,supplement issued in #ahha74 ,complete with ,supplement1 in #aa divisions net #c #aj #j ,ditto ditto in #d vols4 net #c #c #j ,surveying and ,levelling ,instruments4 ,by ,w4,f4 ,,stanley4 ,third edition1 #cgb illus4 #efb pp4 crown #hvo4 7#aija7 #g #f ,surveyor's ,handbook4 ,by ,t4,u4 ,,taylor4 #aaf illus4 #caj pp4 crown #hvo1 leather1 gilt edges4 7,new ,york1 #aijh7 net #h #f ,logarithmic ,land ,measurement4 ,by ,j4 ,,wallace4 #cb pp4 royal #hvo4 7#aiaj7 net #e #j ,hints on ,levelling ,operations4 ,by ,w4,h4 ,,wells4 ,second edition1 #hvo1 sewed4 7#ahij7 net #a #j ,the ,drainage of ,fens and ,low ,lands by ,gravitation and ,steam ,power4 ,by ,w4,h4 ,,wheeler4 #h plates1 #age pp4 #hvo4 7#ahhh7 #ab #f ,stadia ,surveying1 the theory of ,stadia ,measurements4 ,by ,a4 ,,winslow4 ,fifth edition1 #adh pp4 #ahmo1 boards4 7,new ,york1 #aijb7 net #b #j ,handbook on ,tacheometrical ,surveying4 ,by ,c4 ,,xydis4 #ee illus4 #c plates1 #fc pp4 #hvo4 7#aiji7 net #f #j ,,dictionaries4 ,technological ,dictionary in the ,english1 ,spanish1 ,german and ,french ,languages4 ,by ,d4 ,,carlos ,,huelin ,y ,,arssu4 ,crown #hvo4 ,vol4 ,i4 ,,english-,,spanish-,,german-,,french4 #fji pp4 7#aijf7 net #aj #f ,vol4 ,,ii4 ,,german-,,english-,,french-,,spanish4 #gbj pp4 7#aijh7 net #aj #f ,vol4 ,,iii4 ,,french-,,german-,,spanish-,,english4 ,in preparation4 ,vol4 ,,iv4 ,,spanish-,,french-,,english-,,german4 #gej pp4 7#aiaj7 net #aj #f ,english-,french and ,french-,english ,dictionary of the ,motor-,car1 ,cycle and ,boat4 ,by ,f4 ,,lucas4 #aga pp4 crown #hvo4 7#aije7 net #e #j ,spanish-,english ,dictionary of ,mining ,terms4 ,by ,f4 ,,lucas4 #gh pp4 #hvo4 7#aije7 net #e #j ,english-,russian and ,russian-,english ,engineering ,dictionary4 ,by ,l4 ,,meycliar4 #ajj pp4 #afmo4 7#aiji7 net #b #f ,reed's ,polyglot ,guide to the ,marine ,engine1 in ,english1 ,french1 ,german and ,norsk4 ,second edition1 oblong #hvo4 7#aijj74 net #f #j ,,domestic ,,economy4 ,food ,adulteration and its ,detection4 ,by ,j4,p4 ,,battershall4 #ab plates1 #cbh pp4 demy #hvo4 7,new ,york1 #ahhg7 #ae #j ,how to ,check ,electricity ,bills4 ,by ,s4,w4 ,,borden4 #da illus4 #ed pp4 crown #hvo4 7,new ,york1 #aijg7 net #b #j ,practical ,hints on ,taking a ,house4 ,by ,h4,p4 ,,boulnois4 #ga pp4 #ahmo4 7#ahhe7 #a #f ,the ,cooking ,range1 its ,failings and ,remedies4 ,by ,f4 ,,dye4 #eb pp4 fcap4 #hvo1 sewed4 7#ahhh7 #j #f ,the ,kitchen ,boiler and ,water ,pipes4 ,by ,h4 ,,grimshaw4 #hvo1 sewed4 7#ahhg7 net #a #j ,cookery and ,domestic ,management1 including economic and middle class ,practical ,cookery4 ,by ,k4 ,,mellish4 #ef coloured plates and #dda illus4 #ihg pp4 super-royal #hvo4 7#aija7 net #af #j ,spons' ,household ,manual4 #bej illus4 #ajdc pp4 demy #hvo4 7#aijb7 #g #f ,ditto ditto half-bound ,french morocco #i #j ,handbook of ,sanitary ,information for ,householders4 ,by ,r4,s4 ,,tracy4 #cc illus4 #aad pp4 #ahmo4 7,new ,york1 #aijj7 #b #f ,,drawing4 ,the ,ornamental ,penman's1 ,engraver's and ,sign ,writer's ,pocket ,book of ,alphabets4 ,by ,b4 ,,alexander4 ,oblong #abmo1 sewed #j #f ,the ,draughtsman's ,handbook of ,plan and ,map ,drawing4 ,by ,g4,g4 ,,andre4 #hg illus4 and #cd plain and coloured plates1 #afb pp4 crown #dto4 7#ahia7 #i #j ,slide ,valve ,diagrams3 a ,french ,method for their ,construction4 ,by ,l4 ,,bankson4 #ahmo1 boards4 7,new ,york1 #ahib7 4 4 4 net #b #j ,a ,system of ,easy ,lettering4 ,by ,j4,h4 ,,cromwell4 ,with ,supplement by ,g4 ,,martin4 ,sixth thousand1 oblong #hvo4 7,new ,york1 #aijj7 net #b #j ,plane ,geometrical ,drawing4 ,,by ,r4,c4 ,,fawdry4 ,illustrated1 #ahe pp4 crown #hvo4 7#aija7 net #c #j ,twelve ,plates on ,projection ,drawing4 ,by ,o4 ,,gueth4 ,oblong #dto4 7,new ,york1 #aijc7 net #c #j ,hints on ,architectural ,draughtsmanship4 ,by ,g4,w4,t4 ,,hallatt4 ,fourth edition1 #hj pp4 #ahmo4 7#aijf7 net #a #f ,a ,first ,course of ,mechanical ,drawing 7,tracing74 ,by ,g4 ,,halliday4 ,oblong #dto1 sewed #b #j ,drawings for ,medium-sized ,repetition ,work4 ,by ,r4,d4 ,,spinney4 ,with #dg illus4 #acj pp4 #hvo4 7#aiji7 net #c #f ,mathematical ,drawing ,instruments4 ,by ,w4,f4 ,,stanley4 ,seventh edition1 #bfe illus4 #cgj pp4 crown #hvo4 7#aijj7 #e #j ,,electrical ,,engineering4 ,practical ,electric ,bell ,fitting4 ,by ,f4,c4 ,,allsop4 ,tenth edition1 #ahf illus4 including #h folding plates1 #ahe pp4 crown #hvo4 7#aijc7 #c #f ,telephones3 their ,construction and ,fitting4 ,by ,f4,c4 ,,allsop4 ,eighth edition1 #ahd illus4 #bbb pp4 crown #hvo4 7#aiji7 #c #f ,thermo-electric ,reactions and ,currents between ,metals in ,fused ,salts4 ,by ,t4 ,,andrews4 #hvo1 sewed4 7#ahif7 #a #j ,auto-,transformer ,design4 ,by ,a4,h4 ,,avery4 #be illus4 #fj pp4 #hvo4 7#aiji7 net #c #f ,principles of ,electric ,power 7,continuous ,current7 for ,mechanical ,engineers4 ,by ,a4,h4 ,,bate4 #fc illus4 #bjd pp4 crown #hvo4 7#aije7 7,,finsbury ,,technical ,,manual7 net #d #f ,practical ,construction of ,electric ,tramways4 ,by ,,william ,r4 ,,bowker4 #ic illus4 #aai pp4 #hvo4 7#aijc7 net #f #j ,design and ,construction of ,induction ,coils4 ,by ,a4,f4 ,,collins4 #aee illus4 #bgb pp4 demy #hvo4 7,new ,york1 #aiji7 net #ab #f ,switchboard ,measuring ,instruments for ,continuous and ,polyphase ,currents4 ,by ,j4,c4 ,,connan4 #aag illus4 #aej pp4 #hvo1 cloth4 7#aijh7 net #e #j ,electric ,cables1 their ,construction and ,cost4 ,by ,d4 ,,coyle and ,f4,j4 ,o4 ,,howe4 ,with many diagrams and #baf tables1 #dfg pp4 crown #hvo1 leather4 7#aiji7 net #ae #j ,management of ,electrical ,machinery4 ,by ,f4,b4 ,,crocker and ,s4,s4 ,,wheeler4 ,eighth edition1 #aca illus4 #bbc pp4 crown #hvo4 7,new ,york1 #aiji7 net #d #f ,electric ,lighting3 ,a ,practical ,exposition of the ,art4 ,by ,f4,b4 ,,crocker4 ,royal #hvo4 7,new ,york47 ,vol4 ,i4 ,the ,generating ,plant4 ,sixth edition1 #bac illus4 #dgj pp4 7#aijd7 net #ab #f ,vol4 ,,ii4 ,distributing ,systems and ,lamps4 ,second edition1 #cia illus4 #eje pp4 7#aije7 net #ab #f ,the ,care and ,management of ,ignition ,accumulators4 ,by ,h4,h4,u4 ,,cross4 #ab illus4 #gd pp4 crown #hvo1 limp4 7,s4 ,c4 ,,series1 ,,no4 #ai47 7#aiaj7 net #a #f ,elementary ,telegraphy and ,telephony4 ,by ,,arthur ,,crotch4 #bch illus4 #bbc pp4 #hvo4 7#aijc47 7,,finsbury ,,technical ,,manual7 net #d #f ,electricity and ,magnetism in ,telephone ,maintenance4 ,by ,g4,w4 ,,cummings4 #de illus4 #acg pp4 #hvo4 7,new ,york1 #aijh7 4 44 net #f #f ,grouping of ,electric ,cells4 ,by ,w4,f4 ,,dunton4 #d illus4 #ej pp4 fcap4 #hvo4 7#aijf7 net #a #f ,,magnets ,,and ,,electric ,,currents4 ,by ,prof4 ,j4,a4 ,,fleming4 ,second edition1 #acf illus4 #dag pp4 crown #hvo 7#aijb7 net #e #j ,notes on ,design of ,small ,dynamo4 ,by ,,george ,,halliday4 ,second edition1 #h plates1 #hvo4 7#ahie7 #b #f ,practical ,alternating ,currents and ,power ,transmission4 ,by ,n4 ,,harrison4 #agb illus4 #cge pp4 crown #hvo4 7,new ,york1 #aijf7 #aj #f ,making ,wireless ,outfits4 ,by ,n4 ,,harrison4 #bg illus4 #fa pp4 crown #hvo1 limp4 7,s4 ,c4 ,,series1 ,,no4 #aa47 7,new ,york1 #aiji7 net #a #f ,wireless ,telephone ,construction4 ,by ,n4 ,,harrison4 #dc illus4 #gc pp4 crown #hvo1 limp4 7,s4 ,c4 ,series1 ,no4 #ab47 7,new ,york1 #aiji7 net #a #f ,the ,phoenix ,fire ,office ,rules for ,electric ,light and ,electrical ,power ,installations4 ,by ,m4 ,,heaphy4 ,thirty-seventh edition1 #hvo1 sewed4 7#aijh7 #j #f ,testing ,telegraph ,cables4 ,by ,colonel ,v4 ,,hoskioer4 ,third edition1 crown #hvo4 7#ahhi7 #d #f ,long ,distance ,electric ,power ,transmission4 ,by ,r4,w4 ,,hutchinson4 #acf illus4 #cde pp4 crown #hvo4 7,new ,york1 #aijg7 net #ab #f ,theory and ,practice of ,electric ,wiring4 ,by ,w4,s4 ,,ibbetson4 #aai illus4 #cff pp4 crown #hvo4 7#aiji7 net #e #j ,practical ,electrical ,engineering for ,elementary ,students4 ,by ,w4,s4 ,,ibbetson4 ,with #fa illus4 #aee pp4 crown #hvo4 7#aiaj7 net #c #j ,general ,rules recommended for ,wiring for the ,supply of ,electrical ,energy4 ,issued by ,,the ,,institution ,,of ,,electrical ,,engineers4 #hvo1 sewed4 7,revised1 ,april #aijg7 net #j #f ,form of ,model ,general ,conditions recommended by ,,the ,,institution ,,of ,,electrical ,,engineers for use in connection with ,electrical ,contracts4 #hvo1 sewed4 7#aijf7 net #a #j ,a ,handbook of ,electrical ,testing4 ,by ,h4,r4 ,,kempe4 ,seventh edition1 #bhe illus4 #gjf pp4 demy #hvo4 7#aijh7 net #ah #j ,application of ,electricity to ,railway ,working4 ,by ,w4,e4 ,,langdon4 #adb illus4 and #e plates1 #cdg pp4 #hvo4 7#ahig7 #aj #f ,how to ,become a ,competent ,motorman4 ,by ,v4,b4 ,,livermore and ,j4 ,,williams4 #de illus4 #beb pp4 #abmo4 7,new ,york1 #aijc7 net #d #f ,electromagnets1 their design and construction4 ,by ,a4,n4 ,,mansfield4 #cf illus4 #aee pp4 #ahmo1 boards4 7,new ,york1 #aija7 net #b #j ,telephone ,construction1 ,methods and ,cost4 ,by ,c4 ,,mayer4 ,with ,appendices on the cost of materials and labour by ,j4,c4 ,,slippy4 #ajc illus4 #bhd pp4 crown #hvo4 7,new ,york1 #aijh7 net #ab #f ,induction ,coils4 ,by ,n4,h4 ,,schneider4 ,second edition1 #gi illus4 #bhe pp4 crown #hvo4 7,new ,york1 #aija7 net #d #f ,electric ,gas ,lighting4 ,by ,n4,h4 ,,schneider4 #eg illus4 #aja pp4 #abmo4 7,s4 ,c4 ,,series1 ,,no4 #h47 7,new ,york1 #aija7 net #b #j ,how to ,install ,electric ,bells1 ,annunciators and ,alarms4 ,by ,n4,h4 ,,schneider4 #ei illus4 #fc pp4 crown #hvo1 limp4 7,s4 ,c4 ,,series1 ,,no4 #b47 7,new ,york1 #aije7 net #a #f ,modern ,primary ,batteries1 their construction1 use and maintenance4 ,by ,n4,h4 ,,schneider4 #ed illus4 #id pp4 crown #hvo1 limp4 7,s4 ,c4 ,,series1 ,,no4 #a47 7,new ,york1 #aije7 net #a #f ,practical ,engineers' ,handbook on the ,care and ,management of ,electric ,power ,plants4 ,by ,n4,h4 ,,schneider4 #bjc illus4 #bgd pp4 crown #hvo4 7,new ,york1 #aijf7 net #e #j ,electrical ,circuits and ,diagrams1 illustrated and explained4 ,by ,n4,h4 ,,schneider4 #hvo1 limp4 7,s4 ,c4 ,,series1 ,,nos4 #c ,,and #d47 7,new ,york7 ,part #a4 #bag illus4 #gb pp4 7#aije7 net #a #f ,part #b4 #gc pp4 7#aiji7 net #a #f ,electrical ,instruments and ,testing4 ,by ,n4,h4 ,,schneider4 ,third edition4 #acc illus4 #bci pp4 crown #hvo4 7,new ,york1 #aijg7 net #d #f ,experimenting with ,induction ,coils4 ,by ,n4,h4 ,,schneider4 #bf illus4 #gc pp4 crown #hvo1 limp4 7,s4 ,c4 ,,series1 ,,no4 #e47 7,new ,york1 #aijf7 net #a #f ,study of ,electricity for ,beginners4 ,by ,n4,h4 ,,schneider4 #ed illus4 #hh pp4 crown #hvo1 limp4 7,s4 ,c4 ,,series1 ,,no4 #f47 7,new ,york1 #aije7 net #a #f ,practical ,electrics3 a ,universal ,handybook on ,every ,day ,electrical ,matters4 ,seventh edition1 #abf illus4 #ace pp4 #hvo4 7,s4 ,c4 ,,series1 ,,no4 #ac47 7,new ,york1 #aijb7 net #a #f ,the ,voltaic ,accumulator3 an elementary treatise4 ,by ,e4 ,,reynier4 ,translated from the ,french by ,j4,a4 ,,berly4 #fb illus4 #bjb pp4 #hvo #i #j ,dry ,batteries3 how to ,make and ,use them4 ,by a ,,dry ,,battery ,,expert4 ,with additional notes by ,n4,h4 ,,schneider4 #cj illus4 #ei pp4 crown #hvo1 sewed4 7,s4 ,c4 ,,series1 ,,no4 #g47 7,new ,york1 #aije7 net #a #f ,the ,diseases of ,electrical ,machinery4 ,by ,e4 ,,schulz4 ,edited1 with a ,preface1 by ,prof4 ,s4,p4 ,,thompson4 #db illus4 #hd pp4 crown #hvo net #b #j ,electric ,toy-,making4 ,by ,t4,o4 ,,sloane4 ,fifteenth edition1 #gj illus4 #ahc pp4 crown #hvo4 7,new ,york1 #aijc7 net #d #f ,electricity ,simplified4 ,by ,t4,o4 ,,sloane4 ,tenth edition1 #bi illus4 #aeh pp4 crown #hvo4 7,new ,york1 #aija7 net #d #f ,how to become a ,successful ,electrician4 ,by ,t4,o4 ,,sloane4 ,third edition1 illustrated1 crown #hvo4 7,new ,york1 #ahii7 net #d #f ,electricity3 its ,theory1 ,sources and ,applications4 ,by ,j4,t4 ,,sprague4 ,third edition1 #aji illus4 #feh pp4 crown #hvo4 7#ahib7 net #g #f ,telegraphic ,connections4 ,by ,c4 ,,thom and ,w4,h4 ,,jones4 #bj plates1 #ei pp4 oblong #hvo4 7,new ,york1 #ahib7 net #c #f ,rntgen ,rays and ,phenomena of the ,anode and ,cathode4 ,by ,e4,p4 ,,thompson and ,w4,a4 ,,anthony4 #aje illus4 #bjd pp4 #hvo4 7,new ,york1 #ahif7 net #d #f ,dynamo ,electric ,machinery4 ,by ,prof4 ,s4,p4 ,,thompson4 ,seventh edition1 demy #hvo4 7,,finsbury ,,technical ,,manual47 ,vol4 ,i4 ,continuous-,current ,machinery4 ,with #d coloured and #cj folding plates1 #egc illus4 #ihd pp4 7#aijd7 net #a #aj #j ,vol4 ,,ii4 ,alternating ,current ,machinery4 #ae coloured and #bd folding plates1 #edf illus4 #ijj pp4 7#aije7 net #a #aj #j ,design of ,dynamos 7,continuous ,currents74 ,by ,prof4 ,s4,p4 ,,thompson4 #d coloured and #h folding plates1 #bdc pp4 demy #hvo4 7#aijc7 net #ab #j ,schedule for ,dynamo ,design1 issued with the above4 #f;d4 each1 #ds4 per doz41 or #ahs4 per #ajj net ,curves of ,magnetic ,data for ,various ,materials4 ,a reprint on transparent paper for office use of ,plate ,l from ,dynamo ,electric ,machinery1 and measuring #be in4 by #af in4 net #j #g ,the ,electromagnet4 ,by ,c4,r4 ,,underhill4 #fg illus4 #aei pp4 crown #hvo4 7,new ,york1 #aijc7 net #f #f ,practical ,guide to the ,testing of ,insulated ,wires and ,cables4 ,by ,h4,l4 ,,webb4 ,fifth edition1 #ch illus4 #aah pp4 crown #hvo4 7,new ,york1 #aijb7 net #d #f ,,foreign ,,exchange4 ,english ,prices with ,russian ,equivalents 7at ,fourteen ,rates of ,exchange74 ,english prices per lb41 with equivalents in roubles and kopecks per pood4 ,by ,a4 ,,adiassewich4 #ahb pp4 fcap4 #cbmo1 roan4 7#aijh7 net #a #j ,english ,prices with ,german ,equivalents 7at ,seven ,rates of ,exchange74 ,english prices per lb41 with equivalents in marks per kilogramme4 ,by ,st4 ,,koczorowski4 #ie pp4 fcap4 #cbmo1 roan4 7#aiji7 net #a #j ,english ,prices with ,spanish ,equivalents4 ,at ,seven ,rates of ,exchange4 ,english prices per lb41 with equivalents in pesetas per kilogramme4 ,by ,s4 ,,lambert4 #ie pp4 #cbmo1 roan4 7#aiaj7 net #a #j ,english ,prices with ,french ,equivalents 7at ,seven ,rates of ,exchange74 ,english prices per lb4 to francs per kilogramme4 ,by ,h4,p4 ,,mccartney4 #ig pp4 #cbmo1 roan4 7#aijg7 net #a #j ,principles of ,foreign ,exchange4 ,by ,e4 ,,matheson4 ,fourth edition1 #ed pp4 #hvo1 sewed4 7#aije7 net #j #c ,,gas ,,and ,,oil ,,engines4 ,the ,theory of the ,gas ,engine4 ,by ,d4 ,,clerk4 ,edited by ,f4,e4 ,,idell4 ,third edition1 #ai illus4 #ahj pp4 #ahmo1 boards4 7,new ,york1 #aijc7 net #b #j ,the ,design and ,construction of ,oil ,engines4 ,by ,a4,h4 ,,goldingham4 ,third edition1 #aab illus4 #bfj pp4 crown #hvo4 7,new ,york1 #aiaj7 net #aj #f ,gas ,engine in ,principle and ,practice4 ,by ,a4,h4 ,,goldingham4 #ajg illus4 #aie pp4 #hvo1 cloth4 7,new ,york1 #aijg7 net #f #f ,practical ,hand-,book on the ,care and ,management of ,gas ,engines4 ,by ,g4 ,,lieckfeld4 ,third edition1 square #afmo4 7,new ,york1 #ahif7 #c #f ,elements of ,gas ,engine ,design4 ,by ,s4,a4 ,,moss4 #aig pp4 #ahmo1 boards4 7,new ,york1 #aijg7 net #b #j ,gas and ,petroleum ,engines4 ,a ,manual for ,students and ,engineers4 7,,finsbury ,,technical ,,manual47 ,by ,prof4 ,w4 ,,robinson4 ,third edition in preparation ,,gas ,,lighting4 ,gas ,analyst's ,manual 7incorporating ,hartley's ,gas ,analyst's ,manual and ,gas ,measurement74 ,by ,j4 ,,abady4 #ajb illustrations1 #egf pp4 demy #hvo4 7#aijb7 net #ah #j ,gas ,works3 their ,arrangement1 ,construction1 ,plant and ,machinery4 ,by ,f4 ,,colyer4 #ca folding plates1 #acd pp4 #hvo4 7#ahhd7 net #h #f ,transactions of the ,institution of ,gas ,engineers4 ,edited by ,,walter ,t4 ,,dunn1 ,secretary4 ,published annually4 #hvo net #aj #f ,lighting by ,acetylene4 ,by ,f4 ,,dye4 #ge illus4 #bjj pp4 crown #hvo4 7#aijb7 net #f #j ,a ,comparison of the ,english and ,french ,methods of ,ascertaining the ,illuminating ,power of ,coal ,gas4 ,by ,a4,j4 ,,van ,,eijndhoven4 ,illustrated1 crown #hvo4 7#ahig7 #d #j ,gas ,lighting and ,gas ,fitting4 ,by ,w4,p4 ,,gerhard4 ,second edition1 #aij pp4 #ahmo1 boards4 7,new ,york1 #ahid7 net #b #j ,a ,treatise on the ,comparative ,commercial ,values of ,gas ,coals and ,cannels4 ,by ,d4,a4 ,,graham4 #c plates1 #ajj pp4 #hvo4 7#ahhb7 #d #f ,the ,gas ,engineer's ,laboratory ,handbook4 ,by ,j4 ,,hornby4 ,third edition1 revised1 #gj illus4 #ccj pp4 crown #hvo4 7#aiaj7 net #f #j ,,historical ,,and ,,biographical4 ,extracts from the ,private ,letters of the late ,sir ,william ,fothergill ,cooke1 #ahcf-i1 relating to the ,invention and ,development of the ,electric ,telegraph2 also a ,memoir by ,,latimer ,,clark4 ,edited by ,f4,h4 ,,webb4 ,sec4 ,inst4,e4,e4 #hvo4 7#ahie7 #c #j ,a ,chronology of ,inland ,navigation in ,great ,britain4 ,by ,h4,r4 ,,de ,,salis4 ,crown #hvo4 7#ahig7 #d #f ,a ,history of ,electric ,telegraphy to the year #ahcg4 ,by ,j4,j4 ,,fahie4 #ce illus4 #edb pp4 crown #hvo4 7#ahhi7 #b #j ,history and ,development of ,steam ,locomotion on ,common ,roads4 ,by ,w4 ,,fletcher4 #aji illus4 #bhh pp4 #hvo #e #j ,life as an ,engineer3 its ,lights1 ,shades1 and ,prospects4 ,by ,j4,w4,c4 ,,haldane4 #bc plates1 #cch pp4 crown #hvo4 7#aije7 net #e #j ,philipp ,reis1 ,inventor of the ,telephone3 a ,biographical ,sketch4 ,by ,prof4 ,s4,p4 ,,thompson4 #hvo1 cloth4 7#ahhc7 #g #f ,the ,development of the ,mercurial ,air ,pump4 ,by ,prof4 ,s4,p4 ,,thompson4 ,illustrated1 royal #hvo1 sewed4 7#ahhh7 #a #f ,,horology4 ,watch and ,clock ,maker's ,handbook1 ,dictionary and ,guide4 ,by ,f4,j4 ,,britten4 ,tenth edition1 #dej illus4 #dib pp4 crown #hvo4 7#aijb7 net #e #j ,the ,springing and ,adjusting of ,watches4 ,by ,f4,j4 ,,britten4 #ge illus4 #aeb pp4 crown #hvo4 7#ahih7 net #c #j ,prize ,essay on the ,balance ,spring and its ,isochronal ,adjustments4 ,by ,m4 ,,immisch4 #g illus4 #ej pp4 crown #hvo4 7#ahgb7 #b #f ,,hydraulics ,,and ,,hydraulic ,,machinery4 7,see also ,,water ,,supply47 ,pumps3 ,historically1 ,theoretically and ,practically ,considered4 ,by ,p4,r4 ,,bj,,rling4 ,second edition1 #aef illus4 #bcd pp4 crown #hvo4 7#ahie7 #g #f ,pump ,details4 ,by ,p4,r4 ,,bj,,rling4 #bgh illus4 #baa pp4 crown #hvo4 7#ahib7 #g #f ,pumps and ,pump ,motors3 ,a ,manual for the use of ,hydraulic ,engineers4 ,by ,p4,r4 ,,bj,,rling4 ,two vols4 #bfa plates1 #cfi pp4 royal #dto4 7#ahie74 net #a #aj #j ,practical ,handbook on ,pump ,construction4 ,by ,p4,r4 ,,bj,,rling4 ,second edition1 #i plates1 #ij pp4 crown #hvo4 7#aijd7 #e #j ,water or ,hydraulic ,motors4 ,by ,p4,r4 ,,bj,,rling4 #bjf illus4 #bhg pp4 crown #hvo4 7#aijc7 #i #j ,hydraulic ,machinery1 with an ,introduction to ,hydraulics4 ,by ,r4,g4 ,,blaine4 ,second edition with #cjg illus4 #dfh pp4 #hvo4 7,,finsbury ,,technical ,,manual74 7#aije7 net #ad #j ,practical ,hydraulics4 ,by ,t4 ,,box4 ,fifteenth edition1 #h plates1 #hh pp4 crown #hvo4 7#aiji7 net #e #j ,hydraulic1 ,steam1 and ,hand ,power ,lifting and ,pressing ,machinery4 ,by ,f4 ,,colyer4 ,second edition1 #hh plates1 #baa pp4 imperial #hvo4 7#ahib7 net #aj #f ,pumps and ,pumping ,machinery4 ,by ,f4 ,,colyer4 ,vol4 ,i4 ,second edition1 #ec plates1 #bab pp4 #hvo 7#ahib7 net #aj #f ,vol4 ,,ii4 ,second edition1 #dh plates1 #afi pp4 #hvo4 7#aijj7 net #aj #f ,construction of ,horizontal and ,vertical ,water-wheels4 ,by ,w4 ,,cullen4 ,second edition1 small #dto4 7#ahga7 #e #j ,donaldson's ,poncelet ,turbine and ,water ,pressure ,engine and ,pump4 ,by ,w4 ,,donaldson4 #dto4 7#ahhc7 #e #j ,principles of ,construction and ,efficiency of ,water-wheels4 ,by ,w4 ,,donaldson4 #ac illus4 #id pp4 #hvo4 7#ahgf7 #e #j ,practical ,hydrostatics and ,hydrostatic ,formul4 ,by ,e4,s4 ,,gould4 #bg illus4 #aad pp4 #ahmo1 boards4 7,new ,york1 #aijc7 net #b #j ,hydraulic and other ,tables for purposes of ,sewerage and ,water ,supply4 ,by ,t4 ,,hennell4 ,third edition1 #gj pp4 crown #hvo4 7#aijh7 net #d #f ,hydraulic ,tables for finding the ,mean ,velocity and ,discharge in ,open ,channels4 ,by ,t4 ,,higham4 ,second edition1 #ij pp4 super-royal #hvo4 7#ahih7 #g #f ,tables for ,calculating the ,discharge of ,water in ,pipes for ,water and ,power ,supplies4 ,indexed at side for ready reference4 ,by ,a4,e4 ,,silk4 #fc pp4 crown #hvo4 7#ahii7 #e #j ,simple ,hydraulic ,formul4 ,by ,t4,w4 ,,stone4 #i plates1 #ih pp4 crown #hvo4 7#ahha7 #d #j ,,industrial ,,chemistry ,,and ,,manufactures4 ,perfumes and their ,preparation4 ,by ,g4,w4 ,,askinson4 ,translated from the ,third ,german ,edition by ,i4 ,,fuest4 ,third edition1 #cb illus4 #cab pp4 #hvo4 7,new ,york1 #aijg7 net #ab #f ,brewing ,calculations1 ,gauging and ,tabulation4 ,by ,c4,h4 ,,bater4 #cdj pp4 #fdmo1 roan1 gilt edges4 7#ahig7 net #a #f ,a ,pocket ,book for ,chemists1 ,chemical ,manufacturers1 ,metallurgists1 ,dyers1 ,distillers1 etc4 ,by ,t4 ,,bayley4 ,seventh edition1 #eej pp4 royal #cbmo1 roan1 gilt edges4 7#aije7 net #e #j ,practical ,receipts for the ,manufacturer1 the ,mechanic1 and for ,home use4 ,by ,dr4 ,h4,r4 ,,berkeley and ,w4,m4 ,,walker4 #bej pp4 demy #hvo4 7#aijb7 net #g #f ,a ,treatise on the ,manufacture of ,soap and ,candles1 ,lubricants and ,glycerine4 ,by ,w4,l4 ,,carpenter and ,h4 ,,leask4 ,second edition1 #ajd illus4 #def pp4 crown #hvo4 7#ahie7 #ab #f ,a ,text ,book of ,paper ,making4 ,by ,c4,f4 ,,cross and ,e4,j4 ,,bevan4 ,third edition1 #ig illus4 #daa pp4 crown #hvo4 7#aijg7 net #ab #f ,c4,b4,s4 ,standard ,units and ,standard ,paper ,tests4 ,by ,c4,f4 ,,cross1 ,e4,j4 ,,bevan1 ,c4 ,,beadle and ,r4,w4 ,,sindall4 #be pp4 crown #dto4 7#aijc7 net #b #f ,soda ,fountain ,requisites4 ,a ,practical ,receipt ,book for ,druggists1 ,chemists1 etc4 ,by ,g4,h4 ,,dubelle4 ,third edition1 #aeg pp4 crown #hvo4 7,new ,york1 #aije7 net #d #f ,the ,chemistry of ,fire and ,fire ,prevention4 ,by ,h4 and ,h4 ,,ingle4 #de illus4 #bij pp4 crown #hvo4 7#aijj7 #i #j ,ice-,making ,machines4 ,by ,m4 ,ledoux and others4 ,sixth edition4 #aij pp4 #ahmo1 boards4 7,new ,york1 #aijf7 net #b #j ,brewing with ,raw ,grain4 ,by ,t4,w4 ,lovibond4 #ge pp4 crown #hvo4 7#ahhc7 #e #j ,sugar1 a ,handbook for ,planters and ,refiners4 ,by the late ,j4,a4,r4 ,,newlands and ,b4,e4,r4 ,,newlands4 #bcf illus4 #hgf pp4 demy #hvo4 7,london1 #aiji7 net #a #e #j ,principles of ,leather ,manufacture4 ,by ,prof4 ,h4,r4 ,,procter4 #aja illus4 #ebj pp4 medium #hvo4 7#aijh7 net #ah #j ,leather ,industries ,laboratory ,handbook of ,analytical and ,experimental methods4 ,by ,h4,r4 ,,procter4 ,second edition1 #d plates1 #df illus4 #dej pp4 demy #hvo4 7#aijh7 net #ah #j ,theoretical and ,practical ,ammonia ,refrigeration4 ,by ,i4,i4 ,,redwood4 ,sixth thousand1 #ae illus4 #adf pp4 square #afmo4 7,new ,york1 #aiji7 net #d #f ,breweries and ,maltings4 ,by ,g4 ,,scammell and ,f4 ,,colyer4 ,second edition1 #bj plates1 #agh pp4 #hvo4 7#ahhj7 net #f #j ,factory ,glazes for ,ceramic ,engineers4 ,by ,h4 ,,rum-,,bellow4 ,folio4 ,series ,a1 ,leadless ,sanitary ,glazes4 7#aijh7 net #b #b #j ,text ,book of ,physical ,chemistry4 ,by ,c4,l4 ,,speyers4 #bbd pp4 demy #hvo4 7,new ,york1 #ahih7 #i #j ,spons' ,encyclopdia of the ,industrial ,arts1 ,manufactures and ,commercial ,products4 #aejj illus4 #bajj pp4 super-royal #hvo4 7#ahhb7 ,in #b ,vols4 cloth net #b #b #j ,pigments1 ,paints and ,painting4 ,by ,g4 ,,terry4 #di illus4 #cib pp4 crown #hvo4 7#ahic7 #g #f ,tables for the ,quantitative ,estimation of the ,sugars4 ,by ,e4 ,,wein and ,w4 ,,frew4 ,crown #hvo4 7#ahif7 #f #j ,workshop ,receipts4 ,for the use of ,manufacturers1 ,mechanics and ,scientific ,amateurs4 ,new and thoroughly revised edition1 crown #hvo4 7#aiji7 each each net #c #j ,vol4 ,i4 ,,acetylene ,,lighting to ,,drying4 #bbc illus4 #ecb pp4 ,vol4 ,,ii4 ,,dyeing to ,,japanning4 #bei illus4 #edj pp4 ,vol4 ,,iii4 ,,jointing ,,pipes to ,,pumps4 #bef illus4 #ebh pp4 ,vol4 ,,iv4 ,,rainwater ,,separators to ,,wines4 #bej illus4 #ebj pp4 ,practical ,handbook on the ,distillation of ,alcohol from ,farm ,products4 ,by ,f4,b4 ,,wright4 ,second edition1 #fj illus4 #bga pp4 crown #hvo4 7,new ,york1 #aijg7 444 444 net #d #f ,the ,manufacture of ,chocolate and other ,cacao ,preparations4 ,by ,p4 ,,zipperer4 ,second edition1 #hg illus4 #bhj pp4 royal #hvo4 7#aijb7 net #af #j ,,irrigation4 ,the ,irrigation ,works of ,india4 ,by ,r4,b4 ,,buckley4 ,second edition1 with coloured maps and plans4 #ccf pp4 #dto1 cloth4 7#aije7 net #b #b #j ,facts1 ,figures1 and ,formul for ,irrigation ,engineers4 ,by ,r4,b4 ,,buckley4 ,with illus4 #bci pp4 large #hvo4 7#aijh7 net #aj #f ,irrigated ,india4 ,by ,hon4 ,,alfred ,,deakin4 ,with ,map1 #cbb pp4 #hvo4 7#ahic7 #h #f ,indian ,storage ,reservoirs1 with ,earthen ,dams4 ,by ,w4,l4 ,,strange4 #ad plates and #ec illus4 #cgi pp4 demy #hvo4 7#aijd7 net #a #a #j ,irrigation ,farming4 ,by ,l4,m4 ,,wilcox4 ,revised edition1 #aac illus4 #did pp4 crown #hvo4 7,new ,york7 net #h #f ,egyptian ,irrigation4 ,by ,sir ,w4 ,,willcocks4 ,second edition out of ,print4 ,a few copies of the ,first ,edition 7#ahhi7 are still to be had4 ,price #aes4 net4 ,the ,nile ,reservoir ,dam at ,assuan1 and ,after4 ,by ,sir ,w4 ,,willcocks4 ,second edition1 #ac plates1 super-royal #hvo4 7#aijc7 net #f #j ,the ,assuan ,reservoir and ,lake ,moeris4 ,by ,sir ,w4 ,,willcocks4 ,with text in ,english1 ,french and ,arabic4 #e plates1 #aaf pp4 super-royal #hvo4 7#aijd7 net #e #j ,the ,nile in #aijd4 ,by ,sir ,w4 ,willcocks4 #cj plates1 #bjj pp4 super-royal #hvo4 7#aijd7 net #i #j ,,logarithm ,,tables4 ,aldum's ,pocket ,folding ,mathematical ,tables4 ,four-figure logarithms1 and ,anti-logarithms1 ,natural ,sines1 ,tangents1 ,cotangents1 ,cosines1 ,chords and ,radians for all angles from #a to #ij degrees4 ,on folding card4 ,net #d;d4 #bj copies1 net #fs4 ,tables of ,seven-figure ,logarithms of the ,natural ,numbers from #a to #ajh1jjj4 ,by ,c4 ,,babbage4 ,stereotype edition1 #hvo #g #f ,short ,logarithmic and other ,tables4 ,by ,w4,c4 ,,unwin4 ,fourth edition1 small #dto #c #j ,logarithmic ,land ,measurement4 ,by ,j4 ,,wallace4 #cb pp4 royal #hvo4 7#aiaj7 net #e #j ,a4,b4,c4 ,five-figure ,logarithms with ,tables1 for ,chemists4 ,by ,c4,j4 ,,woodward4 ,crown #hvo net #b #f ,a4,b4,c4 ,five-figure ,logarithms for general use1 with lateral index for ready reference4 ,by ,c4,j4 ,,woodward4 ,second edition1 with cut lateral ,index1 #aaf pp4 #abmo1 limp leather net #c #j ,,marine ,,engineering ,,and ,,naval ,,architecture4 ,marine ,propellers4 ,by ,s4,w4 ,,barnaby4 ,fifth edition1 #e plates1 #ef illus4 #ahe pp4 demy #hvo4 7#aijh7 net #aj #f ,marine ,engineer's ,record ,book3 ,engines4 ,by ,b4,c4 ,,bartley4 #hvo1 roan net #e #j ,the ,engineer's and ,draughtsman's ,data ,book for ,workshop and ,office ,use4 ,third edition1 crown #hvo1 roan #c #j ,yachting ,hints1 ,tables and ,memoranda4 ,by ,a4,c4 ,,franklin4 ,waistcoat pocket size1 #ajc pp4 #fdmo1 roan1 gilt edges net #a #j ,steamship ,coefficients1 ,speeds and ,powers4 ,by ,c4,f4,a4 ,,fyfe4 #ca plates1 #bhj pp4 fcap4 #hvo1 leather4 7#aijg7 net #aj #f ,steamships and ,their ,machinery1 from first to last4 ,by ,j4,w4,c4 ,,haldane4 #abj illus4 #ecb pp4 #hvo4 7#ahic7 #ae #j ,tables for ,constructing ,ships' ,lines4 ,by ,a4 ,,hogg4 ,second edition1 #hvo #g #j ,submarine ,boats4 ,by ,g4,w4 ,,hovgaard4 #b plates1 #ih pp4 crown #hvo4 7#ahhg7 #e #j ,tabulated ,weights of ,angle1 ,tee1 ,bulb1 ,round1 ,square1 and ,flat ,iron and ,steel for the use of ,naval ,architects1 ,ship-builders1 etc4 ,by ,c4,h4 ,,jordan4 ,sixth edition1 #fdj pp4 royal #cbmo1 ,french morocco1 gilt edges4 7#aiji7 net #g #f ,particulars of ,dry ,docks1 ,wet ,docks1 ,wharves1 etc4 on the ,river ,thames4 ,compiled by ,c4,h4 ,,jordan4 ,second edition1 #g coloured charts1 #ajc pp4 oblong #hvo4 7#aijd7 net #b #f ,marine ,transport of ,petroleum4 ,by ,h4 ,,little4 #ff illus4 #bfc pp4 crown #hvo4 7#ahij7 #aj #f ,questions and ,answers for ,marine ,engineers1 with a ,practical ,treatise on ,breakdowns at ,sea4 ,by ,t4 ,,lucas4 #ab folding plates1 #eae pp4 gilt edges1 crown #hvo4 7,new ,york1 #aijb7 net #h #j ,reed's ,examination ,papers for ,extra ,first ,class ,engineers4 ,fourth edition1 #ad plates and #ahh illus4 #eej pp4 #hvo4 7#aijb7 net #ah #j ,reed's ,engineers' ,handbook to the ,board of ,trade ,examinations for certificates of ,competency as ,first and ,second ,class ,engineers4 ,nineteenth edition1 #cg plates1 #ceh illus4 #fif pp4 #hvo net #ad #j ,reed's ,marine ,boilers4 ,second edition1 crown #hvo net #d #f ,reed's ,useful ,hints to ,sea-going ,engineers4 ,fourth edition1 #h plates1 #ej illus4 #cab pp4 crown #hvo4 7#aijc7 net #c #f ,,materials4 ,practical ,treatise on the ,strength of ,materials4 ,by ,t4 ,,box4 ,fourth edition1 #bg plates1 #ecf pp4 #hvo4 7#aijb7 net #ab #f ,treatise on the ,origin1 ,progress1 ,prevention and ,cure of ,dry ,rot in ,timber4 ,by ,t4,a4 ,,britton4 #aj plates1 #eai pp4 crown #hvo4 7#ahge7 #g #f ,twenty ,years' ,practical ,experience of ,natural ,asphalt and ,mineral ,bitumen4 ,by ,w4,h4 ,,delano4 #cc illus4 #gc pp4 crown #hvo1 parchment4 7#ahic7 #b #j ,stone3 how to get it and how to use it4 ,by ,major-,gen4 ,c4,e4 ,,luard1 ,r4,e4 #hvo1 sewed4 7#ahij7 #b #j ,testing of ,pipes and ,pipe-joints in the ,open ,trenches4 ,by ,m4,m4 ,,paterson4 #hvo1 sewed 7#ahgi7 #b #j ,solid ,bitumens4 ,by ,s4,f4 ,,peckham4 #bc illus4 #cbd pp4 #hvo4 7,new ,york1 #aiji7 net #a #a #j ,lubricants1 ,oils and ,greases4 ,by ,i4,i4 ,,redwood4 #c plates1 #hvo4 7#ahih7 net #f #f ,practical ,treatise on ,mineral ,oils and their ,by-,products4 ,by ,i4,i4 ,,redwood4 #fg illus4 #ccf pp4 demy #hvo4 7#ahig7 #ae #j ,silico-,calcareous ,sandstones1 or ,building ,stones from ,quartz1 ,sand and ,lime4 ,by ,e4 ,,stoffler4 #e plates1 #hvo1 sewed4 7#aija7 net #d #j ,proceedings of the ,fifth ,congress1 ,international ,association for ,testing ,materials4 ,english edition4 #ahi illus4 #edi pp4 demy #hvo4 7#aiaj74 ,paper net #ae #j ,cloth net #ah #j ,,mathematics4 ,imaginary ,quantities4 ,by ,m4 ,,argand4 ,translated by ,,prof4 ,,hardy4 #ahmo1 boards4 7,new ,york7 net #b #j ,text ,book of ,practical ,solid ,geometry4 ,by ,e4,h4 ,,de ,v4 ,,atkinson4 ,revised by ,,major ,b4,r4 ,,ward1 ,r4,e4 ,second edition1 #ag plates1 #hvo4 7#aija7 #g #f ,quick and ,easy ,methods of ,calculating1 and the ,theory and ,use of the ,slide ,rule4 ,by ,r4,g4 ,,blaine4 ,third edition1 #f illus4 #aeb pp4 #afmo1 leather cloth4 7#aijg7 #b #f ,symbolic ,algebra1 or the ,algebra of ,algebraic ,numbers4 ,by ,w4 ,,cain4 #ahmo1 boards4 7,new ,york7 net #b #j ,nautical ,astronomy4 ,by ,j4,h4 ,,colvin4 #abg pp4 crown1 #hvo4 7#aija7 net #b #f ,chemical ,problems4 ,by ,j4,c4 ,,foye4 ,fourth edition1 #ada pp4 #ahmo1 boards4 7,new ,york1 #ahih7 net #b #j ,primer of the ,calculus4 ,by ,e4,s4 ,,gould4 ,second edition1 #bd illus4 #abb pp4 #ahmo1 boards4 7,new ,york1 #ahii7 net #b #j ,elementary ,treatise on the ,calculus for ,engineering ,students4 ,by ,j4 ,,graham4 ,third edition1 #bgf pp4 crown #hvo4 7#aije74 7,,finsbury ,,technical ,,manual7 #g #f ,manual of the ,slide ,rule4 ,by ,f4,a4 ,,halsey4 ,second edition1 #ca illus4 #hd pp4 #ahmo1 boards4 7,new ,york1 #aija7 net #b #j ,reform in ,chemical and ,physical ,calculations4 ,by ,c4,j4,t4 ,,hanssen4 #dto4 7#ahig7 net #f #f ,algebra ,self-,taught4 ,by ,p4 ,,higgs4 ,third edition1 #ajd pp4 crown #hvo4 7#aijc7 #b #f ,galvanic ,circuit investigated ,mathematically4 ,by ,g4,s4 ,,ohm4 ,translated by ,,william ,,francis4 #bfi pp4 #ahmo1 boards4 7,new ,york1 #ahia7 net #b #j ,elementary ,practical ,mathematics4 ,by ,m4,t4 ,,ormsby4 #dbj pp4 demy #hvo4 7#aijj7 net #g #f ,elements of ,graphic ,statics4 ,by ,k4 ,,von ,,ott4 ,translated by ,g4,s4 ,,clarke4 #ic illus4 #abh pp4 crown #hvo4 7#aija7 #e #j ,figure of the ,earth4 ,by ,f4,c4 ,,roberts4 #ahmo1 boards4 7,new ,york7 net #b #j ,arithmetic of ,electricity4 ,by ,t4 ,o',c4 ,,sloane4 ,thirteenth edition1 crown #hvo4 7,new ,york1 #aija7 net #d #f ,graphic ,method for ,solving certain ,questions in ,arithmetic or ,algebra4 ,by ,g4,l4 ,,vose4 ,second edition with #bh illus4 #fb pp4 #ahmo1 boards4 7,new ,york1 #aijb7 net #b #j ,problems in ,electricity4 ,a ,graduated ,collection comprising all branches of ,electrical ,science4 ,by ,r4 ,,weber4 ,translated from the ,french by ,e4,a4 ,o',,keefe4 #cd illus4 #cff pp4 crown #hvo4 7#aijb74 net #g #f ,,mechanical ,,engineering4 ,,steam ,,engines ,,and ,,boilers1 ,,etc4 ,handbook for ,mechanical ,engineers4 ,by ,,hy4 ,,adams4 ,fourth edition1 #dbf pp4 crown #hvo4 7#ahig7 net #d #f ,appleby's ,handbooks of ,machinery4 ,many illustrations1 #hvo4 ,sections #b1 #c1 #d and #f each #c #f ,section #e #e #j ,section #a4--,prime ,movers4 ,out of ,print4 ,section #b4--;,hoisting ,machinery1 ,winding ,engines1 etc4 ,section #c4--,out of print4 ,section #d4--,machine ,tools and ,accessories4 ,section #e4--;,contractors' ,plant and ,railway ,materials4 ,section #f4--,mining1 ,colonial and ,manufacturing ,machinery4 ,engineers' ,sketch ,book of ,mechanical ,movements4 ,by ,t4,w4 ,,barber4 ,fifth edition1 #cjjj illus4 #cee pp4 #hvo4 7#aijf7 net #aj #f ,the ,repair and ,maintenance of ,machinery4 ,by ,t4,w4 ,,barber4 #dag illus4 #dgf pp4 #hvo4 7#ahie7 #aj #f ,slide ,valve and its ,functions1 with special reference to ,modern ,practice in the ,united ,states4 ,by ,j4 ,,begtrup4 #ij diagrams1 #adf pp4 medium #hvo4 7,new ,york1 #aijb7 net #h #j ,practical ,treatise on ,mill ,gearing4 ,by ,t4 ,,box4 ,fifth edition1 #aa plates1 #abh pp4 crown #hvo4 7#ahib7 #g #f ,safety ,valves4 ,by ,r4,h4 ,,buell4 ,third edition1 #bj illus4 #ajj pp4 #ahmo1 boards4 7,new ,york1 #ahih7 net #b #j ,machine ,design4 ,by ,prof4 ,w4,l4 ,,cathcart4 ,part ,i4 ,,fastenings4 #abc illus4 #bia pp4 demy #hvo4 7,new ,york1 #aijc7 net #ab #f ,chimney ,design and ,theory4 ,by ,w4,w4 ,,christie4 ,second edition1 #ed illus4 #aib pp4 crown #hvo4 7,new ,york1 #aijb7 net #ab #f ,furnace ,draft3 its ,production by ,mechanical ,methods4 ,by ,w4,w4 ,,christie4 #e illus4 #hj pp4 #ahmo1 boards4 7,new ,york1 #aijf7 net #b #j ,working and ,management of ,steam ,boilers and ,engines4 ,by ,f4 ,,colyer4 ,second edition1 #ajh pp4 crown #hvo4 7#aijb7 #c #f ,the ,stokers' ,catechism4 ,by ,w4,j4 ,,connor4 #fc pp4 limp cloth4 7#aijf7 net #a #j ,treatise on the use of ,belting for the ,transmission of ,power4 ,by ,j4,h4 ,,cooper4 ,fifth edition1 #id illus4 #cii pp4 demy #hvo4 7,new ,york1 #aija7 net #ab #f ,the ,steam ,engine considered as a ,thermodynamic ,machine4 ,by ,j4,h4 ,,cotterill4 ,third edition1 #ci diagrams1 #ddd pp4 #hvo4 7#ahif7 #ae #j ,fireman's ,guide1 a ,handbook on the ,care of ,boilers4 ,by ,k4,p4 ,,dahlstrom4 ,ninth edition fcap4 #hvo4 7,new ,york1 #aijb7 net #a #f ,heat for ,engineers4 ,by ,c4,r4 ,,darling4 #aaj illus4 #dcj pp4 #hvo4 7#aijh47 7,,finsbury ,,technical ,,manual47 net #ab #f ,diseases of a ,gasolene ,automobile1 and ,how to ,cure ,them4 ,by ,a4,l4 ,,dyke and ,g4,p4 ,,dorris4 #abg illus4 #bja pp4 crown #hvo4 7,new ,york1 #aijc7 net #f #f ,belt ,driving4 ,by ,g4 ,,halliday4 #c folding plates1 #ajj pp4 #hvo4 7#ahid7 #c #f ,worm and ,spiral ,gearing4 ,by ,f4,a4 ,,halsey4 #ac plates1 #he pp4 #ahmo1 boards4 7,new ,york1 #aijc7 net #b #j ,commercial ,efficiency of ,steam ,boilers4 ,by ,a4 ,,hanssen4 ,large #hvo1 sewed4 7#ahih7 #j #f ,corliss ,engine4 ,by ,j4,t4 ,,henthorn4 ,third edition1 #bc illus4 #ie pp4 square #afmo4 7,s4 ,c4 ,,series1 ,no4 #bj47 7,new ,york1 #aiaj7 net #a #f ,liquid ,fuel for ,mechanical and ,industrial ,purposes4 ,by ,e4,a4 ,,brayley ,,hodgetts4 #ajf illus4 #abi pp4 #hvo4 7#ahij7 #e #j ,elementary ,text-,book on ,steam ,engines and ,boilers4 ,by ,j4,h4 ,,kinealy4 ,fourth edition1 #ajf illus4 #bei pp4 #hvo4 7,new ,york1 #aijc7 net #h #f ,centrifugal ,fans4 ,by ,j4,h4 ,,kinealy4 #cc illus4 #bjf pp4 fcap4 #hvo1 leather4 7,new ,york1 #aije7 net #ab #f ,mechanical ,draft4 ,by ,j4,h4 ,,kinealy4 #bg original tables and #ac plates1 #adb pp4 crown #hvo4 7,new ,york1 #aijf7 net #h #f ,the ,a4,b4,c4 of the ,steam ,engine1 with a description of the ,automatic ,governor4 ,by ,j4,p4 ,,lisk4 #f plates1 #abmo4 7,s4 ,c4 ,,series1 ,no4 #ag47 7,new ,york1 #aiaj7 net #a #f ,valve ,setting ,record ,book4 ,by ,p4,a4 ,,low4 #hvo1 boards4 #a #f ,the ,lay-out of ,corliss ,valve ,gears4 ,by ,s4,a4 ,,moss4 ,second edition1 #c plates1 #ajh pp4 #ahmo1 boards4 7,new ,york1 #aijf7 net #b #j ,steam ,boilers1 their ,management and ,working4 ,by ,j4 ,,peattie4 ,fifth edition1 #ce illus4 #bcj pp4 crown #hvo4 7#aijf7 net #d #f ,treatise on the ,richards ,steam ,engine ,indicator4 ,by ,c4,t4 ,,porter4 ,sixth edition1 #c plates and #gc diagrams1 #bhe pp4 #hvo4 7#aijb7 #i #j ,practical ,treatise on the ,steam ,engine4 ,by ,a4 ,,rigg4 ,second edition1 #ajc plates1 #cgh pp4 demy #dto4 7#ahid7 #a #e #j ,power and its ,transmission4 ,a ,practical ,handbook for the ,factory and ,works ,manager4 ,by ,t4,a4 ,,smith4 #gf pp4 fcap4 #hvo4 7#aiaj7 net #b #j ,drawings for ,medium ,sized ,repetition ,work4 ,by ,r4,d4 ,,spinney4 ,with #dg illus4 #acj pp4 #hvo4 7#aiji7 net #c #f ,slide ,valve ,simply ,explained4 ,by ,w4,j4 ,,tennant4 ,revised by ,j4,h4 ,,kinealy4 #da illus4 #hc pp4 crown #hvo4 7,new ,york1 #ahii7 net #d #f ,shaft ,governors4 ,by ,w4 ,,trinks and ,c4 ,,hoosum4 #bg illus4 #ig pp4 #ahmo1 boards4 7,new ,york1 #aije7 net #b #j ,slide and ,piston ,valve ,geared ,steam ,engines4 ,by ,w4,h4 ,,uhland4 #dg plates and #cad illus4 #aee pp4 ,two vols4 folio1 half morocco4 7#ahhb7 #a #af #j ,how to run ,engines and ,boilers4 ,by ,e4,p4 ,,watson4 ,fifth edition1 #ca illus4 #afj pp4 crown #hvo4 7,new ,york1 #aijd7 #c #f ,position ,diagram of ,cylinder with ,meyer ,cut-off4 ,by ,w4,h4 ,,weightman4 ,on card4 7,new ,york7 net #a #j ,practical ,method of ,designing ,slide ,valve ,gearing4 ,by ,e4,j4 ,,welch4 #fi diagrams1 #bhc pp4 ,crown #hvo4 7#ahij7 #f #j ,elements of ,mechanics4 ,by ,t4,w4 ,,wright4 ,eighth edition1 illustrated1 #chb pp4 #hvo4 7,new ,york1 #aiji7 net #aj #f ,,metallurgy4 ,,iron ,,and ,,steel ,,manufacture4 ,life of ,railway ,axles4 ,by ,t4 ,,andrews4 #hvo1 sewed4 7#ahie7 #a #j ,microscopic ,internal ,flaws in ,steel ,rails and ,propeller ,shafts4 ,by ,t4 ,,andrews4 #hvo1 sewed4 7#ahif7 #a #j ,microscopic ,internal ,flaws1 ,inducing ,fracture in ,steel4 ,by ,t4 ,,andrews4 #hvo1 sewed4 7#ahif7 #b #j ,relations between the ,effects of ,stresses slowly applied and of ,stresses suddenly applied in the case of ,iron and ,steel3 ,comparative ,tests with ,notched and ,plain ,bars4 ,by ,p4 ,,breuil4 #bc plates and #fj illus4 #aea pp4 #hvo4 7#aijd7 net #h #j ,brassfounders' ,alloys4 ,by ,j4,f4 ,,buchanan4 ,illustrated1 #abi pp4 crown #hvo4 7#aije7 net #d #f ,foundry ,nomenclature4 ,the ,moulder's ,pocket ,dictionary and concise guide to ,foundry ,practice4 ,by ,,john ,f4 ,,buchanan4 ,illustrated1 #bbe pp4 crown #hvo4 7#aijc7 net #e #j ,american ,standard ,specifications for ,steel4 ,by ,a4,l4 ,,colby4 ,second edition1 revised1 #ajc pp4 crown #hvo4 7,new ,york1 #aijb7 net #e #j ,galvanised ,iron3 its ,manufacture and ,uses4 ,by ,j4 ,,davies4 #aci pp4 #hvo4 7#ahii7 net #e #j ,management of ,steel4 ,by ,g4 ,,ede4 ,seventh edition1 #baf pp4 crown #hvo4 7#aijc7 #e #j ,galvanising and ,tinning1 with a special ,chapter on ,tinning ,grey ,iron ,castings4 ,by ,w4,t4 ,,flanders4 #hvo4 7,new ,york7 net #h #f ,cupola ,furnace4 ,a practical treatise on the ,construction and ,management of ,foundry ,cupolas4 ,by ,e4 ,,kirk4 ,third edition1 #gh illus4 #dej pp4 demy #hvo4 7,new ,york1 #aiaj7 net #ae #j ,practical ,notes on ,pipe ,founding4 ,by ,j4,w4 ,,macfarlane4 #ae plates1 #adh pp4 #hvo #ab #f ,atlas of ,designs concerning ,blast ,furnace ,practice4 ,by ,m4,a4 ,,pavloff4 #abg plates1 #ad in4 by #aj in4 oblong1 sewed4 7#aijb7 net #a #a #j ,album of ,drawings relating to the ,manufacture of ,open ,hearth ,steel4 ,by ,m4,a4 ,,pavloff4 ,part ,i4 ,open ,hearth ,furnaces4 #eb plates1 #ad in4 by #aj in4 oblong folio in portfolio4 7#aijd7 net #ab #j ,metallography ,applied to ,siderurgic ,products4 ,by ,h4 ,,savoia4 ,translated by ,r4,g4 ,,corbet4 ,with #id illus4 #ahj pp4 crown #hvo4 7#aiaj7 net #d #f ,modern ,foundry ,practice4 ,including revised subject matter and tables from ,,spretson',s ,casting and ,founding4 ,by ,j4 ,,sharp4 ,second edition1 #bgb illus4 #gei pp4 #hvo4 7#aije7 net #a #a #j ,roll ,turning for ,sections in ,steel and ,iron4 ,by ,a4 ,,spencer4 ,second edition1 #gh plates1 #dto4 7#ahid7 #a #aj #j ,,metric ,,tables4 ,french ,measure and ,english ,equivalents4 ,by ,j4 ,,brook4 ,second edition1 #hj pp4 fcap4 #cbmo1 roan4 7#aijf7 net #a #j ,a ,dictionary of ,metric and other useful ,measures4 ,by ,l4 ,,clark4 #aac pp4 #hvo4 7#ahia7 #f #j ,english ,weights1 with their ,equivalents in kilogrammes per cent4 ,by ,f4,w4,a4 ,,logan4 #if pp4 fcap4 #cbmo1 roan4 7#aijf7 net #a #j ,metric ,weights with ,english ,equivalents4 ,by ,h4,p4 ,,mccartney4 #hd pp4 fcap4 #cbmo4 7#aijg7 net #a #j ,metric ,tables4 ,by ,sir ,g4,l4 ,,molesworth4 ,fourth edition1 #ie pp4 royal #cbmo4 7#aiji7 net #b #j ,tables for ,setting out ,curves from #bjj metres to #djjj metres by tangential angles4 ,by ,h4 ,,williamson4 #d illus4 #fj pp4 #ahmo4 7#aijh7 net #b #j ,,mineralogy ,,and ,,mining4 ,rock ,blasting4 ,by ,g4,g4 ,,andre4 #ab plates and #ef illus4 in text1 #bjb pp4 #hvo4 7#ahgh7 #e #j ,winding ,plants for ,great ,depth4 ,by ,h4,c4 ,,behr4 ,in two parts4 #hvo1 sewed4 7#aijb7 net #b #b #j ,practical ,treatise on ,hydraulic ,mining in ,california4 ,by ,a4,j4 ,,bowie1 ,jun4 ,tenth edition1 #gc illus4 #cac pp4 royal #hvo4 7,new ,york1 #aije7 net #a #a #j ,manual of ,assaying ,gold1 ,silver1 ,copper and ,lead ,ores4 ,by ,w4,l4 ,,brown4 ,twelfth edition1 #acb illus4 #ehi pp4 crown #hvo4 7,new ,york1 #aijg7 net #aj #f ,fire ,assaying4 ,by ,e4,w4 ,,buskett4 #fi illus4 #aje pp4 crown #hvo4 7,new ,york1 #aijg7 net #d #f ,tin3 ,describing the ,chief ,methods of ,mining1 ,dressing1 etc4 ,by ,a4,g4 ,,charleton4 #ae plates1 #hc pp4 crown #hvo4 7#ahhd7 #ab #f ,gold ,mining and ,milling in ,western ,australia1 with ,notes upon ,telluride ,treatment1 ,costs and ,mining ,practice in other ,fields4 ,by ,a4,g4 ,,charleton4 #hb illus4 and numerous plans and tables1 #fdh pp4 super-royal #hvo4 7#aijc7 net #a #e #j ,miners' ,geology and ,prospectors' ,guide4 ,by ,g4,a4 ,,corder4 #bi plates1 #bbd pp4 crown #hvo4 7#aijg7 net #e #j ,blasting of ,rock in ,mines1 ,quarries1 ,tunnels1 etc4 ,by ,a4,w4 and ,z4,w4 ,,daw4 ,second edition1 #ij illus4 #caf pp4 demy #hvo4 7#aiji7 net #ae #j ,handbook of ,mineralogy2 determination and description of ,minerals found in the ,united ,states4 ,by ,j4,c4 ,,foye4 #ahmo1 boards4 7,new ,york1 #ahhf7 net #b #j ,conversations on ,mines4 ,by ,w4 ,,hopton4 ,ninth edition1 #cc illus4 #cef pp4 crown #hvo4 7#ahia7 #d #f ,our ,coal ,resources at the ,end of the ,nineteenth ,century4 ,by ,prof4 ,e4 ,,hull4 #aeg pp4 demy #hvo4 7#ahig7 #f #j ,hydraulic ,gold ,miners' ,manual4 ,by ,t4,s4,g4 ,,kirkpatrick4 ,second edition1 #ab illus4 #df pp4 crown #hvo4 7#ahig7 #d #j ,economic ,mining4 ,by ,c4,g4,w4 ,,lock4 #age illus4 #fhj pp4 #hvo4 7#ahie7 net #aj #f ,gold ,milling3 ,principles and ,practice4 ,by ,c4,g4,w4 ,,lock4 #bjj illus4 #hej pp4 demy #hvo4 7#aija7 net #a #a #j ,mining and ,ore-,dressing ,machinery4 ,by ,c4,g4,w4 ,,lock4 #fci illus4 #dff pp4 super-royal #dto4 7#ahij7 #a #e #j ,miners' ,pocket ,book4 ,by ,c4,g4,w4 ,,lock4 ,fifth edition1 #bcc illus4 #fbd pp4 fcap4 #hvo1 roan1 gilt edges4 7#aijh7 net #aj #f ,tests for ,ores1 ,minerals and ,metals of ,commercial ,value4 ,by ,r4,l4 ,,mcmechen4 #aeb pp4 #abmo4 7,new ,york1 #aijg7 net #e #f ,practical ,handbook for the ,working ,miner and ,prospector1 and the ,mining ,investor4 ,by ,j4,a4 ,,miller4 #cd illus4 #bcd pp4 crown #hvo4 7#ahig7 #g #f ,theory and ,practice of ,centrifugal ,ventilating ,machines4 ,by ,d4 ,,murgue4 #g illus4 #ha pp4 #hvo4 7#ahhc7 #e #j ,examples of ,coal ,mining ,plant4 ,by ,j4 ,,povey-,,harper4 ,second edition1 #dj plates1 #bf in4 by #bj in4 7#ahie7 net #d #d #j ,examples of ,coal ,mining ,plant1 ,second ,series4 ,by ,j4 ,,povey-,,harper4 #aj plates1 #bf in4 by #bj in4 7#aijb7 net #a #ab #f ,,organisation4 ,,accounts1 ,,contracts ,,and ,,management4 ,organisation of ,gold ,mining ,business1 with ,specimens of the ,departmental ,report ,books and the ,account ,books4 ,by ,,nicol ,,brown4 ,second edition1 #bbj pp4 fcap4 folio4 7#aijc7 net #a #e #j ,manual of ,engineering ,specifications and ,contracts4 ,by ,l4,m4 ,,haupt4 ,eighth edition1 #cch pp4 #hvo4 7,new ,york1 #aijj7 net #ab #f ,depreciation of ,factories1 ,municipal1 and ,industrial ,undertakings1 and their ,valuation4 ,by ,e4 ,,matheson4 ,fourth edition1 #bcj pp4 #hvo1 cloth4 7#aiaj7 net #aj #f ,aid ,book to ,engineering ,enterprise4 ,by ,e4 ,,matheson4 ,third edition1 #iaf pp4 #hvo1 buckram4 7#ahih7 #a #d #j ,office ,management4 ,a handbook for ,architects and ,civil ,engineers4 ,by ,w4 ,,kaye ,,parry4 ,new impression1 #ahg pp4 medium #hvo4 7#aijh7 net #e #j ,commercial ,organisation of ,engineering ,factories4 ,by ,h4 ,,spencer4 #ib illus4 #bba pp4 #hvo4 7#aijg7 net #aj #f ,,physics4 ,,colour1 ,,heat ,,and ,,experimental ,,science4 ,the ,entropy ,diagram and its ,applications4 ,by ,m4,j4 ,,boulvin4 #ch illus4 #hb pp4 demy #hvo4 7#ahih7 #e #j ,physical ,problems and their ,solution4 ,by ,a4 ,,bourgougnon4 #bbd pp4 #ahmo1 boards4 7,new ,york1 #ahig7 net #b #j ,heat for ,engineers4 ,by ,c4,r4 ,,darling4 #aaj illus4 #dcj pp4 #hvo4 7#aijh7 7,,finsbury ,,technical ,,manual7 net #ab #f ,the ,colourist4 ,a method of determining colour harmony4 ,by ,j4,a4,h4 ,,hatt4 #b coloured plates1 #hj pp4 #hvo4 7,new ,york1 #aijh7 net #f #f ,engineering ,thermodynamics4 ,by ,c4,f4 ,,hirschfeld4 #bb illus4 #aeg pp4 #ahmo1 boards4 7,new ,york1 #aijg7 net #b #j ,experimental ,science3 ,elementary1 ,practical and ,experimental ,physics4 ,by ,g4,m4 ,,hopkins4 ,twenty-third edition1 #ibj illus4 #aajj pp4 large #hvo4 7,new ,york1 #aijb7 net #a #a #j ,reform in ,chemical and ,physical ,calculations4 ,by ,c4,j4,t4 ,,hanssen4 ,demy #dto4 7#ahig7 net #f #f ,introduction to the ,study of ,colour ,phenomena4 ,by ,j4,w4 ,,lovibond4 #aj hand coloured plates1 #dh pp4 #hvo4 7#aije7 net #e #j ,practical ,laws and ,data on the ,condensation of ,steam in ,bare ,pipes2 to which is added a ,translation of ,,peclet',s ,theory and ,experiments on the ,transmission of ,heat through ,insulating ,materials4 ,by ,c4,p4 ,,paulding4 #ahd illus4 #ajb pp4 demy #hvo4 7,new ,york1 #aijd7 net #h #f ,the ,energy ,chart4 ,practical application to reciprocating steam-engines4 ,by ,captain ,h4,r4 ,,sankey4 #aeg illus4 #agj pp4 #hvo4 7#aijg7 net #g #f ,,price ,,books4 ,approximate ,estimates4 ,by ,t4,e4 ,,coleman4 ,third edition1 #dha pp4 oblong #cbmo1 leather4 7#aijg7 net #e #j ,railway ,stores ,price ,book4 ,by ,w4,o4 ,,kempthorne4 #ejj pp4 demy #hvo4 7#aiji7 net #aj #f ,spons' ,engineers' ,price ,book4 ,a ,synopsis of ,current ,prices and ,rates for ,engineering ,materials and ,products4 ,edited by ,t4,g4 ,,marlow4 #fej pp4 folio4 7#aijd7 net #g #f ,spons' ,architects' and ,builders' ,pocket ,price ,book1 ,memoranda1 ,tables and ,prices4 ,edited by ,,clyde ,,young4 ,revised by ,,stanford ,m4 ,,brooks4 ,illustrated1 #eeb pp4 #afmo1 leather cloth 7size #f in4 by #c in4 by in4 thick74 ,issued annually net #c #j ,,railway ,,engineering4 ,practical ,hints to ,young ,engineers ,employed on ,indian ,railways4 ,by ,a4,w4,c4 ,,addis4 ,with #ad illus4 #aed pp4 #abmo4 7#aiaj7 net #c #f ,railroad ,curves and ,earthwork4 ,by ,c4,f4 ,,allen4 ,third edition1 #d plates1 #aih pp4 #abmo1 leather1 gilt edges4 7,new ,york1 #aijc7 net #h #f ,field and ,office ,tables1 specially applicable to ,railroads4 ,by ,c4,f4 ,,allen4 #bic pp4 #afmo1 leather4 7,new ,york1 #aijc7 net #h #f ,the two above combined in one vol4 limp leather net #ab #f ,up-to-date ,air ,brake ,catechism4 ,by ,r4,h4 ,,blackall4 ,twenty-third edit4 #e coloured plates1 #if illus4 #cje pp4 crown #hvo4 7,new ,york1 #aijh7 net #h #f ,simple and ,automatic ,vacuum ,brakes4 ,by ,c4 ,,briggs1 ,g4,n4,r4 #aa plates1 #hvo4 7#ahib7 #d #j ,notes on ,permanent-way ,material1 ,plate-laying1 and ,points and ,crossings4 ,by ,w4,h4 ,,cole4 ,fifth edition1 #cb plates1 #agf pp4 crown #hvo4 7#aije7 net #g #f ,statistical ,tables of the ,working of ,railways in various countries up to the year #aijd4 ,by ,j4,d4 ,,diacomidis4 ,second edition1 #hd pp4 small folio1 sewed4 7#aijf7 net #af #j ,locomotive ,breakdowns1 ,emergencies and their ,remedies4 ,by ,,geo4 ,l4 ,,fowler1 ,m4,e4 and ,w4,w4 ,,wood4 ,fifth edition1 #ib illus4 #bff pp4 #abmo4 7,new ,york1 #aijh7 net #d #f ,permanent-,way ,diagrams4 ,by ,f4,h4 ,,frere4 ,mounted on linen in cloth covers4 7#aijh7 net #c #j ,formul for ,railway ,crossings and ,switches4 ,by ,j4 ,,glover4 #i illus4 #bh pp4 royal #cbmo4 7#ahif7 #b #f ,data relating to ,railway ,curves and ,super elevations1 shown graphically4 ,by ,j4,h4 ,,haiste4 ,on folding card for pocket use net #j #f ,setting out of ,tube ,railways4 ,by ,g4,m4 ,,halden4 #i plates1 #df illus4 #fh pp4 crown #dto4 7#aijg7 net #aj #f ,railway ,engineering1 ,mechanical and ,electrical4 ,by ,j4,w4,c4 ,,haldane1 #ada illus4 #efc pp4 #hvo4 7#ahig7 #ae #j ,tables for setting-out ,railway ,curves4 ,by ,c4,p4 ,,hogg4 ,a series of cards in neat cloth case #d #f ,the ,construction of the ,modern ,locomotive4 ,by ,g4 ,,hughes4 #cjj illus4 #bfa pp4 #hvo4 7#ahid7 #i #j ,practical ,hints for ,light ,railways at ,home and ,abroad4 ,by ,f4,r4 ,,johnson4 #f plates1 #ca pp4 crown #hvo4 7#ahif7 #b #f ,handbook on ,railway ,stores ,management4 ,by ,w4,o4 ,,kempthorne4 #bfh pp4 demy #hvo4 7#aijg7 net #aj #f ,railway ,stores ,price ,book4 ,by ,w4,o4 ,,kempthorne4 #dhg pp4 demy #hvo4 7#aiji7 net #aj #f ,tables for setting out ,curves for ,railways1 ,roads1 ,canals1 etc4 ,by ,a4 ,,kennedy and ,r4,w4 ,,hackwood4 #cbmo net #b #j ,railroad ,location ,surveys and ,estimates4 ,by ,f4 ,,lavis4 #fh illus4 #bgj pp4 #hvo4 7,new ,york1 #aijf7 net #ab #f ,tables for ,computing the ,contents of ,earthwork in the ,cuttings and ,embankments of ,railways4 ,by ,w4 ,,macgregor4 ,royal #hvo #f #j ,bridge and ,tunnel ,centres4 ,by ,j4,b4 ,,mcmasters4 ,illustrated1 #ajf pp4 #ahmo1 boards4 7,new ,york1 #ahic7 net #b #j ,pioneering4 ,by ,f4 ,,shelford4 ,illustrated1 #hh pp4 crown #hvo4 7#aiji7 net #c #j ,handbook on ,railway ,surveying for ,students and ,junior ,engineers4 ,by ,b4 ,,stewart4 #ee illus4 #ih pp4 crown #hvo4 7#aiji7 net #b #f ,spiral ,tables4 ,by ,j4,g4 ,,sullivan4 #dg pp4 #abmo1 leather4 7,new ,york1 #aijh7 net #f #f ,modern ,british ,locomotives4 ,by ,a4,t4 ,,taylor4 #ajj diagrams of principal dimensions1 #aah pp4 oblong #hvo4 7#aijg7 net #d #f ,locomotive ,slide ,valve ,setting4 ,by ,c4,e4 ,,tully4 ,illustrated1 #ahmo net #a #j ,the ,walschaert ,locomotive ,valve ,gear4 ,by ,w4,w4 ,,wood4 #d plates and set of movable cardboard working models of the valves1 #aic pp4 crown #hvo4 7,new ,york1 #aijg7 net #f #f ,the ,westinghouse ,e4,t4 ,air-,brake ,instruction ,pocket ,book4 ,by ,w4,w4 ,,wood4 #dh illus4 including many coloured plates1 #bdb pp4 crown #hvo4 7,new ,york1 #aiji7 net #h #f ,,sanitation1 ,,public ,,health ,,and ,,municipal ,,engineering4 ,sewers and ,drains for ,populous ,districts4 ,by ,j4,w4 ,,adams4 ,ninth edition1 #ha illus4 #bcf pp4 #hvo4 7,new ,york1 #aijb7 net #aj #f ,public ,abattoirs1 their ,planning1 ,design and ,equipment4 ,by ,r4,s4 ,,ayling4 #cc plates1 #ajj pp4 demy #dto4 7#aijh7 net #h #f ,sewage ,purification4 ,by ,e4 ,,bailey-,,denton4 #h plates1 #dd pp4 #hvo4 7#ahif7 #e #j ,water ,supply and ,sewerage of ,country ,mansions and ,estates4 ,by ,e4 ,,bailey-,,denton4 #gf pp4 crown #hvo4 7#aija7 net #b #f ,sewerage and ,sewage ,purification4 ,by ,m4,n4 ,,baker4 ,second edition1 #add pp4 #ahmo1 boards4 7,new ,york1 #aije7 net #b #j ,sewage ,irrigation by ,farmers4 ,by ,r4,w4,p4 ,,birch4 #hvo1 sewed4 7#ahgh7 #b #f ,sanitary ,house ,drainage1 its ,principles and ,practice4 ,by ,t4,e4 ,,coleman4 #ih illus4 #bjf pp4 crown #hvo4 7#ahif7 #f #j ,stable ,sanitation and ,construction4 ,by ,t4,e4 ,,coleman4 #ahc illus4 #bbf pp4 crown #hvo4 7#ahig7 #f #j ,public ,institutions1 their ,engineering1 ,sanitary and other ,appliances4 ,by ,f4 ,,colyer4 #bca pp4 #hvo4 7#ahhi7 net #b #j ,discharge of ,pipes and ,culverts4 ,by ,p4,m4 ,,crosthwaite4 ,large folding sheet in case4 net #b #f ,a ,complete and ,practical ,treatise on ,plumbing and ,sanitation3 ,hot ,water ,supply1 ,warming and ,ventilation1 ,steam ,cooking1 ,gas1 ,electric ,light1 ,bells1 etc41 with a complete ,schedule of ,prices of ,plumber's ,work4 ,by ,g4,b4 ,,davis and ,f4 ,,dye4 #b vols4 #fcg illus4 and #ba folding plates1 #hcj pp4 #dto1 cloth4 7#ahii7 net #a #aj #j ,standard ,practical ,plumbing4 ,by ,p4,j4 ,,davies4 ,vol4 ,i4 ,fourth edition1 #gfh illus4 #cee pp4 royal #hvo4 7#aije7 net #g #f ,vol4 ,,ii4 ,second edition1 #iec illus4 #hje pp4 7#aije7 net #aj #f ,vol4 ,,iii4 #cac illus4 #bjd pp4 7#aije7 net #e #j ,conservancy1 or ,dry ,sanitation versus ,water ,carriage4 ,by ,j4 ,,donkin4 #g plates1 #cc pp4 #hvo1 sewed4 7#aijf7 net #a #j ,sewage ,disposal ,works1 their ,design and ,construction4 ,by ,w4,c4 ,,easdale4 ,with #afj illus4 #bfd pp4 demy #hvo4 7#aiaj7 net #aj #f ,house ,drainage and ,sanitary ,plumbing4 ,by ,w4,p4 ,,gerhard4 ,tenth edition1 #f illus4 #bca pp4 #ahmo1 boards4 7,new ,york1 #aijb7 net #b #j ,engineering ,work in ,towns and ,cities4 ,by ,e4 ,,mcculloch4 #dd illus4 #ejb pp4 crown #hvo4 7,new ,york1 #aijh7 net #ab #f ,the ,treatment of ,septic ,sewage4 ,by ,g4,w4 ,,rafter4 #acg pp4 #ahmo1 boards4 7,new ,york1 #aijd7 net #b #j ,reports and ,investigations on ,sewer ,air and ,sewer ,ventilation4 ,by ,r4,h4 ,,reeves4 #hvo1 sewed4 7#ahid7 #a #j ,the ,law and ,practice of ,paving ,private ,street ,works4 ,by ,w4 ,,spinks4 ,fourth edition1 #bef pp4 #hvo4 7#aijd7 net #ab #f ,,structural ,,design4 7,see ,,bridges ,,and ,,roofs47 ,,telegraph ,,codes4 ,new ,business ,code4 #cbj pp4 narrow #hvo4 7,size #d in4 by #g in4 and in4 thick1 and weight #aj oz47 7,new ,york1 #aiji7 net #a #aj #j ,miners' and ,smelters' ,code 7formerly issued as the ,master ,telegraph ,code74 #ddh pp4 #hvo1 limp leather1 weight #ad oz4 7,new ,york1 #ahii7 net #b #aj #j ,billionaire ,phrase ,code1 containing over two million sentences coded in single words4 #ef pp4 #hvo1 leather4 7,new ,york1 #aijh7 net #f #f ,,warming ,,and ,,ventilation4 ,hot ,water ,supply4 ,by ,f4 ,,dye4 ,fifth edition1 #dh illus4 #hf pp4 crown #hvo4 7#aijb7 net #c #j ,a ,practical ,treatise upon ,steam ,heating4 ,by ,f4 ,,dye4 #abi illus4 #bdf pp4 demy #hvo4 7#aija7 net #aj #j ,practical ,treatise on ,warming ,buildings by ,hot ,water4 ,by ,f4 ,,dye4 #aib illus4 #cai pp4 #hvo4 cloth4 7#aije7 net #h #f ,charts for ,low ,pressure ,steam ,heating4 ,by ,j4,h4 ,,kinealy4 ,small folio4 7,new ,york7 #d #f ,formul and ,tables for ,heating4 ,by ,j4,h4 ,,kinealy4 #ah illus4 #ec pp4 #hvo4 7,new ,york1 #ahii7 #c #f ,mechanics of ,ventilation4 ,by ,g4,w4 ,,rafter4 ,second edition1 #ahmo1 boards4 7,new ,york1 #ahif7 net #b #j ,principles of ,heating4 ,by ,w4,g4 ,,snow4 #fb illus4 #afa pp4 #hvo4 7,new ,york1 #aijg7 net #h #f ,furnace ,heating4 ,by ,w4,g4 ,,snow4 ,fourth edition1 #eb illus4 #baf pp4 #hvo4 7,new ,york1 #aiji7 net #f #f ,ventilation of ,buildings4 ,by ,w4,g4 ,,snow and ,t4 ,,nolan4 #hc pp4 #ahmo1 boards4 7,new ,york1 #aijf7 net #b #j ,heating ,engineers' ,quantities4 ,by ,w4,l4 ,,white and ,g4,m4 ,,white4 #d plates1 #cc pp4 folio4 7#aiaj7 net #aj #f ,,water ,,supply4 7,see also ,,hydraulics47 ,potable ,water and ,methods of ,testing ,impurities4 ,by ,m4,n4 ,,baker4 #ig pp4 #ahmo1 boards4 7,new ,york1 #aije7 net #b #j ,manual of ,hydrology4 ,by ,n4 ,,beardmore4 ,new impression1 #ah plates1 #chd pp4 #hvo4 7#aijf7 net #aj #f ,boiler ,waters1 ,scale1 ,corrosion and ,fouling4 ,by ,w4,w4 ,,christie4 #gg illus4 #bce pp4 #hvo1 cloth4 7,new ,york1 #aijg7 net #ab #f ,water ,softening and ,purification4 ,by ,h4 ,,collet4 ,second edition1 #f illus4 #agj pp4 crown #hvo4 7#aijh7 net #e #j ,treatise on ,water ,supply1 ,drainage and ,sanitary ,appliances of ,residences4 ,by ,f4 ,,colyer4 #ajj pp4 crown #hvo4 7#ahii7 net #a #f ,report on the ,investigations into the ,purification of the ,ohio ,river ,water at ,louisville1 ,kentucky4 ,by ,g4,w4 ,,fuller4 #h plates1 #dto1 cloth4 7,new ,york1 #ahih7 net #b #b #j ,purification of ,public ,water ,supplies4 ,by ,j4,w4 ,,hill4 #cad pp4 #hvo4 7,new ,york1 #ahih7 #aj #f ,well ,boring for ,water1 ,brine and ,oil4 ,by ,c4 ,,isler4 ,new edition in the ,press4 ,method of ,measuring ,liquids ,flowing through ,pipes by means of ,meters of ,small ,calibre4 ,by ,prof4 ,g4 ,,lange4 #a plate1 #af pp4 #hvo1 sewed net #j #f ,on ,artificial ,underground ,water4 ,by ,g4 ,,richert4 #af illus4 #cc pp4 #hvo1 sewed4 7#aijj7 net #a #f ,notes on ,water ,supply in new ,countries4 ,by ,f4,w4 ,,stone4 #ah plates1 #db pp4 crown #hvo4 7#ahhh7 #e #j ,the ,principles of ,waterworks ,engineering4 ,by ,j4,h4,t4 ,,tudsbery and ,a4,w4 ,,brightmore4 ,third edition1 #ac folding plates1 #acj illus4 #ddg pp4 demy #hvo4 7#aije7 net #a #a #j ,,workshop ,,practice4 ,a ,handbook for ,apprenticed ,machinists4 ,by ,o4,j4 ,,beale4 ,second edition1 #hi illus41 #ada pp4 #afmo4 7,new ,york1 #aija7 net #b #f ,bicycle ,repairing4 ,by ,s4,d4,v4 ,,burr4 ,sixth edition1 #bjj illus4 #bjh pp4 #hvo4 7,new ,york1 #aijc7 net #d #f ,practice of ,hand ,turning4 ,by ,f4 ,,campin4 ,third edition1 #ii illus4 #cjg pp4 crown #hvo4 7#ahhc7 #c #f ,calculation of ,change ,wheels for ,screw ,cutting on ,lathes4 ,by ,d4 ,,de ,,vries4 #df illus4 #hc pp4 #hvo4 7#aijh7 net #c #j ,milling ,machines and ,milling ,practice4 ,by ,d4 ,,de ,,vries4 ,with #ecf illus4 #dfd pp4 medium #hvo4 7#aiaj7 net #ad #j ,french-,polishers' ,manual4 ,by a ,french-,polisher4 #ca pp4 royal #cbmo1 sewed4 7#aijb7 net #j #f ,art of ,copper ,smithing4 ,by ,j4 ,,fuller4 ,third edition1 #dge illus4 #cbe pp4 royal #hvo4 7,new ,york1 #aija7 net #ab #f ,saw ,filing and ,management of ,saws4 ,by ,r4 ,,grimshaw4 ,new edition1 #ha illus4 #afmo4 7,new ,york1 #aijf7 net #c #f ,paint and ,colour ,mixing4 ,by ,a4,s4 ,,jennings4 ,fourth edition4 #ad coloured plates1 #aij pp4 #hvo4 7#aiaj7 net #e #j ,the ,mechanician3 a ,treatise on the ,construction and ,manipulation of ,tools4 ,by ,c4 ,,knight4 ,fifth edition1 #if plates1 #cig pp4 #dto4 7#ahig7 #ah #j ,turner's and ,fitter's ,pocket ,book4 ,by ,j4 ,,la ,,nicca4 #ahmo1 sewed #j #f ,tables for ,engineers and ,mechanics1 giving the values of the different trains of wheels required to produce ,screws of any pitch4 ,by ,,lord ,,lindsay4 ,second edition1 royal #hvo1 oblong #b #j ,screw-cutting ,tables4 ,by ,w4,a4 ,,martin4 ,seventh edition1 royal #hvo1 oblong #a #j ,metal ,plate ,work1 its ,patterns and their ,geometry1 for the use of ,tin1 ,iron and ,zinc ,plate ,workers4 ,by ,c4,t4 ,,millis4 ,fourth edition1 #bhj diagrams1 #dgj pp4 crown #hvo4 7#aijf7 #i #j ,engineers' and ,general ,smiths' ,work4 ,the smith and forgeman's handbook of practical smithing and forging4 ,by ,t4 ,,moore4 #dja illus4 #bdh pp4 crown #hvo4 7#aijf7 net #e #j ,modern ,machine ,shop ,construction1 equipment and management4 ,by ,o4,e4 ,,perrigo4 #bjh illus4 #cdc pp4 crown #dto4 7,new ,york1 #aijf7 net #ba #j ,turner's ,handbook on ,screw-cutting1 ,coning1 etc4 ,by ,w4 ,,price4 ,fcap4 #hvo #a #j ,introduction to ,eccentric ,spiral ,turning4 ,by ,h4,c4 ,,robinson4 #ab plates1 #bc illus4 #dh pp4 #hvo4 7#aijf7 net #d #f ,manual of ,instruction in ,hard ,soldering4 ,by ,h4 ,,rowell4 ,sixth edition1 #g illus4 #ff pp4 crown #hvo4 7,new ,york1 #aiaj7 net #c #j ,pocket ,book on ,boilermaking1 ,shipbuilding1 and the ,steel and ,iron ,trades in ,general4 ,by ,m4,j4 ,,sexton4 ,sixth edition1 #he illus4 #cai pp4 royal #cbmo1 roan1 gilt edges4 7#aiji7 net #e #j ,power and its ,transmission4 ,a ,practical ,handbook for the ,factory and ,works ,manager4 ,by ,t4,a4 ,,smith4 #gf pp4 fcap4 #hvo4 7#aiaj7 net #b #j ,spons' ,mechanics' ,own ,book3 ,a ,manual for ,handicraftsmen and ,amateurs4 ,sixth edition1 #adcj illus4 #gbj pp4 demy #hvo4 7#aijc7 #f #j ,ditto ditto half morocco #g #f ,spons' ,workshop ,receipts for ,manufacturers1 ,mechanics and ,scientific ,amateurs4 ,new and thoroughly revised edition1 crown #hvo4 7#aiji7 each net #c #j ,vol4 ,i4 ,,acetylene ,,lighting to ,,drying4 #bbc illus4 #ecb pp4 ,vol4 ,,ii4 ,,dyeing to ,,japanning4 #bei illus4 #edj pp4 ,vol4 ,,iii4 ,,jointing ,,pipes to ,,pumps4 #bef illus4 #ebh pp4 ,vol4 ,,iv4 ,,rainwater ,,separators to ,,wines4 #bej illus4 #ebj pp4 ,gauges at a ,glance4 ,by ,t4 ,,taylor4 ,second edition1 post #hvo1 oblong1 with tape converter4 7#aijj7 net #e #j ,simple ,soldering1 both ,hard and ,soft4 ,by ,e4 ,,thatcher4 #eb illus4 #gf pp4 crown #hvo1 limp4 7,s4 ,c4 ,,series1 ,,no4 #ah47 7,new ,york1 #aiaj7 net #a #f ,the ,modern ,machinist4 ,by ,j4,t4 ,,usher4 ,fifth edition4 #beg illus4 #cbb pp4 #hvo4 7,new ,york1 #aijd7 net #aj #f ,practical ,wood ,carving4 ,by ,c4,j4 ,,woodsend4 #ajh illus4 #hf pp4 #hvo4 7,new ,york1 #ahig7 net #d #f ,american ,tool ,making and ,interchangeable ,manufacturing4 ,by ,j4,w4 ,,woodworth4 #fjj illus4 #edd pp4 demy #hvo4 7,new ,york1 #aije7 net #ag #j ,,useful ,,tables4 ,weights and ,measurements of ,sheet ,lead4 ,by ,j4 ,,alexander4 #cbmo1 roan net #a #f ,tables of ,parabolic ,curves for the use of ,railway ,engineers and others4 ,by ,g4,t4 ,,allen4 ,fcap4 #afmo #d #j ,barlow's ,tables of ,squares1 ,cubes1 ,square ,roots1 ,cube ,roots and ,reciprocals4 ,crown #hvo #f #j ,tables of ,squares4 ,by ,e4,e4 ,,buchanan4 ,ninth edition1 #abmo net #d #f ,land ,area ,tables4 ,by ,w4 ,,codd4 ,square #afmo1 on a sheet mounted on linen and bound in cloth #c #f ,tables for ,setting out ,curves from #aja to #ejjj feet radius4 ,by ,h4,a4 ,,cutler and ,f4,j4 ,,edge4 ,royal #cbmo net #b #f ,transition ,curves4 ,by ,w4,g4 ,,fox4 #ahmo1 boards4 7,new ,york7 net #b #j ,tables of some of the ,principal ,speeds occurring in ,mechanical ,engineering1 expressed in ,metres per second4 ,by ,p4 ,,keerayeff4 #ahmo1 sewed #j #f ,calculating ,scale4 ,a ,substitute for the ,slide ,rule4 ,by ,w4 ,,knowles4 ,crown #hvo1 leather net #a #j ,planimeter ,areas4 ,multipliers for various scales4 ,by ,h4,b4 ,,molesworth4 ,folding sheet in cloth case4 net #a #j ,tables of ,seamless ,copper ,tubes4 ,by ,i4 ,o',,toole4 #fi pp4 oblong fcap4 #hvo4 7#aijh7 net #c #f ,rownson's ,iron ,merchants' ,tables and ,memoranda1 ,weights and ,measures4 #hf pp4 #cbmo1 leather #c #f ,spons' ,tables and ,memoranda for ,engineers4 ,by ,j4,t4 ,,hurst1 ,c4,e4 ,twelfth edition1 #bgh pp4 #fdmo1 roan1 gilt edges4 7#aijg7 net #a #j ,ditto ditto in celluloid case net #a #f ,optical ,tables and ,data1 for the use of ,opticians4 ,by ,prof4 ,s4,p4 ,,thompson4 ,second edition1 #acj pp4 oblong #hvo4 7#aijg7 net #f #j ,traverse ,table1 showing ,latitudes and ,departure for each ,quarter degree of the ,quadrant1 and for distances from #a to #ajj1 etc42 #ahmo1 boards4 net #b #j ,fifty-four ,hours' ,wages ,calculator4 ,by ,h4,n4 ,,whitelaw4 ,second edition1 #hvo4 net #b #f ,wheel ,gearing4 ,tables of ,pitch ,line ,diameters1 etc4 ,by ,a4 ,,wildgoose and ,a4,j4 ,,orr4 #age pp4 fcap4 #cbmo4 7#aijc7 net #b #j ,,miscellaneous4 ,time ,chart4 ,the time of day at any place in the ,world at a glance4 ,by ,dr4 ,f4,j4,b4 ,,cordeiro4 ,on card4 net #a #j ,the ,atmosphere3 ,its ,characteristics and ,dynamics4 ,by ,f4,j4,b4 ,,cordeiro4 ,with #ce illus4 #abi pp4 medium #hvo4 7,new ,york1 #aiaj7 net #aj #f ,model ,steam ,engine ,design4 ,by ,r4,m4 ,,de ,,vignier4 #cd illus4 #id pp4 crown #hvo1 limp4 7,new ,york1 #aijg7 net #a #f ,popular ,engineering4 ,by ,f4 ,,dye4 #gjd illus4 #dgg pp4 crown #dto4 7#ahie7 net #e #j ,the ,phonograph1 and how to construct it4 ,by ,w4 ,,gillett4 #f folding plates1 #hg pp4 crown #hvo4 7#ahib7 #e #j ,particulars of ,dry ,docks1 ,wet ,docks1 ,wharves1 etc4 on the ,river ,thames4 ,by ,c4,n4 ,,jordan4 ,second edition1 #g coloured charts1 #ajc pp4 oblong #hvo4 7#aijd7 net #b #f ,spons' ,engineer's ,diary and ,year ,book1 issued annually4 #dto4 #c #f ,new ,theories in ,astronomy4 ,by ,w4 ,,stirling4 #cce pp4 demy #hvo4 7#aijf7 net #h #f ,the ,american ,hardware ,store4 ,a ,manual of approved methods of arranging and displaying hardware4 ,by ,r4,r4 ,,williams4 #ejj illus4 #ddh pp4 royal #hvo4 7,new ,york1 #ahif7 net #g #f ,practical ,wood ,carving4 ,by ,c4,j4 ,,woodsend4 #ajh illus4 #hf pp4 #hvo4 7,new ,york1 #ahig7 net #d #f ,inventions1 ,how to ,protect1 ,sell and ,buy ,them4 ,by ,f4 ,,wright4 ,crown #hvo1 limp4 7,s4 ,c4 ,,series1 ,no4 #aj47 7,new ,york1 #aijh7 net #a #f ,illustration ,,science ,,abstracts ,,section ,a4--,,physics4 ,,section ,b4--,,engineering4 ,,issued ,,monthly ,,by ,,the ,,institution ,,of ,,electrical ,,engineers1 ,,with ,,the ,,co-,,operation ,,of ,the ,physical ,society of ,london1 ,the ,american ,physical ,society1 ,the ,american ,institute of ,electrical ,engineers1 and ,the ,american ,electro-,chemical ,society4 ,section ,a4--,,physics4 ,annual ,subscription1 #ahs4 net1 post-free4 ,,contents3--,general ,physics--,light--,heat--,electricity and ,magnetism--,chemical ,physics and ,electro-,chemistry4 ,during #aijh and #aiji over #dbjj ,abstracts and ,references were included under the above headings4 ,section ,b4--,,electrical ,,engineering4 ,annual ,subscription1 #ahs4 net1 post-free4 ,,contents3--,steam ,plant1 ,gas and ,oil ,engines--,industrial ,electro-,chemistry1 ,general ,electrical ,engineering1 and ,properties and ,treatment of ,materials--,generators1 ,motors and ,transformers--,electrical ,distribution1 ,traction and ,lighting--,telegraphy and ,telephony4 ,during #aijh and #aiji over #bhjj ,abstracts and ,references were included under the above headings4 ,annual ,subscription for ,both ,sections1 #cjs4 net1 post-free4 ,binding ,cases for all ,vols4 are to be had1 price #as4 each 7post-free #as4 #b;d474 ,e4 ,f4,n4 ,,spon1 ,ltd41 #eg ,haymarket1 ,london1 ,s4,w4 ,the ,journal of the ,iron and ,steel ,institute4 ,edited by ,g4,c4 ,,lloyd1 ,secretary4 ,published ,half-yearly1 #hvo1 cloth1 #afs4 net4 ,the ,journal of the ,institution of ,electrical ,engineers4 ,edited by ,p4,f4 ,,rowell1 ,secretary4 ,the ,proceedings of the ,institution of ,municipal and ,county ,engineers4 ,edited by ,,thomas ,,cole1 ,assoc4 ,m4 ,inst4 ,c4,e4 ,secretary4 ,published ,annually1 #hvo1 cloth1 #bas4 net4 ,the ,transactions of the ,institution of ,mining and ,metallurgy4 ,edited by ,c4 ,,mcdermid1 ,secretary4 ,published ,annually1 boards1 #bas4 net1 or half-bound1 #bes4 net4 ,transactions of the ,institution of ,gas ,engineers4 ,edited by ,,walter ,t4 ,,dunn1 ,secretary4 ,published ,annually1 #hvo1 cloth1 #ajs4 #f;d4 net4 ,proceedings of the ,international ,association for ,testing ,materials4 7,english ,edition47 ,e4 ,f4,n4 ,,spon1 ,ltd41 #eg ,haymarket1 ,london1 ,s4,w4 ,,london3 ,,printed ,,by ,,william ,,clowes ,,and ,,sons1 ,,limited4 ,,just ,,out ,,the ,,latest ,the ,aeroplane ,portfolio ,by ,d4 ,,ross ,,kennedy ,containing nine sheets of scale drawings of the following celebrated ,aeroplanes4 ,biplane type2--,wright1 ,farman1 ,voisin1 ,cody1 ,herring-,curtis4 ,monoplanes2--,rep1 ,antoinette1 ,santos ,dumont1 and ,blriot4 ,each of these machines are here shown in ,end ,view1 ,plan and ,elevation4 ,including booklet which contains a description of each machine4 ,this timely set of drawings should prove of value to everyone interested in this important new industry4 ,the complete set mailed to any part of the world postpaid on receipt of net #ee;c4 ,,spon ,,chamberlain ,,publishers ,,of ,,technical ,,books #abc-e ,liberty ,street1--,new ,york ,illustration ,the ,percy ,pierce ,flyer ,a ,,famous ,,prize ,,winner ,a ,large ,scale ,drawing of this famous model1 with all measurements and details showing a front elevation1 a side elevation and a top plan1 with full descriptive matter4 ,anybody can make an ,,exact ,,duplicate of this ,prize ,winner for himself at small cost4 ,,do ,,it ,,now ,complete set of materials in the rough with drawing and instructions1 ,postpaid1 #a4ae ,the drawing and instructions #ae;c postpaid ,make ,your ,own ,,glider ,how to make a #bj ft4 ,biplane ,gliding ,machine ,that will carry an ordinary man ,practica,i handbook on the construction of a ,biplane ,gliding ,machine enabling an intelligent reader to make his first step in the field of aviation with a comprehensive understanding of some of the principals involved4 ,by ,alfred ,powell ,morgan4 ,contents of ,chapters3 #a4 ,the ,framework1 ,assembling and finishing the wood4 #b4 ,covering the planes1 ,laying out the fabric and fastening it4 #c4 ,trussing1 ,fastening the tie rods and trueing the glider4 #d4 ,gliding flight4 ,the principals involved4 ,instructions and precautions4 #e4 ,remarks4 ,fully illustrated with detail drawings4 ,by ,mail4 ,in paper1 postpaid1 #be;c4 ,in handsome cloth binding1 postpaid1 #ee;c4 ,flying ,machines1 ,past1 ,present and ,future4 ,a popular account of flying machines1 dirigible balloons and aeroplanes4 ,describing many different kinds of machines1 and their chief feature4 ,by ,a4,w4 ,marshall and ,henry ,greenly4 #ach pages #bc illustrations and many plates1 #ab mo4 boards4 ,by mail #ee;c4 ,model ,flying ,machines4 ,their design and construction by ,w4,g4 ,aston4 ,a first rate little book showing numerous methods of propelling models1 making propellors1 construction of different kinds of models1 etc41 etc4 #acj pages1 #id illustrations4 #ab mo4 boards1 by mail #ee;c4 ,model ,aeroplanes4 ,how to ,build and ,fly ,them1 by ,e4,w4 ,twining4 ,a set of #e full-size scale drawings for three different models with descriptive illustrated book explaining how to make and fly them4 ,postpaid 3 3 3 3 #ee;c ,no4 #b ,model4 ,complete set of parts in the rough to make up this model4 7,without drawings71 ,postpaid 3 3 #fe;c ,illustration3 ,no4 #c ,model ,no4 #c ,model4 ,complete set of parts in the rough 7without drawings74 ,this makes up into a beautiful little model4 ,postpaid 3 3 3 3 #a4ae ,model ,gliders1 ,birds1 ,butterflies and ,aeroplanes4 ,how to make and fly them1 by ,e4,w4 ,twining4 ,consisting of one large sheet of #ab butterflies and two birds printed in bright colors4 ,one small cardboard ,model ,glider with descriptive illustrated book showing how to make and fly them4 ,postpaid 3 3 3 3 #ee;c 99 99 99 99 99 ,transcriber's ,notes ,obvious punctuation and spelling errors and inconsistent hyphenation have been corrected4 ,italic text is denoted by underscores and bold text by equal signs4 ,the ,,oe ligature has been replaced by the separate characters4 ,the fractions 1 and are represented using the ,latin-#a characters1 but other fractions use the _/ and - symbols1 e4g4 #c_/h or #b-e_/h4 ,the exponents #b and #c are represented using and respectively1 but other exponents are indicated by the caret character1 for example1 v#ahe ,subscripts are simply enclosed in braces1 e4g4 ,w#j4 ,other symbols that cannot be represented have been replaced by words in braces3 alpha1 pi1 therefore1 square root and proportional to4 ,the skin friction formul given on pages #aa and #abh have been corrected by comparison with other sources4 ,respectively1 the formul were originally printed as f #jjjjjjgghl#icv#ahe and f #jjjjjjgghl - #jjgv#ahe ,in ambiguous cases1 the text has been left as it appears in the original book4