,,an ,,introduction ,,to ,,machine ,,drawing ,,and ,,design ,,by ,,david ,,allan ,,low 7,,whitworth ,,scholar71 ,m4 ,,inst4 ,m4,e4 ,,head ,,master ,,of ,,the ,,people',s ,,palace ,,technical ,,schools1 ,,london ,,author ,,of ',a ,,text-,,book ,,on ,,practical ,,solid ,,or ,,descriptive ,,geometry' ',,an ,,elementary ,,text-,,book ,,of ,,applied ,,mechanics' ,,etc4 ,illustration ,,fourth ,,edition ,,london ,,longmans1 ,,green1 ,,and ,,co4 ,,and ,,new ,,york3 #ae ,,east #afth ,,street #ahij ,,printed ,,by ,,spottiswoode ,,and ,,co41 ,,new-,,street ,,square ,,london ,,preface4 ,it is now generally recognised that the old-fashioned method of teaching machine drawing is very unsatisfactory4 ,in teaching by this method an undimensioned scale drawing1 often of a very elaborate description1 is placed before the student1 who is required to copy it4 ,very often the student succeeds in making a good copy of the drawing placed before him without learning very much about the object represented by it1 and this state of matters is sometimes not much improved by the presence of the teacher1 who is often simply an art master1 knowing nothing about machine design4 ,it is related of one school that a pupil1 after making a copy of a particular drawing1 had a discussion with his teacher as to whether the object represented was a sewing machine or an electrical machine4 ,evidently the publisher of the drawing example in this case did not adopt the precaution which a backward student used at an examination in machine design3 he put on a full title above his drawing1 for the information of his examiner4 ,now1 if machine drawing is to be of practical use to any one1 he must be able to understand the form and arrangement of the parts of a machine from an inspection of suitable drawings of them without seeing the parts themselves4 ,also he ought to be able to make suitable drawings of a machine or parts of a machine from the machine or the parts themselves4 ,in producing this work the author has aimed at placing before young engineers and others1 who wish to acquire the skill and knowledge necessary for making the simpler working drawings such as are produced in engineers' drawing offices1 a number of good exercises in drawing1 sufficient for one session's work1 and at the same time a corresponding amount of information on the design of machine details generally4 ,the exercises set are of various kinds4 ,in the first and simplest certain views of some machine detail are given1 generally drawn to a small scale1 which the student is asked to reproduce to dimensions marked on these views1 and he is expected to keep to these dimensions1 and not to measure anything from the given illustrations4 ,in the second kind of exercise the student is asked to reproduce certain views shown to dimensions given in words or in tabular form4 ,in the third kind of exercise the student is required to make1 in addition to certain views shown to given dimensions1 others which he can only draw correctly if he thoroughly understands the design before him4 ,in the fourth kind of exercise the student is asked to make the necessary working drawings for some part of a machine which has been previously described and illustrated1 the dimensions to be calculated by rules given in the text4 ,the illustrations for this work are all new1 and have been specially prepared by the author from working drawings1 and he believes that they will be found to represent the best modern practice4 ,as exercises in drawing1 those given in this book are not numbered exactly in their order of difficulty1 but unless on the recommendation of a teacher1 the student should take them up in the order given1 omitting the following3--#bf1 #bg1 #bh1 #ce1 #dj1 #db1 #dc1 #de1 #di1 #ej1 #ed1 #fj1 #fa1 as he comes to them1 until he has been right through the book2 afterwards he should work out those which he omitted on first going over the book4 ,in addition to the exercises given in this work the student should practise making freehand sketches of machine details from actual machines or good models of them4 ,upon these sketches he should put the proper dimensions1 got by direct measurement from the machine or model by himself4 ,these sketches should be made in a note-book kept for the purpose1 and no opportunity should be lost of inserting a sketch of any design which may be new to the student1 always putting on the dimensions if possible4 ,these sketches form excellent examples from which to make working drawings4 ,the student should also note any rules which he may meet with for proportioning machines1 taking care1 however1 in each case to state the source of such information for his future guidance and reference4 ,as machine drawing is simply the application of the principles of descriptive geometry to the representation of machines1 the student of the former subject1 if he is not already acquainted with the latter1 should commence to study it at once4 ,d4 ,a4 ,l4 ,,glasgow3 ,march #ahhg4 ,,preface ,,to ,,the ,,third ,,edition4 ,to this edition another chapter has been added1 containing a number of miscellaneous exercises1 which it is hoped will add to the usefulness of the work as a text-book in science classes4 ,the latest examination paper in machine drawing by the ,science and ,art ,department has also been added to the ,appendix4 ,d4 ,a4 ,l4 ,,london3 ,august #ahhh4 ,,contents4 ,,page ,i4 ,,introduction #a ,,ii4 ,,riveted ,,joints #f ,,iii4 ,,screws1 ,,bolts1 ,,and ,,nuts #ad ,,iv4 ,,keys #bb ,v4 ,,shafting #bd ,,vi4 ,,shaft ,,couplings #be ,,vii4 ,,bearings ,,for ,,shafts #cj ,,viii4 ,,pulleys #cf ,,ix4 ,,toothed ,,wheels #ci ,x4 ,,cranks ,,and ,,cranked ,,shafts #dc ,,xi4 ,,eccentrics #dg ,,xii4 ,,connecting ,,rods #di ,,xiii4 ,,cross-,,heads #ef ,,xiv4 ,,pistons #eg ,,xv4 ,,stuffing-,,boxes #fc ,,xvi4 ,,valves #fh ,,xvii4 ,,materials ,,used ,,in ,,machine ,,construction #gf ,,xviii4 ,,miscellaneous ,,exercises #ha ,,appendix ,a #ii ,,appendix ,b #ajb ,,index #aac ,,an ,,introduction ,,to ,,machine ,,drawing ,,and ,,design4 ,i4 ,,introduction4 ,drawing ,instruments4--,for working the exercises in this book the student should be provided with the following3--,a well-seasoned yellow pine drawing-board1 #bd inches long1 #ag inches wide1 and #c_/h inch or #a_/b inch thick1 provided with cross-bars on the back to give it strength and to prevent warping4 ,a ,t square1 with a blade #bd inches long attached permanently to the stock1 but not sunk into it4 ,one #de deg4 and one #fj deg4 set square4 ,the short edges of the former may be about #f inches and the short edge of the latter about #e inches long4 ,a pair of compasses with pen and pencil attachments1 and having legs from #e inches to #f inches long4 ,a pair of dividers1 with screw adjustment if possible4 ,a pair of small steel spring pencil bows for drawing small circles1 and a pair of small steel spring pen bows for inking in the same4 ,a drawing pen for inking in straight lines4 ,all compasses should have round points1 and if possible needle points4 ,a piece of india-rubber will also be required1 besides two pencils1 one marked ,h or ,,hh and one marked ,,hb or ,f2 the latter to be used for lining in a drawing which is not to be inked in1 or for freehand work4 ,pencils for mechanical drawing should be sharpened with a chisel point1 and those for freehand work with a round point4 ,do not wet the pencil1 as the lines afterwards made with it are very difficult to rub out4 ,drawing-paper for working drawings may be secured to the board by drawing-pins1 but the paper for finished drawings or drawings upon which there is to be a large amount of colouring should be stretched upon the board4 ,the student should get the best instruments he can afford to buy1 and he should rather have a few good instruments than a large box of inferior ones4 ,drawing-paper4--,the names and sizes of the sheets of drawing paper are given in the following table3-- ,inches ,demy #bj x #ae ,medium #bb x #ag ,royal #bd x #ai ,imperial #cj x #bb ,atlas #cd x #bf ,double ,elephant #dj x #bg ,antiquarian #eb x #ca ,the above sizes must not be taken as exact4 ,in practice they will be found to vary in some cases as much as an inch4 ,cartridge-paper is made in sheets of various sizes1 and also in rolls4 ,hand-made paper is the best1 but it is expensive4 ,good cartridge-paper is quite suitable for ordinary drawings4 ,centre ,lines4--,drawings of most parts of machines will be found to be symmetrical about certain lines called centre lines4 ,these lines should be drawn first with great care4 ,on a pencil drawing centre lines should be thin continuous lines2 in this book they are shown thus -- - -- - --4 ,after drawing the centre line of any part the dimensions of that part must be marked off from the centre line1 so as to insure that it really is the centre line of that part3 thus in making a drawing of a rivet1 such as is shown at 7a7 fig4 #a1 after drawing the centre line1 half the diameter of the rivet would be marked off on each side of that line1 in order to determine the lines for the sides of the rivet4 ,inking4--,for inking in drawings the best ,indian ink should be used1 and not common writing ink4 ,common ink does not dry quick enough1 and rapidly corrodes the drawing pens4 ,the pen should be filled by means of a brush or a narrow strip of paper1 and not by dipping the pen into the ink4 ,in cases where there are straight lines and arcs of circles touching one another ink in the arcs first1 then the straight lines2 in this way it is easier to hide the joints4 ,colouring4--,camel's-hair or sable brushes should be used2 the latter are the best1 but are much more expensive than the former4 ,the colour should be rubbed down in a dish1 and the tint should be light4 ,the mistake which a beginner invariably makes is in having the colour of too dark a tint4 ,first go over the part to be coloured with the brush and clean water for the purpose of damping it4 ,next dry with clean blotting-paper to take off any superfluous water4 ,then take another brush with the colour1 and beginning at the top1 work from left to right and downwards4 ,if it is necessary to recolour any part let the first coating dry before beginning4 ,engineers have adopted certain colours to represent particular materials2 these are given in the following table3-- ,table showing ,colours used to represent ,different ,materials4 ,,material ,,colour ,cast iron ,payne's grey or neutral tint4 ,wrought iron ,prussian blue4 ,steel ,purple 7mixture of ,prussian blue and crimson lake74 ,brass ,gamboge with a little sienna or a very little red added4 ,copper ,a mixture of crimson lake and gamboge1 the former colour predominating4 ,lead ,light ,indian ink with a very little indigo added4 ,brickwork ,crimson lake and burnt sienna4 ,firebrick ,yellow and ,vandyke brown4 ,greystones ,light sepia or pale ,indian ink1 with a little ,prussian blue added4 ,brown freestone ,mixture of pale ,indian ink1 burnt sienna1 and carmine4 ,soft woods ,for ground work1 pale tint of sienna4 ,hard woods ,for ground work1 pale tint of sienna with a little red added4 ,for graining woods use darker tint with a greater proportion of red4 ,printing4--,a good drawing should have its title printed1 a plain style of letter being used for this purpose1 such as the following3-- ,illustration3 ,,abcdefghijklmnopqrst ,,uvwxyz #abcdefghij ,illustration3 ,,abcdefghijklmnopqr ,,stuvwxyz #abcdefghij ,the following letters look well if they are well made1 but they are much more difficult to draw4 ,illustration3 ,,abcdefghijklmnop ,,qrstuvwxyz #abcdefghij ,for remarks on a drawing the following style is most suitable3-- ,illustration3 abcdefghijklmnopqrstuvwxyz ,all printing should be done by freehand4 ,border lines are seldom put on engineering drawings4 ,working ,drawings4--,a good working drawing should be prepared in the following manner4 ,it must first be carefully outlined in pencil and then inked in4 ,after this all parts cut by planes of section should be coloured1 the colours used indicating the materials of which the parts are made4 ,parts which are round may also be lightly shaded with the brush and colours to suit the materials4 ,the centre lines are now inked in with red or blue ink4 ,the red ink may be prepared by rubbing down the cake of crimson lake1 and the blue ink in like manner from the cake of ,prussian blue4 ,next come the distance or dimension lines1 which should be put in with blue or red ink1 depending on which colour was used for the centre lines4 ,dimension lines and centre lines are best put in of different colour4 ,the arrow-heads at the ends of the dimension lines are now put in with black ink1 and so are the figures for the dimensions4 ,the arrow-heads and the figures should be made with a common writing pen4 ,the dimensions should be put on neatly4 ,many a good drawing has its appearance spoiled through being slovenly dimensioned4 ,we may here point out the importance of putting the dimensions on a working drawing4 ,if the drawing is not dimensioned1 the workman must get his sizes from the drawing by applying his rule or a suitable scale4 ,now this operation takes time1 and is very liable to result in error4 ,time is therefore saved1 and the chance of error reduced1 by marking the sizes in figures4 ,in practice it is not usual to send original drawings from the drawing office to the workshop1 but copies only4 ,the copies may be produced by various 'processes1' or they may be tracings drawn by hand4 ,many engineers do not ink in their original drawings1 but leave them in pencil2 especially is this the case if the drawings are not likely to be much used4 ,scales4--,the best scales are made of ivory1 and are twelve inches long4 ,boxwood scales are much cheaper1 although not so durable as those made of ivory4 ,if the student does not care to go to the expense of ivory or boxwood scales1 he can get paper ones very cheap1 which will be quite sufficient for his purpose4 ,the divisions of the scale should be marked down to its edge1 so that measurements may be made by applying the scale directly to the drawing4 ,for working such exercises as are in this book the student should be provided with the following scales3-- ,a scale of #a1 or #ab inches to a foot4 #a_/b #f #a_/c #d #a_/d #c #a_/f #b ,a scale of #a is spoken of as 'full size1' and a scale of #a_/b as 'half size4' ,engineers in this country state dimensions of machines in feet1 inches1 and fractions of an inch1 the latter being the #a_/b1 #a_/d1 #a_/h1 #a_/af1 c4 ,in making calculations it is generally more convenient to use decimal fractions1 and then substitute for the results the equivalent fractions in eighths1 sixteenths1 c4 ,the following table will be found useful for this purpose3-- ,decimal ,equivalents of ,fractions of an ,inch4 ------------------------------ ,fraction ,decimal ,equivalent ------------------------------ #a_/cb 4#jcabe #a_/af 4#jfbe #c_/cb 4#jicge #a_/h 4#abe #e_/cb 4#aefbe #c_/af 4#ahge #g_/cb 4#bahge #a_/d 4#be #i_/cb 4#bhabe #e_/af 4#cabe #aa_/cb 4#cdcge #c_/h 4#cge #ac_/cb 4#djfbe #g_/af 4#dcge #ae_/cb 4#dfhge #a_/b 4#e #ag_/cb 4#ecabe #i_/af 4#efbe #ai_/cb 4#eicge #e_/h 4#fbe #ba_/cb 4#fefbe #aa_/af 4#fhge #bc_/cb 4#gahge #c_/d 4#ge #be_/cb 4#ghabe #ac_/af 4#habe #bg_/cb 4#hdcge #g_/h 4#hge #bi_/cb 4#ijfbe #ae_/af 4#icge #ca_/cb 4#ifhge #a #a4j ------------------------------ ,engineers use a single accent 7'7 to denote feet1 and a double accent 77 to denote inches4 ,thus #b' #i reads two feet nine inches4 ,,ii4 ,,riveted ,,joints4 ,two plates or pieces to be riveted together have holes punched or drilled in them in such a manner that one may be made to overlap the other so that the holes in the one may be opposite the holes in the other4 ,the rivets1 which are round bars of iron1 or steel1 or other metal1 are heated to redness and inserted in the holes2 the head already formed on the rivet1 and called the tail1 is then held up1 and the point is hammered or pressed so as to form another head4 ,this process of forming the second head on the rivet is known as riveting1 and may be done by hand-hammering or by a machine4 ,forms of ,rivet ,heads4--,in fig4 #a are shown four different forms of rivet heads3 7a7 is a snap head1 7b7 a conical head 7c7 a pan head1 and 7d7 a countersunk head4 ,proportions of ,rivet ,heads4--,the diameter of the snap head is about #a4g times the diameter of the rivet1 and its height about 4#f of the diameter of the rivet4 ,the conical head has a diameter twice and a height three quarters of the rivet diameter4 ,the greatest diameter of the pan head is about #a4f1 and its height 4#g of the rivet diameter4 ,the greatest diameter of the countersunk head may be one and a half1 and its depth a half of the diameter of the rivet4 ,illustration3 ,,fig4 #a4 ,in fig4 #a at 7a7 and 7b7 are shown geometrical constructions devised by the author for drawing the snap and conical head for any size of rivet1 the proportions being nearly the same as those given above4 ,geometrical ,construction for ,proportioning ,snap ,heads4--,with centre ,a1 and radius equal to half diameter of rivet1 describe a circle cutting the centre line of the rivet at ,b and ,c4 ,with centre ,b and radius ,,bc describe the arc ,,cd4 ,make ,,be equal to ,,ad4 ,with centre ,e and radius ,,ed describe the arc ,,dfh4 ,construction for ,conical ,head4--,with centre ,k1 and radius equal to diameter of rivet1 describe the semicircle ,,lmn1 cutting the side of the rivet at ,m4 ,with centre ,m and radius ,,mn describe the arc ,,np to cut the centre line of rivet at ,p4 ,join ,,pl and ,,pn4 ,when a number of rivets of the same diameter have to be shown on the same drawing the above constructions need only be performed on one rivet4 ,after the point ,e has been discovered the distance ,,ae may be measured off on all the other rivets1 and the arcs corresponding to ,,dfh drawn with radii equal to ,,ed4 ,in like manner the height ,,kp of the conical head may be marked off on all rivets of the same diameter with conical heads4 ,caulking4--,in order to make riveted joints steam- or water-tight the edges of the plates and the edges of the heads of the rivets are burred down by a blunt chisel or caulking tool as shown at ,q and ,r4 ,illustration3 ,,fig4 #b4 ,illustration3 ,,fig4 #c4 ,,exercise #a3 ,forms of ,rivets4--,draw1 full size1 the rivets and rivet heads shown in fig4 #a4 ,the diameter of the rivet in each case to be #a-a_/h inches1 and the thickness of the plates #g_/h inch4 ,,exercise #b3 ,single ,riveted ,lap ,joint4--,draw1 full size1 the plan and sectional elevation of the single riveted lap joint shown in fig4 #b4 ,table showing the ,proportions of ,single ,riveted ,lap ,joints for various ,thicknesses of ,plates4 7,plates and ,rivets ,wrought ,iron47 ---------------------------------------- ----------- ,thickness of ,diameter of ,pitch of ,width of lap plates rivets rivets ---------------------------------------- ----------- #a_/d #i_/af #a-e_/h #a-c_/d #e_/af #e_/h #a-c_/d #b #c_/h #aa_/af #a-g_/h #b-a_/d #g_/af #c_/d #b #b-a_/b #a_/b #ac_/af #b-a_/h #b-c_/d #i_/af #g_/h #b-a_/d #b-g_/h #e_/h #ae_/af #b-e_/af #c #aa_/af #a #b-c_/h #c-a_/h #c_/d #a-a_/af #b-a_/b #c-a_/d ---------------------------------------- -------------- ,all the dimensions are in inches4 ,illustration3 ,,fig4 #d4 ,,exercise #c4--;,draw1 half size1 a plan and section of a single riveted lap joint for plates #c_/d thick to the dimensions given in the above table4 ,,exercise #d3 ,double ,riveted ,lap ,joint4--,draw1 full size1 the two views of the double riveted lap joint shown in fig4 #c4 ,table showing the ,proportions of ,double ,riveted ,lap ,joints for various ,thicknesses of ,plates4 7,plates and ,rivets ,wrought ,iron47 ---------------------------------------- ---------------------- ,thickness ,diameter of ,pitch of ,distance between ,width of of plates rivets rivets rows of rivets lap ---------------------------------------- ---------------------- #c_/h #aa_/af #b-a_/b #a-a_/h #c-a_/b #g_/af #c_/d #b-e_/h #a-a_/d #c-c_/d #a_/b #ac_/af #b-c_/d #a-c_/h #d #i_/af #g_/h #b-g_/h #a-g_/af #d-a_/d #e_/h #ae_/af #c #a-i_/af #d-a_/b #aa_/af #a #c-a_/h #a-c_/d #d-c_/d #c_/d #a-a_/af #c-a_/d #a-g_/h #e #ac_/af #a-a_/af #c-c_/h #a-g_/h #e #g_/h #a-a_/h #c-a_/b #a-ae_/af #e-a_/d #ae_/af #a-a_/h #c-e_/h #a-ae_/af #e-a_/d #a #a-c_/af #c-c_/d #b #e-a_/b ---------------------------------------- ---------------------- ,illustration3 ,,fig4 #e4 ,,exercise #e4--;,draw1 half size1 a plan and section of a double riveted lap joint for plates #g_/h inch thick to the dimensions given in the above table4 ,,exercise #f3 ,single ,riveted ,butt ,joints4--,in fig4 #d are shown single riveted butt joints4 ,one of the sectional views shows a butt joint with one cover plate or butt strap2 the other sectional view shows the same joint with two cover plates2 the third view is a plan of both arrangements4 ,draw all these views full size4 ,,exercise #g4--;,fig4 #e shows a plan and sectional elevation of the connection of three plates together1 which are in the same plane1 by means of single riveted butt joints and single cover plates4 ,the butt straps where they overlap are forged so as to fit one another as shown1 and thus form a close joint4 ,draw these views to the scale of #f inches to a foot4 ,the plates are #a_/b inch thick and the butt straps #i_/af inch thick4 ,all other dimensions must be deduced from the table for single riveted lap joints4 ,,exercise #h4--,the connection of three plates by single riveted lap joints is shown in fig4 #f4 ,to make the joint close one plate has a portion of its edge thinned out1 and the plate above it is set up at this part so as to lie close to the former4 ,draw the three views shown in fig4 #f to the same scale as the last exercise4 ,the plates are #g_/af inch thick4 ,all other dimensions to be obtained from table for single riveted lap joints4 ,,exercise #i3 ,corner of ,wrought-iron ,tank4--,this exercise is to illustrate the connection of plates which are at right angles to one another by means of angle irons4 ,fig4 #g is a plan and elevation of the corner of a wrought-iron tank4 ,the sides of the tank are riveted to a vertical angle iron1 the cross section of which is clearly shown in the plan4 ,another angle iron of the same dimensions is used in the same way to connect the sides with the bottom4 ,the sides do not come quite up to the corner of the vertical angle iron1 excepting at the bottom where the horizontal angle iron comes in4 ,at this point the vertical plates meet one another1 and the edge formed is rounded over to fit the interior of the bend of the horizontal angle iron so as to make the joint tight4 ,draw half size4 ,the dimensions are as follows3 angle irons #b-a_/b inches x #b-a_/b inches x #c_/h inch2 plates #c_/h inch thick2 rivets #aa_/af inch diameter and #b inches pitch4 ,,exercise #aj3 ,gusset ,stay4--,in order that the flat ends of a steam boiler may not be bulged out by the pressure of the steam they are strengthened by means of stays4 ,one form of boiler stay1 called a 'gusset stay1' is shown in fig4 #h4 ,this stay consists of a strip of wrought-iron plate which passes in a diagonal direction from the flat end of the boiler to the cylindrical shell4 ,one end of this plate is placed between and riveted to two angle irons which are riveted to the shell of the boiler4 ,a similar arrangement connects the other end of the stay plate to the flat end of the boiler4 ,in this example the stay or gusset plate is #c_/d of an inch thick2 the angle irons are #d inches broad and #a_/b inch thick4 ,the rivets are #a inch in diameter4 ,the same figure also illustrates the most common method of connecting the ends of a boiler to the shell4 ,the end plates are flanged or bent over at right angles and riveted to the shell as shown4 ,the radius of the inside curve at the angle of the flange is #a-a_/d inches4 ,draw this example to a scale of #c inches to #a foot4 ,illustration3 ,,fig4 #f4 ,illustration3 ,,fig4 #g4 ,illustration3 ,,fig4 #h4 ,,iii4 ,,screws1 ,,bolts1 ,,and ,,nuts4 ,screw ,threads4--,the various forms of screw threads used in machine construction are shown in fig4 #i4 ,the ,whitworth ,v thread is shown at 7a74 ,this is the standard form of triangular thread used in this country4 ,the angle between the sides of the ,v is #ee deg41 and one-sixth of the total depth is rounded off both at the top and bottom4 ,at 7b7 is shown the ,sellers ,v thread1 which is the standard triangular thread used by engineers in ,america4 ,in this form of thread the angle between the sides of the ,v is #fj deg41 and one-eighth of the total depth is cut square off at the top and bottom4 ,the ,square thread is shown at 7c74 ,this form is principally used for transmitting motion4 ,illustration3 ,,fig4 #i4 ,comparing the triangular and square threads1 the former is the stronger of the two2 but owing to the normal pressure on the ,v thread being inclined to the axis of the screw1 that pressure must be greater than the pressure which is being transmitted by the screw2 and therefore1 seeing that the normal pressure on the square thread is parallel1 and therefore equal to the pressure transmitted in the direction of the axis of the screw1 the friction of the ,v thread must be greater than the friction of the square thread4 ,in the case of the triangular thread there is also a tendency of the pressure to burst the nut4 ,the ,buttress thread shown at 7e7 is designed to combine the advantages of the ,v and square threads1 but it only has these advantages when the pressure is transmitted in one direction2 if the direction of the pressure be reversed1 the friction and bursting action on the nut are even greater than with the ,v thread1 because of the greater inclination of the slant side of the buttress thread4 ,the angles of the square thread are frequently rounded to a greater or less extent to render them less easily damaged4 ,if this rounding is carried to excess we get the ,knuckle thread shown at 7d74 ,the rounding of the angles increases both the strength and the friction4 ,,exercise #aa3 ,forms of ,screw ,threads4--,draw to a scale of three times full size the sections of screw threads as shown in fig4 #i4 ,the pitch for the ,whitworth1 ,sellers1 and buttress threads to be #c_/h inch1 and the pitch of the square and knuckle threads to be #a_/b inch4 ,dimensions of ,whitworth ,screws4 ----------------------------------- ,diameter ,number ,diameter of screw of threads at bottom per inch of thread --------------------------------- #a_/h #dj 4#jic #c_/af #bd 4#acd #a_/d #bj 4#ahf #e_/af #ah 4#bda #c_/h #af 4#bie #g_/af #ad 4#cdf #a_/b #ab 4#cic #e_/h #aa 4#ejh #c_/d #aj 4#fbb #g_/h #i 4#gcc #a #h 4#hdj #a-a_/h #g 4#idb #a-a_/d #g #a4jfg #a-c_/h #f #a4afb #a-a_/b #f #a4bhf #a-e_/h #e #a4cfi #a-c_/d #e #a4did #a-g_/h #d-a_/b #a4eij #b #d-a_/b #a4gae #b-a_/d #d #a4icj #b-a_/b #d #b4ahj #b-c_/d #c-a_/b #b4chd #c #c-a_/b #b4fcd #c-a_/d #c-a_/d #b4hef #c-a_/b #c-a_/d #c4ajf #c-c_/d #c #c4cbc #d #c #c4egc #d-a_/d #b-g_/h #c4hje #d-a_/b #b-g_/h #d4jee #d-c_/d #b-c_/d #d4bhd #e #b-c_/d #d4ecd #e-a_/d #b-e_/h #d4gfb #e-a_/b #b-e_/h #e4jab #e-c_/d #b-a_/b #e4bch #f #b-a_/b #e4dhh ----------------------------------- ,gas ,threads#a 7,whitworth ,standard74 #a ,used for wrought-iron and brass tubes4 ---------------------------------------- --------------------- ,diameter of ,screw #a_/h #a_/d #c_/h #a_/b #e_/h #c_/d #a ---------------------------------------- --------------- ,number of threads per inch #bh #ai #ai #ad #ad #ad #aa ---------------------------------------- --------------------- ---------------------------------------- --------- ,diameter of ,screw #a-a_/d #a-a_/b #a-c_/d #b ---------------------------------------- ----- ,number of threads per inch #aa #aa #aa #aa ---------------------------------------- --------- ,representation of ,screws4--,the correct method of representing screw threads involves considerable trouble1 and is seldom adopted by engineers for working drawings4 ,for an explanation of the method see the author's ,text-book on ,practical ,solid ,geometry1 ,part ,,ii41 problem #acd4 ,a method very often adopted on working drawings is shown in fig4 #ae2 here the thin lines represent the points1 and the thick lines the roots of the threads4 ,at fig4 #af is shown a more complete method4 ,the simplest method is illustrated by figs4 #aj1 #aa1 #ac1 and #ad4 ,here dotted lines are drawn parallel to the axis of the screw as far as it extends1 and at a distance from one another equal to the diameter of the screw at the bottom of the thread4 ,illustration3 ,,fig4 #aj4 ,illustration3 ,,fig4 #aa4 ,forms of ,nuts4--,the most common form of nut is the hexagonal shown in figs4 #aj1 #ac1 #ad1 #ae1 and #af2 next to this comes the square nut shown in fig4 #aa4 ,the method of drawing these nuts will be understood by reference to the figures2 the small circles indicate the centres1 and the inclined lines passing through them the radii of the curves which represent the chamfered or bevelled edge of the nut4 ,in all the figures but the first the chamfer is just sufficient to touch the middle points of the sides1 and in these cases the drawing of the nut is simpler4 ,illustration3 ,,fig4 #ab4 ,illustration3 ,,fig4 #ac4 ,illustration3 ,,fig4 #ad4 ,forms of ,bolts4--,at 7a71 fig4 #ab1 is shown a bolt with a square head and a square neck4 ,if this form of bolt is passed through a square hole the square neck prevents the bolt from turning when the nut is being screwed up4 ,instead of a square neck a snug may be used for the same purpose1 as shown on the cup-headed bolt at 7b74 ,the snug fits into a short groove cut in the side of the hole through which the bolt passes4 ,at 7a7 the diagonal lines are used to distinguish the flat side of the neck from the round part of the bolt above it4 ,at 7c7 is shown a tee-headed bolt1 and at 7d7 an eye-bolt4 ,fig4 #ac represents a hook bolt4 ,a bolt with a countersunk head is shown in fig4 #aa4 ,if the countersunk head be lengthened so as to take up the whole of the unscrewed part of the bolt1 we get the taper bolt shown in fig4 #ad1 which is often used in the couplings of the screw shafts of steamships4 ,the taper bolt has the advantage of having no projecting head1 and it may also be made a tight fit in the hole with less trouble than a parallel bolt4 ,bolts may also have hexagonal heads4 ,illustration3 ,,fig4 #ae ,illustration3 ,,fig4 #af ,studs1 or stud bolts1 are shown in figs4 #ae and #af2 that in fig4 #ae is a plain stud1 while that in fig4 #af has an intermediate collar forged upon it1 and is therefore called a collared stud4 ,proportions of ,nuts and ,bolt-heads4--,in the hexagonal nut the diameter ,d across the flats is #a-a_/b;d #a_/h1 where d is the diameter of the bolt4 ,the same rule gives the width of a square nut across the flats4 ,a rule very commonly used in making drawings of hexagonal nuts is to make the diameter ,d1 across the angles equal to #b;d4 ,h1 the height of the nut1 is equal to the diameter of the bolt4 ,in square and hexagonal headed bolts the height of the head varies from d to #b_/c;d2 the other dimensions are the same as for the corresponding nuts4 ,washers are flat1 circular1 wrought-iron plates1 having holes in their centres of the same diameter as the bolts on which they are used4 ,the object of the washer is to give a smooth bearing surface for the nut to turn upon1 and it is used when the surfaces of the pieces to be connected are rough1 or when the bolt passes through a hole larger than itself1 as shown in fig4 #aj4 ,the diameter of the washer is a little more than the diameter of the nut across the angles1 and its thickness about #a_/h of the diameter of the bolt4 ,,exercise #ab4--;,draw1 full size1 the views shown in fig4 #aj of an hexagonal nut and washer for a bolt #a-a_/d inches in diameter4 ,the bolt passes through a hole #a-c_/d x #a-a_/d4 ,all the dimensions are to be calculated from the rules which have just been given4 ,,exercise #ac4--;,draw1 full size1 the plan and elevation of the square nut and bolt with countersunk head shown in fig4 #aa1 to the dimensions given4 ,,exercise #ad4--;,draw1 full size1 the elevation of the hook bolt with hexagonal nut shown in fig4 #ac to the dimensions given1 and show also a plan4 ,,exercise #ae4--;,draw1 to a scale of #d inches to a foot1 the conical bolt for a marine shaft coupling shown in fig4 #ad4 ,all the parts are of wrought iron4 ,,exercise #af4--;,fig4 #ae is a section of the mouth of a small steam-engine cylinder1 showing how the cover is attached2 draw this full size4 ,,exercise #ag4--;,fig4 #af shows the central portion of the india-rubber disc valve which is described on page #fh4 ,a is the central boss of the grating1 into which is screwed the stud ,b1 upon which is forged the collar ,c4 ,the upper part of the stud is screwed1 and carries the guard ,d and an hexagonal nut ,e4 ,f is the india-rubber4 ,the grating and guard are of brass4 ,the stud and nut are of wrought iron4 ,draw full size the view shown4 ,lock ,nuts4--,in order that a nut may turn freely upon a bolt1 there is always a very small clearance space between the threads of the nut and those of the bolt4 ,this clearance is shown exaggerated at 7a71 fig4 #ag1 where ,a is a portion of a bolt within a nut ,b4 ,suppose that the bolt is stretched by a force ,w4 ,when the nut ,b is screwed up1 the upper surfaces of the projecting threads of the nut will press on the under surfaces of the threads of the bolt with a force ,p equal and opposite to ,w1 as shown at 7b71 fig4 #ag4 ,when in this condition the nut has no tendency to slacken back1 because of the friction due to the pressure on the nut4 ,now suppose that the tension ,w on the bolt is momentarily diminished1 then the friction which opposes the turning of the nut may be so much diminished that a vibration may cause it to slacken back through a small angle4 ,if this is repeated a great many times the nut may slacken back so far as to become useless4 ,illustration3 ,,fig4 #ag4 ,illustration3 ,,fig4 #ah4 ,a very common arrangement for locking a nut is shown at 7a71 fig4 #ah4 ,c is an ordinary nut1 and ,b one having half the thickness of ,c4 ,b is first screwed up tight so as to act on the bolt1 as shown at 7b71 fig4 #ag4 ,c is then screwed on top of ,b4 ,when ,c is almost as tight as it can be made1 it is held by one spanner1 while ,b is turned back through a small angle with another4 ,the action of the nuts upon the bolt and upon one another is now as shown at 7b71 fig4 #ah4 ,it will be seen that the nuts are wedged tight on to the bolt1 and that this action is independent of the tension ,w in the bolt4 ,the nuts will1 therefore1 remain tight after the tension in the bolt is removed4 ,it is evident that if the nuts are screwed up in the manner explained1 the outer nut ,c will carry the whole load on the bolt2 hence ,c should be the thicker of the two nuts4 ,in practice1 the thin nut1 called the lock nut1 is often placed on the outside1 for the reason that ordinary spanners are too thick to act on the thin nut when placed under the other4 ,another very common arrangement for locking a nut is shown in fig4 #ai4 ,a is the bolt and ,b the nut1 the lower part of which is turned circular4 ,a groove ,c is also turned on the nut at this part4 ,the circular part of the nut fits into a circular recess in one of the parts connected by the bolt4 ,through this part passes a set screw ,d1 the point of which can be made to press on the nut at the bottom of the groove ,c4 ,d is turned back when the nut ,b is being moved1 and when ,b is tightened up1 the set screw is screwed up so as to press hard on the bottom of the groove ,c4 ,the nut ,b is thus prevented from slackening back4 ,the screw thread is turned off the set screw at the point where it enters the groove on the nut4 ,illustration3 ,,fig4 #ai ,the use of the groove for receiving the point of the set screw is this3 ,the point of the set screw indents the nut and raises a bur which would interfere with the free turning of the nut in the recess if the bur was not at the bottom of a groove4 ,additional security is obtained by drilling a hole through the point of the bolt1 and fitting it with a split pin ,e4 ,locking arrangements for nuts are exceedingly numerous1 and many of them are very ingenious1 but want of space prevents us describing them4 ,we may point out1 however1 that many very good locking arrangements have the defect of only locking the nut at certain points of a revolution1 say at every #cj deg44 ,it will be noticed that the two arrangements which we have described are not open to this objection4 ,,exercise #ah4--;,draw1 full size1 a plan1 front elevation1 and side elevation of the arrangement of nuts shown in fig4 #ah1 for a bolt #g_/h inch diameter4 ,,exercise #ai4--;,draw the plan and elevation of the nut and locking arrangement shown in fig4 #ai4 ,make also an elevation looking in the direction of the arrow4 ,scale #f inches to a foot4 ,,iv4 ,,keys4 ,keys are wedges1 generally rectangular in section1 but sometimes circular2 they are made of wrought iron or steel1 and are used for securing wheels1 pulleys1 cranks1 c41 to shafts4 ,illustration3 ,fig4 #bj4 ,various sections of keys are shown in fig4 #bj4 ,at 7a7 is the hollow or saddle key4 ,with this form of key it is not necessary to cut the shaft in any way1 but its holding power is small1 and it is therefore only used for light work4 ,at 7b7 is the key on a flat1 sometimes called a flat key4 ,the holding power of this key is much greater than that of the saddle key4 ,at 7c7 is the sunk key1 a very secure and very common form4 ,the part of the shaft upon which a key rests is called the key bed or key way1 and the recess in the boss of the wheel or pulley into which the key fits is called the key way2 both are also called key seats4 ,with saddle1 flat1 and sunk keys the key bed is parallel to the axis of the shaft2 but the key way is deeper at one end than the other to accommodate the taper of the key4 ,the sides of the key are parallel4 ,the round key or taper pin shown at 7d7 is in general only used for wheels or cranks which have been previously shrunk on to their shafts or forced on by great pressure4 ,after the wheel or crank has been shrunk on1 a hole is drilled1 half into the shaft and half into the wheel or crank1 to receive the pin4 ,when the point of a key is inaccessible the other end is provided with a gib head as shown at 7e71 to enable the key to be withdrawn4 ,a sliding or feather key secures a piece to a shaft so far as to prevent the one from rotating without the other1 but allows of relative motion in the direction of the axis of the shaft4 ,this form of key has no taper1 and it is secured to the piece carried by the shaft1 but is made a sliding fit in the key way of the shaft4 ,in one form of feather key the part within the piece carried by the shaft is dovetailed as shown at 7f74 ,in another form the key has a round projecting pin forged upon it1 which enters a corresponding hole as shown at 7g74 ,the feather key may also be secured to the piece carried by the shaft by means of one or more screws as shown at 7h74 ,the key way in the shaft is made long enough to permit of the necessary sliding motion4 ,cone ,keys4--,these are sometimes fitted to pulleys1 and are shown in fig4 #cb1 page #ch4 ,in this case the eye of the pulley is tapered and is larger than the shaft4 ,the space between the shaft and the boss of the pulley is filled with three saddle or cone keys4 ,these keys are made of cast iron and are all cast together1 and before being divided the casting is bored to fit the shaft and turned to fit the eye of the pulley4 ,by this arrangement of keys the same pulley may be fixed on shafts of different diameters by using keys of different thicknesses2 also the pulley may be bored out large enough to pass over any boss which may be forged on the shaft4 ,proportions of ,keys4--,the following rules are taken from ,unwin's ',machine ,design1' pp4 #adb-dc4 ,diameter of eye of wheel1 or boss of shaft d4 ,width of key #c_/d;d #a_/h4 ,mean thickness of sunk key #a_/h;d #a_/h4 key on flat #a_/af;d #a_/af4 ,the following table gives dimensions agreeing with average practice4 ,dimensions of ,keys4 ,d diameter of shaft4 ,b breadth of key4 ,t thickness of sunk key4 ,t#a thickness of flat key1 also thickness of saddle key4 ,taper of key #a_/h inch per foot of length1 i4e4 #a in #if4 ---------------------------------------- ----------------------- ,d #c_/d #a #a-a_/d #a-a_/b #a-c_/d #b #b-a_/d #b-a_/b ---------------------------------------- --------------- ,b #e_/af #c_/h #g_/af #a_/b #i_/af #e_/h #aa_/af #aa_/af ,t #a_/d #a_/d #a_/d #e_/af #e_/af #e_/af #c_/h #c_/h ,t#a #c_/af #c_/af #c_/af #c_/af #a_/d #a_/d #a_/d #e_/af ---------------------------------------- ----------------------- ---------------------------------------- --------------------------- ,d #b-c_/d #c #c-a_/b #d #d-a_/b #e #e-a_/b #f ---------------------------------------- ------------------- ,b #c_/d #g_/h #a #a-a_/h #a-a_/d #a-c_/h #a-a_/b #a-e_/h ,t #c_/h #g_/af #a_/b #a_/b #i_/af #e_/h #aa_/af #c_/d ,t#a #e_/af #e_/af #c_/h #g_/af #a_/b #a_/b #i_/af #e_/h ---------------------------------------- --------------------------- ---------------------------------------- --------------- ,d #g #h #i #aj #aa #ab ---------------------------------------- --------- ,b #a-g_/h #b-a_/h #b-c_/h #b-e_/h #b-g_/h #c-a_/h ,t #ac_/af #ae_/af #a #a-a_/af #a-c_/af #a-a_/d ,t#a #aa_/af #c_/d #g_/h #ae_/af #a-a_/af #a-a_/h ---------------------------------------- --------------- ,v4 ,,shafting4 ,shafting is nearly always cylindrical and made of wrought iron or steel4 ,cast iron is rarely used for shafting4 ,axles are shafts which are subjected to bending without twisting4 ,the parts of a shaft or axle which rest upon the bearings or supports are called journals1 pivots1 or collars4 ,in journals the supporting pressure is at right angles to the axis of the shaft1 while in pivots and collars the pressure is parallel to that axis4 ,shafts may be solid or hollow4 ,hollow shafts are stronger than solid shafts for the same weight of material4 ,thus a hollow shaft having an external diameter of #aj-a_/d inches and an internal diameter of #g inches would have about the same weight as a solid shaft of the same material #g-a_/b inches in diameter1 but the former would have about double the strength of the latter4 ,hollow shafts are also stiffer and yield less to bending action than solid shafts1 which in some cases1 as in propeller shafts1 is an objection4 ,,vi4 ,,shaft ,,couplings4 ,for convenience of making and handling1 shafts used for transmitting power are generally made in lengths not exceeding #cj feet4 ,these lengths are connected by couplings1 of which we give several examples4 ,illustration3 ,,figs4 #ba and #bb4 ,solid1 ,box1 or ,muff ,couplings4--,one form of box coupling is shown in fig4 #ba4 ,here the ends of the shafts to be connected butt against one another1 meeting at the centre of the box1 which is made of cast iron4 ,the shafts are made to rotate as one by being secured to the box by two wrought-iron or steel keys1 both driven from the same end of the box4 ,a clearance space is left between the head of the forward key and the point of the hind one1 to facilitate the driving of them out1 as then only one key needs to be started at a time4 ,sometimes a single key the whole length of the box is used1 in which case it is necessary that the key ways in the shafts be of exactly the same depth4 ,the half-lap coupling1 introduced by ,sir ,william ,fairbairn1 is shown in fig4 #bb4 ,in this form of box coupling the ends of the shafts overlap within the box4 ,it is evident that one shaft cannot rotate without the other as long as the box remains over the lap4 ,to keep the box in its place it is fitted with a saddle key4 ,it will be noticed that the lap joint is sloped in such a way as to prevent the two lengths of shaft from being pulled asunder by forces acting in the direction of their length4 ,half-lap couplings are not used for shafts above #e inches in diameter4 ,it may here be pointed out that the half-lap coupling is expensive to make1 and is now not much used4 ,as shafts are weakened by cutting key ways in them1 very often the ends which carry couplings are enlarged in diameter1 as shown in fig4 #ba1 by an amount equal to the thickness of the key4 ,an objection to this enlargement is that wheels and pulleys require either that their bosses be bored out large enough to pass over it1 or that they be split into halves1 which are bolted together after being placed on the shaft4 ,dimensions of ,box ,couplings4 ,d diameter of shaft4 ,t thickness of metal in box4 ,l length of box for butt coupling4 ,l#a length of box for lap coupling4 l length of lap4 ,d#a diameter of shaft at lap4 ---------------------------------------- ----------------------- ,d #a-a_/b #b #b-a_/b #c #c-a_/b #d ---------------------------------------- ----------------- ,t #a-a_/h #a-e_/af #a-a_/b #a-c_/d #a-ae_/af #b-a_/h ,l #e-c_/d #g #h-a_/d #i-a_/b #aj-c_/d #ab ,l#a #d-a_/h #e-a_/d #f-c_/h #g-a_/b #h-e_/h #i-c_/d l #a-g_/af #a-g_/h #b-e_/af #b-c_/d #c-c_/af #c-e_/h ,d#b #b-e_/af #c #c-aa_/af #d-c_/h #e-a_/af #e-c_/d ---------------------------------------- ----------------------- ---------------------------------------- ------ ,d #d-a_/b #e #e-a_/b #f ---------------------------------------- -- ,t #b-e_/af #b-a_/b #b-c_/d #b-ae_/af ,l #ac-a_/d #ad-a_/b #ae-c_/d #ag ,l#a #aj-g_/h #ab -- -- l #d-a_/af #d-a_/b -- -- ,d#b #f-g_/af #g-a_/h -- -- ---------------------------------------- ------ ,slope of lap #a in #ab4 ,,exercise #bj3 ,solid ,butt ,coupling4--,from the above table of dimensions make a longitudinal and a transverse section of a solid butt coupling for a shaft #b-a_/b inches in diameter4 ,scale #f inches to a foot4 ,,exercise #ba3 ,fairbairn's ,half-,lap ,coupling4--,make the same views as in the last exercise of a half-lap coupling for a #c-;inch shaft to the dimensions in the above table4 ,scale #f inches to a foot4 ,flange ,couplings4--,the form of coupling used for the shafts of marine engines is shown in fig4 #bc4 ,the ends of the different lengths of shaft have flanges forged on them1 which are turned along with the shaft4 ,these flanges butt against one another1 and are connected by bolts4 ,these bolts may be parallel or tapered2 generally they are tapered4 ,a parallel bolt must have a head1 but a tapered bolt will act without one4 ,in fig4 #bc the bolts are tapered1 and also provided with heads4 ,in fig4 #ad1 page #ag1 is shown a tapered bolt without a head4 ,the variation of diameter in tapered bolts is #c_/h of an inch per foot of length4 ,illustration3 ,,fig4 #bc4 ,sometimes a projection is formed on the centre of one flange which fits into a corresponding recess in the centre of the other1 for the purpose of ensuring the shafts being in line4 ,occasionally a cross-key is fitted in between the flanges1 being sunk half into each1 for the purpose of diminishing the shearing action on the bolts4 ,,exercise #bb3 ,marine ,coupling4--,draw the elevation and section of the coupling shown in fig4 #bc2 also an elevation looking in the direction of the arrow4 ,scale #c inches to a foot4 ,the following table gives the dimensions of a few marine couplings taken from actual practice4 ,examples of ,marine ,couplings4 ---------------------------------------- ---------------------------- ,diameter of shaft #b-c_/h #i-c_/d #ab-g_/h #af-a_/b #bb-a_/b #bc ---------------------------------------- ---------------------- ,diameter of flange #f #ai #bd #cb #ce #ch ,thickness of flange #a #b-c_/d #c-a_/h #d-a_/d #f #e ,diameter of bolts #c_/d #b-c_/d #b-aa_/af #c-a_/b #d-a_/d #d-a_/d ,number of bolts #c #f #f #h #i #h ,diameter of bolt circle #d-a_/h #ad-a_/hah-ac_/af #be #bh-c_/d #cj-c_/h ---------------------------------------- ---------------------------- ,all the above dimensions are in inches4 ,,exercise #bc4--,select one of the couplings from the above table1 and make the necessary working drawings for it to a suitable scale4 ,the cast-iron flange coupling is shown in fig4 #bd4 ,in this kind of coupling a cast-iron centre or boss provided with a flange is secured to the end of each shaft by a sunk key driven from the face of the flange4 ,these flanges are then connected by bolts and nuts as in the marine coupling4 ,to ensure the shafts being in line the end of one projects into the flange of the other4 ,in order that the face of each flange may be exactly perpendicular to the axis of the shaft they should be 'faced' in the lathe1 after being keyed on to the shaft4 ,if the coupling is in an exposed position1 where the nuts and bolt-heads would be liable to catch the clothes of workmen or an idle driving band which might come in the way1 the flanges should be made thicker1 and be provided with recesses for the nuts and bolt-heads4 ,illustration3 ,,fig4 #bd4 ,dimensions of ,cast-iron ,flange ,couplings4 ---------------------------------------- ---------------------------- ,diameter ,depth ,diameter,diameter ,diameter of ,thickness,diameter at ,number of of bolt of shaft flange of flange of boss boss of bolts circle ,d ,f ,t ,b ,l bolts d ,c ---------------------------------------- --------------------- #a-a_/b #g-a_/d #g_/h #c-a_/b #b-e_/h #c #e_/h #e-a_/b #b #h-g_/h #a-a_/af #d-c_/h #c-c_/af #d #c_/d #f-c_/d #b-a_/b #aj-e_/h #a-a_/d #e-e_/af #c-c_/d #d #g_/h #h-a_/h #c #ab-c_/h #a-g_/af #f-a_/d #d-e_/af #d #a #i-a_/b #c-a_/b #ac-a_/h #a-e_/h #g-a_/h #d-g_/h #d #a #aj-e_/af #d #ad #a-c_/d #h #e-g_/af #f #a #aa-a_/d #d-a_/b #ae-e_/h #b #h-g_/h #f #f #a-a_/h #ab-a_/b #e #ag-c_/h #b-a_/h #i-ac_/aff-e_/h #f #a-a_/dac-ac_/af #e-a_/b #ah-a_/d #b-e_/af #aj-c_/d #g-a_/d #f #a-a_/d #ad-c_/d #f #ai-g_/h #b-a_/b #aa-e_/h #g-c_/d #f #a-c_/h #af ---------------------------------------- ---------------------------- ,the projection of the shaft p varies from #a_/d inch in the small shafts to #a_/b inch in the large ones4 ,,exercise #bd3 ,cast-iron ,flange ,coupling4--,draw the views shown in fig4 #bd of a cast-iron flange coupling1 for a shaft #d-a_/b inches in diameter1 to the dimensions given in the above table4 ,scale #d inches to a foot4 ,,vii4 ,,bearings ,,for ,,shafts4 ,an example of a very simple form of bearing is shown in fig4 #be1 which represents a brake shaft carrier of a locomotive tender4 ,the bearing in this example is made of cast iron and in one piece4 ,through the oval-shaped flange two bolts pass for attaching the bearing to the wrought-iron framing of the tender4 ,with this form of bearing there is no adjustment for wear1 so that when it becomes worn it must be renewed4 ,illustration3 ,,fig4 #be4 ,,exercise #be3 ,brake ,shaft ,carrier4--,draw the elevation and sectional plan of the bearing shown in fig4 #be4 ,draw also a vertical section through the axis4 ,the latter view to be projected from the first elevation4 ,scale #f inches to a foot4 ,pillow ,block1 ,plummer ,block1 or ,pedestal4--,the ordinary form of plummer block is represented in fig4 #bf4 ,a is the block proper1 ,b the sole through which pass the holding-down bolts4 ,c is the cap4 ,between the block and the cap is the brass bush1 which is in halves1 called brasses or steps4 ,the bed for the steps in this example is cylindrical1 and is prepared by the easy process of boring4 ,the steps are not supported throughout their whole length1 but at their ends only where fitting strips are provided as shown4 ,as the wear on a step is generally greatest at the bottom1 it is made thicker there than at the sides1 except where the fitting strips come in4 ,to prevent the steps turning within the block they are generally furnished with lugs1 which enter corresponding recesses in the block and cover4 ,illustration3 ,,fig4 #bf ,in the block illustrated the journal is lubricated by a needle lubricator2 this consists of an inverted glass bottle fitted with a wood stopper1 through a hole in which passes a piece of wire1 which has one end in the oil within the bottle1 and the other resting on the journal of the shaft4 ,the wire or needle does not fill the hole in the stopper1 but if the needle is kept from vibrating the oil does not escape owing to capillary attraction4 ,when1 however1 the shaft rotates1 the needle begins to vibrate1 and the oil runs down slowly on to the journal2 oil is therefore only used when the shaft is running4 ,,exercise #bf3 ,pillow ,block for a ,four-inch ,shaft4--,draw the views shown of this block in fig4 #bf4 ,make also separate drawings1 full size1 of one of the steps4 ,scale #f inches to a foot4 ,proportions of ,pillow ,blocks4--,the following rules may be used for proportioning pillow blocks for shafts up to #h inches diameter4 ,it should be remembered that the proportions used by different makers vary considerably1 but the following rules represent average practice4 ,diameter of journal d4 ,length of journal l4 ,height to centre #a4je;d 4#e4 ,length of base #c4f;d #e4 ,width of base 4#hl4 block 4#gl4 ,thickness of base 4#c;d 4#c4 cap 4#c;d 4#d4 ,diameter of bolts 4#be;d 4#be4 ,distance between centres of cap bolts #a4f;d #a4e4 base bolts #b4g;d #d4b4 ,thickness of step at bottom t 4#ji;d 4#ae4 sides #c_/d t4 ,the length of the journal varies very much in different cases1 and depends upon the speed of the shaft1 the load which it carries1 the workmanship of the journal and bearing1 and the method of lubrication4 ,for ordinary shafting one rule is to make l d #a4 ,some makers use the rule l #a4e;d2 others make l #b;d4 ,,exercise #bg3 ,design for ,pillow ,block4--,make the necessary working drawings for a pillow block for a shaft #e inches in diameter1 and having a journal #g inches long4 ,illustration3 ,,fig4 #bg4 ,brackets4--,when a pillow block has to be fixed to a wall or column a bracket such as that shown in figs4 #bg and #bh may be used4 ,the pillow block rests between the joggles ,a ,a1 and is bolted down to the bracket and secured in addition with keys at the ends of the base of the block1 in the same manner as is shown1 for the attachment of the bracket to the column4 ,,exercise #bh3 ,pillar ,bracket4--,fig4 #bg shows a side elevation and part horizontal section1 and fig4 #bh shows an end elevation of a pillar bracket for carrying a pillow block for a #c-;inch shaft4 ,draw these views properly projected from one another1 showing the pillow block1 which is to be proportioned by the rules given on page #cb4 ,draw also a plan of the whole4 ,scale #d inches to a foot4 ,illustration3 ,,fig4 #bh4 ,hangers4--,when a shaft is suspended from a ceiling it is carried by hangers1 one form of which is shown in fig4 #bi1 and which will be readily understood4 ,the cap of the bearing1 it will be noticed1 is secured by means of a bolt1 and also by a square key4 ,,exercise #bi3 ,shaft ,hanger4--,draw the two elevations shown in fig4 #bi1 and also a sectional plan4 ,the section to be taken at a point #e inches above the centre of the shaft4 ,scale #f inches to a foot4 ,wall ,boxes4--,in passing from one part of a building to another a shaft may have to pass through a wall4 ,in that case a neat appearance is given to the opening and a suitable support obtained for a pillow block by building into the wall a wall box1 one form of which is shown in fig4 #cj4 ,,exercise #cj3 ,wall ,box4--,draw the views of the wall box shown in fig4 #cj1 and also a sectional plan2 the plane of section to pass through the box a little above the joggles for the pillow block4 ,scale #c inches to a foot4 ,illustration3 ,,fig4 #bi4 ,illustration3 ,,fig4 #cj4 ,,viii4 ,,pulleys4 ,velocity ,ratio in ,belt ,gearing4--,let two pulleys ,a and ,b be connected by a belt1 and let their diameters be ,d#a and ,d#b2 and let their speeds1 in revolutions per minute1 be ,n#a and ,n#b respectively4 ,if there is no slipping1 the speeds of the rims of the pulleys will be the same as that of the belt1 and will therefore be equal4 ,now the speed of the rim of ,a is evidently ,d#a x #c4adaf x ,n#a2 while the speed of the rim of ,b is ,d#b x #c4adaf x ,n#b4 ,hence ,d#a x #c4adaf x ,n#a ,d#b x #c4adaf x ,n#b1 and therefore ,n#a ,d#b ----- -----4 ,n#b ,d#a ,pulleys for ,flat ,bands4--,in cross section the rim of a pulley for carrying a flat band is generally curved as shown in figs4 #ca and #cb1 but very often the cross section is straight4 ,the curved cross section of the rim tends to keep the band from coming off as long as the pulley is rotating4 ,sometimes the rim of the pulley is provided with flanges which keep the band from falling off4 ,pulleys are generally made entirely of cast iron1 but a great many pulleys are now made in which the centre or nave only is of cast iron1 the arms being of wrought iron cast into the nave1 while the rim is of wrought sheet iron4 ,the arms of pulleys when made of wrought iron are invariably straight1 but when made of cast iron they are very often curved4 ,in fig4 #ca1 which shows an arrangement of two cast-iron pulleys1 the arms are straight2 while in fig4 #cb1 which shows another cast-iron pulley1 the arms are curved4 ,through unequal cooling1 and therefore unequal contraction of a cast-iron1 pulley in the mould1 the arms are generally in a state of tension or compression2 and if the arms are straight they are very unyielding1 so that the result of this initial stress is often the breaking of an arm1 or of the rim where it joins an arm4 ,with the curved arm1 however1 its shape permits it to yield1 and thus cause a diminution of the stress due to unequal contraction4 ,the cross section of the arms of cast-iron pulleys is generally elliptical4 ,illustration3 ,fig4 #ca4 ,,exercise #ca3 ,fast and ,loose ,pulleys4--,fig4 #ca shows an arrangement of fast and loose pulleys4 ,a is the fast pulley1 secured to the shaft ,c by a sunk key2 ,b is the loose pulley1 which turns freely upon the shaft4 ,the loose pulley is prevented from coming off by a collar ,d1 which is secured to the shaft by a tapered pin as shown4 ,the nave or boss of the loose pulley is here fitted with a brass liner1 which may be renewed when it becomes too much worn4 ,draw the elevations shown1 completing the left-hand one4 ,scale #f inches to a foot4 ,by the above arrangement of pulleys a machine may be stopped or set in motion at pleasure4 ,when the driving band is on the loose pulley the machine is at rest1 and when it is on the fast pulley the machine is in motion4 ,the driving band is shifted from the one pulley to the other by pressing on that side of the band which is advancing towards the pulleys4 ,illustration3 ,,fig4 #cb4 ,,exercise #cb3 ,cast-iron ,pulley with ,curved ,arms and ,cone ,keys4--,draw a complete side elevation and a complete cross section of the pulley represented in fig4 #cb to a scale of #c inches to a foot4 ,in drawing the side elevation of the arms first draw the centre lines as shown2 next draw three circles for each arm1 one at each end and one in the middle2 the centres of these circles being on the centre line of the arm1 and their diameters equal to the widths of the arm at the ends and at the middle respectively4 ,arcs of circles are then drawn to touch these three circles4 ,the centres and radii of these arcs may be found by trial4 ,the cone keys for securing the pulley to the shaft were described on p4 #bc4 ,pulleys for ,ropes4--,ropes made of hemp are now extensively used for transmitting power4 ,these ropes vary in diameter from #a inch to #b inches1 and are run at a speed of about #d1ejj feet per minute4 ,the pulleys for these ropes are made of cast iron1 and have their rims grooved as shown in fig4 #cc1 which is a cross section of the rim of a pulley carrying three ropes4 ,the angle of the ,v is usually #de deg41 and the rope rests on the sides of the groove1 and not on the bottom1 so that it is wedged in1 and has therefore a good hold of the pulley4 ,the diameter of the pulley should not be less than #cj times the diameter of the rope4 ,two pulleys connected by ropes should not be less than thirty feet apart from centre to centre1 but this distance may be as much as #ajj feet4 ,illustration3 ,,fig4 #cc4 ,,exercise #cc3 ,section of ,rim of ,rope ,pulley4--,draw1 half size1 the section of the rim of a rope pulley shown in fig4 #cc4 ,,ix4 ,,toothed ,,wheels4 ,pitch ,surfaces of ,spur ,wheels4--,let two smooth rollers be placed in contact with their axes parallel1 and let one of them rotate about its axis2 then if there is no slipping the other roller will rotate in the opposite direction with the same surface velocity2 and if ,d#a1 ,d#b be the diameters of the rollers1 and ,n#a1 ,n#b their speeds in revolutions per minute1 it follows as in belt gearing that-- ,n#a ,d#b ----- -----4 ,n#b ,d#a ,if there be considerable resistance to the motion of the follower slipping may take place1 and it may stop4 ,to prevent this the rollers may be provided with teeth2 then they become spur wheels2 and if the teeth be so shaped that the ratio of the speeds of the toothed rollers at any instant is the same as that of the smooth rollers1 the surfaces of the latter are called the pitch surfaces of the former4 ,pitch ,circle4--,a section of the pitch surface of a toothed wheel by a plane perpendicular to its axis is a circle1 and is called a pitch circle4 ,we may also say that the pitch circle is the edge of the pitch surface4 ,the pitch circle is generally traced on the side of a toothed wheel1 and is rather nearer the points of the teeth than the roots4 ,pitch of ,teeth4--,the distance from the centre of one tooth to the centre of the next1 or from the front of one to the front of the next1 measured at the pitch circle1 is called the pitch of the teeth4 ,if ,d be the diameter of the pitch circle of a wheel1 n the number of teeth1 and p the pitch of the teeth1 then ,d x #c4adaf n x p4 ,illustration3 ,,fig4 #cd4 ,by the diameter of a wheel is meant the diameter of its pitch circle4 ,form and ,proportions of ,teeth4--,the ordinary form of wheel teeth is shown in fig4 #cd4 ,the curves of the teeth should be cycloidal curves1 although they are generally drawn in as arcs of circles4 ,it does not fall within the scope of this work to discuss the correct forms of wheel teeth4 ,the student will find the theory of the teeth of wheels clearly and fully explained in ,goodeve's ',elements of ,mechanism1' and in ,unwin's ',machine ,design4' ,the following proportions for the teeth of ordinary toothed wheels may be taken as representing average practice3-- ,pitch of teeth p arc a b c 7fig4 #cd74 ,thickness of tooth b c 4#dhp4 ,width of space a b 4#ebp4 ,total height of tooth h 4#gp4 ,height of tooth above pitch line k 4#cp4 ,depth of tooth below pitch line l 4#dp4 ,width of tooth #bp to #cp4 ,,exercise #cd3 ,spur ,wheel4--,fig4 #ce shows the elevation and sectional plan of a portion of a cast-iron spur wheel4 ,the diameter of the pitch circle is #bc-g_/h inches1 and the pitch of the teeth is #a-a_/b inches1 so that there will be #ej teeth in the wheel4 ,the wheel has six arms4 ,draw a complete elevation of the wheel and a half sectional plan1 also a half-plan without any section4 ,draw also a cross section of one arm4 ,scale #d inches to a foot4 ,illustration3 ,,fig4 #ce4 ,mortise ,wheels4--,when two wheels gearing together run at a high speed the teeth of one are made of wood4 ,these teeth1 or cogs1 as they are generally called1 have tenons formed on them1 which fit into mortises in the rim of the wheel4 ,this wheel with the wooden teeth is called a mortise wheel4 ,an example of a mortise wheel is shown in fig4 #cf4 ,illustration3 ,,fig4 #cf4 ,bevil ,wheels4--,in bevil wheels the pitch surfaces are parts of cones4 ,bevil wheels are used to connect shafts which are inclined to one another1 whereas spur wheels are used to connect parallel shafts4 ,in fig4 #cf is shown a pair of bevil wheels in gear1 one of them being a mortise wheel4 ,at 7a7 is a separate drawing1 to a smaller scale1 of the pitch cones4 ,the pitch cones are shown on the drawing of the complete wheels by dotted lines4 ,the diameters of bevil wheels are the diameters of the bases of their pitch cones4 ,,exercise #ce3 ,pair of ,bevil ,wheels4--,draw the sectional elevation of the bevil wheels shown in gear in fig4 #cf4 ,commence by drawing the centre lines of the shafts1 which in this example are at right angles to one another2 then draw the pitch cones shown by dotted lines4 ,next put in the teeth which come into the plane of the section1 then complete the sections of the wheels4 ,the pinion or smaller wheel has #be teeth1 and the wheel has #ej teeth1 which makes the pitch a little over #c inches4 ,each tooth of the mortise wheel is secured as shown by an iron pin #e_/af inch diameter4 ,scale #c inches to a foot4 ,x4 ,,cranks ,,and ,,cranked ,,shafts4 ,the most important application of the crank is in the steam-engine1 where the reciprocating rectilineal motion of the piston is converted into the rotary motion of the crank-shaft by means of the crank and connecting rod4 ,at one time steam-engine cranks were largely made of cast iron1 now they are always made of wrought iron or steel4 ,the crank is either forged in one piece with the shaft1 or it is made separately and then keyed to it4 ,overhung ,crank4--,fig4 #cg shows a wrought-iron overhung crank4 ,a is the crank-shaft1 ,b the crank arm1 provided at one end with a boss ,c1 which is bored out to fit the shaft2 at the other end of the crank arm is a boss ,d1 which is bored out to receive the crank-pin ,e1 which works in one end of the connecting rod4 ,the crank is secured to the shaft by the sunk key ,f4 ,it is also good practice to shrink the crank on to the shaft4 ,the process of shrinking consists of boring out the crank a little smaller than the shaft1 and then heating it1 which causes it to expand sufficiently to go on to the shaft4 ,as the crank cools1 it shrinks and grips the shaft firmly4 ,the crank may also be shrunk on to the crank-pin1 the latter being then riveted over as shown in fig4 #cg4 ,illustration3 ,,fig4 #cg4 ,a good plan to adopt in preference to the shrinking process is to force the parts together by hydraulic pressure4 ,this method is adopted for placing locomotive wheels on their axles1 and for putting in crank-pins4 ,as to the amount of pressure to be used1 the practice is to allow a force of #aj tons for every inch of diameter of the pin1 axle1 or shaft4 ,instead of being riveted in1 the crank pin may be prolonged and screwed1 and fitted with a nut4 ,another plan is to put a cotter through the crank and the crank-pin4 ,the distance from the centre of the crank-shaft to the centre of the crank-pin is called the radius of the crank4 ,the throw of the crank is twice the radius4 ,in a direct-acting engine the throw of the crank is equal to the stroke of the piston4 ,,exercise #cf3 ,wrought-iron ,overhung ,crank4--,draw the two elevations shown in fig4 #cg1 also a plan4 ,scale #a-a_/b inches to a foot4 ,proportions of ,overhung ,cranks4 ,d diameter of shaft4 d crank-pin4 ,length of large boss 4#i ,d4 ,diameter #a4h ,d4 ,length of small boss #a4a d4 ,diameter #a4h d4 ,width of crank arm at centre of shaft #a4c ,d4 crank-pin #a4e d4 ,the thickness of the crank arm may be roughly taken as 4#g ,d4 ,,exercise #cg4--;,design a wrought-iron crank for an engine having a stroke of #d feet4 ,the crank-shaft is #i inches in diameter1 and the crank-pin is #d-c_/d inches in diameter and #f-a_/b inches long4 ,illustration3 ,,fig4 #ch4 ,locomotive ,cranked ,axle4--,as an example of a cranked shaft we take the cranked axle for a locomotive with inside cylinders shown in fig4 #ch2 here the crank and shaft or axle are forged in one piece4 ,a is the wheel seat1 ,b the journal1 ,c the crank-pin1 and ,d and ,e the crank arms4 ,only one half of the axle is shown in fig4 #ch1 but the other half is exactly the same4 ,the cranks on the two halves are1 however1 at right angles to one another4 ,the ends of the crank arms are turned in the lathe1 the crank-pin ends being turned at the same time as the axle1 and the other ends at the same time as the crank-pin4 ,this consideration determines the centres for the arcs shown in the end view4 ,,exercise #ch4--;,draw to a scale of #b inches to a foot the side and end elevations of the locomotive cranked axle partly shown in fig4 #ch4 ,the distance between the centre lines of the cylinders is #b feet4 ,illustration3 ,,fig4 #ci4 ,built-up ,cranks4--,the form of cranked shaft shown in fig4 #ch is largely used for marine engines1 but for the very powerful engines now fitted in large ships this design of shaft is very unreliable1 the built-up crank shown in fig4 #ci being preferred1 although it is much heavier than the other4 ,it will be seen from the figure that the shaft1 crank arms1 and crank-pin are made separately4 ,the arms are shrunk on to the pin and the shaft1 and secured to the latter by sunk keys4 ,these heavy shafts and cranks are generally made of steel4 ,,exercise #ci4--,keeping to the dimensions marked in fig4 #ci1 draw the views there shown of a built-up crank-shaft for a marine engine4 ,scale #c_/d inch to a foot4 ,,xi4 ,,eccentrics4 ,the eccentric is a particular form of crank1 being a crank in which the crank-pin is large enough to embrace the crank-shaft4 ,in the eccentric what corresponds to the crank-pin is called the sheave or pulley4 ,the advantage which an eccentric possesses over a crank is that the shaft does not require to be divided at the point where the eccentric is put on4 ,the crank1 however1 has this advantage over the eccentric1 namely1 that it can be used for converting circular into reciprocating motion1 or vice versa1 while the eccentric can only be used for converting circular into reciprocating motion4 ,this is owing to the great leverage at which the friction of the eccentric acts4 ,the chief application of the eccentric is in the steam-engine1 where it is used for working the valve gear4 ,to permit of the sheave being placed on the shaft without going over the end 7which could not be done at all in the case of a cranked axle1 and would be a troublesome operation in most cases7 it is generally made in two pieces1 as shown in fig4 #dj1 which represents one of the eccentrics of a locomotive4 ,the two parts of the sheave are connected by two cotter bolts4 ,the part which embraces the sheave is called the eccentric strap1 and corresponds to1 and is1 in fact1 a connecting rod end3 the rod proceeding from this is called the eccentric rod4 ,the distance from the centre of the sheave to the centre of the shaft is called the radius or eccentricity of the eccentric4 ,the throw is twice the eccentricity4 ,the sheave is generally made of cast iron4 ,the strap may be of brass1 cast iron1 or wrought iron2 when the strap is made of wrought iron it is commonly lined with brass4 ,illustration3 ,,fig4 #dj4 ,,exercise #dj3 ,locomotive ,eccentric4--,in fig4 #dj ,d ,e is the sheave1 ,f ,h the strap1 and ,k the eccentric rod4 ,the sheave and strap are made of cast iron1 and the eccentric rod is made of wrought iron4 7a7 is a vertical cross section through the oil-box of the strap2 7b7 is a plan of the end of the eccentric rod and part of the strap4 ,all the nuts are locked by means of cotters4 ,draw first the elevation1 partly in section as shown4 ,next draw two end elevations1 one looking each way4 ,afterwards draw a horizontal section through the centre1 and also a plan4 ,scale #d inches to a foot4 ,,xii4 ,,connecting ,,rods4 ,the most familiar example of the use of a connecting rod is in the steam-engine1 where it is used to connect the rotating crank with the reciprocating piston4 ,the rod itself is made of wrought iron or steel1 and is generally circular or rectangular in section4 ,the ends of the rod are fitted with steps1 which are held together in a variety of ways4 ,strap ,end4--,a form of connecting rod end1 which is not so common as it used to be1 is shown in fig4 #da4 ,at 7a7 is shown a longitudinal section with all the parts put together1 while at 7b71 7c71 7d7 and 7e7 the details are shown separately4 ,a ,b is the end of the rod which butts against the brass bush ,c ,d1 which is in two pieces4 ,a strap ,e passes round the bush and on to the end of the rod as shown4 ,the arms of the strap have rectangular holes in them1 which are not quite opposite a similar hole in the rod when the parts are put together4 ,if a wedge or cotter ,f be driven into these three holes they will tend to come into line1 and the parts of the bush will be pressed together4 ,to prevent the cotter opening out the strap1 and to increase the sliding surface1 a gib ,h is introduced4 ,the gib is provided with horns at its ends to keep it in its place4 ,sometimes two gibs are used1 one on each side of the cotter2 this makes the sliding surface on both sides of the cotter the same4 ,the cotter is secured by a set screw ,k4 ,the unsectioned portion of fig4 7a7 to the right of the gib1 or to the left of the cotter1 is called the clearance or draught4 ,illustration3 ,,fig4 #da4 ,,exercise #da3 ,connecting ,rod ,end4--,make the following views of the connecting rod end illustrated by fig4 #da4 ,first1 a vertical section1 the same as shown at 7a74 ,second1 a horizontal section4 ,third1 side elevation4 ,fourth1 a plan4 ,or the first and third views may be combined in a half vertical section and half elevation2 and the second and fourth views may be combined in a half horizontal section and half plan4 ,all the dimensions are to be taken from the detail drawings 7b71 7c71 7d71 and 7e71 but the details need not be drawn separately4 ,the brass bush is shown at 7d7 by half elevation1 half vertical section1 half plan1 and half horizontal section4 ,the draught or clearance is #g-afths of an inch4 ,box ,end4--,at 7a71 fig4 #db1 is shown what is known as a box end for a connecting rod4 ,the part which corresponds to the loose strap in the last example is here forged in one piece with the connecting rod4 ,in this form the brass bush is provided with a flange all round on one side1 but on the opposite side the flange is omitted except at one end2 this is to allow of the bush being placed within the end of the rod4 ,the construction of the bush will be understood by reference to the sketch shown at 7b74 ,the bush is in two parts1 which are pressed tightly together by means of a cotter4 ,this cotter is prevented from slackening back by two set screws4 ,each set screw is cut off square at the point1 and presses on the flat bottom of a very shallow groove cut on the side of the cotter4 ,the top1 bottom1 and ends of this box end are turned in the lathe at the same time as the rod itself2 this accounts for the curved sections of these parts4 ,it is clear from the construction of a box end that it is only suitable for an overhung crank4 ,,exercise #db3 ,locomotive ,connecting ,rod4--,in fig4 #db is shown a connecting rod for an outside cylinder locomotive4 7a7 is the crank-pin end1 and 7c7 the cross-head end4 ,the end 7a7 has just been described under the head 'box end4' ,we may just add that in this particular example the brass bush is lined with white metal as shown1 and that the construction of the oil-box is the same as that on the coupling rod end shown in fig4 #dd4 ,the end 7c7 is forked1 and through the prongs of the fork passes the cross-head pin1 of which a separate dimensioned drawing is shown at 7d74 ,observe that the tapered parts ,a and ,b of this pin are parts of the same cone4 ,the rotation of the pin is prevented by a small key as shown4 ,the cross-head pin need not be drawn separately1 and the isometric projection of the bush at 7b7 may be omitted1 but all the other views shown are to be drawn to a scale of #f inches to a foot4 ,marine ,connecting ,rod4--,the form of connecting rod shown in fig4 #dc is that used in marine engines1 but it is also used extensively in land engines4 ,a ,b is the crank-pin end1 and ,c the cross-head end4 ,the end ,a ,b is forged in one piece1 and after it is turned1 planed1 and bored it is slotted across1 so as to cut off the cap ,a4 ,the parts ,a and ,b are held together by two bolts as shown4 ,this end of the rod is fitted with brass steps1 which are lined with white metal4 ,the cross-head end is forked1 and through the prongs of the fork passes a pin ,d1 which also passes through the cross-head1 which is forged on to the piston rod or attached to it in some other way4 ,illustration3 ,,fig4 #db4 ,illustration3 ,,fig4 #dc4 ,,exercise #dc3 ,marine ,connecting ,rod4--,draw all the views shown in fig4 #dc of one form of marine connecting rod4 ,for detail drawings of the locking arrangement for the nuts see fig4 #ai1 page #ba4 ,scale #d inches to a foot4 ,coupling ,rods4--,a rod used to transmit the motion of one crank to another is called a coupling rod4 ,a familiar example of the use of coupling rods will be found in the locomotive4 ,coupling rods are made of wrought iron or steel1 and are generally of rectangular section4 ,the ends are now generally made solid and lined with solid brass bushes1 without any adjustment for wear4 ,this form of coupling rod end is found to answer very well in locomotive practice where the workmanship and arrangements for lubrication are excellent4 ,when the brass bush becomes worn it is replaced by a new one4 ,fig4 #dd shows an example of a locomotive coupling rod end for an outside cylinder engine4 ,in this case it is desirable to have the crank-pin bearings for the coupling rods as short as possible1 for a connecting rod and coupling rod in this kind of engine work side by side on the same crank-pin1 which1 being overhung1 should be as short as convenient for the sake of strength4 ,the requisite bearing surface is obtained by having a pin of large diameter4 ,the brass bush is prevented from rotating by means of the square key shown4 ,the oil-box is cut out of the solid1 and has a wrought-iron cover slightly dovetailed at the edges4 ,this cover fits into a check round the top inner edge of the box1 which is originally parallel1 but is made to close on the dovetailed edges of the cover by riveting4 ,a hole in the centre of this cover1 which gives access to the oil-box1 is fitted with a screwed brass plug4 ,the brass plug has a screwed hole in the centre1 through which oil may be introduced to the box4 ,dust is kept out of the oil-box by screwing into the hole in the brass plug a common cork4 ,the oil is carried slowly but regularly from the oil-box over to the bearing by a piece of cotton wick4 ,illustration3 ,,fig4 #dd4 ,,exercise #dd3 ,coupling ,rod ,end4--,draw first the side elevation and plan1 each partly in section as shown in fig4 #dd4 ,then instead of the view to the left1 which is an end elevation partly in section1 draw a complete end elevation looking to the right1 and also a complete vertical cross section through the centre of the bearing4 ,scale #f inches to a foot4 ,,xiii4 ,,cross-,,heads4 ,an example of a steam-engine cross-head is shown in fig4 #de4 ,a is the end of the piston rod which has forged upon it the cross-head ,b4 ,the cross-head pin shown at 7d71 fig4 #db1 and to which the connecting rod is attached1 works in the bearing ,c4 ,projecting pieces ,d1 forged on the top and bottom of the cross-head1 carry the slide blocks ,e which work on the slide bars1 and thus guide the motion of the piston rod4 ,illustration3 ,,fig4 #de4 ,,exercise #de3 ,locomotive ,cross-head4--,in fig4 #de are shown side and end elevations1 partly in section1 of the cross-head and slide blocks for an outside cylinder locomotive4 ,draw these views half size1 showing also on the end elevation the cross-head pin and a vertical section of the connecting rod end from fig4 #db4 ,the bush in the cross-head which forms the bearing for the cross-head pin is of wrought iron1 case-hardened1 and is prevented from rotating by the key shown4 ,the cross-head is of wrought iron1 and the slide blocks are of cast iron1 and are fitted with white metal strips as shown4 ,a short brass tube leads oil from the upper slide block into a hole in the cross-head as shown1 which carries it to a slot in the bush which distributes it over the cross-head pin4 ,,xiv4 ,,pistons4 ,a piston is generally a cylindrical piece which slides backwards and forwards inside a hollow cylinder4 ,the piston may be moved by the action of fluid pressure upon it as in a steam-engine1 or it may be used to give motion to a fluid as in a pump4 ,a piston is usually attached to a rod1 called a piston rod1 which passes through the end of the cylinder inside which the piston works1 and which serves to transmit the motion of the piston to some piece outside the cylinder1 or vice versa4 ,illustration3 ,,fig4 #df4 ,a plunger is a piston made in one piece with its piston rod1 the piston and the rod being of the same diameter4 ,a piston which is provided with one or more valves which allow the fluid to pass through it from one side to the other is called a bucket4 ,simple ,piston4--,the simplest form of piston is a plain cylinder fitting accurately another1 inside which it moves4 ,such a piston works with very little friction1 but as there is no adjustment for wear1 such a piston is not suitable for a high fluid pressure if it has to work constantly4 ,this simple form of piston is used in the steam-engine indicator1 and also in pumps4 ,fig4 #df shows the piston of the circulation pump of a marine engine4 ,a is the cast-iron casing or barrel of the pump2 ,b is a brass liner fitting tightly into the former at its ends1 and secured by eight screwed ,muntz metal pins ,c1 four at each end2 ,d is the piston1 which is made of brass1 and is attached to a ,muntz metal piston rod ,e4 ,the liner is bored out smooth and true from end to end1 and the piston is turned so as to be a sliding fit to the liner4 ,the wear in this form of piston is diminished by making the rubbing surface large4 ,,exercise #df3 ,piston for ,circulating ,pump4--,draw the vertical sectional elevation of the piston1 c41 shown in fig4 #df1 also a half plan and half horizontal section through the centre4 ,scale #d inches to a foot4 ,pump ,bucket4--,the next form of piston which we illustrate is shown in fig4 #dg4 ,this represents the air-pump bucket of a marine engine4 ,the bucket is made of brass1 and is provided with six india-rubber disc valves4 ,the rod is in this case made of ,muntz metal4 ,air-pump rods for marine engines are very often made of wrought iron cased with brass4 ,it will be observed that there is a wide groove around the bucket1 which is filled with hempen rope or gasket4 ,this gasket forms an elastic packing which prevents leakage4 ,this is an old-fashioned form of packing1 and is now only used for pump buckets4 ,illustration3 ,,fig4 #dg4 ,,exercise #dg3 ,air-pump ,bucket4--,draw the sectional elevation of the air-pump bucket shown in fig4 #dg4 ,also draw a half plan looking downwards and a half plan looking upwards4 ,scale #d inches to a foot4 ,ramsbottom's ,packing4--,the form of packing used in the air-pump bucket1 fig4 #dg1 is not suitable for steam pistons4 ,for the latter the packing is now always metallic4 ,the simplest form of metallic packing is that known as ,ramsbottom's4 ,this form is very largely used for locomotive pistons1 and for small pistons in many kinds of engines besides4 ,a locomotive piston for an #ah-;inch cylinder with ,ramsbottom's packing is shown in fig4 #dh4 ,the particular piston there illustrated is made of brass1 and is secured to a wrought-iron piston rod by a brass nut4 ,two circumferential grooves of rectangular section are turned out of the piston1 and into these fit two corresponding rings1 which may be of brass1 cast iron1 or steel4 ,in this example the rings are of cast iron4 ,these rings are first turned a little larger in diameter than the bore of the cylinder 7in this example #a_/b inch71 and then sprung over the piston into the groves prepared for them4 ,their own elasticity causes the rings to press outwards on the cylinder4 ,at the point where a ring is split a leakage of steam will take place1 but with quick-running pistons this leakage is unimportant4 ,the points where the rings are cut should be placed diametrically opposite1 so as to diminish the leakage of steam4 ,illustration3 ,,fig4 #dh4 ,,exercise #dh3 ,locomotive ,piston4--,a part elevation and part section of a locomotive piston1 for a cylinder having a bore #ah inches in diameter1 is shown in fig4 #dh4 ,draw this1 and also a view looking on the nut in the direction of the axis of the piston rod4 ,scale #f inches to a foot4 ,note4--,the reason why the part of the piston rod within the piston has such a quick taper is that the piston has to be taken off the rod while it is in the cylinder4 ,the cross-head being forged on the end of the piston rod prevents the piston and piston rod being withdrawn together4 ,large ,pistons4--,pistons of large diameter are generally provided with two cast-iron packing rings placed within the same groove4 ,these rings are pressed outwards against the cylinder1 and also against the sides of the groove by one or more springs4 ,one form of this packing 7,lancaster's7 is shown in fig4 #di4 ,here one spring only is used1 and it is first made a straight spiral spring1 and then bent round and its ends united4 ,the action of the spring will be clearly understood from the illustration4 ,for the purpose of admitting the packing rings the piston is divided into two parts1 one the piston proper1 and the other the junk ring4 ,in fig4 #di1 ,a is the junk ring1 which is secured to the piston by means of bolts as shown4 ,illustration3 ,,fig4 #di4 ,,exercise #di3 ,marine ,engine ,piston4--,the piston illustrated by fig4 #di is for the high-pressure cylinder of a marine engine4 ,the piston1 junk ring1 and packing rings are of cast iron4 ,the piston rod and nut are of wrought iron1 so also are the junk ring bolts4 ,the nuts for the latter are of brass4 ,the spiral spring is made from steel wire #c_/h inch diameter4 ,an enlarged section of one of the packing rings is shown at 7a74 ,a front elevation of the locking arrangement for the piston rod nut is shown at 7b74 ,a sectional plan of one of the nuts for the junk ring bolts is shown at 7c74 ,first draw the vertical section of this piston1 next draw a plan1 one-third of which is to show the piston complete1 one-third to show the junk ring removed1 and the remaining third to be a horizontal section through between the packing rings4 ,the details 7a7 and 7c7 need not be drawn separately4 ,scale #c inches to a foot4 ,proportions of ,marine ,engine ,pistons4--,mr4 ,seaton1 in his ',manual of ,marine ,engineering1' gives the following rules for designing marine engine pistons3-- ,d diameter of piston in inches4 p effective pressure in lbs4 per square inch4 x ,d_/#ej x sqrt 7p7 #a4 ,thickness of front of piston near boss #j4b x x4 rim #j4ag x x4 back of piston #j4ah x x4 boss around rod #j4c x x4 flange inside packing ring #j4bc x x4 at edge #j4be x x4 junk ring at edge #j4bc x x4 inside packing ring4 #j4ba x x4 at bolt-holes #j4ce x x4 metal around piston edge #j4be x x4 ,breadth of packing ring #j4fc x x4 ,depth of piston at centre #a4d x x4 ,lap of junk ring on piston #j4de x x4 ,space between piston body and packing ring #j4c x x4 ,diameter of junk-ring bolts #j4a x x 4#be inch4 ,pitch of junk-ring bolts #aj diameters4 ,number of webs in piston 7,d #bj7_/ab4 ,thickness #j4ah x x4 ,,exercise #ej3 ,design for ,marine ,engine ,piston4--,calculate by ,seaton's rules the dimensions for a marine engine piston #dj inches in diameter1 and subjected to an effective pressure of #cf lbs4 per square inch4 ,then make the necessary working drawings for this piston to a scale of1 say1 #c inches to a foot4 ,note4--,take the dimensions got by calculation to the nearest #a-afth of an inch4 ,,xv4 ,,stuffing-,,boxes4 ,illustration3 ,,fig4 #ej4 ,in fig4 #ej is shown a gland and stuffing-box for the piston rod of a vertical engine4 ,a ,b is the piston rod1 ,c ,d a portion of the cylinder cover1 and ,e ,f the stuffing-box4 ,fitting into the bottom of the stuffing-box is a brass bush ,h4 ,the space ,k around the rod ,a ,b is filled with packing1 of which there is a variety of kinds1 the simplest being greased hempen rope4 ,the packing is compressed by screwing down the cast-iron gland ,l ,m1 which is lined with a brass bush ,n4 ,in this case the gland is screwed down by means of three stud-bolts ,p1 which are screwed into a flange cast on the stuffing-box4 ,surrounding the rod on the top of the gland there is a recess ,r for holding the lubricant4 ,illustration3 ,,fig4 #ea4 ,illustration3 ,,fig4 #eb4 ,the object of the gland and stuffing-box is to allow the piston rod to move backwards and forwards freely without any leakage of steam4 ,fig4 #ea shows a gland and stuffing-box for a horizontal rod4 ,the essential difference between this example and the last is in the mode of lubrication4 ,the gland flange has cast within it an oil-box which is covered by a lid2 this lid is kept shut or open by the action of a small spring as shown4 ,a piece of cotton wick 7not shown in the figure7 has one end trailing in the oil in the oil-box1 while the other is carried over and passed down the hole ,a ,b4 ,the wick acts as a siphon1 and drops the oil gradually on to the rod4 ,in this example only two bolts are used for screwing in the gland2 and the flanges of the gland and stuffing-box are not circular1 but oval-shaped4 ,in the case of small rods the gland is made entirely of brass1 and no liner is then necessary4 ,fig4 #eb shows a form of gland and stuffing-box sometimes used for small rods4 ,the stuffing-box is screwed externally1 and carries a nut ,a ,b which moves the gland4 ,,exercise #ea3 ,gland and ,stuffing-box for a ,vertical ,rod4--,draw the views shown in fig4 #ej to the dimensions given4 ,scale #f inches to a foot4 ,,exercise #eb3 ,gland and ,stuffing-box for a ,horizontal ,rod4--,fig4 #ea shows a plan1 half in section1 and an elevation half of which is a section through the gland flange4 ,draw these to a scale of #f inches to a foot1 using the dimensions marked in the figure4 ,,exercise #ec3 ,screwed ,gland and ,stuffing-box4--,draw1 full size1 the views shown in fig4 #eb to the given dimensions4 ,a more elaborate form of gland and stuffing-box is shown in fig4 #ec4 ,this is for a large marine engine with inverted cylinders1 such as is used on board large ocean steamers4 ,the stuffing-box is cast separate from the cylinder cover to which it is afterwards bolted4 ,the lubricant is first introduced to the oil-boxes marked ,a1 from which it passes to the recess ,b1 where it comes in contact with the piston rod4 ,to prevent the lubricant from being wasted by running down the rod1 the main gland is provided with a shallow gland and stuffing-box which is filled with soft cotton packing1 which soaks up the lubricant4 ,the main gland is screwed up by means of six bolts1 and to prevent the gland from locking itself in the stuffing-box1 it is necessary that the nuts should be turned together4 ,this is done in a simple and ingenious manner4 ,one-half of each nut is provided with teeth1 and these gear with a toothed wheel which has a rim only2 this rim is held up by a ring ,c4 ,when one nut is turned1 all the rest follow in the same direction4 ,illustration3 ,,fig4 #ec4 ,,exercise #ed3 ,gland and ,stuffing-box for ,piston ,rod of ,large ,inverted ,cylinder ,engine4--,the lower view in fig4 #ec is a half plan looking upwards1 and a half section of the gland looking downwards4 ,the upper view is a vertical section4 ,complete all these views and add an elevation4 ,scale #c inches to a foot4 ,note4--,the large nuts1 the wheel1 the supporting ring1 and small gland are made of brass4 ,dimensions of ,stuffing-boxes and ,glands4 d diameter of rod4 t#a thickness of d#a diameter of box 7inside74 stuffing-box flange4 l length of stuffing-box t#b thickness of gland bush4 flange4 l#a length of packing space4 t#c thickness of bushes in l#b length of gland4 box and gland4 t thickness of metal in d#b diameter of gland bolts4 stuffing-box4 n number of bolts4 ---------------------------------------- ------------------ d d#a l l#a l#b t t#a ---------------------------------------- ------------ #a #a-c_/d #c_/d #b #a-a_/b #g_/af #a_/b #a-a_/b #b-a_/b #a-a_/d #b-e_/h #b #i_/af #aa_/af #b #c-a_/b #a-c_/d #c-a_/d #b-a_/b #aa_/af #g_/h #b-a_/b #d-a_/h #b-a_/d #c-g_/h #b-g_/h #ac_/af #a-a_/af #c #d-c_/d #b-c_/d #d-a_/b #c-a_/d #ae_/af #a-a_/d #c-a_/b #e-a_/d #c #e-a_/h #c-e_/h #a #a-c_/h #d #e-g_/h #c-a_/d #e-c_/d #d #a #a-c_/h #d-a_/b #f-c_/h #c-a_/b #f-c_/h #d-c_/h #a-a_/af #a-i_/af #e #g #c-c_/d #g #d-e_/h #a-a_/af #a-i_/af #f #h #d-a_/d #h-a_/d #e #a-a_/h #a-aa_/af ---------------------------------------- ------------------ ---------------------------------------- --------- d t#b t#c d#b n ---------------------------------------- ----- #a t#bt #c_/af #g_/af #b #a-a_/b when gland #a_/d #e_/h #b #b flange is #e_/af #c_/d #b #b-a_/b made of cast #e_/af #g_/h #b #c iron and #c_/h #a #b #c-a_/b t#bt#a #c_/h #a #b #d when gland #g_/af #a #b #d-a_/b flange is #g_/af #g_/h #d #e made of #g_/af #a #d #f brass4 #a_/b #a-a_/d #d ---------------------------------------- --------- ,the proportions of glands and stuffing-boxes vary considerably but the above table represents average practice4 ,,exercise #ee3--,make the necessary working drawings for a gland and stuffing-box for a locomotive engine piston rod #b-a_/b inches in diameter1 to the dimensions given in the table4 ,,xvi4 ,,valves4 ,professor ,unwin divides valves1 according to their construction into three classes as follows3--7#a7 flap valves1 which bond or turn upon a hinge2 7#b7 lift valves1 which rise perpendicularly to the seat2 7#c7 sliding valves1 which move parallel to the seat4 ,examples of flap valves are shown in figs4 #ed and #ee2 two forms of lift valves are shown in figs4 #ef and #eg1 and in figs4 #eh and #ei are shown two forms of slide valve4 ,the slide valve shown in fig4 #eh moves in a straight line1 while that shown in fig4 #ei 7called a cock7 moves in circle4 ,india-rubber ,valves4--,in india-rubber valves there is a grating covered by a piece of india-rubber1 which may be rectangular1 but is generally circular1 and which is held down along one edge if rectangular1 or at the centre if circular4 ,water or other fluid can pass freely upwards through the grating1 but when it attempts to return the elasticity of the india-rubber1 and the pressure of the water upon it1 cause it to lie close on the grating1 and thus prevent the return of the water4 ,the india-rubber is prevented from rising too high by a perforated guard4 ,in fig4 #ed is shown an example of an india-rubber disc valve4 ,a is the grating1 ,b the india-rubber1 ,c the guard secured to the grating or seat by the stud ,d and nut ,e4 ,the grating is held in position by bolts and nuts ,f4 ,the grating and guard are generally of brass4 ,india-rubber disc valves are also shown on the air-pump bucket1 fig4 #dg4 ,,exercise #ef3 ,india-rubber ,disc ,valve4--,fig4 #ed shows a vertical section and a plan of an india-rubber disc valve4 ,in the plan one-half of the guard and india-rubber are supposed to be removed so as to show the grating or seat4 ,draw these views1 and also an elevation4 ,a detail drawing of the central stud is shown in fig4 #af1 page #ah4 ,in fig4 #ed the elevation of the guard is drawn as it is usually drawn in practice1 but if the student has a sufficient knowledge of descriptive geometry he should draw the elevation completely showing the perforations4 ,scale #f inches to a foot4 ,illustration3 ,,fig4 #ed4 ,illustration3 ,,fig4 #ee4 ,kinghorn's ,metallic ,valve4--,the action of this valve is the same as that of an india-rubber valve1 but a thin sheet of metal 7phosphor bronze7 takes the place of the india-rubber4 ,this valve is now largely used in the pumps of marine engines1 and is shown in fig4 #ee as applied to an air-pump bucket4 ,three valves like the one shown are arranged round the bucket4 ,,exercise #eg3 ,kinghorn's ,metallic ,valve4--,fig4 #ee shows an elevation and plan of one form of this valve4 ,in the plan one-half of the guard and metal sheet are supposed to be removed1 so as to show the grating1 which in this case is part of an air-pump bucket4 ,draw the views shown1 and also a vertical section of the guard through the centres of the bolts4 ,all the parts are of brass except the valve proper1 which is of phosphor bronze4 ,scale #f inches to a foot4 ,conical ,disc ,valves4--,a very common form of valve is that shown in figs4 #ef and #eg4 ,this form of valve consists of a disc1 the edge of which 7called the face7 is conical4 ,the conical edge of this disc fits accurately on a corresponding seat4 ,the angle which the valve face makes with its axis is generally #de deg44 ,if the disc is raised1 either by the action of the fluid as in the india-rubber valve1 or by other means1 an opening is formed around the disc through which the fluid can pass4 ,the valve is guided in rising and falling either by three feathers underneath it1 as in fig4 #ef1 or by a central spindle which moves freely through a hole in the centre of a bridge which stretches across the seat1 as in fig4 #eg4 ,the lift of the valve is limited by a stop above it1 which forms part of the casing containing the valve4 ,the lift should in no case exceed one-fourth of the diameter of the valve1 and it is generally much less than this4 ,the guiding feathers 7fig4 #ef7 are notched immediately under the disc for the purpose of making available the full circumferential opening of the valve for the passage of the fluid4 ,these notches also prevent the feathers from interfering with the turning or scraping of the valve face4 ,conical disc valves and their seats are nearly always made of brass4 ,,exercise #eh3 ,conical ,disc ,valves4--,draw1 half size1 the plans and elevations shown in figs4 #ef and #eg4 ,in fig4 #eg the valve is shown open in the elevation1 and in the plan it is removed altogether in order to show the seat with its guide bridge4 ,illustration3 ,plan of ,valve4 ,,fig4 #ef4 ,illustration3 ,plan of ,seat4 ,,fig4 #eg4 ,simple ,slide ,valve4--,the form of valve shown in fig4 #eh1 often called the locomotive slide valve1 is very largely used in all classes of steam-engines for distributing the steam in the steam cylinders4 ,the valve is shown separately at 7d71 7e71 and 7f71 while at 7a71 7b71 and 7c7 is shown its connection with the steam cylinder4 ,it will be observed that the valve itself is in the shape of a box with one side open1 the edges of the open side being flanged4 ,when the valve is in its middle position1 as shown at 7a71 two of these flanged edges completely cover two rectangular openings ,s#a and ,s#b1 called steam ports1 while the hollow part of the valve is opposite to a third port ,e1 called the exhaust port4 ,as shown at 7a7 the piston ,p would be moving upwards and the valve downwards4 ,by the time the piston has reached the top of its stroke the valve will have moved so far down as to partly uncover the steam port ,s#a1 and admit steam from the valve casing ,c through ,s#a and the passage ,p#a to the top of the piston4 ,the pressure of this steam on the top of the piston will force the latter down4 ,while the above action has been going on1 the port ,s#b will have become uncovered1 and the hollow part of the valve will be opposite both the steam port ,s#b and the exhaust port ,e1 so that the steam from the under side of the piston1 and which forced the piston up1 can now escape by the passage ,p#b1 the steam port ,s#b1 and the exhaust port ,e to the exhaust outlet ,o1 and thence into the atmosphere1 if it is a non-condensing engine1 or into the condenser if it is a condensing engine1 or into another cylinder if it is a compound engine4 ,after the piston has performed1 a certain part of its downward stroke1 the valve1 which has been moving downwards1 will commence to move upwards1 and when it has reached a certain point it will cover the port ,s#a1 and shut off the supply of steam to the top of the piston4 ,it is generally arranged that the steam shall be cut off before the piston reaches the end of the stroke4 ,when the piston reaches the bottom of its stroke the valve has moved far enough up to uncover the port ,s#b and admit steam to the bottom of the piston1 and to uncover the port ,s#a and allow the steam to escape from the top of the piston through the passage ,p#a1 the port ,s#a1 the port ,e1 and outlet ,o4 ,in this way the piston is moved up and down in the cylinder4 ,the valve is attached to a valve spindle ,s by nuts as shown1 the hole in the valve through which the spindle passes being oval-shaped to permit of the valve adjusting itself so as to always press on its seat4 ,when the valve is in its middle position it generally more than covers the steam ports4 ,the amount which the valve projects over the steam port on the outside1 the valve being in its middle position1 is called the outside lap of the valve1 and the amount which it projects on the inside is called the inside lap4 ,when the term lap is used without any qualification1 outside lap is to be understood4 ,in fig4 #eh it will be seen that the valve has no inside lap1 and that the outside lap is three-eighths of an inch4 ,the inside lap is generally small compared with the outside lap4 ,illustration3 ,,fig4 #eh4 ,when the piston is at the beginning of its stroke the steam port is generally open by a small amount called the lead of the valve4 ,the reciprocating motion of the slide valve is nearly always derived from an eccentric fixed on the crank-shaft of the engine4 ,slide valves are generally made of brass1 bronze1 or cast iron4 ,,exercise #ei3 ,simple ,slide ,valve4--,at 7d71 fig4 #eh1 is shown a sectional elevation of a simple slide valve for a steam-engine1 the section being taken through the centre line of the valve spindle1 while at 7e7 is shown a cross section and elevation1 and at 7f7 a plan of the same4 ,draw all these views full size1 and also a sectional elevation at ,a ,b4 ,the valve is made of brass1 and the valve spindle and nuts of wrought iron4 ,,exercise #fj3 ,slide ,valve ,casing1 c41 for ,steam-engine4--,draw1 half size1 the views shown at 7a71 7b71 and 7c71 fig4 #eh2 also a sectional plan at ,l ,m4 7b7 is an elevation of the valve casing with the cover and the valve removed4 7a7 is a sectional elevation1 the section being taken through the axes of the steam cylinder and valve spindle4 7c7 is a sectional plan1 the section being a horizontal one through the centre of the exhaust port4 ,the inlet and outlet for the steam are clearly shown in the sectional plan3 in the sectional elevation their positions are shown by dotted circles4 ,the stroke of the piston is in this case #ab inches1 so that from the dimensions given at 7a7 it must come within a quarter of an inch of each end of the cylinder2 this is called the cylinder clearance4 ,the piston has three ,ramsbottom rings1 a quarter of an inch wide and a quarter of an inch apart4 ,the steam cylinder and valve casing are made of cast iron4 ,cocks4--,a cock consists of a slightly conical plug which fits into a corresponding casing cast on a pipe4 ,through the plug is a hole which may be made by turning the plug to form a continuation of the hole in the pipe1 and thus allow the fluid to pass1 or it may be turned round so that the solid part of the plug lies across the hole in the pipe1 and thus prevent the fluid from passing4 ,as the student will be quite familiar with the common water cock or tap such as is used in dwelling-houses we need not illustrate it here4 ,illustration3 ,,fig4 #ei4 ,fig4 #ei shows a cock of considerable size1 which may be used for water or steam under high pressure4 ,the plug in this example is hollow1 and is prevented from coming out by a cover which is secured to the casing by four stud bolts4 ,an annular ridge of rectangular section projecting from the under side of the cover1 and fitting into a corresponding recess on the top of the casing1 serves to ensure that the cover and plug are concentric1 and prevents leakage4 ,leakage at the neck of the plug is prevented by a gland and stuffing-box4 ,the top end of the plug is made square to receive a handle for turning it4 ,the size of a cock is taken from the bore of the pipe in which it is placed2 thus fig4 #ei shows a #b-a_/d-;inch cock4 ,,exercise #fa3 #b-a_/d-;inch ,steam or ,water ,cock4--,first draw the views of this cock shown in fig4 #ei1 then draw a half end elevation and half cross section through the centre of the plug4 ,scale #f inches to a foot4 ,instead of drawing the parts of the pipe on the two sides of the plug in the same straight line as in fig4 #ei1 one may be shown proceeding from the bottom of the casing1 so that the fluid will have to pass through the bottom of the plug and through one side4 ,this is a common arrangement4 ,all the parts of the valve and casing in this example are made of brass4 ,,xvii4 ,,materials ,,used ,,in ,,machine ,,construction4 ,cast ,iron4--,the essential constituents of cast iron are iron and carbon1 the latter forming from #b to #e per cent4 of the total weight4 ,cast iron1 however1 usually contains varying small amounts of silicon1 sulphur1 phosphorus1 and manganese4 ,in cast iron the carbon may exist partly in the free state and partly in chemical combination with the iron4 ,in white cast iron the whole of the carbon is in chemical combination with the iron1 while in grey cast iron the carbon is principally in the free state1 that is1 simply mixed mechanically with the iron4 ,it is the free carbon which gives the grey iron its dark appearance4 ,a mixture of the white and grey varieties of cast iron when melted produces mottled cast iron4 ,the greater the amount of carbon chemically combined with the iron1 the whiter1 harder1 and more brittle does it become4 ,the white cast iron is stronger than the grey1 but being more brittle it is not so suitable for resisting suddenly applied loads4 ,white iron melts at a lower temperature than grey iron1 but after melting it does not flow so well1 or is not so liquid as the grey iron4 ,white iron contracts while grey iron expands on solidifying4 ,the grey iron1 therefore1 makes finer castings than the white4 ,castings after solidifying contract in cooling about #a_/h of an inch per foot4 ,castings possessing various degrees of strength and hardness are produced by melting mixtures of various proportions of white and grey cast irons4 ,white cast iron has a higher specific gravity than grey cast iron4 ,cast iron gives little or no warning before breaking4 ,the thickness of the metal throughout a casting in cast iron should be as uniform as possible1 so that it may cool and therefore contract uniformly throughout2 otherwise some parts may be in a state of initial strain after the casting has cooled1 and will therefore be easier to fracture4 ,re-entrant angles should be avoided2 such should be rounded out with fillets4 ,the presence of phosphorus in cast iron makes it more fusible1 and also more brittle4 ,the presence of sulphur diminishes the strength considerably4 ,the grey varieties of cast iron are called foundry irons or foundry pigs1 while the white varieties are called forge irons or forge pigs1 from the fact that they are used for conversion into wrought iron4 ,amongst iron manufacturers the different varieties of cast iron are designated by the numbers #a1 #b1 #c1 c41 the lowest number being applied to the greyest variety4 ,chilled ,castings4--,when grey cast iron is melted a portion of the free carbon combines chemically with the iron2 this1 however1 separates out again if the iron is allowed to cool slowly2 but if it is suddenly cooled a greater amount of the carbon remains in chemical combination1 and a whiter and harder iron is produced4 ,advantage is taken of this in making chilled castings4 ,in this process the whole or a part of the mould is lined with cast iron1 which1 being a comparatively good conductor of heat1 chills a portion of the melted metal next to it1 changing it into a hard white iron to a depth varying from #a_/h to #a_/b an inch4 ,to protect the cast-iron lining of the mould from the molten metal it is painted with loam4 ,malleable ,cast ,iron4--,this is prepared by imbedding a casting in powdered red hematite 7an oxide of iron71 and keeping it at a bright red heat for a length of time varying from several hours to several days according to the size of the casting4 ,by this process a portion of the carbon in the casting is removed1 and the strength and toughness of the latter become more like the strength and toughness of wrought or malleable iron4 ,wrought or ,malleable ,iron4--,this is nearly pure iron1 and is made from cast iron by the puddling process1 which consists chiefly of raising the cast iron to a high temperature in a reverberatory furnace in the presence of air1 which unites with the carbon and passes off as gas4 ,in other words the carbon is burned out4 ,the iron is removed from the puddling furnace in soft spongy masses called blooms1 which are subjected to a process of squeezing or hammering called shingling4 ,these shingled blooms still contain enough heat to enable them to be rolled into rough puddled bars4 ,these puddled bars are of very inferior quality1 having less than half the strength of good wrought iron4 ,the puddled bars are cut into pieces which are piled together1 reheated1 and again rolled into bars1 which are called merchant bars4 ,this process of piling1 reheating1 and re-rolling may be repeated several times1 depending on the quality of iron required4 ,up to a certain point the quality of the iron is improved by reheating and rolling or hammering1 but beyond that a repetition of the process diminishes the strength of the iron4 ,the process of piling and rolling gives wrought iron a fibrous structure4 ,when subjected to vibrations for a long time1 the structure becomes crystalline and the iron brittle4 ,the crystalline structure induced in this way may be removed by the process of annealing1 which consists in heating the iron in a furnace1 and then allowing it to cool slowly4 ,forging and ,welding4--,the process of pressing or hammering wrought iron when at a red or white heat into any desired shape is called forging4 ,if at a white heat two pieces of wrought iron be brought together1 their surfaces being clean1 they may be pressed or hammered together1 so as to form one piece4 ,this is called welding1 and is a very valuable property of wrought iron4 ,steel4--,this is a compound of iron with a small per-centage of carbon1 and is made either by adding carbon to wrought iron1 or by removing some of the carbon from cast iron4 ,in the cementation process1 bars of wrought iron are imbedded in powdered charcoal in a fireclay trough1 and kept at a high temperature in a furnace for several days4 ,the iron combines with a portion of the carbon to form blister steel1 so named because of the blisters which are found on the surface of the bars when they are removed from the furnace4 ,the bars of blister steel are broken into pieces about #ah inches long1 and tied together in bundles by strong steel wire4 ,these bundles are raised to a welding heat in a furnace1 and then hammered or rolled into bars of shear steel4 ,to form cast steel the bars of blister steel are broken into pieces and melted into crucibles4 ,in the ,siemens-,martin process for making steel1 cast and wrought iron are melted together on the hearth of a regenerative gas-furnace4 ,bessemer steel is made by pouring melted cast iron into a vessel called a converter1 through which a blast of air is then urged4 ,by this means the carbon is burned out1 and comparatively pure iron remains4 ,to this is added a certain quantity of 'spiegeleisen1' which is a compound of iron1 carbon1 and manganese4 ,hardening and ,tempering of ,steel4--,steel1 if heated to redness and cooled suddenly1 as by immersion in water1 is hardened4 ,the degree of hardness produced varies with the rate of cooling2 the more rapidly the heated steel is cooled1 the harder does it become4 ,hardened steel is softened by the process of annealing1 which consists in heating the hardened steel to redness1 and then allowing it to cool slowly4 ,hardened steel is tempered1 or has its degree of hardness lowered1 by being heated to a temperature considerably below that of a red heat1 and then cooling suddenly4 ,the higher the temperature the hardened steel is raised to1 the lower does its 'temper' become4 ,case-hardening4--,this is the name given to the process by which the surfaces of articles made of wrought iron are converted into steel1 and consists in heating the articles in contact with substances rich in carbon1 such as bone-dust1 horn shavings1 or yellow prussiate of potash4 ,this process is generally applied to the articles after they are completely finished by the machine tools or by hand4 ,the coating of steel produced on the article by this process is hardened by cooling the article suddenly in water4 ,copper4--,this metal has a reddish brown colour1 and when pure is very malleable and ductile1 either when cold or hot1 so that it may be rolled or hammered into thin plates1 or drawn into wire4 ,slight traces of impurities cause brittleness1 although from #b to #d per cent4 of phosphorus increases its tenacity and fluidity4 ,copper is a good conductor of heat and of electricity4 ,copper is largely used for making alloys4 ,alloys4--,brass contains two parts by weight of copper to one of zinc4 ,muntz metal consists of three parts of copper to two of zinc4 ,alloys consisting of copper and tin are called bronze or gun-metal4 ,bronze is harder the greater the proportion of tin which it contains2 five parts of copper to one of tin produce a very hard bronze1 and ten of copper to one of tin is the composition of a soft bronze4 ,phosphor bronze contains copper and tin with a little phosphorus2 it has this advantage over ordinary bronze1 that it may be remelted without deteriorating in quality4 ,this alloy also has the advantage that it may be made to possess great strength accompanied with hardness1 or less strength with a high degree of toughness4 ,wood4--,in the early days of machines wood was largely used in their construction1 but it is now used to a very limited extent in that direction4 ,beech and hornbeam are used for the cogs of mortise wheels4 ,yellow pine is much used by pattern-makers4 ,box1 a heavy1 hard1 yellow-coloured wood1 is used for the sheaves of pulley blocks1 and sometimes for bearings in machines4 ,lignum-vitae is a very hard dark-coloured wood1 and remarkable for its high specific gravity1 being #a-a_/c times the weight of the same volume of water4 ,this wood is much used for bearings of machines which are under water4 ,,xviii4 ,,miscellaneous ,,exercises4 ,the illustrations in this chapter are in most cases not drawn to scale2 they are also in some parts incomplete1 and in others some of the lines are purposely drawn wrong4 ,the student must keep to the dimensions marked on the drawings1 and where no sizes are given he must use his own judgment in proportioning the parts4 ,all errors must be corrected1 and any details required1 but not shown completely in the illustrations1 must be filled in4 ,,exercise #fb3 ,single ,riveted ,butt ,joint with ,tee-iron ,cover ,strap4--,two views1 one a side elevation and the other a sectional elevation1 of a riveted joint are shown in fig4 #fj4 ,draw these views1 and also a plan projected from one of them4 ,show the rivets completely in all the views4 ,scale #d inches to a foot4 ,illustration3 ,,fig4 #fj4 ,illustration3 ,,fig4 #fa4 ,,exercise #fc3 ,girder ,stay for ,steam ,boiler4--,the flat crown of the fire-box of locomotive and marine boilers is generally supported or stayed by means of girder stays1 an example of which is shown in fig4 #fa4 ,a ,b is the side elevation of a portion of one of these girders4 ,each girder is supported at its ends by the plates forming the vertical sides of the fire-box4 ,the flat crown is bolted to the girders as shown4 ,observe that the girders are in contact with the crown only in the neighbourhood of the bolts4 ,consider carefully this part of the design1 and then answer the following questions3 7#a7 ,what objections are there to supporting the girders at the ends only without the contact pieces at the bolts8 7#b7 ,what objections are there to having the girders in contact with the crown plate of the fire-box throughout their whole length8 ,draw the views shown in fig4 #fa1 and from the right-hand one project a plan4 ,scale #d inches to a foot4 ,illustration3 ,,fig4 #fb4 ,,exercise #fd3 ,end of ,bar ,stay for ,steam ,boiler4--,on page #ab one form of stay for supporting the flat end of a steam boiler is described4 ,another form of stay for the same purpose is shown in fig4 #fb4 ,a ,b is a portion of the end of a steam boiler4 ,c ,d is one end of a bar which extends from one end of the boiler to the other4 ,the ends of this bar are screwed1 and when the bar is of wrought iron the screwed parts are generally larger in diameter than the rest of the bar4 ,when made of steel the bar is generally of uniform diameter throughout4 ,in the case of wrought-iron bar stays the enlarged ends are welded on to the smaller parts4 ,welding is not so reliable with steel as with wrought iron4 ,write out answers to the following questions3 7#a7 ,what is the advantage of having the screwed part of the bar larger in diameter than the rest8 7#b7 ,why are steel bar stays not generally enlarged at their screwed ends8 ,draw the views shown in fig4 #fb1 and project from one of them a third view4 ,scale #d inches to a foot4 ,,exercise #fe3 ,knuckle ,joint4--,draw the plan and elevation of this joint shown in fig4 #fc1 and also draw an end elevation looking in the direction of the arrow4 ,the parts at ,a and ,b are octagonal in cross section4 ,scale #d inches to a foot4 ,illustration3 ,,fig4 #fc4 ,,exercise #ff3 ,locomotive ,coupling ,rod ,ends4--,a form of knuckle joint used on locomotive coupling rods is shown in fig4 #fd4 ,in this case two rods meet and work on the same pin1 as shown at 7a7 fig4 #fd4 ,draw1 in addition to the views shown in fig4 #fd1 a plan and a vertical section through the axis of the pin4 ,scale #f inches to a foot4 ,would it be practicable to replace the two rods ,a ,b and ,b ,c by a single rod working on the crank pins at ,a1 ,b1 and ,c8 ,give reasons for your answer4 ,illustration3 ,,fig4 #fd4 ,,exercise #fg3 ,bell ,crank ,lever4--,draw the plan and elevation of the lever shown in fig4 #fe4 ,scale #f inches to a foot4 ,illustration3 ,,fig4 #fe4 ,,exercise #fh3 ,back ,stay for ,lathe4--,draw a plan and two elevations of the stay shown in fig4 #ff4 ,make all necessary corrections and show all the details in each view4 ,scale full size4 ,illustration3 ,,fig4 #ff4 ,illustration3 ,,fig4 #fg4 ,,exercise #fi3 ,conical ,disc ,valve and ,casing4--,draw1 half size1 the views shown in fig4 #fg of the conical disc valve and casing1 and also add an elevation looking in the direction of the arrow4 ,,exercise #gj3 ,connecting ,rod ,end4--,the student should carefully compare this connecting rod end 7fig4 #fh7 with those illustrated on pages #ej and #eb4 ,the lower part of fig4 #fh is a half plan and half horizontal section1 and the upper part is a half side elevation and half vertical section4 ,draw these views and also an end elevation4 ,scale #f inches to a foot4 ,illustration3 ,,fig4 #fh4 ,illustration3 ,,fig4 #fi4 ,illustration3 ,,fig4 #gj4 ,illustration3 ,,fig4 #ga4 ,illustration3 ,,fig4 #gb4 ,illustration3 ,,fig4 #gc4 ,illustration3 ,,fig4 #gd4 ,,exercise #ga3 ,engine ,cross-head4--,the cross-head shown in fig4 #fi is for an inverted cylinder marine engine4 ,a is the piston rod1 and ,b ,b are pins1 forged in one piece with ,c1 to which the forked end of the connecting rod is attached4 ,draw the upper view with the central part in section as shown4 ,make the right-hand half of the lower view a plan without any section1 and make the left-hand half a horizontal section through the axis of the pins ,b ,b4 ,scale #d inches to a foot4 ,,exercise #gb3 ,ratchet ,lever4--,the lever shown in fig4 #gj is used for turning the horizontal screw of a traversing screw jack4 ,draw the two views shown1 and from one of them project a plan4 ,scale full size4 ,,exercise #gc3 ,steam ,whistle4--,draw1 full size1 the elevation and section of the steam whistle shown in fig4 #ga4 ,draw also horizontal sections at ,a ,b1 ,c ,d1 and ,e ,f4 ,illustration3 ,,fig4 #ge4 ,,exercise #gd3 ,screw ,coupling for ,railway ,carriages4--,draw the three views of the screw coupling shown in fig4 #gb4 ,scale #f inches to a foot4 ,if the link ,a is fixed1 through what distance will the link ,b move for two turns of the lever8 ,illustration3 ,,fig4 #gf4 ,,exercise #ge3 ,loose ,headstock for a #f-;inch ,lathe4--,two views of this headstock are shown in fig4 #gc4 ,on one of these views a few of the chief dimensions are marked4 ,the details1 fully dimensioned1 are shown separately in figs4 #gd1 #ge1 and #gf4 ,explain clearly how the centre is moved backwards and forwards1 and also how the spindle containing it is locked when it is not required to move4 ,draw1 half-size1 the views shown in fig4 #gc1 and from the left-hand view project a plan4 ,draw also the detail of the locking arrangement shown in fig4 #gd4 ,,appendix ,a4 ,,science ,,and ,,art ,,department1 ,,south ,,kensington4 ,,syllabus4 ,,subject ,,ii4--,,machine ,,construction ,,and ,,drawing4 ,it is assumed that the student has already learnt to draw to scale1 and that he can draw two or more views of the same object in simple or orthographic projection4 ,to pass in machine construction and drawing1 he must be able to apply this knowledge to the representation of machinery4 ,he must be acquainted with the form and purpose of the simpler parts of which machines are built up and must have had some practice in drawing them4 ,to test his knowledge1 rough dimensioned sketches1 more or less incomplete1 of simple machine details will be given him1 and he will be required to produce a complete drawing in pencil to a given scale4 ,two or more views of at least one subject will be required1 and these must be so drawn as to be properly projected one from the other1 in order to show that the student appreciates that he is producing a representation of a solid piece of machinery1 and not merely copying a sketch4 ,no credit will be given unless some knowledge of projection is shown4 ,the centre lines of the drawings should be shown1 and parts cut by planes of section should be indicated by diagonal shading4 ,bolts and other fastenings should be carefully shown where required4 ,any indication that a candidate has merely copied the sketches given1 without understanding the part represented1 will invalidate his examination4 ,,first ,,stage ,,or ,,elementary ,,course4 ,in the elementary stage1 a knowledge is required of the simple parts only of machines in common use4 ,some of these are enumerated in the following list4 ,the student should be practised in drawing them till he recognises their forms1 and the object of the arrangement should be explained to him4 ,he should also know the simple technical terms used in describing them4 ,a few very simple questions relating to the arrangement1 proportions1 and strength of the simplest machine details will be set in the examination paper4 ,in drawing the examples set to test a student's knowledge and skill in machine drawing1 it must be remembered that only a limited time is available4 ,it is only possible to set an example to be drawn in pencil1 and the points which will receive attention are 7#a7 accuracy of scale and projection2 7#b7 power of reading a drawing1 shown by the ability to transfer portions of the mechanism and dimensions from one view to another2 7#c7 knowledge of machines1 as shown by the ability to fill in small details1 such as nuts1 keys1 etc41 omitted in the sketches given4 ,bearing in mind the limited time available1 the student should try to make his outline clear and decisive and complete4 ,but the diagonal lines necessary for sectional parts may be done rapidly1 though neatly1 by freehand if necessary4 ,riveted ,joints4--,forms of rivets and arrangement of rivets in lap and butt joints with single and double riveting4 ,junction of plates by angle and ,t-irons4 ,bolts1 ,studs1 and ,set ,screws4--,forms of these fastenings4 ,forms and proportions of nuts and bolt-heads4 ,arrangement of flanges for bolting4 ,pins1 ,keys1 and ,cotters4--,form of ordinary knuckle joint4 ,use of split pins4 ,connection of parts by a key4 ,connection of parts by a cotter4 ,gib and cotter4 ,pipes and ,cylinders4--,forms of ordinary pipes and cylinders and their flanges and covers4 ,shafting4--,forms of shafts and axles and of journals and pivots4 ,use of collars and bosses4 ,half-lap coupling4 ,box coupling4 ,flange coupling4 ,pedestals and ,plummer ,blocks4--,simplest forms of pedestals and hangers for shafts4 ,form and arrangement of brass steps4 ,arrangements for fixing pedestals and for neutralising the effects of wear4 ,toothed ,gearing4--,forms of ordinary spur and bevil wheels4 ,meaning of the terms pitch1 breadth of face1 thickness of tooth1 pitch line1 rim1 nave1 arm4 ,mode of drawing bevil wheels in section4 ,belt ,pulleys4--,forms of belt pulleys for flat and round belts4 ,stepped speed cones4 ,drawing of pulleys with curved arms4 ,cranks and ,levers4--,forms of ordinary cast-iron and wrought-iron cranks and levers4 ,modes of fixing crank pin4 ,modes of fixing crank shaft4 ,double cranks4 ,form of eccentrics4 ,links4--,most simple forms of connecting rod ends1 open or closed4 ,use of steps in connecting rods4 ,use of cotters to tighten the steps4 ,pistons4--,simple forms of piston4 ,use of piston packing4 ,modes of attaching piston rod4 ,stuffing-,boxes4--,simple form of stuffing-box and gland4 ,use of packing4 ,mode of tightening gland4 ,valves4--,simple conical of puppet valve4 ,simple slide valve4 ,cock or conical sliding valve4 ,,appendix ,b4 ,,examination ,,papers ,,set ,,by ,,the ,,science ,,and ,,art ,,department4 ,,subject ,,ii4--,,machine ,,construction ,,and ,,drawing4 ,examiners1 ,,prof4 ,t4 ,a4 ,,hearson1 ,m4,inst4,c4,e41 and ,j4 ,,harrison1 ,,esq41 ,m4,inst4,m4,e4 ,,general ,,instructions4 ,if the rules are not attended to1 the paper will be cancelled4 ,you may take the ,elementary1 or the ,advanced1 or the ,honours paper1 but you must confine yourself to one of them4 ,put the number of the question before your answer4 ,you are expected to prove your knowledge of machinery as well as your power of drawing neatly to scale4 ,you are therefore to supply details omitted in the sketches1 to fill in parts left incomplete1 and to indicate1 by diagonal lines1 parts cut by planes of section4 ,no credit will be given unless some knowledge of projection is shown1 so that at least two views of one of the examples will be required properly projected one from the other4 ,the centre lines should be clearly drawn4 ,the figured dimensions need not be inserted4 ,your answers should be clearly and cleanly drawn in pencil4 ,no extra marks will be allowed for inking in4 ,all figures must be drawn on the single sheet of paper supplied1 for no second sheet will be allowed4 ,the value attached to each question is shown in brackets after the question4 ,but a full and correct answer to an easy question will in all cases secure a larger number of marks than an incomplete or inexact answer to a more difficult one4 ,your name is not given to the ,examiner1 and you are forbidden to write to him about your answers4 ,you are to confine your answers strictly to the questions proposed4 ,a single accent 7'7 signifies feet2 a double accent 77 inches4 ,the examination in this subject lasts for four hours4 99 99 99 99 99 ,first ,stage or ,elementary ,examination4 #ahhe4 ,,instructions4 ,read the ,general ,instructions above4 ,answer briefly any three1 but not more than three1 of the following questions1 and draw two1 but not more than two1 of the examples4 ,questions4 7a47 ,show two methods by which a cotter may be prevented from slacking back4 7#f47 7b47 ,sketch the brasses for a bearing1 and show how they are prevented from turning in the pedestal4 7#f47 7c47 ,explain the object of the construction of the connecting rod end shown in fig4 #gh4 ,describe how the adjustment must be made and how it is locked4 7#aj47 7d47 ,show the form of the ,whitworth screw thread by drawing to scale a part section of two or three threads taking a pitch of #a-a_/b inches4 ,figure the dimensions on the sketch4 ,how many threads to the inch are used on an inch bolt8 7#aj47 7e47 ,make a sketch showing how the adjustment is made in the sliding parts of machine tools3 as1 for example1 in the slide rest of a lathe4 7#aj47 7f47 ,describe with sketches two methods by which the joints are made in connecting lengths of cast-iron pipes4 7#f47 ,examples to be drawn4 #a4 ,jaw for four-screw dog chuck for #e lathe4 ,draw the two views as shown 7fig4 #gg74 ,scale full size4 7,note4--,the other three jaws of the chuck are not to be drawn47 7#ce47 #b4 ,connecting rod end4 ,draw the two views as shown1 partly in section 7fig4 #gh74 ,draw full size4 7#ce47 #c4 ,hooke's coupling4 ,draw the three views shown 7fig4 #gi71 adding any omitted lines where the views are incomplete4 ,draw to scale of #a_/d full size4 7#ce47 ,illustration3 ,,figs4 #gg ,,and #gh4 ,illustration3 ,,fig4 #gi4 99 99 99 99 99 ,first ,stage or ,elementary ,examination4 #ahhf4 ,,instructions4 ,read the ,general ,instructions 7page #ajb74 ,answer briefly any three1 but not more than three1 of the following questions1 and draw two1 but not more than two1 of the examples4 ,questions4 7a47 ,give sketches showing how the cutting tool of a lathe or other machine is secured in place4 7#f47 7b47 ,make a sketch of a stud1 describe how it is screwed into place1 and state some circumstances under which it is used in preference to a bolt4 7#f47 7c47 ,give sketches showing one method of attaching the valve rod to an ordinary slide valve4 7#f47 7d47 ,sketch a connecting rod end1 with strap1 gib1 and cotter4 ,explain the use of the gib4 7#aj47 7e47 ,explain the use of the quadrant for change wheels for a screw-cutting lathe shown in ,example #a1 fig4 #hj1 by making a sketch showing it in place on a lathe with wheels in gear4 7#aj47 7f47 ,sketch one form of hanger suitable for supporting mill-shafting4 7#aj47 ,examples to be drawn4 #a4 ,quadrant for change wheels for screw-cutting lathe4 ,draw the two views shown 7fig4 #hj74 ,scale half-size4 7#ce47 #b4 ,crank-shaft4 ,draw the two views as shown1 partly in section 7fig #ha74 ,scale #a_/h full size4 7#ce47 #c4 ,ball bearing for tricycle4 ,draw the two views as shown1 partly in section 7fig4 #hb74 ,draw full size4 7#ce47 ,illustration3 ,,figs4 #hj ,,and #ha4 ,illustration3 ,,fig4 #hb4 99 99 99 99 99 ,first ,stage or ,elementary ,examination4 #ahhg4 ,,instructions4 ,read the ,general ,instructions 7page #ajb74 ,answer briefly any three1 but not more than three1 of the following questions1 and draw two1 but not more than two1 of the examples4 ,questions4 7a47 ,explain how the piston rings in ,example #a1 fig4 #hd1 are made so that the piston may work steam-tight in the cylinder4 ,how are these rings got into place8 7#h47 7b47 ,give two views of a double riveted lap joint for boiler-plates4 7#h47 7c47 ,show by sketches how a wheel is fixed on a shaft by means of a sunk key4 ,explain how the key may be withdrawn when it cannot be driven from the point end4 7#h47 7d47 ,give sketches showing the construction of a conical metal lift or puppet valve and seating4 7#aj47 7e47 ,with the aid of sketches explain how a piston rod is made to work steam-tight through the end of the cylinder4 7#aj47 7f47 ,explain how the slotting machine ram of ,example #h1 fig4 #he1 may be made to move up and down when at work4 ,how is the length of the stroke altered1 and what is the object of the slotway in the upper part of the ram8 7#aj47 ,examples to be drawn4 #a4 ,piston for steam-engine4 ,draw and complete the two views shown 7fig4 #hd71 the top half of the left-hand view to be in section4 ,scale #a_/b size4 7#cj47 #b4 ,plan and sectional elevation of a footstep bearing for an upright shaft 7fig4 #hc74 ,draw and complete these views4 ,scale #a_/d size4 7#ce47 #c4 ,ram of slotting machine4 ,draw and complete the two elevations shown 7fig4 #he74 ,the tool-holders must be drawn in their proper positions in the ram1 and not separate as in the diagram4 ,scale #a_/d size4 7#ce47 ,illustration3 ,,figs4 #hc ,,and #hd4 ,illustration3 ,,fig4 #he4 99 99 99 99 99 ,first ,stage or ,elementary ,examination4 #ahhh4 ,,instructions4 ,read the ,general ,instructions on p4 #ajb4 ,answer briefly any three1 but not more than three1 of the following questions1 and draw two1 but not more than two1 of the examples4 ,questions4 7a47 ,give sketches showing how the separate lengths of a line of shafting may be connected together4 7#h47 7b47 ,what is the object of using chipping or facing strips in fitting up machine parts8 ,give one or two examples4 7#h47 7c47 ,give sketches showing how you would grip and drive a round iron bar for the purpose of turning it between the centres of a lathe4 7#aj47 7d47 ,explain the action of the governor shown in ,example #a 7fig4 #hf74 7#aj47 7e47 ,describe in detail how the mud-hole door in ,example #b 7fig4 #hh7 is removed for the purpose of cleaning the boiler and how it is replaced and the joint made steam-tight4 7#aj47 7f47 ,describe how the parts of the spur wheel in ,example #c 7fig4 #hg7 are put together1 and explain why the wheel is made in segments4 7#aj47 ,examples to be drawn4 #a4 ,loaded governor for small gas engine4 ,draw and complete the two views1 partly in section as shown 7fig4 #hf74 ,scale full size4 7#ce47 #b4 ,mud-hole mouth-piece for ,lancashire boiler4 ,draw and complete the two views shown 7fig4 #hh74 ,scale #c_/hths4 7#ce47 #c4 ,point for segments of large spur wheel4 ,draw and complete the views shown 7fig4 #hg74 ,scale #c_/afths4 ,note4--,as the radius of the wheel is too large for your instruments1 the circumference at the joint may be set out straight1 as in a rack4 7#ce47 ,illustration3 ,,figs4 #hf ,,and #hg4 ,illustration3 ,,fig4 #hh4 ,,index ,air-pump bucket1 #eh ,alloys1 #hj ,angle irons1 #ab ,annealing1 #gi1 #hj ,axles1 #bd ,back stay for lathe1 #hf ,bar stay1 #hc ,bearings for shafts1 #cj ,beech-wood1 #ha ,bell crank lever1 #hf ,bessemer steel1 #gi ,bevil wheels1 #dc ,blister steel1 #gi ,blooms1 #gh ,bolt-heads1 proportions of1 #ah ,bolts1 forms of1 #ag ,border lines1 #d ,box couplings1 #be -- end1 connecting rod1 #ea ,box-wood1 #ha ,brackets1 #cc ,brake shaft carrier1 #cj ,brass1 #hj ,brasses1 #cj ,bucket1 #eh ,built-up cranks1 #df ,bush1 #cj1 #di1 #ea1 #ed1 #ef1 #fc ,butt joints1 #aj1 #aa -- strap1 #aj ,buttress screw thread1 #ae ,case-hardening1 #hj ,cast iron1 #gf ,cast iron flange coupling1 #bh1 #bi -- steel1 #gi ,caulking1 #h ,cementation process1 #gi ,centre lines1 #b1 #d ,chilled castings1 #gh ,circulating pump piston1 #eh ,clearance1 cylinder1 #gd -- of cotter1 #di ,cocks1 #gd ,cogs1 #da -- wood for1 #ha ,collared stud1 #ah ,collars1 #bd ,colouring1 #c ,colours for different materials1 #c ,compasses1 #a ,cone keys1 #bc1 #ch ,conical disc valve1 #gj1 #ga1 #hi -- head1 #g ,connecting rod1 locomotive1 #ea -- -- marine1 #ea -- rods1 #di1 #hi ,construction for rivet heads1 #g ,contraction of castings1 #gg ,copper1 #hj ,cotters1 #dh1 #di ,countersunk head1 #g1 #ah ,coupling rod ends1 #ee1 #hd -- rods1 #ed -- screw1 #if ,couplings1 shaft1 #be ,cover plate1 #aj ,cranked axle1 #de ,cranks1 #dc -- built-up1 #df ,cross-head pin1 #ea ,cross-heads1 #ef1 #hi ,cross-key1 #bh ,cup-headed bolt1 #ag ,decimal equivalents1 #f ,dimension lines1 #e ,dimensions1 #e -- of box couplings1 #bf -- cast-iron flange couplings1 #bi -- keys1 #bd -- stuffing-boxes and glands1 #fg -- ,whitworth screws1 #ae ,distance lines1 #e ,dividers1 #a ,draught of cotter1 #di ,drawing board1 #a -- instruments1 #a -- paper1 #b -- pen1 #a -- pins1 #b ,eccentrics1 #dg ,exhaust port1 #ga ,eye-bolt1 #ah ,fairbairn's coupling1 #bf ,fast and loose pulleys1 #cg ,feather key1 #bc ,flange couplings1 #bg ,flap valves1 #fh ,flat key1 #bb ,forge irons1 #gg ,forging1 #gi ,form of wheel teeth1 #dj ,forms of nuts1 #af -- rivet heads1 #g -- screw threads1 #ae ,foundry irons1 #gg ,gasket1 #eh ,gas threads1 #ae ,gib1 #di -- head1 #bc ,girder stay1 #ha ,gland1 #fd ,grey cast iron1 #gg ,gun-metal1 #hj ,gusset stay1 #ab ,half-lap coupling1 #bf ,hangers1 #cd ,hardening of steel1 #hj ,headstock lathe1 #if ,hexagonal nut1 #af ,hollow key1 #bb ,hook bolt1 #ah ,hornbeam1 #ha ,india-rubber disc valves1 #eh1 #fh ,inking drawings1 #b ,inside lap of valve1 #gb ,joggles1 #cc ,joint1 knuckle1 #hd ,journals1 #bd -- length of1 #cb ,junk ring1 #fa ,keys1 #bb -- proportions of1 #bc ,kinghorn's metallic valve1 #gj ,knuckle joint1 #hd -- screw thread1 #ae ,lancaster's piston packing1 #fa ,lap joints1 #h1 #i1 #aj1 #ab -- of slide valve1 #gb ,lathe headstock1 #if ,lead of valve1 #gd ,lever1 bell crank1 #hf -- ratchet1 #if ,lignum-vitae1 #ha ,locking arrangements for nuts1 #ba1 #fb ,lock nuts1 #ai ,locomotive connecting rod1 #ea -- cranked axle1 #de -- cross-head1 #ef ,locomotive eccentric1 #dg -- piston1 #fj ,lubricator1 needle1 #cb ,malleable cast iron1 #gh -- iron1 #gh ,marine connecting rod1 #ea -- coupling1 #bh -- crank-shaft1 #df -- piston1 #fa ,merchant bars1 #gh ,mortise wheels1 #da ,mottled cast iron1 #gg ,muff couplings1 #be ,muntz metal1 #hj ,needle lubricator1 #cb ,nuts1 forms of1 #af -- lock1 #ai -- proportions of1 #ah ,oil-box1 #ed1 #fe ,outside lap of slide valve1 #gb ,overhung crank1 #dc -- cranks1 proportions of1 #de ,packing1 #fc ,pan head1 #g ,pedestal1 shaft1 #cj ,pencils1 drawing1 #a ,phosphor bronze1 #hj ,pillar bracket1 #cd ,pillow block1 #cj1 #cb ,pin1 cross-head1 #ea1 #ed -- split1 #ba ,piston rod1 #eg ,pistons1 #eg ,pitch circle1 #dj -- of wheel teeth1 #dj -- surfaces of wheels1 #ci1 #dc ,pivots1 #bd ,plummer block1 #cj ,plunger1 #eg ,printing1 #d ,proportions of bolt-heads1 #ah -- keys1 #bc ,proportions of lap joints1 #i1 #aj -- marine engine pistons1 #fb -- nuts1 #ah -- overhung cranks1 #de -- pillow blocks1 #cb -- rivet heads1 #g -- wheel teeth1 #dj ,puddled bars1 #gh ,puddling process1 #gh ,pulley1 eccentric1 #dg ,pulleys1 #cf ,pump bucket1 #eh ,ramsbottom's packing1 #fj ,ratchet lever1 #if ,riveted joints1 #h ,rivet heads1 forms of1 #g1 #h -- -- proportions of1 #g ,riveting1 #g ,rivets1 #f ,rope pulley1 #ci ,round key1 #bc ,saddle key1 #bb ,scales1 #e ,screw coupling1 #if ,screwed gland and stuffing-box1 #fe ,screw threads1 #ad1 #ae ,screws1 representation of1 #af ,sellers ,v screw thread1 #ad ,set screw1 #ba1 #di -- squares1 #a ,shaft couplings1 #be -- hanger1 #cd ,shafting1 #bd ,shear steel1 #gi ,sheave1 eccentric1 #dg ,shingling1 #gh ,shrinking1 process of1 #dd ,siemens-,martin steel1 #gi ,slide blocks1 #ef -- valves1 #fh1 #ga ,sliding key1 #bc ,snap head1 #g ,snug1 #ag ,spiegeleisen1 #hj ,spring bows1 #a ,spur wheel1 #da ,square nut1 #af -- screw thread1 #ad ,stay1 back1 for lathe1 #hf -- bar1 #hc -- girder1 #ha -- gusset1 #ab ,steam ports1 #ga -- whistle1 #if ,steel1 #gi ,steps1 #cj ,strap1 #di -- eccentric1 #dg -- end of connecting rod1 #di ,stud bolts1 #ah ,studs1 #ah ,stuffing-boxes1 #fc ,sunk key1 #bb ,taper bolt1 #ah1 #bg -- pin1 #bc ,tee-headed bolt1 #ah ,tee-iron cover strap1 #ha ,tee square1 #a ,teeth of wheels1 form and proportions of1 #dj ,teeth1 pitch of1 #dj ,tempering of steel1 #hj ,throw of crank1 #dd -- eccentric1 #dg ,toothed wheels1 #ci ,valve ,kinghorn's metallic1 #gj -- slide1 #fh1 #ga ,valves1 #fh -- conical disc1 #gj -- india-rubber1 #eh1 #fh ,velocity ratio in belt gearing1 #cf ,wall boxes1 #cd ,washers1 #ai ,welding1 #gi ,whistle1 steam1 #if ,white cast iron1 #gg ,whitworth screws1 dimensions of1 #ae -- ,v screw thread1 #ad ,wood1 #ha ,working drawings1 #d ,wrought iron1 #gh ,yellow pine1 #ha ,,printed ,,by ,,spottiswoode ,,and ,,co41 ,,new-,,street ,,square ,,london 99 99 99 99 99 ,,text-,,books ,,of ,,science ,,photography4 ,by ,captain ,w4 ,,de ,,wiveleslie ,,abney1 ,c4,b4 ,f4,r4,s4 late ,instructor in ,chemistry and ,photography at the ,school of ,military ,engineering1 ,chatham4 ,with #aje ,woodcuts4 ,price #cs4 #f;d4 ,the ,,strength of ,,materials and ,,structures2 the ,strength of ,materials as depending on their quality and as ascertained by ,testing ,apparatus2 the ,strength of ,structures as depending on their form and arrangement1 and on the materials of which they are composed4 ,by ,sir ,j4 ,,anderson1 ,c4,e4 c4 ,with #ff ,woodcuts4 ,price #cs4 #f;d4 ,,introduction to the ,,study of ,,organic ,,chemistry2 the ,,chemistry of ,,carbon and its ,,compounds4 ,by ,,henry ,e4 ,,armstrong ,ph4,d4 ,f4,r4,s4 ,with #h ,woodcuts4 ,price #cs4 #f;d4 ,,elements of ,,astronomy4 ,by ,sir ,r4 ,s4 ,,ball1 ,,ll4,d4 ,f4,r4,s4 ,andrews ,professor of ,astronomy in the ,univ4 of ,dublin1 ,royal ,astronomer of ,ireland4 ,with #acf ,woodcuts4 ,price #fs4 ,,railway ,,appliances4 ,a ,description of ,details of ,railway ,construction subsequent to the completion of ,earthworks and ,structures1 including a short ,notice of ,railway ,rolling ,stock4 ,by ,,john ,,wolfe ,,barry1 ,m4,i4,c4,e4 ,with #bjg ,woodcuts4 ,price #cs4 #f;d4 ,,systematic ,,mineralogy4 ,by ,,hilary ,,bauerman1 ,f4,g4,s4 ,associate of the ,royal ,school of ,mines4 ,with #cgc ,woodcuts4 ,price #fs4 ,,descriptive ,,mineralogy4 ,by ,,hilary ,,bauerman1 ,f4,g4,s4 c4 ,with #bcf ,woodcuts4 ,price #fs4 ,,metals1 their ,,properties and ,,treatment4 ,by ,c4 ,l4 ,,bloxam and ,a4 ,k4 ,,huntington1 ,professors in ,king's ,college1 ,london4 ,with #acj ,woodcuts4 ,price #es4 ,,practical ,,physics4 ,by ,r4 ,t4 ,,glazebrook1 ,m4,a4 ,f4,r4,s4 and ,w4 ,n4 ,,shaw1 ,m4,a4 ,with #hj ,woodcuts4 ,price #fs4 ,,physical ,,optics4 ,by ,r4 ,t4 ,,glazebrook1 ,m4,a4 ,f4,r4,s4 ,fellow and ,lecturer of ,trin4 ,coll4 ,demonstrator of ,physics at the ,cavendish ,laboratory1 ,cambridge4 ,with #ahc ,woodcuts4 ,price #fs4 ,the ,,art of ,,electro-,,metallurgy1 including all known ,processes of ,electro-,deposition4 ,by ,g4 ,,gore1 ,,ll4,d4 ,f4,r4,s4 ,with #ef ,woodcuts4 ,price #fs4 ,,algebra and ,,trigonometry4 ,by ,,william ,,nathaniel ,,griffin1 ,b4,d4 ,price #cs4 #f;d4 ,,notes ,,on1 with ,,solutions of the more difficult ,,questions4 ,price #cs4 #f;d4 ,the ,,steam ,,engine4 ,by ,,george ,c4 ,v4 ,,holmes1 ,whitworth ,scholar2 ,secretary of the ,institution of ,naval ,architects1 ,with #bab ,woodcuts4 ,price #fs4 ,,electricity and ,,magnetism4 ,by ,,fleeming ,,jenkin1 ,f4,r4,,ss4 ,l4 ,e4 late ,professor of ,engineering in the ,university of ,edinburgh4 ,with #agg ,woodcuts4 ,price #cs4 #f;d4 ,,theory of ,,heat4 ,by ,j4 ,,clerk ,,maxwell1 ,m4,a4 ,,ll4,d4 ,edin4 ,f4,r4,,ss4 ,l4 ,e4 ,with #da ,woodcuts4 ,price #cs4 #f;d4 ,,technical ,,arithmetic and ,,mensuration4 ,by ,,charles ,w4 ,,merrifield1 ,f4,r4,s4 ,price #cs4 #f;d4 ,,key1 by the ,rev4 ,,john ,,hunter1 ,m4,a4 ,price #cs4 #f;d4 ,,introduction to the ,,study of ,,inorganic ,,chemistry4 ,by ,,william ,,allen ,,miller1 ,m4,d4 ,,ll4,d4 ,f4,r4,s4 ,with #gb ,woodcuts4 ,price #cs4 #f;d4 ,,telegraphy4 ,by ,w4 ,h4 ,,preece1 ,f4,r4,s4 ,m4,i4,c4,e1 and ,j4 ,,sivewright1 ,m4,a4 ,c4,m4,g4 ,with #afj ,woodcuts4 ,price #es4 ,the ,,study of ,,rocks1 an ,,elementary ,text-,book of ,,petrology4 ,by ,,frank ,,rutley1 ,f4,g4,s4 of ,her ,majesty's ,geological ,survey4 ,with #f ,plates and #hh ,woodcuts4 ,price #ds4 #f;d4 ,,workshop ,,appliances1 including ,descriptions of some of the ,gauging and ,measuring ,instruments--,hand-,cutting ,tools1 ,lathes1 ,drilling1 ,planing1 and other ,machine ,tools used by ,engineers4 ,by ,c4 ,p4 ,b4 ,,shelley1 ,m4,i4,c4,e4 ,with #bia ,woodcuts4 ,price #ds4 #f;d4 ,,structural and ,,physiological ,,botany4 ,by ,dr4 ,,otto ,,wilhelm ,,thome1 ,rector of the ,high ,school1 ,cologne1 and ,a4 ,w4 ,,bennett1 ,m4,a4 ,b4,sc4 ,f4,l4,s4 ,with #fjj ,woodcuts and a ,coloured ,map4 ,price #fs4 ,,quantitative ,,chemical ,,analysis4 ,by ,t4 ,e4 ,,thorpe1 ,f4,r4,s4 ,ph4,d4 ,professor of ,chemistry in the ,andersonian ,university1 ,glasgow4 ,with #hh ,woodcuts4 ,price #ds4 #f;d4 ,,qualitative ,,analysis and ,,laboratory ,,practice4 ,by ,t4 ,e4 ,,thorpe1 ,ph4,d4 ,f4,r4,s4 ,professor of ,chemistry in the ,andersonian ,university1 ,glasgow1 and ,m4 ,m4 ,,pattison ,,muir1 ,m4,a4 and ,f4,r4,s4,e4 ,with ,plate of ,spectra and #eg ,woodcuts4 ,price #cs4 #f;d4 ,,introduction to the ,,study of ,,chemical ,,philosophy2 the ,,principles of ,,theoretical and ,,systematical ,,chemistry4 ,by ,,william ,a4 ,,tilden1 ,d4,sc4 ,london1 ,f4,r4,s4 ,with #e ,woodcuts4 ,with or without ,answers to ,problems1 #ds4 #f;d4 ,,elements of ,,machine ,,design2 an ,introduction to the ,principles which determine the ,arrangement and ,proportion of the ,parts of ,machines1 and a ,collection of ,rules for ,machine ,design4 ,by ,w4 ,,cawthorne ,,unwin1 ,b4,sc4 ,m4,i4,c4,e4 ,with #cbe ,woodcuts4 ,price #fs4 ,,plane and ,,solid ,,geometry4 ,by ,h4 ,w4 ,,watson1 ,m4,a4 formerly ,fellow of ,trinity ,college1 ,cambridge4 ,price #cs4 #f;d4 ,london3 ,,longmans1 ,,green1 ,,co4 ,,scientific ,,class-,,books4 ,,ganot',s ,,natural ,,philosophy for ,,general ,,readers and ,,young ,,persons3 a ,course of ,physics divested of ,mathematical ,formulae1 expressed in the language of daily life4 ,translated and edited1 from ,ganot's ,cours ,elementaire de ,physique1 by ,e4 ,,atkinson1 ,ph4,d4 ,f4,c4,s4 ,sixth ,edition1 with #cd pages of new matter1 #b ,plates1 #eah ,woodcuts1 and an ,appendix of ,questions4 ,crown #hvo4 #gs4 #f;d4 ,,ganot',s ,,elementary ,,treatise on ,,physics1 ,experimental and ,applied1 for the use of ,colleges and ,schools4 ,translated and edited1 from ,ganot's ,elements de ,physique1 by ,e4 ,,atkinson1 ,ph4,d4 ,f4,c4,s4 ,twelfth ,edition1 revised and enlarged2 with #e ,coloured ,plates and #ibc ,woodcuts4 ,cr4 #hvo4 #aes4 ,,lessons in ,,elementary ,,mechanics4 ,designed for the use of ,schools1 and of ,candidates for the ,london ,matriculation1 and other ,examinations2 with #eb ,examples1 nearly #ejj ,exercises and ,examination ,questions with ,answers1 and #abd ,woodcuts4 ,by ,sir ,,philip ,,magnus1 ,b4,sc4 ,b4,a4 ,thirteenth ,edition4 ,fcp4 #hvo4 #cs4 #f;d4 ,,principles of ,,mechanics4 ,by ,t4 ,m4 ,,goodeve1 ,m4,a4 ,professor of ,mechanics at the ,royal ,school of ,mines4 ,new ,edition4 ,with #bec ,woodcuts4 ,crown #hvo4 #fs4 ,the ,,elements of ,,mechanism4 ,by ,t4 ,m4 ,,goodeve1 ,m4,a4 ,professor of ,mechanics at the ,royal ,school of ,mines4 ,new ,edition4 ,with #cdb ,woodcuts4 ,crown #hvo4 #fs4 ,,practical ,,mechanics3 an ,elementary ,introduction to their ,study4 ,with #hee ,exercises with ,answers and #ahd ,diagrams4 ,by the ,rev4 ,j4 ,f4 ,,twisden4 ,crown #hvo4 #ajs4 #f;d4 ,,theoretical ,,mechanics4 ,by the ,rev4 ,j4 ,f4 ,,twisden4 ,with #agb ,examples1 numerous ,exercises1 and #aed ,diagrams4 ,crown #hvo4 #hs4 #f;d4 ,,lessons in ,,elementary ,,mechanics4 ,by ,w4 ,h4 ,,grieve1 ,demonstrator in ,mechanics to the ,london ,school ,board4 ,fully ,illustrated4 ,stage ,,iii4 ,fcp4 #hvo4 #as4 #f;d4 ,stage ,,ii4 #as4 #f;d4 ,stage ,i4 #as4 #f;d4 ,,experimental ,,chemistry for ,junior ,students4 ,by ,j4 ,,emerson ,,reynolds1 ,m4,d4 ,f4,r4,s4 ,professor of ,chemistry1 ,university ,dublin4 ,fcp4 #hvo4 with numerous ,woodcuts4 ,,part ,i4 ,,introductory4 #as4 #f;d4 ,,part ,,ii4 ,,non-,,metals4 #bs4 #f;d4 ,,part ,,iii4 ,,metals ,,and ,,allied ,,bodies4 #cs4 #f;d4 ,,part ,,iv4 ,,carbon ,,compounds4 #ds4 ,london3 ,,longmans1 ,,green1 ,,co4 ,,longmans' ,,elementary ,,science ,,manuals1 ,written specially to meet the requirements of the ,elementary ,stage of ,science ,subjects as laid down in the ,syllabus of the ,directory of the ,science and ,art ,department1 ,south ,kensington4 ,,sound1 ,,light1 and ,,heat4 ,by ,,mark ,r4 ,,wright 7,hon4 ,inter4 ,b4,sc4 ,london74 ,with #afj ,illustrations4 ,crown #hvo4 #bs4 #f;d4 ,an ,,introduction to ,,machine ,,drawing and ,,design4 ,by ,,david ,,allan ,,low4 ,with #fe ,illustrations4 ,crown #hvo4 #bs4 ,,text-,,book on ,,practical ,,solid or ,,descriptive ,,geometry4 ,by ,,david ,,allan ,,low4 ,part4 ,i4 #bs4 ,part ,,ii4 #cs4 ,,elementary ,,physiography4 ,by ,j4 ,,thornton1 ,m4,a4 ,with #aj ,maps and #aej ,illustrations4 ,crown #hvo4 #bs4 #f;d4 ,a ,,manual of ,,mechanics3 an ,elementary ,text-,book for ,students of ,applied ,mechanics4 ,with #ach ,illustrations and ,diagrams1 and #ahh ,examples taken from the ,science ,department ,examination ,papers1 with ,answers4 ,by ,t4 ,m4 ,,goodeve1 ,m4,a4 ,fcp4 #hvo4 #bs4 #f;d4 ,,inorganic ,,chemistry1 ,,theoretical and ,,practical4 ,with an ,introduction to the ,principles of ,chemical ,analysis4 ,by ,,william ,,jago4 ,with #di ,woodcuts and ,questions and ,exercises4 ,fcp4 #hvo4 #bs4 #f;d4 ,an ,,introduction to ,,practical ,,inorganic ,,chemistry4 ,by ,,william ,,jago1 ,f4,c4,s4 ,f4,i4,c4 ,crown #hvo4 #as4 #f;d4 ,,practical ,,chemistry3 the ,principles of ,qualitative ,analysis4 ,by ,,william ,a4 ,,tilden1 ,d4,sc4 ,fcp4 #hvo4 #as4 #f;d4 ,,elementary ,,inorganic ,,chemistry4 ,alternative ,course4 ,by ,w4 ,,furneaux1 ,f4,r4,g4,s4 #bs4 #f;d4 ,,elementary ,,botany1 ,,theoretical and ,,practical4 ,by ,,henry ,,edmonds1 ,b4,sc4 ,london4 ,with #cai ,woodcuts4 ,cr4 #hvo #bs4 #f;d4 ,an ,,elementary ,,course of ,,mathematics4 ,specially adapted to the requirements of the ,science and ,art ,department4 ,crown #hvo4 #bs4 #f;d4 ,,building ,,construction4 ,by ,,edward ,j4 ,,burrell1 ,teacher of ,building ,construction at the ,technical ,school of the ,people's ,palace1 ,mile ,end4 ,with #cjh ,illustrations1 c4 ,crown #hvo4 #bs4 #f;d4 ,,theoretical ,,mechanics4 ,,by ,j4 ,,edward ,,taylor1 ,m4,a4 ,lond1 ,with #age ,illustrations and ,examples and ,answers4 ,cr4 #hvo4 #bs4 #f;d4 ,,animal ,,physiology4 ,by ,,william ,s4 ,,furneaux1 ,special ,science ,teacher1 ,london ,school ,board4 ,with #bah ,illustrations4 ,crown #hvo4 #bs4 #f;d4 ,,magnetism and ,,electricity4 ,by ,a4,w4 ,,poyser1 ,m4,a4 ,with #bce ,illustrations4 ,crown #hvo4 #bs4 #f;d4 ,,steam4 ,by ,,william ,,ripper1 ,member of the ,institution of ,mechanical ,engineers4 ,with #adb ,illustrations4 ,crown #hvo4 #bs4 #f;d4 ,,physics3 ,alternative ,course4 ,by ,,mark ,r4 ,,wright4 ,with #bdb ,illustrations4 ,crown #hvo4 #bs4 #f;d4 ,london3 ,,longmans1 ,,green1 ,,co4 ,,transcriber',s ,,notes #a4 ,passages in italics are surrounded by underscores4 #b4 ,mixed fractions are represented using hyphen and forward slash4 ,for instance1 five and a half is shown as #e-a_/b4 #c4 ,obvious misprints in spelling and punctuation have been silently corrected4