,transcriber's ,notes3 ,the spelling1 hyphenation1 punctuation and accentuation are as the original1 except for apparent typographical errors which have been corrected4 ,italic text is denoted thus4 ,bold text is denoted thus4 ,,scaffolding ,,printed ,,by ,,spottiswoode ,,and ,,co4 ,,ltd41 ,,new-,,street ,,square ,,london ,illustration3 ,,plate ,i4 ,photo by ,thatcher #bh ,cobourg ,road1 ,s4,e4 ,,derrick ,,staging4 ,,scaffolding ,a ,,treatise ,,on ,,the ,,design ,,erection ,,of ,,scaffolds1 ,,gantries1 ,,and ,,stagings1 ,with an ,account of the ,appliances used in connection therewith ,,for ,,the ,,use ,,of ,,contractors1 ,,builders1 ,,clerks ,,of ,,works1 ,,etc4 ,with a ,chapter on the ,legal ,aspect of the ,question4 ,by ,a4 ,g4 ,h4 ,,thatcher1 ,,building ,,surveyor ,,second ,,edition1 ,,revised ,,with #adf ,,diagrams ,,and #f ,,full-,,page ,,plates4 ,,london3 ,b4 ,t4 ,,batsford1 #id ,,high ,,holborn #aijg4 ,,preface ,scaffolding up to quite recent years has been considered by builders and others concerned1 with the exception of the actual workmen1 to be a matter of small importance and consequently unworthy of study4 ,recent legislation1 however 7the ,workmen's ,compensation ,act1 #ahig1 and the ,factory and ,workshop ,act1 #aija1 and preceding dates71 has brought it into greater prominence1 with the result that more attention has lately been given to it4 ,special study of the subject has1 however1 remained very difficult owing to the lack of accessible information4 ,the author1 in the course of considerable experience in the building trade1 has had opportunities of examining a large number of scaffolds throughout the country1 affording him exceptional facilities for thoroughly studying the subject1 and he has been led to prepare this treatise in the hope that it may prove useful to those engaged both in the design and erection of scaffolds for building purposes4 ,while special attention has been given to practical details1 the theory has not been neglected1 but has been dealt with by the use of terms well understood in the building trade4 ,the various formul given have been simplified as far as possible1 and it is hoped that in these days of technical education they will not be beyond the scope of the reader4 ,the illustrations have generally been drawn to scale1 but for the sake of clearness1 details are given to a larger scale where necessary4 ,the practice of allowing workmen to erect scaffolds without the aid of expert supervision1 as is generally the case1 is to be strongly deprecated4 ,the architect1 builder1 or clerk of works1 should in all cases be responsible for their erection--the risk of defective or unsafe work being thereby minimised1 and an economy often effected in both labour and material4 ,the author desires to acknowledge his indebtedness to ,mr4 ,g4 ,thatcher1 of ,h4,m4 ,office of ,works and ,hampton ,court ,palace1 for valuable information contributed by him1 and to ,mr4 ,j4 ,clark1 of the ,factory ,department of the ,home ,office1 for his very careful reading of the proofs2 while his best thanks are due to the following manufacturers3--,mr4 ,c4 ,batchelor1 ,messrs4 ,bullivant ,co41 ,ltd41 ,messrs4 ,butters ,bros41 ,mr4 ,j4 ,fishburn1 ,messrs4 ,frost ,co41 and ,mr4 ,e4 ,palmer1 who have furnished him with particulars of their various specialities4 ,a4 ,g4 ,h4 ,t4 ,,london3 ,february #aijd4 ,,note ,,to ,,the ,,second ,,edition ,recent alterations in and additions to the legal enactments affecting scaffolding and the persons employed in its erection have rendered necessary a second edition of this work4 ,the author has accordingly revised the information relating to the law of the subject1 and has embodied the important series of suggestions for the guidance of those engaged in building operations1 published in the ,annual ,report of the ,chief ,inspector of ,factories1 which1 if followed out1 will undoubtedly be the means of reducing the number of fatal and other accidents occurring at such works4 ,a4 ,g4 ,h4 ,t4 ,october #aijg4 ,,contents ,,page ,,preface v ,,chapter ,i ,,scaffolding ,scaffolding--,definition of--,northern system--,derrick stagings--,working platforms--,south country system--,gantries1 commonly called travellers--,travelling gantry--,gantries which serve as a base for lighter forms of scaffolding--,stagings--,pole scaffolds--,bricklayers' scaffolds--,masons' scaffolds--,connections #a-bi ,,chapter ,,ii ,,scaffolds ,,for ,,special ,,purposes ,needle scaffolding--,scaffolds for chimney shafts1 towers and steeples--,domes and arches--,swinging scaffolds--,painters' boats--,boatswain's boat--,ladder scaffolds--,supported painter's boat #cj-dh ,,chapter ,,iii ,,shoring ,,and ,,underpinning ,shoring--,flying shores--,raking shores--,underpinning #di-fa ,,chapter ,,iv ,,timber ,classification and structure--,defects in the living tree--,felling--,conversion--,seasoning- -,description--,selection --,decay--,preservation--,durability--,u se of scaffolding timber #fb-ge ,,chapter ,v ,,cordage ,,and ,,knots ,cordage--,strength of--,knots #gf-hi ,,chapter ,,vi ,,scaffolding ,,accessories ,,and ,,their ,,use ,ladders--,trestles--,cripples--,buckets and skips--,baskets--,barrows--,stone bogies--,hand barrows--,hods--,timber trucks--,sack trucks--,crates--,ashlar shears--,stone clips and slings--,stone lewises--,stone cramps--,wire and chain scaffold lashings--,tightening screws--,rollers--,levers--,dog irons--,bolts--,straps--,wire ropes--,chains--,slater's truss--,duck runs--,mortar boards--,wedges--,nails--,spikes--,scaff older's hatchet #ij-aad ,,chapter ,,vii ,,the ,,transport ,,of ,,material ,crane engines--,the crane--,pulleys--,differential pulleys--,winch--,jibs--,shears--,gin--, rails--,sack trucks--,attachment of material--,ironwork--,timber --,bricks--,slates--,stone #aae-acj ,,chapter ,,viii ,,the ,,stability ,,of ,a ,,scaffold ,stability--,wind pressures--,force of weight or gravity--,to find the centre of gravity of a body--,two or more bodies--,of a dependent scaffold and the effect of loads upon it--,of a gantry--,of a ,scotch derrick #aca-adb ,,chapter ,,ix ,,the ,,strength ,,of ,a ,,scaffold ,failure of beams--,pillars and struts--,ties and traces--,dead loads--,live loads--,breaking weight--,safe load--,constants--,beams subject to a transverse strain--,posts and struts subject to compression--,braces and ties subject to a tensional strain #adc-aec ,,chapter ,x ,,the ,,prevention ,,of ,,accidents ,short ladders--,sagging of ladders--,guard rails--,well holes--,edge boards--,traps--,runs--,supports to centering--,damp cordage--,sound material--,competent control--,fan guards--,due care by workmen #aed-afj ,,chapter ,,xi ,,legal ,,matters ,,affecting ,,scaffolding ,scaffolding bye-laws--,burgh ,police 7,scotland7 ,act--,factory and ,workshop ,act1 #aija--;,abstract of same1 issued from the ,home ,office--,notice of ,accident ,act--,report on ,building ,accidents by a ,home ,office ,inspector--,workmen's ,compensation ,act1 #aijf--;,application of ,act and definitions #afa-agh;,c ,,appendix3 ,weight of ,material #agi ,,index #ahc ,,list ,,of ,,illustrations ,,plates ,i4 ,derrick staging ,frontispiece ,,ii4 ,external chimney scaffold ,facing p4 #cc ,,iii4 ,knots #gi ,,iv4 ,knots #ha ,v4 ,knots #he ,,vi4 ,knots #hg ,,illustrations ,,in ,,text ,,fig4 ,,page #a4 ,elevation of staging for derrick crane #d #b4 ,plan of king leg #f #c4 ,showing shoring to central standard #f #d4 ,plan of derrick platform partially covered #g #e4 ,showing method of fixing ladders #h #f4 ,showing derrick staging mounted on travelling bogie #aj #g4 ,elevation of square derrick staging #aa #h and #h;,a4 ,elevation of gantry for traveller #ac #i4 ,footing blocks for struts #ae #aj4 ,elevation of travelling gantry #ae #aa4 ,gantry or elevated platform over footpaths #ag #ab4 ,example of stagings #ah #ac4 ,elevation of pole scaffold #bj #ad4 ,method of fixing rising standard #ba #ae4 ,method of connecting ledgers #bb #af4 ,method of connecting ledgers #bb #ag4 ,method of connecting ledgers #bc #ah4 ,method of connecting ledgers #bc #ai4 ,method of supporting putlogs where windows occur #bd #bj4 ,method of supporting putlogs where windows occur #bd #ba4 ,shores and ties for dependent scaffolds #be #bb4 ,methods of laying boards #bf #bc4 ,methods of laying boards #bf #bd4 ,masons' scaffold3 end elevation #bg #be4 ,landing stages #bh #bf4 ,needle scaffold #ca #bg4 ,internal chimney #cc #bh4 ,method of climbing chimneys1 steeples1 c4 #ce #bi4 ,method of climbing chimneys1 steeples1 c4 #cf #cj4 ,brackets for climbing chimneys1 steeples1 c4 #cg #ca4 ,methods of slinging painters' boats on chimneys1 c4 #ch #cb4 ,chimney scaffolds for repairs1 c4 #ci #cc4 ,details of chimney scaffolds for repairs1 c4 #ci #cd4 ,details of chimney scaffolds for repairs1 c4 #dj #ce4 ,details of chimney scaffolds for repairs1 c4 #dj #cf4 ,details of chimney scaffolds for repairs1 c4 #da #cg4 ,method of supporting standards within high towers #da #ch4 ,scaffold designed for repairing roofs or arches where roadway has to be kept open #db #ci4 ,painters' boats or cradles #dc #dj4 ,method of slinging cradle to move horizontally #dd #da4 ,improved painter's boat #dd #db4 ,boatswain's boat #de #dc4 ,elevation of ladder scaffolding #df #dd4 ,details of ladder scaffolding #dg #de4 ,details of ladder scaffolding #dg #df4 ,details of ladder scaffolding #dg #dg4 ,examples of flying shores #ea #dh4 ,examples of single raking shore #eb #di4 ,examples of system of raking shores #ec #ej4 ,details of raking shores #ed #ea4 ,details of raking shores #ee #eb4 ,details of raking shores #ef #ec4 ,example of underpinning #ei #ed4 ,example of window strutting #fj #ee4 ,example of cup shakes in timber #fc #ef4 ,example of radial shakes in timber #fc #eg4 ,method of cutting stiffest beam from log #ff #eh4 ,method of cutting strongest beam from log #ff #ei4 ,method of cutting planks from log #fg #fj4 ,method of stacking timber for seasoning #fh #fa4 ,examples of weather shakes in balks #fh #fb4 ,method of strapping ends of boards #gd #fc4 ,details of ladder construction #ia #fd4 ,details of ladder construction #ia #fe4 ,example of painters' trestles #ib #ff4 ,example of cripples #ic #fg4 ,example of cripples #ic #fh4 ,example of tipping pail #id #fi4 ,details of improved safety baskets #ie #gj4 ,details of improved safety baskets #ie #ga4 ,details of improved safety baskets #if #gb4 ,details of improved safety baskets #if #gc4 ,details of improved safety baskets #if #gd4 ,example of navvy's barrow #ih #ge4 ,example of stone bogie #ih #gf4 ,example of hand barrows #ih #gg4 ,example of labourer's hod #ih #gh4 ,example of timber trucks #ih #gi4 ,example of sack trucks #ih #hj4 ,example of brick crates #ii #ha4 ,example of ashlar shears #ajj #hb4 ,example of ashlar shears #ajj #hc4 ,example of stone clips #aja #hd4 ,method of slinging stone #aja #he4 ,method of slinging stone #aja #hf4 ,method of hoisting by means of the lewis #ajb #hg4 ,method of hoisting by means of the lewis #ajb #hh4 ,method of hoisting by means of the lewis #ajb #hi4 ,method of hoisting by means of the lewis #ajb #ij4 ,example of the stone cramp #ajc #ia4 ,wire rope lashing #ajd #ib4 ,chain and bracket lashing #aje #ic4 ,coupling links #aje #id4 ,rollers #ajf #ie4 ,levers #ajf #if4 ,dog irons #ajg #ig4 ,methods of fixing dog irons #ajg #ih4 ,methods of fixing dog irons #ajg #ii4 ,methods of fixing dog irons #ajg #ajj4 ,iron bolts #ajh #aja4 ,iron straps #aji #ajb4 ,slaters' truss #aab #ajc4 ,duck runs #aab #ajd4 ,scaffolder's hatchet #aac #aje4 ,manual building crane #aag #ajf4 ,example of pulley wheel #aah #ajg4 ,example of groove for pulley wheel #aai #ajh4 ,example of groove for pulley wheel #aai #aji4 ,example of groove for pulley wheel #aai #aaj4 ,example of groove for pulley wheel #aai #aaa4 ,example of groove for pulley wheel #aai #aab4 ,example of sprocket wheel #aai #aac4 ,example of single movable pulley #abj #aad4 ,example of blocks and tackle #abj #aae and #aaf4 ,example of differential pulley #abb #aag4 ,the winch #abd #aah4 ,the winch in use with a double rope #abe #aai4 ,example of a jib #abe #abj4 ,example of a jib for fixing purposes #abf #aba4 ,example of a mason's jib #abg #abb4 ,example of shear legs #abg #abc4 ,example of shear legs to carry jib #abh #abd4 ,example of movable shear legs #abh #abe4 ,example of a gin #abi #abf4 ,method of slinging girders #abi #abg4 ,diagram showing method of finding the centre of gravity of a rectangular body #acf #abh4 ,diagram showing method of finding the centre of gravity between two combined weights #acg #abi4 ,diagram showing method of finding the centre of gravity between three or more combined bodies #ach #acj4 ,method of finding the centre of gravity of a rectangular surface #aci #aca4 ,method of finding the centre of gravity of a triangular surface #ada #acb4 ,diagram showing the method of calculating the breaking weights of beams #adg #acc4 ,diagram showing the method of calculating the breaking weights of beams #adg #acd4 ,diagram showing the method of calculating the breaking weights of beams #adh #ace4 ,diagram showing the method of calculating the breaking weights of beams #adh #acf4 ,diagram showing the method of calculating the breaking weights of beams #adh #acg4 ,diagram showing the method of calculating the breaking weights of beams #adh #ach4 ,diagram suggestion for preventing accidents on short ladders #aed #aci4 ,method of staying ladder to prevent sagging #aee #adj4 ,method of staying ladder to prevent sagging #aee #ada4 ,illustrating dangerously laid boards #aef #adb4 ,illustrating the danger of a trap #aef #adc4 ,illustrating method of supporting centering #aeg #add4 ,illustrating method of supporting centering #aeh #ade4 ,fan guards #aeh #adf4 ,illustrating cause of fatal accident #aei ,,scaffolding ,,chapter ,i ,,scaffolding ,scaffolding is the art of arranging and combining pieces of timber in order to enable workmen to proceed with their work1 and from which1 if required1 to lift and carry the material necessary for their purpose4 ,many definitions of a scaffold have been given by authorities on building construction2 some of the best known are as follows3-- ,mitchell 7,c4 ,f473 ',temporary erections constructed to support a number of platforms at different heights1 raised for the convenience of workmen to enable them to get at their work and to raise the necessary material for the same4' ,tredgold 7,hurst73 ',a scaffold as used in building is a temporary structure supporting a platform by means of which the workmen and their materials are brought within reach of their work4' ,rivington3 ',scaffolds are temporary erections of timber supporting platforms close to the work1 on which the workmen stand and deposit their materials4' ,banister ,f4 ,fletcher1 in ',carpentry and ,joinery'3 ',a scaffold is a temporary structure placed alongside a building to facilitate its erection by supporting workmen and raising materials during the construction1 or for the repair of buildings4' ,recent cases tried under the ,workmen's ,compensation ,act have given a wider meaning to the word1 and the following definition is perhaps the most comprehensive at the present time3 ,a scaffold1 as used in building1 is a temporary arrangement of timbers combined and supported in various ways to enable the workmen to proceed with their work1 and where required1 to afford facilities for the lifting and carrying of the materials4 ,the two principal methods of scaffolding are known respectively as the ,north and ,south country systems4 ,the northern1 as indicated by the name1 was at one time in use only in ,scotland and the north of ,england1 but its many advantages1 more especially for the transport of material1 have now caused it to become general throughout the country4 ,the second method is essentially the ,south country system1 and is of greater use when power is not necessary for the construction of the building4 ,a combination of both methods is commonly seen1 and found useful in practice4 ,in scaffolding1 the vertical timbers are known as standards or uprights4 ,the horizontal timbers between the standards are known as ledgers when of cylindrical section1 but as transoms and runners when of rectangular section4 ,braces1 shores1 struts and ties of any section are pieces used to stiffen the structure4 ,the putlogs1 or joists as they are called when of greater length1 carry the boards which form the working platform4 ,the ,northern ,system4--,this scaffolding can be divided into two parts4 ,first1 the derrick staging from which the transporting power acts2 and1 second1 the platforms1 which bring the workmen within reach of their work4 ,derrick ,stagings4--,these stagings1 also known as ,scotch derricks and ',scotchmen1' are erected to carry the power required1 usually a steam crane4 ,they consist of three or four timber towers or legs supporting a platform upon which the crane stands4 ,the number of legs depends upon the area over which the power is required to act4 ,when one crane is to be erected1 three legs are sufficient to carry the platform4 ,if the building is a large one1 several such stagings may be constructed2 but in some cases two cranes are required where the size of the building will not allow of two stagings4 ,in these cases the platform is square and supported at each angle by a leg4 ,the cranes are then fixed diametrically opposite each other4 ,in determining the position of the legs they must be placed where the effective range of the crane is most required1 and also where they will cause the least possible obstruction to the progress of the building4 ,the position of the tower that carries the crane1 and which is known as the principal or king leg1 is first fixed4 ,the secondary or queen legs are set out from it in the form of an isosceles triangle4 ,the distance between the king and queen legs depends upon the length of the sleepers4 ,these run from below the engine to the lower ends of the guys1 and average from #be to #cj feet in length4 ,the legs1 especially the king legs1 if intended to rise from the earth1 must have a foundation of two thicknesses of #c-;inch timbering laid crosswise4 ,this is unnecessary if there is a concrete or other solid foundation4 ,apart from the necessity for any foundation1 the standards should rise from a framework of balk timbers of about #ab in4 by #ab in41 laid on the ground1 and halved at their intersection 7fig4 #a74 ,illustration3 ,,fig4 #a4--;,,elevation ,,of ,,staging ,,for ,,derrick ,,crane ,in the case of the queen legs an extra balk is placed under the framework1 as shown in fig4 #a4 ,the legs are from #f to #aj feet square on plan1 the king legs being the larger4 ,each leg comprises four standards1 either of whole timbers or battens bolted together4 ,the standards for the king legs should measure not less than #i in4 by #i in42 if of battens1 then three pieces #i in4 by #c in4 should be used4 ,for the queen legs1 balks #g in4 by #g in41 or three pieces #g in4 by #b-a_/b in41 are sufficient sectional area4 ,where battens are used they are given a lap equal to one-third of their full length1 and are bolted together by #c_/d-;inch wrought-iron bolts4 ,whole timbers are used when they can be obtained in one piece of sufficient length4 ,as the standards rise they are divided into bays by transoms4 ,these are made out of about #i-;in4 by #c-;in4 deals1 placed from about #f to #aj feet apart4 ,the bays are triangulated by cross-braces #g in4 by #b-a_/b in42 both of these are usually placed on the outside of the bay1 but one or both may be placed on the inside4 ,the first method is the better1 as the braces1 by butting against the transoms1 give an increased resistance to movement4 ,the king leg1 having to carry the weight of the engine1 requires greater strength4 ,this is gained by running an extra standard up the centre of the leg4 ,if it is whole timber1 balks about #ad in4 by #ad in4 are required2 if built up1 four deals #af in4 by #d in4 are used4 ,it should stand upon an extra balk laid with the horizontal framing at the bottom of the leg1 and should rest on a solid foundation4 ,to prevent any tendency to flexure this extra standard should be strutted from all four of the outer standards behind each transom 7see fig4 #b74 ,another method is to shore the central standard from the foundation1 as in fig4 #c4 ,the legs in this manner can be made to support a platform up to #abj feet in height4 ,the required height having been reached1 the legs are connected by trussed beams in the following manner3 ,two balk timbers of about #ab in4 by #h in4 are laid immediately above each other between the king leg and each queen leg1 resting on the two top transoms1 as shown in fig4 #a4 ,they are from #f to #i feet apart1 the top bay being sometimes made slightly lower than the others4 ,the lower balks are connected to the centre standard of the king leg by wrought-iron straps4 ,illustration3 ,,fig4 #b4--,,plan ,,of ,,king ,,leg ,illustration3 ,a1 ,central ,standard4 ,b1 ,shorings4 ,,fig4 #c4--,,showing ,,shoring ,,to ,,central ,,standard ,the top balks project from #f to #aj feet beyond the king leg1 and are halved at their point of intersection4 ,the projecting ends are connected to each other by pieces #h in4 by #f in41 and again to the return balk by similar pieces 7see fig4 #d74 ,they are also supported by struts from the central standard1 as shown in fig4 #a4 ,the upper and lower balks are connected by iron bolts about #aj feet apart1 and each bay thus formed is cross-braced in the same manner as the legs4 ,the iron bolts are covered by pieces of the same scantling as the braces4 ,in the single derricks the queen legs can be connected by a trussed beam similarly formed1 or by a single balk carried across and laid on the top transom4 ,illustration3 ,,fig4 #d4--,,plan ,,of ,,top ,,platform ,,partially ,,covered ,if the span is considerable1 struts can be carried from the queen legs towards the centre of the underside of the balk to prevent sagging4 ,on the trussed beams thus formed1 joists of #i in4 by #c in4 or ordinary poles are laid about #c feet apart4 ,they are laid parallel to one another1 and in a direction at right angles to the truss or single beam forming the back support of the platform4 ,the centre joists are continued to the ends of the balks which project beyond the king leg4 ,the advantage of having continued the top balks can now be seen1 as it gives greater area to the platform immediately round the engine4 ,the boards #i in4 by #a-a_/b in4 are laid at right angles to the joists4 ,another way of forming the platform is to cover only partially the surface between the legs4 ,in this case two additional joists1 #f in4 by #f in41 are thrown across the king leg 7see fig4 #d71 the boards not extending beyond their length4 ,when this is done1 the workmen reach the platform from the communicating ladder which usually passes up a queen leg1 by means of a run two boards wide4 ,it is better to lay the larger platform1 as1 apart from the question of safety to the men1 it serves as a storage for coal for the engine1 the weight of which tends to keep the erection steady4 ,double boards should be laid under coals or other heavy stores4 ,to reach the platform1 ladders are fixed in different ways4 ,they can run up inside1 or be fixed to the outside of the queen legs4 ,in either case they are nearly or entirely upright4 ,a better method is shown in fig4 #e1 and should be carried out wherever possible4 ,illustration3 ,,fig4 #e4--,,showing ,,method ,,of ,,fixing ,,ladders ,the derrick sleepers1 two in number1 are of balk timber1 and lie across the platform from beneath the engine bed to which they are connected1 to the centre of the queen legs4 ,the guys or stays1 also of balk timbers1 besides being connected to the mast1 are attached to the sleepers over the queen legs 7see fig4 #a74 ,to counteract the overturning force exerted by the jib and the material lifted1 the guys are chained down to the timber balk at the bottom of the queen legs 7fig4 #a74 ,this balk supports a platform which is loaded with bricks or stones more than equal to double the weight that will be lifted4 ,the chain1 which works loose with the vibration of the scaffold1 is tightened by means of a screw coupler fixed in its length4 ,the arrangement is as follows3--,two lengths of heavy chain with large links at each end are required4 ,one length is carried round the sleeper and then taken down the centre of the leg4 ,the other length is taken round the balk which is placed underneath the staging1 and carried up through the load1 when the tightening screw can be applied and the correct tension brought up4 ,to prevent lateral motion the legs are cross-braced by poles or deals between each leg as shown on frontispiece4 ,the poles are tied to the legs just beneath the platform and connected at their meeting point4 ,when crossing they should be at right angles to each other4 ,deals #i in4 by #c in4 can take the place of the poles if required1 bolts in this case being used instead of tyings4 ,at the building of the new ,post ,office1 ,leeds1 #ahic1 a different method of raising the platform for the crane was adopted4 ,the legs1 instead of being framed1 consisted of a single balk of timber strutted on each side from the ground level1 the sleepers and guys being firmly attached to the standards themselves4 ,when erecting long ranges of buildings it may be more convenient to have the derrick mounted upon a travelling bogie than to dismantle the structure in order to re-erect at another point4 ,fig4 #f illustrates the system1 the travelling power being usually manual4 ,the arrangement is suitable for small derricks1 and is employed where the crane is erected outside the building4 ,illustration3 ,,fig4 #f4--,,showing ,,staging ,,mounted ,,on ,,travelling ,,bogie ,another method of using travelling cranes is to erect a platform as shown in fig4 #g4 ,the standards1 which may be of balk timber or built up1 as previously shown1 are about #aj feet apart longitudinally and #bj to #cj feet transversely4 ,they stand upon sills of the same section where the foundation is not solid4 ,on the head of the standards1 the runners are laid connecting all the standards in the same row4 ,head pieces may be fitted between the standards and runners2 this serves to distribute pressure4 ,all the connections are securely made by dog irons1 bolts1 and straps4 ,the stability depends entirely upon the bracing1 and this1 it is important to note1 should be between each bay longitudinally1 and at least every second bay transversely4 ,illustration3 ,front ,elevation ,end ,elevation ,,fig4 #g4--;,,elevation ,,of ,,derrick ,,staging ,timbers placed as ,a in fig4 #g give rigidity to the standards by preventing flexure1 and are necessary when the lengths of the uprights exceed #cj times their least diameter4 ,the deals used for braces are bolted to the standards2 for poles1 tying is resorted to4 ,working ,platforms4--,the working platforms used in conjunction with overhead or overhand work depend upon the requirements of the building4 ,by over head or hand work is meant that the material upon which the mechanic is to be employed reaches him from over head or hand4 ,when no outside scaffolding is needed1 the platforms are laid upon the floor joints in the interior of the building1 being raised upon trestles as the work proceeds1 and until the next floor is reached4 ,light forms of scaffolds1 as the ordinary masons' and bricklayers' pole scaffolds1 are now frequently used as working platforms in connection with the ,scotch system4 ,the ,south ,country ,system4--,this system is divided into two classes according to the strength required4 ,for the first1 square timbers are used2 for the second1 poles are employed4 ,the scaffolds built of square timbers are known as gantries and stagings1 and the pole erections are termed bricklayers'1 and masons' or independent scaffolds4 ,gantries4--,the term gantry was originally given to erections constructed with a view to the easy carriage of heavy material1 but of late it has also come to mean a structure arranged to support lighter forms of scaffolding over footpaths which have to be kept open for public use4 ,illustration3 ,,fig4 #h4--;,,elevation ,,of ,,gantry ,,for ,,traveller ,illustration3 ,,fig4 #h;,a4--,,end ,,elevation ,,of ,,gantry ,,shown ,,in ,,fig4 #h #ast4 ,gantries for transport of material1 commonly called travellers4 ,figs4 #h and #h;a show the general construction4 ,the distance between the outer rows of standards and the wall depends upon circumstances4 ,if possible1 the space should be allowed for a cart-way1 as the material can thus be brought quite close to the work before being lifted4 ,if1 owing to adjacent footpaths or any other reason1 this cannot be done1 the uprights should be placed close to the wall on either side1 the material being lifted at the end of the gantry or other convenient spot1 over which the lifting gear can be brought4 ,the standards of square timber for the gantry are from #f in4 to #ab in4 square1 and are erected upon sleepers1 or1 as they are sometimes termed1 sills laid in the same direction as the run of the scaffold4 ,one row of standards is placed on each side of the wall4 ,the standards are placed #h to #aj feet apart4 ,on the top of the standards runners are fixed connecting each standard in the same row4 ,sills1 standards1 and runners should be of the same sectional area4 ,the runners are strutted on their underside1 from the standards by pieces of1 at least1 half the sectional area of the supported timbers4 ,if the struts are of equal size to the runners1 double the weight can be carried4 ,the cleats from which the struts rise1 are simply spiked to the standards1 but if designed to carry excessive weights they are slightly housed in4 ,as the space between each row of standards has to be kept open for the building1 no cross bracing can be allowed except at the ends4 ,strutting is therefore resorted to in order to give stability4 ,the struts1 one to each standard1 are bolted to the upright near the top1 and again to a foot block driven into the ground4 ,other methods of fastening down the bottom ends of the struts are shown in fig4 #i2 the use of each depends upon the nature of the soil4 ,struts are also fixed at the ends to prevent lateral movement4 ,head pieces1 or corbels1 as they are sometimes termed1 are occasionally inserted between the standards and runners1 and serve to distribute pressure4 ,straining pieces spiked on the underside of the runners1 for the struts to pitch against1 are used when the standards are considerably apart4 ,illustration3 ,,fig4 #i4--;,,footing ,,blocks ,,for ,,struts ,rails upon which the travelling engine or traveller can move are laid on top of the runners1 and are turned up at the ends of the platform to serve as buffers to the engine platform4 ,illustration3 ,end ,elevation ,side ,elevation ,,fig4 #aj4--;,,elevation ,,of ,,travelling ,,gantry ,the engine platform consists of two trussed beams of timber about #c feet apart1 connected at their ends with short pieces of the same scantling1 and fitted with grooved wheels to move upon the rails4 ,rails are also laid upon each beam and serve for the traversing motion of the crab4 ,movement of the traveller is obtained from the crab1 which is worked either by manual or steam power1 and acts through a system of shafting and geared wheels4 ,movement in three directions is necessary from the crab3 vertically for lifting1 and horizontally in two directions1 transversely and longitudinally4 ,travellers are made up to #ej feet wide and any required length4 ,another method of building travellers is shown in fig4 #aj4 ,in this case1 the rails upon which the traveller moves in a longitudinal direction are fixed on sleepers on the ground level1 and the standards and runners of the first example are not required4 ,in their place is constructed a triangulated system of balk timber framing4 ,the platform is fixed to the head pieces1 and is braced as shown4 ,less timber is used in their construction1 but owing to the greater weight a steam winch is required to impart motion4 ,gantries which serve as a base for lighter forms of scaffolding4--,these erections are in reality elevated platforms1 and allow of a clear way for a footpath where required4 ,they are constructed of two frames1 placed apart according to the width of the path over which the platform stands 7fig4 #aa74 ,the method of erection1 so far as the side frames are concerned1 is the same as for the first example of travelling gantries4 ,stability is1 however1 gained by cross-bracing as shown in figure1 thus making strutting unnecessary4 ,the platform can be laid by placing short boards #i in4 by #c in4 across the runners when the platform is narrow4 ,it is more usual1 however1 to place joists #aj in4 by #b in4 across1 and on these to lay the boards longitudinally4 ,the joists average #b to #c feet apart1 the braces are about #b in4 by #g in4 ,on the outside of the scaffold1 parallel to the sills1 balk timbers are placed forming a 'fender' to prevent the vehicular traffic from injuring or disturbing the erection4 ,illustration3 ,front ,elevation ,end ,elevation ,,fig #aa4--;,,gantry ,,or ,,elevated ,,platform ,,over ,,footpaths ,stagings4--,stagings are erected in a manner similar to travelling gantries1 but are carried more than one storey high 7fig4 #ab74 ,it is a form of scaffolding rarely seen1 more especially since the introduction of the ,scotch derrick system4 ,the timbers are erected to the height of the first runner in the same manner as the frames in fig4 #aa4 ,in order to carry the scaffold higher1 horizontal pieces are laid across the scaffold1 over the standards1 and are made to project #i or #aj feet on each side of the runners4 ,on these beams1 uprights1 as in the first tier1 are raised1 being connected in like manner1 longitudinally by transoms4 ,the rising tiers of standards are strutted by timbers ,a ,a1 rising from the projecting portion of the beam called the footing piece1 which serves in the same manner as a footing block4 ,the footing piece is supported by struts1 ,b ,b1 rising from the lower standards4 ,the struts ,b ,b are in two pieces1 being bolted to the sides of the footing pieces and uprights4 ,this allows the shores ,a ,a to pass between them4 ,illustration3 ,front ,elevation ,cross ,section ,,fig4 #ab4--;,,example ,,of ,,stagings ,strutting within the bays formed by the standards is carried out on each tier with the exception of the top1 where braces are fixed1 as shown at ,c4 ,on the top runners rails are laid for a traveller4 ,in constructing the foregoing square timber erection1 note should be taken of the following points3-- ,that the uprights of the upper tiers should stand immediately over those of the lower tiers1 in order to prevent cross strains on the runners4 ,that the timbers should fit as evenly as possible1 as thereby the whole erection is rendered more stable4 ,that joints between the runners should occur immediately over the standards4 ,the several parts of this structure1 if for temporary purposes1 can be connected by dog irons2 if for a more permanent use1 by bolts and straps4 ,,pole ,,scaffolds ,bricklayers' ,scaffolds4--,a bricklayer's scaffold consists of a series of upright poles or standards1 to which are lashed horizontal poles1 termed ledgers4 ,the ledgers and the wall of the building carry the putlogs1 on which boards are laid to support the workman1 his material1 and tools 7fig4 #ac74 ,the standards are first erected1 and may stand singly or in pairs4 ,in a repairing job1 unless of great height1 and where there is no great weight of material1 single poles are sufficient4 ,where double poles are required1 the first pair are erected of different lengths4 ,the short pole is termed a puncheon4 ,the difference of length allows of a lap in connecting the succeeding poles4 ,the lap should equal half of the full-length pole4 ,the standards are placed #f to #h feet apart1 and from #d to #f feet away from the building4 ,illustration3 ,,fig4 #ac4--;,,elevation ,,of ,,pole ,,scaffold ,the butt-ends are embedded about #b feet in the ground1 which affords some resistance to overturning4 ,if they cannot be embedded1 they should be placed on end in barrels filled with earth tightly rammed4 ,as the building rises additional poles are added1 being lashed to the standards already erected4 ,if the standard is a single pole1 the second pole1 having a lap of #aj or #ae feet1 stands upon a putlog placed close to the first pole for that purpose 7fig4 #ad74 ,the inner end of the putlog is securely fastened down to the scaffold or inserted into the building4 ,if the standard is double1 the rising pole is placed upon the top end of the puncheon1 and afterwards others are placed on end upon the lowest free end of the standards already fixed4 ,illustration3 ,,fig4 #ad4--,,method ,,of ,,fixing ,,rising ,,standard ,as the standards rise1 they are spliced or 'married' together with band ties4 ,at a height of #e feet1 this distance being the greatest at which a man can work with ease1 a ledger is tied across the standards to form a support for the working platform4 ,where a single pole is insufficient in length to form a continuous ledger1 two are joined in one of three ways4 ,illustration3 ,,fig4 #ae ,in the first they are lapped over each other as fig4 #ae4 ,this method gives a strong connection1 but prevents the putlogs being laid evenly4 ,illustration3 ,,fig4 #af ,the second way provides that the ledgers shall lap horizontally side by side4 ,this allows of evenness of line for the putlogs1 but is not so strong 7fig4 #af74 ,in both of these methods the lap should cover two standards1 and not as shown in fig4 #ag4 ,the third manner of connection 7fig4 #ah7 is the best4 ,the ledgers butt end to end4 ,underneath1 a short pole is placed crossing two standards4 ,the tying at the standard embraces the double ledger4 ,a band tie is run round the supporting pole and the ends of the ledgers where they butt4 ,great strength is obtained in this way and the putlogs can be evenly laid4 ,additional ledgers are fixed as the work proceeds4 ,illustration3 ,,fig4 #ag ,on the ledgers1 and at right angles to them1 putlogs are laid1 resting outwardly on the ledgers and inwardly on the wall1 where header bricks have been left out for their reception4 ,illustration3 ,,fig4 #ah ,the putlogs1 which are placed about #c or #d feet apart1 should be tied to the ledgers and fastened by wedges into the wall4 ,this is not often done1 but at least one putlog to every tying between standard and ledger should be so treated4 ,where the putlogs cannot be carried by the wall owing to an aperture in the building1 such as a window1 they are supported by bearers fixed as shown in figs4 #ai and #bj4 ,illustration3 ,,fig4 #ai ,illustration3 ,,fig4 #bj ,by wedging the inner end of the putlog into the wall1 some stability is given to the scaffold1 but the connection cannot be considered satisfactory1 as the putlog would draw under very little strain4 ,greater stability can be gained if the outer frame of the scaffold is supported by one of the three methods given as follows4 ,illustration3 ,,fig4 #ba4--,,shores ,,and ,,ties ,,for ,,dependent ,,scaffolds ,a shore or tie can be fixed between the erection and the ground as shown in fig4 #ba1 or1 if there are openings in the wall1 supports can be fixed as ties shown in the same diagram4 ,the ties or struts should be placed to every third or fourth standard at about #be feet from the ground1 and their fastenings made good4 ,additional ties should be carried within the building at a greater height where possible4 ,the stability of the scaffold under loads and cross wind pressure1 depends greatly upon the ties or shores1 and their fastenings should be well made and kept in good order4 ,the historical instance of the mechanic who1 to escape a shower of rain1 stood upon the inner board of the platform1 and by leaning against the building pushed the scaffold over1 should have no opportunity of recurrence4 ,illustration3 ,,fig4 #bb ,to stiffen the scaffold longitudinally braces are tied on the outside of the scaffold in the form of a ,st4 ,andrew's cross 7see fig4 #ac74 ,they start from the lower end of one standard and rise obliquely across the scaffold to near the top1 or some distance up a standard in the same run4 ,tied at their crossing-point1 connections are made to all the main timbers of the scaffold with which they come in contact4 ,braces are fixed in all exposed situations1 and generally where the scaffold is more than one pole 7#cj feet7 in height4 ,illustration3 ,,fig4 #bc ,the only exception to effective bracing being carried out is where the building1 being of irregular form1 creates many breaks and returns in the scaffolding4 ,it is obvious that where a scaffold butts against or breaks with a return wall1 the tendency to lateral motion is lessened4 ,the boards1 which are placed longitudinally across the putlogs1 can be laid to lap or butt at their ends4 ,when lapping1 one putlog only is required to carry the ends of two series of boards 7fig4 #bb74 ,when butting1 two putlogs are required placed about #d inches apart 7fig4 #bc74 ,the second method is the better1 as the boards are not so likely to lose their place or to trip the workmen4 ,if heavy work is in progress the boards are laid double4 ,as the building rises1 the boards are carried up to each successive platform1 but each tied putlog is left in its place4 ,illustration3 ,,fig4 #bd4--,,masons' ,,scaffolds3 ,,end ,,elevation ,masons' ,scaffolds4--,masons'1 or independent scaffolds differ from the bricklayers' in that they have to be self-contained4 ,owing to the different material of which the building is erected1 the putlogs cannot rest upon the wall4 ,if openings were left for them1 as in brickwork1 the wall would be permanently disfigured1 more especially when ashlar fronted4 ,in order to gain the necessary support two parallel frames of standards and ledgers are erected along the line of wall to be built 7fig4 #bd74 ,they are from #d to #e feet apart1 the inner frame being as close to the wall as possible4 ,as a heavier material has to be dealt with1 the standards are placed closer together1 say from #d to #e feet4 ,illustration3 ,,fig4 #be4--,,landing ,,stages ,the ledgers and braces are placed as before1 the putlogs now resting on ledgers at each end1 and not on the wall at the innermost end1 as in the bricklayer's scaffold4 ,to prevent cross movement of the scaffold1 an additional method of bracing is available in this system4 ,an inner and outer standard are connected by short braces across each bay1 as shown in fig4 #bd4 ,this method of cross-bracing can be continued to the top of the scaffold1 and the braces should be put in longitudinally1 about #bj feet apart4 ,the platforms laid on all pole-scaffolds are from #d to #e feet wide4 ,it is usually necessary1 on anything but the smallest jobs1 to keep this width free for the workman and his material4 ,in order1 therefore1 to provide a platform on which the material can be landed1 it is convenient to erect1 on the outside of the scaffold1 an additional platform from #e to #aj feet square 7fig4 #be74 ,it is constructed of standards1 ledgers1 and braces1 in like manner as the scaffold to which it is attached4 ,the face-boards1 as shown in this figure1 should be fixed wherever material is being hoisted1 to prevent any projection of the load catching under a ledger and upsetting4 ,connections4--,the members of pole scaffolds are connected by cordage4 ,the names of the various knots are given in ,chapter ,v4 ,the arranging of the various timbers used in erecting scaffolds is a dangerous occupation1 and one requiring skill and considerable nerve on the part of the workmen4 ,in the majority of cases1 the timbers on the ground level are placed in position by manual labour only1 shear legs being used to facilitate matters4 ,when the scaffold rises1 advantage is taken of any rigid member on which pulley wheels can be hung1 and by this means the succeeding poles1 c4 are raised1 manual dexterity and strength being responsible for their final position4 ,,chapter ,,ii ,,scaffolds ,,for ,,special ,,purposes ,when applying the given methods for scaffolding1 difficulties arise owing to the varying designs of the buildings under construction or repair4 ,it is impossible to deal with these cases in detail2 they must be left to the scaffolder1 who1 while holding closely to the principles1 by the exercise of ingenuity will make combinations and variations of the various systems to suit the special requirements demanded in each case4 ,there are1 however1 certain types of scaffolding which occur with some regularity1 and these will now be dealt with4 ,needle ,scaffolding4--,needle scaffolding is necessary where it is impossible or too expensive to carry the scaffold from the ground level or other solid base4 ,it is used both for repairing and new erections4 ,the needles from which the scaffold takes its name are timbers 7usually poles or balks7 placed horizontally through and at right angles1 or nearly so1 to the wall of the building4 ,the projections support a platform upon which an ordinary pole scaffold is erected 7fig4 #bf74 ,windows1 or other openings in the wall1 are utilised where possible for the poles to pass through4 ,in other cases holes have to be made in the walls1 cut as nearly as can be to the size of the needles in use4 ,the needles must be of sufficient scantling to carry the weight of the scaffold and attendant loads4 ,the stability of the structure depends upon the means taken to fasten down the inner end of the needle4 ,the usual plan is to tie it down to a convenient joist or other rigid member of the building itself1 but the method shown on the diagram is better1 as resistance to movement is gained both from above and below4 ,struts from the building below the needles to their outer end1 give greater strength to the beam4 ,when erecting needle scaffolding around buildings of small area1 say of a tower or chimney shaft1 the needles can be laid across the building in one length1 piercing the wall on opposite sides4 ,in these cases1 if the needles are wedged in1 the weight of the building and the scaffold itself on the opposite ends of the needles1 is sufficient to maintain equilibrium4 ,illustration3 ,,fig4 #bf4--,,needle ,,scaffold ,the platform is formed of #i-;in4 by #c-;in4 deals1 and on this is erected whatever scaffolding may be necessary4 ,scaffolds for ,chimney ,shafts1 ,towers1 and ,steeples4--,the erection of chimney shafts can be carried on entirely by the aid of internal scaffolding4 ,as the work rises putlogs are laid across the shaft1 the ends being well built into the wall4 ,on the putlogs the platform is laid1 being carried up as the work proceeds4 ,the putlogs may be left in for the time1 and struck on completion4 ,the platform is fitted in its centre with a hinged flap door through which the material is hoisted as required4 ,there is some objection to this method of scaffolding where the wall is more than #a foot #aj-a_/b inches thick 7which is the greatest depth of brickwork over which a man can reach and do finished work71 for the mechanics1 in order to reach the outside joints1 have to kneel on the freshly laid material1 which is detrimental to good workmanship4 ,for this reason the system of carrying up an ordinary pole scaffold externally until the height is reached where the wall is reduced to #a foot #aj-a_/b inches in thickness1 is to be preferred4 ,the walls of a chimney shaft decrease in thickness #d-a_/b inches at a time1 forming an internal set-back of that width at every #bj feet in height4 ,this set-back is of advantage to internal scaffolding when the full height of the brickwork is reached1 and the cap has to be fixed4 ,the cap or coping1 when of stone or iron1 does not admit of the insertion of putlogs4 ,to overcome the difficulty1 four or more standards are erected at equal distances1 and standing upon the top set-back 7fig4 #bg74 ,the standards project sufficiently to carry the pulley wheel well above the total height of the chimney1 in order to give head room and to assist the workman in fixing the coping4 ,to stiffen the standards1 short ledgers are tied across as shown in fig4 #bg4 ,illustration3 ,,plate ,,ii4 ,photo by ,w4 ,cottrell ,hightown1 ,manchester4 ,,external ,,chimney ,,scaffold4 ,erected for the ,willesden ,electric ,lighting ,works1 under the supervision of ,e4 ,willis1 ,esq41 ,a4,m4,i4,c4,e41 etc4 ,when the chimney is to be erected by external scaffolding the ordinary mason's or bricklayer's scaffold is used4 ,owing to the small area of the erection the outside frames of the scaffold have a quick return4 ,this makes it practically impossible for the scaffold to fail by breaking away from the building under the influence of the loads it may carry4 ,shoring or tying is therefore not so important4 ,wind pressures have1 however1 a greater effect1 especially when the direction is not at right angles to one of the faces of the scaffold4 ,if in that direction1 the tied putlogs would offer resistance4 ,braces are therefore imperative1 and they should be fixed at right angles to each other1 each pair thus bracing a portion of the height of the scaffold equal to its width4 7,see plate #b47 ,for the repair of chimney shafts without scaffolding from the ground level1 means have to be taken to bring1 first the mechanic1 and afterwards his material1 within reach of the work4 ,illustration3 ,,fig4 #bg ,the preliminary process of kite-flying is now rarely seen1 except for square-topped chimneys1 and even in these cases the delay that may arise while waiting for a suitable steady wind is a drawback to its practice4 ,the kites used are about #aj feet long and #h feet wide4 ,they are held at four points by cords which continue for a distance of about #af feet1 and then unite into one4 ,near this point on the single rope another cord is attached1 which serves to manipulate the kite into position4 ,stronger ropes or chains are then pulled over the shaft1 after which a workman ascends1 and the necessary pulley wheels and timbers to form a regular means of ascent are sent up after him4 ,a light line carried up in the interior of the shaft by a hot-air balloon is another means of communication4 ,the most certain and safest method of ascent is to raise on the exterior of the shaft a series of light ladders1 which are lashed to each other and firmly fixed to the chimney as they ascend4 ,the ladders have parallel sides1 and are used up to #bb feet in length4 ,one method of fixing is as follows3-- ,a ladder is placed against the shaft on its soundest side4 ,it rests at its top end against a block of wood slightly longer than the width of the ladder1 and which keeps it from #g to #i inches away from the wall4 ,this space allows room for the workmen's feet when climbing4 ,the ladder is then fixed by two hooks of round steel driven into the wall1 one on each side immediately under the blocks1 the hooks turning in and clipping the sides of the ladder 7fig4 #bh74 ,the hooks1 which have straight shanks of #g_/h-;inch diameter with wedge-shaped points1 are driven well home1 as the stability of the erection depends upon their holding firmly4 ,above the top end of the ladder a steel hook is driven into the wall on which a pulley block can be hung1 or instead1 a pin with a ring in its head can be so fixed4 ,a rope from the ground level is passed through this block or ring1 and reaches downward again for connection to the ladder next required4 ,the connection is made by lashing the rope to the top rung and tying the end to the seventh or eighth rung from the bottom2 this causes the ladder to rise perpendicularly4 ,the steeplejack who is standing on the already fixed ladder cuts the top lashing as the hoisted ladder reaches him1 and guides it into its place as it rises4 ,when the rung to which the rope is tied reaches the pulley block1 the ladders should overlap about #e feet4 ,they are at once lashed together at the sides1 not round the rungs4 ,illustration3 ,,fig4 #bh ,the workmen can now climb higher1 driving in hooks round the sides1 and under the rungs of the ladder alternately1 lashings being made at each point4 ,a wooden block is placed under the top end of the last ladder and fixed as before4 ,the hoisting rope1 which has been kept taut meanwhile1 is now loosened and the process repeated4 ,the ladders rise in this manner until the coping of the shaft is reached4 ,here1 owing to the projection of the cap which throws the ladders out of line1 it is impossible to lash the top ladder to the lower4 ,to overcome the difficulty1 the wall is drilled in two places immediately over the topmost fixed ladder1 and expansion bolts are fitted therein4 ,to these bolts the lower end of the top ladder is tied4 ,the hoisting rope is then tightened sufficiently to hold the ladder1 and by this means the workmen are enabled to reach the top of the shaft4 ,a variation of this method of climbing is to replace the wooden blocks by iron dogs with #i-;inch spikes1 which should be driven well into the wall4 ,short ladders of about #aj feet in length are then used1 these being lashed to the dogs as they rise4 ,another method of fixing the ladders is shown in fig4 #bi4 ,illustration3 ,,fig4 #bi ,in this case eye-bolts are driven horizontally into the wall in pairs1 rather wider apart than the width of the ladders4 ,iron rods hook into these and are fastened to the ladder sides by thumb screws4 ,the ladders rise above each other and are connected by #c-;inch sockets4 ,when fixed1 they stand about #ah inches from the wall4 ,this is an advantage1 as it enables the workmen to climb on the inside of the ladders1 thus lessening the strain on the eye-bolts1 and the ladder can more easily pass a projecting chimney cap4 ,on the other hand1 the whole weight of the ladders rests upon the bottom length1 so that if through any cause it gave way1 for instance under accidental concussion1 the entire length would most certainly collapse4 ,this danger could be avoided if the ladders were supported on brackets as fig4 #cj4 ,no reliance should be placed upon the thumb screws1 as they may work loose under vibration4 ,danger from this source would be avoided if the slot in which the ladder peg moved was made as shown in fig4 #cj4 ,illustration3 ,,fig4 #cj ,the necessary repairs can be carried out by means of boats1 cradles1 or scaffolding4 ,cradles and boats are swung from balk timbers laid across the top of the shaft1 or from hooks where the design of the chimney permits1 as shown in fig4 #ca4 ,the common method of fixing light scaffolds round a chimney or steeple is shown in fig4 #cb4 ,they are most easily fixed to square or other flat-sided erections4 ,the scaffolder having by means of ladders or boats reached the desired height1 fixes a putlog by means of holdfasts to one of the walls4 ,another putlog is then fixed on the opposite side of the building at the same level4 ,the two are next bolted together by #a-;inch iron bolts of the required length4 ,the bolts are kept as near to the wall as possible4 ,the process is repeated again about #f feet higher on the building4 ,the boards for the platforms are next laid4 ,the first are placed at right angles to the putlogs and project sufficiently to carry the boards which are laid parallel to the putlogs4 ,to prevent the boards rising when weight is applied at one side of the scaffold1 iron plates bolted together 7fig4 #cc7 are fixed at the corners1 and clips 7fig4 #cd7 connect them to the putlogs4 ,illustration3 ,,fig4 #ca ,illustration3 ,,fig4 #cb ,illustration3 ,,fig4 #cc ,the stability of these scaffolds depends upon fixing at least two sets of putlogs1 connected by means of stays as shown in fig4 #cb4 ,bracing is unnecessary if the putlogs and bolts tightly grip the building4 ,when these scaffolds are used on circular chimneys1 chucks have to be fitted on the inside of the putlogs to prevent them being drawn by the bolts to a curve4 ,the chucks 7fig4 #ce7 can be fastened to the putlogs before they are fixed1 if the curve of the building is accurately known4 ,when this is not the case1 the putlogs are fixed by a holdfast at their centre4 ,the chucks are then placed in position1 and clamped to the putlogs as shown in fig4 #cf4 ,additional holdfasts are then driven into the wall immediately under the chucks1 so that the putlogs are kept level4 ,illustration3 ,,fig4 #cd ,illustration3 ,,fig4 #ce ,the putlogs are fixed on edge1 and when not exceeding #af feet in length are #g in4 by #c in4 ,above that length they are #i in4 by #c in4 ,the stays should be #d in4 by #b in41 and connected to the putlogs by #e_/h-;inch iron bolts4 ,the platform is usually of three boards #aa in4 by #b in4 ,illustration3 ,,fig4 #cf ,illustration3 ,,fig4 #cg ,hollow towers are erected or repaired in the same manner as chimney shafts1 except that climbing ladders are not often required4 ,external or internal scaffolds may be erected4 ,towers being usually of larger area than chimney shafts1 the putlogs for internal scaffolding are often of short poles from #f to #h inches diameter4 ,even these may require extra support4 ,this is gained by carrying standards from the ground level or other solid foundation and tying to the putlogs4 ,if of great height the standards may be unable to carry their own weight4 ,for the cases where danger might be apprehended from this cause1 fig4 #cg shows a system of framing1 which1 being supported by the set-back in the thickness of the wall1 will carry the upper standards4 ,steeples are generally built by the aid of external scaffolds1 which1 as in the case of chimney shafts1 should be well braced4 ,the lower portion may also be repaired in this way1 the standards rising from the ground level1 or1 if so designed1 from the top of the tower4 ,a series of needles could be arranged for the higher portions4 ,illustration3 ,,fig4 #ch ,domes and arches4--,the scaffolding for domes and arches consists of a series of standards standing upon the area covered by the building1 and connected by ledgers and braces in directions at right angles to each other4 ,the platform is laid on the top ledgers4 ,when the building is of large span square timbers are often used1 balks for standards and runners1 and half timbers for struts and braces4 ,fig4 #ch shows a design for repairing roofs and arches where a roadway has to be kept below4 ,swinging scaffolds4 ,painters' boats or cradles4--,painters' boats are useful scaffolds for the repair of buildings1 more especially where the work is light4 ,fig4 #ci shows the general construction4 ,they are suspended from jibs1 fixed usually on the roof for outside work1 and by means of blocks and falls they can be moved in a vertical direction by the workmen when in the boat4 ,illustration3 ,,fig4 #ci ,the boats are fitted with guard boards and rails1 and their safety1 providing the jibs are well fixed by balancing weights1 is in their favour4 ,they are not self-supporting1 and there is a distinct danger of their running down if the sustaining ropes are not securely fastened off4 ,the wind causes them to sway considerably1 and their use is confined chiefly to faade work4 ,an improved cradle is now in general use1 which is slung by head blocks from a wire cable running between two jibs 7see fig4 #dj74 ,by the aid of guy lines movement in this case can be also obtained horizontally1 which removes the necessity of shifting the jibs or employing a greater number of boats as in the older method4 ,illustration3 ,,fig4 #dj ,illustration3 ,,fig4 #da ,another cradle as shown in fig4 #da has advantages which cannot be ignored4 ,it has steel cables with a breaking weight of #ae cwt4 instead of fibre ropes1 and the cradle is raised and lowered by means of gearing and a drum fixed in the gear case ,a4 ,it is self-supporting1 and therefore safer than the cradle mentioned above4 ,the lower ends of the cable are fastened to the drum1 and the gearing gives sufficient mechanical advantage for one man to raise the scaffold by turning the handle ,b4 ,the uprights and rails are of angle steel or barrel and will take apart and fold4 ,illustration3 ,,fig4 #db ,the boatswain's boat 7see fig4 #db7 is useful under some circumstances1 especially for making examinations of buildings for possible damage4 ,it is dangerous and awkward to work from1 and is also acted upon considerably by the wind4 ,the boat is slung from a single needle4 ,the workman has no control over its movement1 as he has to be raised or lowered as required by men having charge of the other end of the fall4 ,illustration3 ,,fig4 #dc ,illustration3 ,,fig4 #dd ,illustration3 ,,fig4 #de ,illustration3 ,,fig4 #df ,ladder scaffolds4--,a light scaffold of ladders braced1 and connected by rails1 which also serve the purpose of guard rails1 is shown in fig4 #dc4 ,the ladders1 which have parallel sides1 are placed about #b feet away from the building4 ,the boards forming the platform can be laid on the ladder rungs1 or if necessary on brackets as shown in fig4 #dd4 ,the ladders are prevented from falling away from the building by ties which are connected to the ladder as shown in fig4 #de1 and fastened to the window openings by extension rods as shown in fig4 #df4 ,the same figure illustrates the method of tying in the scaffold when the ladders are not opposite to the windows1 the rail ,a being connected to at least two ladders4 ,the braces and guard rails are bored for thumb screws at one end1 the other being slotted so that they can be adjusted as required4 ,this form of scaffold is only suitable for repairing purposes1 and no weight of material can be stored upon it4 ,a light repairing scaffold lately put on the market has a platform which is supported and not suspended1 but otherwise affords about the same scope to the workmen as the painters' boats4 ,it consists of one pole and a platform1 the latter being levered up and down the pole as required by a man standing on the platform itself4 ,the whole apparatus can be moved by one man standing at the bottom4 ,it is an arrangement comparatively new to the ,english trade1 but is in considerable use in ,denmark1 ,germany1 and ,sweden4 ,,chapter ,,iii ,,shoring ,,and ,,underpinning ,shoring is the term given to a method of temporarily supporting buildings by a framing of timber acting against the walls of the structure4 ,if the frame consists of more than one shore1 it is called a system2 if of two or more systems1 it becomes a series4 ,the forces that tend to render a building unstable are due primarily to gravity1 but owing to the various resistances set up by the tying together of the building1 the force does not always exert itself vertically downwards4 ,this instability may arise from various causes1 the most common being the unequal settlement of materials in new buildings1 the pulling down of adjoining buildings1 structural alterations and defects1 and alterations or disturbances of the adjacent ground which affect the foundations4 ,the pulling down of an adjoining building would1 by removing the corresponding resistance1 allow the weight of the internal structure of the building to set up forces which at first would act in a horizontal direction outwards4 ,structural defects1 such as an insufficiently tied roof truss1 would have the same effect4 ,structural alterations1 such as the removal of the lower portion of a wall in order to insert a shop front would allow a force due to gravity to act vertically downwards4 ,to resist these forces1 three different methods of shoring are in general use1 and they are known as flying or horizontal shores1 raking shores1 and underpinning4 ,flying ,shores4--,where the thrusts acting upon the wall are in a horizontal direction1 flying or raking shores are used to give temporary support4 ,the most direct resistance is gained by the first-named1 the flying or horizontal shore4 ,there are1 however1 limits to its application1 as1 owing to the difficulty of obtaining sound timber of more than #ej to #fj feet in length1 a solid body is necessary within that distance1 from which the required purchase can be obtained4 ,it is a method of shoring generally used where one house in a row is to be taken down1 the timbers being erected as demolition proceeds1 and taken down again as the new work takes its place4 ,fig4 #dg shows a half-elevation of two general systems of construction4 ,the framing1 as at ,a1 may be used alone where the wall to be supported is of moderate height and the opening narrow1 but larger frames should be combined1 as at ,b4 ,the framework ,c is for wide openings and walls of considerable height4 ,the wall plates1 #i in4 by #b in4 or #i in4 by #c in41 are first fixed vertically on the walls by wall hooks4 ,then1 in a line with the floors1 rectangular holes #d in4 by #c in4 are cut in the centre of wall plates4 ,into these holes1 and at least #d-a_/b inches into the brickwork1 needles 7also known as tossles and joggles7 of the same size are fitted1 leaving a projection out from the wall plate of #e in4 or #f in41 sufficient to carry the shore of about #g in4 by #g in4 ,the shore1 prior to being fixed1 has nailed on its top and under sides straining pieces #b inches thick1 and of the same width as the shore4 ,to tighten1 oak folding wedges are driven at one end between the shore and wall plate4 ,illustration3 ,,fig4 #dg ,to stiffen the shore1 and to further equalise the given resistance over the defective wall1 raking struts are fixed between the straining pieces1 and cleats are nailed above and below the shore4 ,these raking struts are tightened by driving wedges between their ends and the straining pieces4 ,the cleats previous to1 and in addition to being nailed1 should be slightly mortised into the wall plate4 ,this lessens the likelihood of the nails drawing under the pressure4 ,a ,raking ,shore consists of a triangulated system of timber framing1 and is used to support defective walls where the resistance to the threatened rupture has to be derived from the ground surrounding the building4 ,in its simplest form a raking shore is a balk of timber of varying scantlings1 but as a rule of square section1 inclined from the ground to the defective wall4 ,the angle of inclination is taken from the horizon1 and should vary between #fj and #ge degrees4 ,in settling this the space available at the foot of the wall has to be taken into consideration1 especially in urban districts where the wall abuts on the footpath4 ,illustration3 ,,fig4 #dh ,fig4 #dh shows a raking shore in its simplest form1 but usually two or more shores are used 7see fig4 #di74 ,the following table from ,mr4 ,stock's book#a shows the general rule and also the scantlings to be used3 ,for walls from #ae to #cj feet high #b shores are necessary in each system ,for walls from #cj to #dj feet high #c shores are necessary in each system ,for walls from #dj feet high and upwards #d shores are necessary in each system ,illustration3 ,,fig4 #di4--;,,example ,,of ,,raking ,,shore ,taking the angle of the shore at from #fj to #ge degrees3 ,for walls from #ae to #bj feet high #e in4 by #e in4 may be the scantling for each shore ,for walls from #bj to #cj feet high #f in4 by #f in4 may be the scantling for each shore ,for walls from #cj to #ce feet high #g in4 by #g in4 may be the scantling for each shore ,for walls from #ce to #dj feet high #h in4 by #h in4 may be the scantling for each shore ,for walls from #dj to #ej feet high #i in4 by #i in4 may be the scantling for each shore ,for walls from #ej feet and upwards #ab in4 by #i in4 may be the scantling for each shore ,in the greatest length1 the beams are #ab in4 by #i in4 to give increased rigidity1 which prevents any likelihood of sagging4 ,the wall plate is the first timber put into position4 ,it is placed vertically down the face of the wall1 and held in its position by wall hooks4 ,note should then be taken of the position of floors4 ,if the floor joists run at right angles to the wall1 the shore should abut on the wall in such position that it points directly below the wall plate carrying the floor joist4 ,if the joists run parallel to the wall1 the shore should act directly on a point representing the meeting of lines drawn down the centre of the wall and across the centre of the floor 7see fig4 #ej74 ,illustration3 ,,fig4 #ej ,to enable the shore to fulfil this condition1 the needle 7of #d in4 by #c in47 should be let through the plate #d-a_/b inches into the wall below the point in question4 ,to strengthen the needle cleats are nailed1 and slightly let into the plate immediately above4 ,the footing1 or sole piece1 has next to be laid4 ,it consists of a timber #aa in4 by #c in41 and long enough to take the bottom ends of the required number of shores4 ,attention should be paid to the ground in which it is to be bedded1 and if this is at all soft1 additional timbers should be laid under1 and at right angles with it1 to give greater bearing4 ,the sole piece should not be laid at right angles to the shore1 but its face should form1 with the outside line of the top shore1 an angle somewhat wider1 say of #ic degrees4 ,the advantage of this will be seen presently4 ,the shore itself has now to be prepared4 ,its top end should be grooved sufficiently 7fig4 #ea7 to receive the needle4 ,this will prevent lateral motion when under pressure4 ,illustration3 ,,fig4 #ea ,the bottom end should be slightly slotted1 in order to receive the end of a crowbar 7see fig4 #eb74 ,it is now placed in position1 and gently tightened up by the leverage of a crowbar acting in the slot1 and using the sole piece as a fulcrum4 ,the advantage of the sole piece not being at right angles to the shore can now be seen1 as if it were so laid no tightening could be gained by the leverage4 ,this system is an improvement upon the tightening up by wedges1 as the structure is not jarred in any manner4 ,if the frame is to have more than one shore1 they are erected in the same manner1 the bottom shore being the first put up1 the others succeeding in their turn4 ,when in position the shores are dogged to the sole piece and a cleat is nailed down on the outer side of the system4 ,the bottom ends are then bound together by hoop iron just above the ground level4 ,to prevent the shores sagging1 struts are fixed as shown on fig4 #di4 ,illustration3 ,,fig4 #eb ,besides preventing the sagging these struts serve the purpose of keeping the shores in position4 ,they may be fixed as nearly at right angles to the shores as possible1 or at right angles to the wall2 in any case they should reach to the wall plate at a point just below the needle4 ,the struts should be nailed to the shores and wall plate4 ,if the latter is wider than the shores1 it should be cut to receive the struts4 ,it sometimes occurs that the timbers are of insufficient length to reach from the sole piece to wall plate4 ,to overcome this difficulty1 a short timber is laid on the sole piece against and parallel to the next middle raker1 and on this short timber a rider shore stands reaching to its position on the wall plate 7see fig4 #di74 ,when this is done the top middle raker should be stiffer to resist the increased cross strain4 ,stiffness is gained by increasing the depth4 ,a rider shore is tightened by oak folding wedges driven between the foot of the shore and the short timber which supports it4 ,note must be taken that the outer raker is not carried too near the top of the building1 or else the upward thrust of the shores1 which always exists with raking shores1 might force the bond or joints4 ,fir is the best wood for shoring owing to the ease with which it can be obtained in good length4 ,another advantage is its straightness of fibre2 although1 as it is more easily crushed by pressure across the grain1 it does not answer so well as oak for wedges1 sole pieces1 c4 ,in erecting flying or raking shores1 notice should be taken of the following points4 ,the systems should be placed from #ab to #ae feet apart if on a wall without openings1 otherwise on the piers between the openings4 ,in very defective walls it is an advantage to use lighter scantlings1 the systems being placed closer together4 ,heavy timbers handled carelessly may precipitate the collapse which it is the intention to avoid4 ,wedge driving and tightening should be done as gently as possible4 ,it should be remembered that support only is to be given1 and not new thrusts set up1 which may result in more harm than good4 ,underpinning4--,underpinning is necessary to carry the upper part of a wall1 while the lower part is removed2 for instance1 the insertion of a shop front1 or the repairing of a foundation4 ,it is only kept in position until a permanent resistance to the load is effected4 ,underpinning is1 as a rule1 unnecessary when the opening to be made is of less width than five feet4 ,this method of shoring is a simple operation1 but yet requires great care in its execution4 ,the first thing to be done is to remove from the wall all its attendant loads4 ,this is accomplished by strutting from the foundation floor upwards from floor to floor until the roof is reached 7see fig4 #ec74 ,header and sole plates #i in4 by #b in4 are put in at right angles to the joists in order to give bearing to the struts4 ,the portion of the wall to be taken down having been marked out1 small openings are made1 slightly above the proposed removal1 at from #e to #g feet apart1 and through these1 at right angles to the face of the wall itself1 steel joists or balk timbers #ac in4 by #ac in41 called needles1 are placed4 ,these are supported at each end by vertical timbers #ac in4 by #ac in41 called dead shores1 which again rest upon sleepers4 ,the sleepers serve as a bed to the dead shores to which they are dogged1 and by distributing the weight over a larger area1 they prevent the dead shores sinking under the pressure4 ,the dead shores1 if well braced1 may be of smaller scantling4 ,where it is impossible to arrange for the dead shores to be in one length1 the lower pieces are first fixed4 ,they must be of uniform length1 and across their top end a transom is carried to support the upper pieces1 the bottom ends of which must stand directly over the top ends of the lower pieces 7see fig4 #ec74 ,having placed all the timbers in position1 and before the tightening up takes place1 the windows or other openings in the wall are strutted to prevent any twisting which may take place4 ,this is done as shown on fig4 #ed1 but small windows do not require the centering4 ,illustration3 ,,fig4 #ec4--;,,example ,,of ,,underpinning ,the tightening up is caused by the driving home of oak folding wedges placed in the joints between the needles and the dead shores4 ,this position is better than between the shore and sleeper1 as any inequality of driving here would have the tendency to throw the shore out of the perpendicular4 ,for a similar reason the wedges should be driven in the same line as the run of the needle1 as cross driving1 if unequal1 would cause the needle to present an inclined surface to the wall to be carried4 ,illustration3 ,,fig4 #ed ,in carrying out these operations note should be taken of the following points3-- #a4 ,that the dead shores should not stand over cellars or such places4 ,it is better to continue the needle to such a length that solid ground is reached1 and the needle can then be strutted from the dead shore4 #b4 ,that extra needles should be placed under chimney breasts1 should there be any in the wall which is to be supported4 ,the same applies where corbels1 piers1 c4 occur4 #c4 ,sleepers and shores should be so placed that they do not interfere with the proper construction of the new foundations or portions of the building4 #d4 ,the inside shores should be carried freely through the floors until a solid foundation is reached4 #e4 ,the removal of the shores after the alterations have been made is one requiring great care4 ,it should be remembered1 that while the work is new it cannot offer its greatest resistance to its intended load4 ,time should therefore be given for the work to well set1 and then the timbers1 eased gradually by the wedges being loosened1 should be finally taken out4 #f4 ,the raking shores1 if used in conjunction with underpinning1 should be left to the last4 ,,chapter ,,iv ,,timber ,classification and ,structure4--,a short study of the classification and structure of wood will be useful1 as it will enable the scaffolder to use material free from the inherent defects of its growth4 ,the trees used by the scaffolder are known as the exogens or outward-growing trees4 ,the cross section of an exogenous tree shows1 upon examination1 that the wood can be divided into several parts4 ,near the centre will be seen the pith or medulla1 from which radiate what are known as the medullary rays4 ,these in the pine woods are often found full of resinous matter4 ,next will be noted the annual rings forming concentric circles round the pith4 ,they are so called because in temperate climates a new ring is added every year by the rising and falling of the sap4 ,as the tree ages1 the first-laid rings harden and become what is known as duramen or heartwood4 ,the later rings are known as alburnum or sapwood4 ,the distinction between the two is in most trees easily recognised1 the sapwood being lighter and softer than the heartwood1 which is the stronger and more lasting4 ,the bark forms the outer covering of the tree4 ,defects in the living tree4--,shakes or splits in the interior of the wood are the most common defects in the living tree1 and are known as star or radial and cup or ring shakes4 ,the cause of these defects is imperfectly understood4 ,they are rarely found in small trees1 say those of under #aj inches diameter4 ,stevenson1 in his book on wood1 puts forward the following reason1 which1 up to now1 has not been refuted by any practical writer4 ',in the spring1 when the sap rises1 the sapwood expands under its influence and describes a larger circle than in winter4 ,the heartwood1 being dead to this influence1 resists1 and the two eventually part company1 a cup or ring shake being the result' 7see fig4 #ee1 where the cup shake is shown in its commonest form74 ,illustration3 ,,fig4 #ee ,illustration3 ,,fig4 #ef ,the star or radial shake is a variant of the same defect4 ,in this case the cohesion between the sapwood and the heartwood is greater than the expansive forces can overcome1 the result being that the heartwood breaks up into sections as shown in fig4 #ef4 ,the star shake may have two or more arms4 ,more than one cup shake1 and sometimes both cup and star shakes are found in a single tree4 ,the radial shake is probably the most common4 ,the branches suffer in this respect in like manner as the trunk1 the same shakes being noticeable throughout ,the development of these defects is the forerunner of further decay in the tree1 giving1 as they do1 special facilities for the introduction of various fungi1 more especially that form of disease known as the rot4 ,wet rot is found in the living tree and occurs where the timber has become saturated by rain4 ,other authorities believe that these defects are caused by severe frost1 and their idea receives support from the fact that in timber from warmer climates this fault is less often seen4 ,this may be so for the reason that it would not pay traders to ship inferior timber from a great distance4 ,loose hearts3 in the less resinous woods1 as those from the ,white ,sea1 the pith or medulla gradually dries and detaches itself1 becoming what is known as a loose heart4 ,in the more resinous woods1 such as the ,baltic and ,memel1 this defect is rare4 ,rind galls are caused by the imperfect lopping of the branches1 and show as curved swellings under the bark4 ,upsets are the result of a well-defined injury to the fibres caused by crushing during the growth4 ,this defect is most noticeable in hard woods4 ,it will be of no practical use to follow the living tree further in its steady progress towards decay1 but take it when in its prime1 and study the processes which fit it for the purpose of scaffolding4 ,felling4--,the best time to fell timber1 according to ,tredgold1 is mid-winter1 as the vegetative powers of the tree are then at rest1 the result being that the sapwood is harder and more durable2 the fermentable matters which tend to decay having been used up in the yearly vegetation4 ,evelyn1 in his ',silva1' states that3 ',to make excellent boards and planks it is the advice of some1 that you should bark your trees in a fit season1 and so let them stand naked a full year before felling4' ,it is questionable if this is true of all trees1 but it is often done in the case of the oak4 ,the consensus of opinion is that trees should be felled in the winter1 during the months of ,december1 ,january and ,february1 or if in summer1 during ,july4 ,winter felling is probably the better1 as the timber1 drying more slowly1 seasons better4 ,the spruce from ,norway and the northern fir are generally cut when between #gj and #ajj years old4 ,when required for poles1 spruce is cut earlier1 it having the advantage of being equally durable at all ages4 ,ash1 larch and elm are cut when between #ej and #ajj years old4 ,conversion4--,by this is meant cutting the log to form balks1 planks1 deals1 c4 ,it is generally carried out before shipment4 ,a log is the trunk 7sometimes called the stem or bole7 of a tree with the branches cut off4 ,a balk is a log squared4 ,masts are the straight trunks of trees with a circumference of more than #bd inches4 ,when of less circumference they are called poles4 ,according to size1 timbers are classed as follow3-- ,balks #ab in4 by #ab inches to #ah in4 by #ah inches ,whole timber #i in4 by #i inches to #ae in4 by #ae inches ,half timber #i in4 by #d inches to #ah in4 by #i inches ,quartering #b in4 by #b inches to #f in4 by #f inches ,planks #aa in4 to #ah inches by #c in4 to #f inches ,deals #i inches by #b in4 to #d inches ,battens #d in4 to #g inches by in4 to #c inches ,when of equal sides they are termed die square4 ,in conversion the pith should be avoided1 as it is liable to dry rot4 ,when the logs are to be converted to whole timbers for use in that size1 consideration has to be given as to whether the stiffest or the strongest balk is required4 ,the stiffest beam is that which gives most resistance to deflection or bending4 ,the strongest beam is that which resists the greatest breaking strain4 ,the determination of either can be made by graphic methods4 ,illustration3 ,,fig4 #eg ,to cut the stiffest rectangular beam out of a log1 divide the diameter of the cross section into four parts 7see fig4 #eg74 ,from each outside point1 ,a and ,b1 at right angles to and on different sides of the diameter1 draw a line to the outer edge of the log4 ,the four points thus gained on the circumferential edge1 ,c1 ,d1 ,e1 ,f1 if joined together1 will give the stiffest possible rectangular beam that can be gained from the log4 ,illustration3 ,,fig4 #eh ,to cut the strongest beam3--,in this case the diameter is divided into three parts4 ,from the two points ,a and ,b thus marked again carry the lines to the outer edge as before4 ,join the four points ,c1 ,d1 ,e1 ,f1 together1 and the outline of the strongest possible rectangular beam will result 7see fig4 #eh74 ,boards--a term which embraces planks1 deals1 and battens--should be cut out of the log in such a manner that the annual rings run parallel to the width of the board4 ,this method of conversion allows the knots1 which are a source of weakness1 to pass directly through the board1 as ,a1 fig4 #ei1 and not run transversely across as other sections 7,b7 allow4 ,illustration3 ,,fig4 #ei ,seasoning4--,poles and scantlings1 after conversion1 are next prepared for seasoning4 ,the drying yard1 where the timbers are seasoned1 should give protection from the sun and high winds1 although a free current of air should be allowed4 ,it should be remembered that rapid drying tends to warping and twisting of the timbers4 ,the ground on which the timbers are stacked should be drained and kept dry4 ,the method of stacking is as follows3 ,the timbers are laid upon supports a few inches above the ground at sufficient intervals to allow of a free circulation of air between them1 and on these others are laid at right angles4 ,it is usual to put long strips of wood about inch square between each row to prevent the timbers touching1 as1 after a shower1 the timbers cannot dry for a long time if one is resting on the other4 ,planks1 deals1 c4 can be stacked by laying them in one direction throughout1 provided that the space which is left between the boards occurs in one layer immediately over the centre of the boards beneath 7see fig4 #fj74 ,in many cases very little drying takes place before shipment1 but the same methods of stacking should be observed whenever it takes place4 ,stacking poles by placing them on end is not recommended1 as they may warp from insufficient support4 ,this point is more important when the poles are required for ladder sides4 ,illustration3 ,,fig4 #fj ,timber may be considered to be sufficiently seasoned for rough work when it has lost one-fifth of its weight by evaporation4 ,illustration3 ,,fig4 #fa ,the poles from ,st4 ,petersburg have a narrow strip of bark removed in four equidistant longitudinal lines throughout their entire length4 ,this treatment assists drying1 and tends to prevent dry rot4 ,weather shakes sometimes form on the outside of the wood while seasoning 7see fig4 #fa74 ,they arise owing to the sapwood contracting more when drying than the heartwood4 ,unless they extend to a considerable depth they do not affect the quality of the wood4 ,balk timbers1 where the sapwood is uncut1 and whole timbers principally suffer in this manner4 ,water seasoning--that is1 having the timbers completely immersed in water for a short time before drying4 ,this is a common practice4 ,it is frequently carried out at the docks1 where the balks may be seen floating about on the surface of the water4 ,this is a bad method1 as the wood is at the same time under the influence of water1 sun and air4 ,water seasoning may make the wood more suitable for some purposes1 but ,duhamel1 while admitting its merits1 says3 ',where strength is required it ought not to be put in water4' ,description4--,pine or northern fir 7,pinus sylvestris7 is light and stiff1 and is good for poles and scaffolding purposes1 but only the commonest of the ,swedish growths are used for this purpose4 ,the hardest comes from the coldest districts4 ,it has large red knots fairly regularly placed1 inclined to be soft1 and starting at acute angles4 ,it grows chiefly in ,northern ,europe4 ,white spruce or white fir 7,abies excelsa74--,the knots are small and irregularly placed1 are dark in colour1 and start at an obtuse angle1 showing an absence of clean wood4 ,it is used principally for scaffold poles and ladder sides4 ,it will snap under live loads1 and is not so strong as pine4 ,it also chiefly grows in ,northern ,europe4 ,larch 7genus ,larix7 is imported from ,northern ,europe and ,america4 ,it is yellow in colour1 tough1 and is suitable for poles1 very durable1 free from knots1 but warps easily4 ,elm 7genus ,ulmus7 grows in the ,british ,isles4 ,the colour varies from the reddish-brown of the heartwood to yellowish white of the sapwood4 ,it bears considerable pressure across the grain1 and is most useful in balks1 as it is liable to warp when in smaller sizes4 ,is suitable where bolts and nails have to be used4 ,birch 7,betula alba74--,light brown in colour1 hard1 even grain1 which enables it to be easily and readily split in the direction of its length4 ,it is not considered durable4 ,it is used chiefly for putlogs4 ,is exported from ,europe and ,america4 ,ash 7,fraxinus excelsior74--,very light brown in colour1 extremely tough1 and makes excellent rungs for ladders4 ,it is found in ,europe4 ,oak 7genus ,quercus71 also known as the common ,british oak1 is a native of all parts of ,europe1 from ,sweden to the ,mediterranean4 ,the wood has often a reddish tinge2 and the grain is fairly straight1 and splits easily4 ,it is generally free from knots1 and is most suitable where a stiff1 straight-grained wood is desirable4 ,it also offers considerable resistance to pressure across the grain4 ,selection4--,the importation of scaffolding timber commences in ,march4 ,in ,june the ,russian timbers are on the market1 and the arrivals continue until ,october4 ,poles are selected from spruce1 pine1 and larch trees4 ,balk timbers are of elm and fir and spruce4 ,the putlogs are from the birch4 ,poles are known in two qualities--'prime' and 'brack4' ,these terms refer to their straightness of grain1 freedom from knots1 regularity of taper1 which should be slight1 and condition as to seasoning4 ,buyers take them usually unbarked1 as they rise from the stack1 and sort them afterwards for their different purposes4 ,as soon as possible the bark should be removed1 as it holds the water and insects1 and encourages the growth of a white fungus which is the precursor of dry rot4 ,the ,st4 ,petersburg poles are the most generally used for scaffolding4 ,they are weaker than the ,christiania poles1 breaking shorter under cross strains1 are whiter in colour1 have a smoother bark1 are straighter in grain1 and therefore make better ladder sides4 ,christiania poles are more yellow in colour1 and break longer under a cross strain than other poles4 ,they are only to be obtained early in the year1 and are soon bought up when on the market4 ,to test a pole remove the bark1 then prise across the grain with a penknife4 ,if the fibres break up short and brown1 the pole is decayed and useless4 ,to test a pole for any local weakness lift one end1 leaving the other on the ground4 ,two or three sharp jerks will cause undue bending at any spot that may be seriously defective4 ,balk timbers ring1 if in a sound condition1 when struck with a hammer4 ,a fresh-cut surface should be firm1 shining1 and somewhat translucent4 ,a dull1 chalky1 or woolly appearance is a sign of bad timber4 ,poles1 unlike most converted timbers1 are not branded4 ,those known as prime should certainly be used for scaffolding purposes4 ,the brack are rough and irregular in growth4 ,balk timbers and smaller scantlings are1 in the finest qualities1 branded1 the different countries from which they are exported being ,russia1 ,norway and ,sweden4 ,russian woods are generally hammer branded1 no colour being used4 ,norwegian woods are marked a blue colour1 and ,swedish wood a red colour4 ,straight-grained timber should be chosen4 ,twisting1 which may occur to the extent of #de1 is not so apparent in young trees4 ,the beam is thereby weakened as regards tension and compression4 ,large knots should be avoided4 ,they weaken the beam for tension and cross strains1 but serve good purpose when in compression4 ,sap in the wood is denoted by a blue stain1 and betokens inferiority as to strength and lasting qualities4 ,this blueness is more noticeable when the wood is wet4 ,it must not be confounded with dark weather stains4 ,the ,decay of ,timber4--,timber exposed to the constant changes of weather tends to decay early4 ,it has been noticed that wood when dried after being exposed to dampness not only lost the moisture it had absorbed1 but also part of its substance4 ,this loss occurs in a greater degree when these changes take place a second time4 ,it is therefore apparent that scaffolding timber1 exposed as it is to the vicissitudes of the weather1 without any protection such as would be gained by painting1 will soon from this cause show signs of decay4 ,quicklime1 when wet1 has also a most destructive effect upon timber2 the lime1 by abstracting carbon1 helping the decomposition materially4 ,scaffold boards suffer most in this respect from contact with fresh mortar1 the lime in which has not had time to become mild4 ,from a similar cause1 the ends of putlogs which are inserted in a newly built wall1 as when used in a bricklayer's scaffold1 tend to decay rapidly4 ,scaffolding poles1 when used as standards1 have an increased tendency to decay at their butt ends1 owing to their being imbedded in the ground to a distance of two or three feet4 ,the presence of sap in improperly seasoned wood is also conducive to early decay4 ,preservation of ,timber4--,scaffolding timber being comparatively cheap has little attention paid to it in regard to preservation4 ,when out of use the poles should be stacked1 and a free current of air around each ensured1 not laid carelessly on the ground1 which is too frequently the case4 ,the same remarks apply to the care of boards4 ,nails which have been driven into the timber should1 after use1 be carefully drawn4 ,when left in the wood they rust1 and set up a new source of decay4 ,as before noted1 the butt ends of standards tend to decay early4 ,a fairly effective method of preventing this is to bore the butt end upwards to a distance of about #b feet4 ,the bore1 which should be about #a_/b inch in diameter1 should then be filled with pitch and plugged4 ,the pitch will find its way by capillarity into the pores of the wood and tend to keep the dampness out4 ,coating the outsides of the butts with pitch is also useful1 and a combination of the two would no doubt be effectual2 this is especially recommended where the standards have to remain in one place for a long time4 ,ladders and fittings that are expensive are generally painted4 ,the ,durability of ,wood4--,in ,young's ',annals of ,agriculture' it is stated that experiments were made on some #a-;inch planks of #cj to #de years' growth4 ,they were placed in the weather for ten years1 and then examined1 with the following result3 ,larch--heart sound1 sapwood decayed4 ,spruce fir--sound4 ,scotch fir--much decayed4 ,birch--quite rotten4 ,this experiment1 while useful to show the natural resistance of the wood to the weather1 does not take into account the effect of wear and tear4 ,it is almost impossible1 in fact1 to arrive at any data from which the life of scaffolding timbers can be gauged2 but1 roughly speaking1 poles may be expected to last from six to ten years according to the care exercised4 ,balk timbers1 being usually cut up after a time for other purposes1 have only a short life on a scaffold1 and therefore seldom decay while in use4 ,illustration3 ,,fig4 #fb ,the ,use of ,scaffolding ,timber4--,poles vary up to #dj and #ej feet in length and up to #h inches in diameter at the butt end4 ,as decay1 which usually commences at this end1 sets in1 the poles can be shortened and made into sound puncheons or splicing pieces for the ledgers4 ,balks are used up to #ej or #fj feet in length2 and their period of service on a scaffold is often an interval during which they become well seasoned and suitable for other requirements4 ,putlogs are about #f feet in length and #d inches square in cross section1 tapering sharply to #b-a_/b by #c-a_/b inches at the ends where required for insertion in the wall4 ,being of square section they are not liable to roll on the ledgers4 ,they should be split1 not sawn1 in the direction of their length4 ,the fibres are thus uncut and absorb moisture less easily4 ,this procedure it is found increases their durability4 ,when treated in this manner they are also stronger1 as the fibres1 being continuous1 give greater resistance to a load1 the strength not depending wholly on the lateral adhesion1 but also upon the longitudinal cohesion4 ,when partly decayed they can be shortened and make good struts for timbering excavations4 ,the boards are usually from #g in4 to #i in4 wide and #a in4 to #b in4 thick4 ,their length averages up to #ad feet4 ,the ends are sawn as fig4 #fb and strapped with iron to prevent splitting4 ,when decayed they are a source of danger for which there is only one remedy--smash them up4 ,,chapter ,v ,,cordage ,,and ,,knots ,the fibres used for the ropes and cords for scaffolding purposes are of jute and hemp4 ,the strongest rope is made of the latter variety1 and the best quality is termed the ,manilla4 ,the cords are generally tarred for preservation1 but this process has a bad effect upon the strength of the fibre1 more especially if the tar is impure4 ,the process of tarring is as follows3-- ,the fibres before they are formed into strands are passed through a bath of hot tar4 ,immediately afterwards1 and while still hot1 the material is squeezed through nippers1 by which means any surplus tar is removed4 ,the ropes1 as used in scaffolding1 are known as shroud laid or three strand4 ,a shroud-laid rope consists of three strands wound round a core1 each containing a sufficient number of fibres to make an equal thickness4 ,a three-strand rope is similar1 but has no core4 ,the following gives the breaking weights of scaffold cords and falls according to circumference#b3-- ,size ,cwts4 qrs4 lbs4 ,tarred hemp scaffold #b inches in circumference #bj #j #j ,cords #b inches in circumference #be #j #j ,tarred jute scaffold #b inches in circumference #ad #j #j ,cords #b inches in circumference #ah #j #j ,white ,manilla scaffold #b inches in circumference #cb #j #j ,cord #b inches in circumference #ci #j #j #b inches in circumference #dd #j #j ,white ,manilla rope for #c inches in circumference #gj #j #j pulleys and block ropes #c inches in circumference #ih #j #j #d inches in circumference #abf #j #j #d inches in circumference #aeh #j #j ,it should be noted that all these weights are the actual breaking strains of the ropes tested to destruction4 ,in practice1 one sixth of the breaking weights only should be allowed1 in order to leave a sufficient margin for safety4 ,the strength of a rope is the combined strength of each separate yarn4 ,therefore1 if the fibres are not carefully twisted together1 so that each bears an equal strain1 the rope is unsafe4 ,care should be taken when choosing a rope that the strands are closely1 evenly and smoothly laid4 ,the rope is strongest when the fibres are at an angle of #de degrees to the run of the rope4 ,when at a greater angle than this1 the fibres are apt to break1 and when at a less angle1 the friction between the parts--upon which the strength of a rope greatly depends--is lessened4 ,the durability of tarred ropes is greater than when untarred1 but not to such an extent if kept dry4 ,a splice weakens a rope about one eighth4 ,ropes are adulterated by the admixture of rubbish fibre termed 'batch4' ,to test a rope as to condition1 untwist it and notice whether any short ends break upwards4 ,if so1 or if the tarring has decayed internally1 the rope must be viewed with suspicion4 ,hemp ropes1 after four to six months' wear1 are often one fourth weaker than new ones4 ,scaffold cords are from #ae to #ah feet in length4 ,moisture will cause a shrinkage of #f inches in an #ah-;foot cord4 ,a good hemp rope is more reliable than an iron chain1 as the latter sometimes snaps on surgeing4 ,the following diagrams show the various knots used in scaffolding1 both in the erection of the scaffold and for attaching materials to a hoist4 ,they are shown in a loose condition as being more useful for study by a pupil4 ,several knots are1 however1 too intricate to explain by diagram1 and in these cases an attempt has been made1 with but scant success1 to instruct as to their method of creation in the notes4 ,it will1 however1 be found by the student that half an hour with an expert scaffolder1 preferably an old sailor1 will afford more instruction than hours spent in studying diagrams4 ,the art of knot making is governed by three principles4 ,first1 a knot must be made quickly4 ,secondly1 it must not jam1 as this prevents it being undone easily4 ,lastly1 under strain1 it should break before slipping4 ,illustration3 ,,plate ,,iii4 ,plate ,,iii4--,no4 #a4 ,overhand or thumb knot4 ,prevents the end of a rope opening out or passing through the sheaves of a block4 ,no4 #b4 ,figure of eight knot4 ,used as ,no4 #a4 ,no4 #c4 ,square or reef knot4 ,will sometimes jam with small ropes4 ,no4 #d4 ,the knot we all make until we learn better1 known as the granny1 and will both slip and jam4 ,no4 #e4 ,the bend or weaver's knot1 used for joining ropes together or securing a rope through an eye splice4 ,no4 #f4 ,wolding stick hitch1 is serviceable only in connection with a pole used as a lever4 ,no4 #g4 ,bale sling1 for hanging on to hook of lifting tackle4 ,no4 #h4 ,magnus hitch1 or rolling hitch1 for lifting material4 ,no4 #i4 ,two half hitches1 or builder's knot1 or clove hitch4 ,used for tying ledgers to standards4 ,no4 #aj4 ,loop knot1 used where ends of rope are not available4 ,no4 #aa4 ,loop knot1 used where ends of pole are not available4 ,no4 #ab4 ,boat knot4 ,no4 #ac4 ,sheepshank1 or dogshank1 a method of shortening a rope without cutting it or reducing its strength4 ,illustration3 ,,plate ,,iv4 ,plate ,,iv4--,no4 #ad4 ,blackwall hitch1 very powerful1 but requires watching or may slip4 ,no4 #ae4 ,midshipman's hitch1 used as shown with a rounded hook4 ,no4 #af4 ,catspaw is an endless loop1 and is used where great power is required4 ,no4 #ag4 ,capstan knot1 or bowline4 ,after tightening it will not slip4 ,no4 #ah4 ,timber hitch1 for carrying scaffold poles4 ,take one turn round the pole and standing part1 and finish with jamming turns4 ,no4 #ai4 ,artificer's knot1 or half hitch and overhand4 ,no4 #bj4 ,topsail halliard bend1 used as a timber hitch4 ,no4 #ba4 ,bowline on a bight4 ,a board across the loops makes a useful seat4 ,no4 #bb4 ,racking or nippering is a method of temporarily joining two ropes for lengthening purposes4 ,the ends are laid side by side for about #ah inches1 and the marline or spunyarn is taken for about a dozen turns round both1 then by round turns over all and fastened with a reef knot4 ,nos4 #bc and #bd4 ,round seizing4 ,with a slip knot at the end of the spunyarn take a turn round the ropes to be nipped together4 ,this turn should be pulled tight1 and continued for about a dozen turns 7,no4 #bb72 then take the end through the last turn1 and take turns over the first laid1 finishing by carrying the spunyarn two or three times between the rope and the seizing4 ,knot the end by jamming turns1 keeping the whole well taut 7,no4 #bd74 ,illustration3 ,,plate ,v4 ,plate ,v4--,no4 #be4 ,butt or barrel sling when placed horizontally4 ,no4 #bf4 ,butt or barrel sling when placed vertically4 ,no4 #bg4 ,double overhand knot4 ,no4 #bh4 ,running bowline4 ,nos4 #bi and #cj4 ,band tie1 marrying or splicing4 ,commence as ,no4 #bi1 and after continuing the turns until near the end of the rope1 take the rope twice between the poles and round the turns first laid1 and finish with jamming turns4 ,tighten with a wedge4 ,nos4 #ca1 #cb and #cc4 ,tying between standard and ledger4 ,commence with two half hitches as ,no4 #ca4 ,then twist ropes together as far as they will go1 and place ledger in position above the hitches 7,no4 #cb74 ,the twisted ropes are then drawn up in the front of the ledger to the left of the standard1 taken round the back of the standard1 brought again to the front and round ledger at the right of the standard1 then cross in front of the standard and round the ledger at the left of the standard1 and brought up and carried round the back of the standard4 ,this process is repeated until the end of the rope is nearly reached1 when it is given two or three turns round the ledger and fastened off with jamming turns 7,no4 #cc74 ,to tighten1 drive a wedge at back of standard4 ,illustration3 ,,plate ,,vi4 ,plate ,,vi4--,no4 #cd4 ,portuguese knot for shear legs1 made by several turns of the rope round the poles1 and interlaced at the ends4 ,no4 #ce4 ,running bow knot--inferior to ,no4 #bh4 ,no4 #cf4 ,bowline--inferior to ,no4 #ag4 ,no4 #cg4 ,double bend--useful where a small rope is bent on to a larger4 ,the end of the rope is given one extra turn round the bight of the other1 with the consequence of a great increase of strength4 ,no4 #ch4 ,fisherman's knot4 ,no4 #ci4 ,lark's head1 fastened to a running knot4 ,no4 #dj4 ,where increased strength is required a small rope can be attached to a larger one by means of a rolling hitch4 ,the whole arrangement comes apart as soon as the strain is removed4 ,no4 #da4 ,a method of lifting scaffold poles in a vertical position by the use of the timber hitch and half hitch4 ,if it is required to free the upper end while the pole is being carried1 the half hitch can be replaced by a cord tied round the pole and the lifting rope4 ,,chapter ,,vi ,,scaffolding ,,accessories ,,and ,,their ,,use ,ladders4--,a ladder consists of a pair of sides connected by a series of oak or ash treads or rungs4 ,the sides of long ladders are formed by cutting lengthwise a straight fir pole into two pieces4 ,short ladders are made with square sides1 but they are heavier and1 as the grain seldom runs continuously throughout their length1 also weaker4 ,the pole for the sides is selected for its straightness of fibre1 for a twisted pole cannot be sawn lengthwise without cutting across part of the grain1 which as before stated is a source of weakness4 ,the pole has to be bored for the rungs1 and this may be done either before or after it has been cut lengthwise4 ,it is better to bore first1 as then the holes occur at coincident intervals on each side2 the rungs by this means are kept parallel and level4 ,the rungs are placed #i inches apart1 and are from #a in4 to #a-a_/b-;in4 in depth in the centre1 decreasing to #e_/h-;inch diameter at the ends4 ,the ends of the rungs are painted with red lead before insertion1 and any projections are afterwards cut off flush with the sides4 ,they can be fastened at each end with wedges 7see fig4 #fc71 or pins of #a_/d-;inch diameter can be cut through the sides1 as fig4 #fd1 to fix every fifth or sixth rung4 ,the first method is the better1 as cross boring of the sides greatly weakens them2 but as the wedges may work out1 an iron rod #e_/af-;inch in diameter should be placed below every eighth or ninth rung1 and bolted on the outside for extra security4 ,the iron rods should not be used as treads instead of the wooden rungs as they offer an insecure foothold4 ,the rungs are considered to be dangerous for use when they have been reduced by wear to one half of their original depth4 ,the best rungs are made from old wheel-spokes1 as they are well seasoned4 ,the sides1 which may be of sufficient length to receive #ajj rungs1 are #i inches apart at the top and from #ab to #ac inches apart at the bottom1 according to the length of the ladder4 ,illustration3 ,,fig4 #fc ,illustration3 ,,fig4 #fd ,extension ladders are useful where1 owing to the varying heights of the work1 different lengths of ladders are required4 ,the two halves of the ladder are connected in various ways1 but if well made they are easily raised and lowered4 ,they should be used only for the very lightest work1 such as painting1 cleaning down1 c4 ,trestles4--,trestles are used chiefly by painters plasterers1 and mechanics engaged on work that is not at a great height from the ground or floor level1 and for which a platform is required4 ,they stand from #f to #ab feet in height1 and the rungs should be sufficiently wide to carry three boards for the working platform4 ,they are made of yellow deal1 with mortised joints and wrought-iron hinges 7fig4 #fe74 ,illustration3 ,,fig4 #fe ,steps4--,steps are built up with two sides of the required height1 about #e inches wide and #a inch thick2 the top and bottom are sawn to a bevel so that they stand inclined4 ,the steps1 which are grooved into the sides and fixed with screws1 are about #f inches wide by #a-a_/b inches thick1 and increase slightly in length as they descend4 ,this increase adds to the stability of the steps as the width of the base is increased4 ,the distance between each step is from #g to #i inches4 ,at the back of the top step two legs about #b-a_/b inches wide by #a inch thick are secured by strong flap hinges4 ,the legs are framed together by two cross pieces1 #c or #d inches wide and #a inch thick4 ,the back legs1 by opening out on the flap hinges1 enable the entire framework to stand upon an even surface4 ,to prevent the legs opening too far1 they are connected to the sides of the steps by cords4 ,cripples4--,the simplest form of cripple is shown on fig4 #ff1 which sufficiently explains the design4 ,this cripple forms a fixed angle with the ladder1 which1 in order to keep the platform level1 can be laid only at one slope against the wall4 ,the defect is removed if the cripple is hinged and fitted with a quadrant and pin1 as shown on fig4 #fg4 ,the platform in this case can be kept level by adjustment irrespective of slope of ladder4 ,the bracket should be long enough to carry a platform three boards wide1 but as a rule it carries two4 ,illustration3 ,,fig4 #ff ,illustration3 ,,fig4 #fg ,cripples may project from either side of the ladder1 and are usually hung on the rungs4 ,an advantage is gained if1 in addition to this1 clips are provided to clutch the sides of the ladder4 ,buckets and ,skips4--,besides the ordinary pail1 which needs no description1 larger buckets are commonly used for carrying concrete1 mortar1 earth1 or any other moist or friable material4 ,fig4 #fh shows the tipping bucket1 or skip1 which balances on its hinges at ,a4 ,the hinges are so placed that they are above the centre of gravity of the bucket when empty1 and below the centre of gravity when full4 ,this position allows the bucket to remain upright when empty1 but it will make half a revolution and empty its contents when full4 ,to prevent this action occurring before it is required1 a catch on hinges is fixed on the rim of the bucket at ,b4 ,illustration3 ,,fig4 #fh ,while the catch is in the position shown1 the bucket cannot tilt1 but if it is turned back the bucket makes the half revolution required1 and after emptying its contents1 swings upright of its own accord4 ,buckets are constructed of steel1 and the standard sizes vary in capacity from #a_/d to #a cubic yard4 ,for a similar purpose a steel box is used4 ,in this case the bottom of the box is hinged1 and on the catch being released1 drops out1 allowing the material to fall over any desired spot4 ,the catch can be released from above or below by means of a chain connected thereto1 and the bottom of the box regains its position when lowered to the ground for refilling4 ,each box is fitted with a bow for chain hook1 or lugs for chain slings2 has a capacity of about #c cubic feet1 is made of steel plates1 and may be round or square on plan4 ,baskets4--,baskets 7as shown in figs4 #fi-gc7 have a capacity of about #a cubic foot4 ,there are three qualities of cane used in their construction3 ',mackerel back1' recognised by its peculiar markings1 ',short ,nature1' and ',squeaky4' ,of these1 the first is the best1 the others following in the order named4 ,it is a defect of the baskets as ordinarily constructed that their handles and bottoms give way after very little wear4 ,several improvements have been put on the market1 the best of which are shown as follows4 ,illustration3 ,,fig4 #fi ,illustration3 ,,fig4 #gj ,in fig4 #fi the black line represents an iron hook bent to the shape required1 and the cane plaited round as for the ordinary basket4 ,it is claimed that the handles and bottoms of these baskets cannot give way1 and it is a claim that is probably correct4 ,owing to the difficulties of construction due to the rigidity of the iron hoop1 they cost more than the ordinary basket1 and this1 with their extra weight1 is unfortunately against their general adoption4 ,variations of the same idea are shown on figs4 #gj and #ga4 ,illustration3 ,,fig4 #ga ,illustration3 ,,fig4 #gb ,in the first case 7fig4 #gj7 the iron is in two parts1 which theoretically would allow of weakness1 but in practice the basket answers its purpose well4 ,in fig4 #ga the rigid ironwork is placed by a wire rope spliced to make a complete circle4 ,this kind of basket is easier to make and less in weight than those just mentioned1 but the cost of the rope keeps the price high4 ,illustration3 ,,fig4 #gc ,fig4 #gb shows another safety arrangement4 ,a is a tarred hemp rope built into the basket as shown1 and the ends fitted with eyelets for hoisting purposes1 the handles being kept for use by the workmen4 ,the arrangement is a practical one1 and gives the required element of safety to the baskets so long as the rope remains sound4 ,ordinarily constructed baskets can be made temporarily safe by passing the slinging rope or chain through the handles and round the bottom of the basket1 as shown on fig4 #gc4 ,to prevent the rope slipping1 and to give the basket a flat bottom1 pieces of wood can be fitted as shown4 ,navvy ,barrows4--,navvy barrows 7fig4 #gd7 are of hard wood1 wrought and cast iron fittings and steel axles4 ,they are fitted with iron1 or wooden wheels bound with iron1 and vary in weight from #fj to #ge lbs41 and have a capacity of about #a_/aj of a cubic yard4 ,a barrow of this class can be slung by passing a hook through the wheel and rings round the handles4 ,stone ,bogies4--,stone bogies 7fig4 #ge7 can be fitted with plain wheels for running on flat surfaces1 or flanged wheels for rails4 ,they are of oak1 with steel axles and cast-iron wheels4 ,the handles for pulling are detachable and adjustable to either end4 ,hand ,barrows4--,hand barrows as fig4 #gf are useful for carrying light loads1 and1 when bearing material that cannot roll1 may also be slung4 ,hods4--,hods 7fig4 #gg7 are used on small jobs in which to carry mortar1 bricks1 c4 ,in capacity they will hold #b_/c of a cubic foot of mortar or twenty bricks1 but an ordinary load is #af walling or #ab facing bricks1 the weight of which is considered to be enough for a man to carry up a ladder4 ,illustration3 ,,fig4 #gd ,illustration3 ,,fig4 #ge ,illustration3 ,,fig4 #gf ,illustration3 ,,fig4 #gg ,illustration3 ,,fig4 #gh ,illustration3 ,,fig4 #gi ,timber ,trucks4--,timber trucks 7fig4 #gh7 are used for carrying timber balks1 iron girders1 c4 ,they are usually #c or #d feet in length1 with a width of about #bd inches and a height of #bb inches4 ,they are made sufficiently strong to carry #f1jjj lbs4 ,illustration3 ,,fig4 #hj ,sack ,trucks4--,sack trucks 7fig4 #gi7 are constructed of hard wood1 with fittings of wrought and cast iron and steel axles4 ,they vary in length up to #d feet #d inches1 and the foot iron projects from #f to #i inches4 ,crates1 as shown on fig4 #hj1 are constructed of oak with iron bindings4 ,they will carry a weight of #a1ejj lbs4 and hold #cej bricks4 ,they can be filled in the builder's yard and transferred direct to the working platform without disturbing the material1 which1 for saving time1 is often of great advantage4 ,the absence of sides facilitates loading1 but on the other hand1 if any materials1 say bricks1 are put in loosely1 they may fall out during transference1 causing danger to the workmen4 ,when used to carry rubble work which cannot be stacked1 it is better that sides should be fitted4 ,when used to carry a roll of lead1 a stay should be placed1 as shown by dotted line on figure4 ,this will prevent the crate buckling at the bottom4 ,these crates are sometimes fitted with wheels to run on rails4 ,ashlar ,shears4--,the shears 7figs4 #ha and #hb7 are useful for lifting dressed work1 the points fitting into small holes which have been cut out for their reception in the ends or sides of the stone4 ,there is danger in their use if the points drag upwards and outwards4 ,to prevent this as far as possible1 the holes should be cut low1 but not below the centre of gravity of the stone1 or else it would turn over and perhaps fall4 ,illustration3 ,,fig4 #ha ,illustration3 ,,fig4 #hb ,fig4 #hb is a bad form of shears1 as1 owing to the sharp curve1 the points can only clutch near the top of the stone4 ,illustration3 ,,fig4 #hc ,illustration3 ,,fig4 #hd ,illustration3 ,,fig4 #he ,stone ,clips and ,slings4--,the clips 7fig4 #hc7 are useful for lifting stone slabs4 ,the hook rings slide along the chain1 and the clips are therefore adjustable to any stone not exceeding in width half the total length of the chain4 ,the chain slings have a ring at one end and a hook at the other1 and are useful for a similar purpose2 but the manner of slinging depends upon the thickness of the stone4 ,for instance fig4 #hd1 known as jack slinging1 answers well with a slab1 say1 of over #f inches in depth1 but a thinner slab lifted in this way would be liable to break in the middle4 ,if1 however1 the chain were placed as fig4 #he1 and which is known as figure-eight slinging1 this risk would be removed4 ,stone ,lewises4--,lewises may be divided into two classes1 curved and straight-sided4 ,fig4 #hf shows the first1 and fig4 #hg the second class4 ,illustration3 ,,fig4 #hf ,illustration3 ,,fig4 #hg ,illustration3 ,,fig4 #hh ,illustration3 ,,fig4 #hi ,the first class is the inferior1 as1 when fitted into the stone1 any jerk of the supporting chain would act at the points ,a as a blow on the stone1 thus increasing any tendency to fracture4 ,the hole for the reception of the lewis is cut1 so that a line down its centre would run across the centre of gravity of the stone2 and it is made as deep as may be required by the weight and hardness of the material4 ,the side or splayed pieces of the lewis shown on fig4 #hg are fitted first1 and the centre piece last4 ,a bolt through the top fixes their position and also the ring by which it is to be lifted4 ,care should be taken that the sides of the second class of lewis fit accurately1 for if they fit as fig4 #hh they may flush the edge and break out1 or if they fit as fig4 #hi the risk of fracture1 as in the first class1 presents itself4 ,in any case there is always a danger of mishaps occurring1 especially where the stone is not free from vents4 ,their use with safety can only be left to the judgment of the mason4 ,stone ,cramps4--,the cramps tighten on the stone by means of a screw thread1 as shown on fig4 #ij4 ,illustration3 ,,fig4 #ij ,they are useful for lifting light finished work4 ,packing should be placed at ,,aa to prevent damage4 ,the ring by which it is slung is movable to preserve equilibrium4 ,wire and ,chain ,scaffold ,lashings4--,wire rope scaffold lashings are now to be obtained for use in place of fibre cords4 ,they are made in lengths from #ab to #ah feet1 and are fitted at one end with an eyelet4 ,in fixing1 they commence with a clove hitch1 the knot being continued as with a fibre cord until near the end1 when the lash is taken through the eyelet 7see fig4 #ia7 and finished with jamming turns4 ,illustration3 ,,fig4 #ia ,it is claimed that no wedges are required for tightening wire rope lashings1 as they do not shrink or swell2 on the other hand1 owing to their small circumference1 they cannot be pulled very tight by the workmen1 and it is questionable if they would bear being twisted round the scaffolder's hammer without injury4 ,accidents also might happen if the poles shrank at all after being fixed4 ,tests have been made from which it has been estimated that each lashing will carry a direct load of #f tons4 ,a chain and bracket arrangement for tying ledgers to standards is shown on fig4 #ib4 ,it is easily and rapidly adjusted1 and is tightened by means of screw nuts at ,a and ,b4 ,illustration3 ,,fig4 #ib ,permanent injury might1 however1 be done to the standards by the cutting in of the brackets when screwed up1 especially after regular use4 ,the possible loss of the parts and their weight and consequent disadvantage in transport are against their general adoption4 ,tightening ,screws4--,tightening screws or coupling links 7fig4 #ic7 are fixed in the length of chain that connects the guys of the ,scotch cranes to the base of the queen legs4 ,illustration3 ,,fig4 #ic ,under the continuous vibration of the scaffold they run down and release the chain considerably4 ,this can be prevented to some extent by inserting a piece of wood as shown on fig4 #ic1 and tying its other end to a rigid member of the leg4 ,in any case the chain requires frequent examination1 and1 if necessary1 retightening4 ,rollers4--,rollers 7fig4 #id7 are used for moving heavy material along a smooth surface4 ,illustration3 ,,fig4 #id ,pegs should be fixed at their ends1 as shown on fig4 #id1 to form a handle by which they can be moved when under the material without danger to the workman's hands1 or better still1 they should always be longer than the load is wide4 ,levers4--,levers of ash1 fitted with iron shoes1 as fig4 #ie1 are used to prise heavy material off the ground1 to facilitate removal on rollers or otherwise4 ,in this case the lever acts as one of the first order4 ,by connecting the weight to the rings ,a and ,b it can be used as a lever of the second or the third order4 ,illustration3 ,,fig4 #ie ,dog ,irons4--,dog irons 7fig4 #if7 are bars of flat or round wrought iron1 turned up at the ends1 which are pointed4 ,if both ends point in the same plane they are termed 'male1' if otherwise 'female4' ,the shank is about #ab inches long4 ,besides holding the timbers together1 they exert a certain power of compression upon the joint they enclose4 ,this is gained by hammering the inside of the spikes to a splay1 leaving the outside to form a right angle with the shank4 ,illustration3 ,,fig4 #if ,illustration3 ,,fig4 #ig ,illustration3 ,,fig4 #ih ,illustration3 ,,fig4 #ii ,they may be described as inferior straps1 and their holding power is from #fjj to #ijj lbs4 per inch in length of spikes1 as deduced from experiments by ,captain ,fraser1 ,r4,e4 ,dog irons have the advantage that their use does not injure the timber to any extent1 and so depreciate its value4 ,dogs are fixed according to the joint to be enclosed4 ,if the joint is at right angles to the run of the timbers1 they are fixed as fig4 #ig4 ,if the timbers are at right angles they are fixed as fig4 #ih4 ,if both these joints occur the irons are placed as fig4 #ii4 ,they should be fixed on both sides of the timbers joined4 ,bolts4--,bolts 7fig4 #ajj7 are of wrought iron1 and their different parts should be in the following proportions3 ,thickness of nut #a diameter of bolt ,thickness of head #c_/d diameter of bolt ,diameter of head or nut over sides #a-c_/d diameter of bolt ,size of square washer for fir #c-a_/b diameter of bolt ,size of square washer for oak #b-a_/b diameter of bolt ,thickness of washer #a_/c diameter of bolt ,there are disadvantages to the use of bolts in scaffolding4 ,for instance1 the beams are weakened by the cutting of the fibres2 and1 if the timber shrinks1 the bolts may become loose4 ,on the other hand1 they can be easily tightened after the framing has settled into position4 ,illustration3 ,,fig4 #ajj ,their strength depends upon the quality of the iron1 but varies between #bj and #be tons of tensile strain per square inch of the smallest sectional area 7,anderson74 ,washers are used to prevent the nut sinking into the wood when tightened1 and are equally necessary1 but not always seen1 under the head4 ,they should not be cut into the under side of timbers subjected to a cross strain1 as the cutting of any fibres is a source of weakness4 ,bolts are used where dogs and spikes are of insufficient length or holding power4 ,straps4--,straps are wrought-iron bands of different designs1 and are used to form a connection between timbers4 ,branched straps 7fig4 #aja7 are used to strengthen angle joints4 ,they are usually fixed in pairs1 and being fastened on the surface of the timbers they have an advantage over bolts in that they do not cut into the material4 ,if the timbers settle at all1 the straps may become subject to cross strains4 ,illustration3 ,,fig4 #aja ,wire ,ropes4--,wire ropes are now in general use for heavy purposes4 ,they are stranded and laid similarly to fibre ropes4 ,they should be of mild plough steel wire4 ,the number of wires in a strand varies from #ab to #cg1 and the number of strands is usually #f4 ,the following table gives the breaking strains of the ropes according to their circumference1 and the least diameter of barrel and sheaves around which they may be worked at slow speeds4 ,in the table 7p4 #aaj7 the diameters of the pulleys1 c4 may be slightly reduced for the more flexible ropes1 but better results can always be gained by using pulleys and sheaves of larger diameters4 ,a few points on the working of these ropes may be useful4 ,to remove a kink throw a turn out2 it cannot be taken out by strain4 ,the ropes should be ungalvanised1 and kept greased with any oil that does not contain acid or alkali4 ,a rope running in a ,v groove has a short life4 ,a rope that is allowed to ride1 chafe on its own part or to overlap1 will be almost immediately crippled4 ,the sign of an overloaded rope is excessive stretching4 ---------------------------------------- ------------------------- ,extra ,special ,extra ,flexible ,rope4 ,flexible ,rope4 ,flexible ,rope4 #f strands1 each #ab wires #f strands1 #f strands1 each each #bd wires #cg wires ---------------------------------------- ------------------------ ,diam4 of barrel ,size or sheave round ,guaranteed ,guaranteed ,guaranteed ,circum4which it may be ,breaking ,breaking ,breaking worked at a ,strain ,strain ,strain slow speed ---------------------------------------- ------------------------ ,inches ,inches ,tons ,tons ,tons #a-a_/b #i #d #g-a_/b #h #a-c_/d #aj-a_/b #e-a_/b #i-c_/d #aa #b #ab #g #ac #ad-a_/b #b-a_/d #ac-a_/b #i #af-a_/d #ag-a_/b #b-a_/b #ae #ab #bj-a_/b #bb #b-c_/d #af-a_/b #ae #bd #bf-a_/b #c #ah #ah #bh-a_/b #cb-a_/d #c-a_/d #ai-a_/b #bb #cd #cg-a_/b #c-a_/b #ba #bf #ci #dc #c-c_/d #bb-a_/b #bi #de-a_/b #ej #d #bd #cc #ea-a_/b #ef-a_/b #d-a_/d #be-a_/b #cf #ei #fe #d-a_/b #bg #ci #fe #gj-a_/b #d-c_/d #gd #gi #e #hb-a_/b #hh ---------------------------------------- ------------------------ 7,bullivant ,co4 ,ltd47 ,chains4--,the strength of a chain depends upon the diameter and quality of the iron of which the links are formed1 governed by good workmanship4 ,the safe load for working can be calculated approximately by the following method3-- ,square the number of eighths of an inch which are contained in the diameter of the iron of which the link is made1 and strike off the last figure as a decimal4 ,for example1 where the iron is of #a_/b-;inch diameter1 square the number of #a_/h in the diameter1 i4e4 #d #d #af #af tons4 ,generally before leaving the factory1 chains are tested up to half the weight they should break under1 and which is about double the load they are intended to carry in practice4 ,this test cannot be relied upon for the future working of the chain1 as any stretching of a link1 which would ultimately result in fracture1 would probably not be apparent under it4 ,the links should therefore be examined periodically for any appearance of weakness or stretching4 ,a stretched link should at once be cut out1 as it may break with much less load than that which it was first tested to carry4 ,a chain during use also deteriorates in quality1 and it is a good rule to have it periodically annealed4 ,the links should then be re-tested up to double the weight they are again required to carry4 ,a reliable chain is made of the treble best ,staffordshire scrap iron4 ,crane and pulley chains should be made with the shortest link possible1 according to the diameter of the iron used1 as there is a considerable leverage exerted on a long link when running round a pulley1 more especially where the diameter of the pulley is small4 ,a ,slater's ,truss4--,slaters' trusses 7fig4 #ajb7 are used in pairs by slaters and tilers when laying their material4 ,boards are laid across the trusses and form an effective platform on which the workman can kneel without damage to that part of the roof already covered4 ,they are slung from the ridge or other suitable fixture1 and can be pulled higher as the work proceeds4 ,an old sack or similar material laid under the truss will prevent any possible damage during the progress of the work4 ,illustration3 ,,fig4 #ajb ,duck ,runs4--,duck runs 7fig4 #ajc7 are laid upon slate and tile roofs to give footing to1 and to prevent damage being done by1 the workmen4 ,they should be firmly fixed1 either by slinging from the ridge or butting against a solid resistance4 ,illustration3 ,,fig4 #ajc ,mortar ,boards4--,a mortar board is used as a bed on which mortar can be mixed or deposited4 ,it is roughly made of four or five #i-;inch boards each #c or #d feet long1 framed together on the under side4 ,their use prevents the new mortar coming in contact with the scaffold boards with an injurious effect4 ,wedges4--,a wedge is a movable1 double-inclined plane1 used for separating bodies1 and by this means1 tightening any connections between the bodies they tend to separate4 ,for scaffolding purposes they should be of oak1 or other wood which gives considerable resistance to pressure across the grain4 ,for tightening cordage wedges should be about #ab inches in length and1 as far as possible1 split to shape4 ,in cross section they should be semicircular4 ,their taper should be gradual and not too sudden1 as otherwise they might work out4 ,when used in pairs as for shoring purposes1 they are rectangular in cross section1 and are termed folding wedges4 ,nails4--,cut nails stamped out of plates are best for scaffolds4 ,these nails have the advantage of being easily drawn out of timber4 ,when driven with their flat sides the way of the grain1 they do not tend to split the wood4 ,they are used to fix platform boards1 and sometimes guard boards1 on edge4 ,spikes4--,spikes are nails above #d inches in length4 ,they form a cheap method of fixing4 ,captain ,fraser1 ,r4,e41 has computed from experiments that their holding power in fir is from #dfj to #gjj pounds per inch of length the depth of cover plate being deducted4 ,illustration3 ,,fig4 #ajd ,scaffolder's hatchet4--,the scaffolder's hatchet 7fig4 #ajd7 is an ordinary shingling hatchet with a hammer head4 ,it is practically the only tool used by the scaffolder4 ,with it he can shape the ends of the putlogs1 drive wedges1 nails1 c41 and1 by giving the cord a turn round the middle of the handle1 tighten knots by using it as a lever4 ,,chapter ,,vii ,,the ,,transport ,,of ,,material ,the transportation of material is not altogether within the province of a scaffolder1 but it is so intimately connected--indeed1 it is difficult to say where his connection with the lifting and carrying of material commences and finishes--that the subject is here briefly commented upon4 ,crane ,engines4--,the engines of the crane are so arranged that all motions in connection with the derrick are under the control of the driver4 ,the engines are double cylinder with link-motion reversing gear4 ,the gearing is single and double purchase for lifting2 the jib barrel is fitted with steel catch wheel and double-lock safety catch to prevent the jib running down4 ,the slewing gear is worked from the crank shaft1 connected to the upright shaft from bottom race or spur wheel1 and is wrought by worm and worm wheel with double-cone friction slewing gear4 ,this arrangement permits of slewing the crane in either direction without reversing the engine4 ,it might also be mentioned that the clutch for the jib motion is hooped with malleable iron to prevent the possibility of its bursting4 ,crane engines can be worked by electrical1 steam1 or manual power4 ,the smaller cranes are now so made that either steam or manual power can be used as required4 ,it is of recent date that these engines have been supplied with electrical power1 and of course their use is restricted to where this power is obtainable4 ,the ,crane4--,the crane consists of four parts1 the mast1 jib1 sleepers1 and guys or stays4 ,the mast1 which rises vertically1 is connected at its base to the platform on which the engine stands2 and at the top1 to the guys by a pivot which allows of rotation in a horizontal plane4 ,it may be of iron1 balk timber of oak or pitch pine1 or in two pieces of the same1 strutted and braced4 ,the jib1 which may be built of the same materials as the mast1 is fastened to the lower end of the mast by a joint which allows of rotary movement in a vertical plane4 ,the steel rope or chain which supports the weight runs from the drum placed near the engine and over the top of the mast and jib4 ,wheels are placed at these points to lessen friction4 ,the combination of movement allowed by the pivot of the mast and joints of the jib1 enables the load to be carried to any point commanded by the effective length of the jib1 except that it cannot be placed behind the guys4 ,jibs are used up to #gj feet in length4 ,to prevent slewing under wind pressure1 jibs over #ej feet long should be fitted with wind brakes1 especially on exposed situations4 ,the crane will stand the greatest strain when the jib is most upright1 and1 reversely1 less strain as it approaches the horizontal4 ,it is a good rule1 and one which works for safety1 not to allow the top end of the jib to reach a lower level than the top of the mast1 whatever the weight of the load carried may be4 ,cranes are made suitable for derrick staging to carry a weight of #g tons4 ,if the boiler is attached to the rotating platform of the crane1 it helps to counterbalance the load4 ,cranes1 while offering the readiest means of dealing with heavy weights1 do not give the best results when used for placing material in its final position on the building4 ,the vibration of the engine1 the swaying of the supporting rope from the jib1 and the unevenness of lowering under the band brake1 prevent that steadiness of the material which is necessary for good fixing4 ,illustration3 ,,fig4 #aje ,fig4 #aje shows a small building crane2 it is worked by manual power1 and is very suitable for light work4 ,the illustration shows the general method of construction1 but there are other patterns which give greater power4 ,the crane is fitted with two hoisting ropes which are wound on the drum at ,a4 ,one rope rises while the other descends4 ,the ropes pass through the arms ,b1 and when the catch ,c rises against the slot1 it lifts the arm up4 ,the base of the jib to which it is connected then rises in the sliding groove and swings inward1 carrying the load well over the platform where it is to be deposited4 ,when the new load begins to rise1 the jib swings outward and downward1 the rope paying out as required4 ,by this means the jibs are in use alternately for lifting4 ,pulleys4--,the pulley 7fig4 #ajf7 is a circular iron disc which revolves freely on an axle fitted into an iron box4 ,the circumferential edge is grooved to receive the rope or chain which passes round it4 ,illustration3 ,,fig4 #ajf ,fig4 #ajg is the section of a groove suitable for fibre rope driving4 ,the rope is gripped at its sides1 thus increasing its driving power4 ,fig4 #ajh is the section of a groove where the pulley is used as a guide only1 the rope being allowed to rest on the bottom4 ,fig4 #aji is the section of a groove used for wire rope4 ,the groove is lined on the bottom with pieces of wood or leather to give greater friction1 as the rope would be injured if it were gripped in a groove as fig4 #ajg4 ,figs4 #aaj and #aaa are the sections of grooves suitable for chains1 the groove receiving every other link1 the alternate links lying flat4 ,fig4 #aaj is suitable where the pulley is used as a guide only1 and fig4 #aaa is used for driving pulleys as in ,weston's blocks4 ,the part elevation shown in fig4 #aab is known as a sprocket wheel1 and shows the sprockets cast in the groove upon which the links catch4 ,it is used for driving purposes4 ,illustration3 ,,fig4 #ajg ,illustration3 ,,fig4 #ajh ,illustration3 ,,fig4 #aji ,illustration3 ,,fig4 #aaj ,illustration3 ,,fig4 #aaa ,illustration3 ,,fig4 #aab ,when the pulley cannot rise or fall1 it is termed a fixed pulley1 otherwise it is considered movable4 ,the fixed pulley1 sometimes known as a gin wheel1 can only change the direction of a force1 and gives no mechanical advantage1 but when used in conjunction with a movable pulley a mechanical advantage is gained4 ,fig4 #aac is an illustration of the single movable pulley4 ,the rope is connected to the beam at ,a1 and passes round the pulley ,b and over the fixed pulley ,c ,now1 if power be exerted on the free end of the rope sufficient to move the machine1 it will be seen that for every one inch ,w rises1 ,p will descend two inches1 therefore the mechanical advantage is #b4 ,in other words1 a workman pulling at ,p with a force equal to #ajj lbs41 will lift ,w weighing #bjj lbs41 but the weight will rise at only half the speed at which ,p falls4 ,various combinations of pulleys are possible1 but the most common in use on buildings is shown in fig4 #aad1 which is an illustration of the system of pulleys known as block and tackle4 ,illustration3 ,,fig4 #aac ,illustration3 ,,fig4 #aad ,the power obtained by this machine is calculated as follows3 ,divide the weight by double the number of pulleys in the lower block2 the quotient is the power 7in the same units as the weight7 required to balance the load4 ,theoretically1 there is no limit to the number of pulleys and consequent mechanical advantage1 but the friction produced1 and want of perfect flexibility in the rope1 prevent any great increase in the number4 ,differential ,pulleys4--,a differential block on ,weston's principle 7fig4 #aae7 consists of a compound pulley of two different diameters but of one casting1 and therefore rotating together4 ,the chain is an endless one1 and passes in turn over each diameter of the pulley4 ,one of the loops thus formed carries a single movable pulley1 while the other loop hangs loose 7see fig4 #aaf74 ,the power which may be applied to the loose loop on the side which comes from the largest diameter will cause rotation of the pulley4 ,the chain must be four times in length the distance through which it is required to raise the load4 ,these pulleys are tested to #ej per cent4 above the weight they will have to lift in practice1 and the maximum load they will carry is stamped on the castings4 ,the mechanical advantage derived depends upon the difference of diameter in the compound pulley4 ,usually with these machines two men are required to lift one ton4 ,another common form of differential pulley is known as the worm block1 and consists of two cast-iron toothed wheels at right angles to each other1 connected by a worm thread of case-hardened1 mild steel forging4 ,the wheel upon which the power acts is worked by an endless chain1 and the lift wheel may be fitted with a chain or wire rope to which the load is attached4 ,pulleys of this kind possess in a great degree steadiness in lifting or in lowering4 ,this is due to the great mechanical advantage that can be gained by their method of construction4 ,by these pulleys one man can lift up to #c tons4 ,they are tested and stamped with the maximum safe load1 as are those on ,weston's principle4 ,the friction between the parts is sufficient to sustain the loads when the power is removed4 ,the steadiness of action allows of their use to lift stones of great weight1 and lower direct into position for fixing on the building4 ,illustration3 ,,fig4 #aae ,illustration3 ,,fig4 #aaf ,the ,winch4--,a winch is a hoisting machine in which an axle is turned by a crank handle1 and a rope or chain wound round it so as to raise a weight4 ,it is actually a form of lever whereby a weight may be moved through the distance required4 ,fig4 #aag gives a type of winch in its simplest form4 ,the mechanical advantage gained by its use depends upon the difference between the radius of the driving wheel and the radius of the axle2 or the circumference of the wheel and the circumference of the axle4 ,if the radius of the axle were the same as the radius of the wheel1 no mechanical advantage would be gained by its use4 ,the advantage that is gained by the arrangement can be calculated as follows3 ,as the radius of the wheel is to the radius of the drum so is the weight that can be lifted to the power applied to the handle4 ,example4 ,let radius of wheel ,r1 radius of drum r1 power applied to handle ,p1 and weight lifted ,w4 7,r ,p7_/r ,w4 ,then if ,r #ab inches1 r #d inches1 ,p #fj lbs4 7#ab #fj7_/d #gbj_/d #ahj lbs4 weight that can be lifted1 giving a mechanical advantage of #c4 ,it is obvious that1 owing to the restriction of size1 the mechanical advantage that can be gained by the simple machine shown on this figure is limited4 ,to overcome this difficulty one1 two1 or three pairs of toothed wheels are introduced into the machine1 being thus known as a single1 double1 or treble purchase winch or crab4 ,the difference in the number of teeth between the pinions and wheels gives the increased mechanical advantage that is required4 ,the method by which to find the mechanical advantage gained is as follows3 ,the pressure exerted on the handle is to the weight lifted as the radius of the drum multiplied by the number of teeth in the pinions is to the radius of handle multiplied by the number of teeth in the wheels4 ,winches1 besides lifting from the barrel1 are also used in conjunction with pulley wheels to change the direction of the force and to gain additional mechanical advantage4 ,if a double rope be used1 considerable time will be saved in the progress of the work4 ,illustration3 ,,fig4 #aag ,fig4 #aah shows the double rope4 ,the middle of the rope is given a few turns round the drum1 and the ends are continued over the pulleys1 one sufficiently far to reach the ground4 ,on raising the load the higher end of the rope descends1 and is ready to carry up the next load by the time the first has been taken off4 ,the illustration also shows the winch at work in connection with one movable pulley2 but unless the material is to be raised to different heights1 the same system of pulleys should be used on each rope4 ,illustration3 ,,fig4 #aah ,an improved winch with an advantage over those ordinarily used has the drum grooved in three diameters1 so that1 with a minimum of trouble1 a choice of mechanical advantages is gained4 ,there is no need with these winches to pass the rope several times round the drum1 for as the rope works in a groove1 greater friction is set up2 and the clutches provided to keep the rope in contact with the barrel for three quarters of its circumference1 still further prevent any likelihood of slipping4 ,illustration3 ,,fig4 #aai ,jibs4--,for the fixing of the gear a jib 7fig4 #aai7 is sufficient to carry a fixed pulley4 ,a jib is a single pole attached horizontally to the standards or ledgers above the platform upon which it is intended to deposit the material4 ,it should project slightly more than half the width of the load to be hoisted1 usually from #ah inches to #b feet4 ,illustration3 ,,fig4 #abj ,it is useful at times to have a pulley block fixed over the work in hand1 especially for fixing purposes4 ,in these cases1 the loads being usually heavy1 the jib requires extra support1 which is obtained by fixing it as a continuous beam supported at both ends 7fig4 #abj74 ,this is arranged by carrying up on the interior of the building a series of standards and ledgers2 these rise from each floor as the work proceeds4 ,the jib can be carried right across the work in hand and the gear fixed as required4 ,illustration3 ,,fig4 #aba ,another form of jib known as the 'mason's' is shown in fig4 #aba4 ,it is of framed timber from #i in4 by #c in4 to #aa in4 by #c in41 leaving a #d-;inch opening down the centre1 and rests across the ledgers4 ,it allows the pulleys which are hung on to the iron movable axle1 to be shifted horizontally throughout its length4 ,for heavy material this is invaluable1 as the load can be raised1 moved to its position for fixing1 and lowered as required4 ,illustration3 ,,fig4 #abb ,shears4--,the shears or shear legs is another contrivance for supporting heavy weights4 ,it consists of two legs forming two sides of a triangle1 and may carry a pulley at the apex as shown in fig4 #abb1 or a jib as shown in fig4 #abc4 ,in the first case the legs are not rigidly fixed1 but are kept in position by ropes1 ,a and ,b1 which1 on being slackened1 allow the shears to move from the perpendicular 7fig4 #abd74 ,in this manner loads can be lifted and placed in a different position other than that immediately over the one they first occupied4 ,the range is1 however1 limited1 as in practice the shears should not move more than #ah inches to #b feet from the perpendicular4 ,illustration3 ,,fig4 #abc ,illustration3 ,,fig4 #abd ,shears are useful for raising and lowering the machinery on ,scotch derricks1 and are often fixed on gantries to carry jibs4 ,for heavy weights1 the legs and also the jib can be of two or three poles tied together4 ,gin4--,the gyn1 or gin1 consists of three legs usually from #ab to #ac feet long4 ,they are set up and joined together at the top1 thus forming a triangulated frame4 ,a pulley wheel or block is fastened at the apex1 and extra power can be gained if they are furnished with a crab winch standing between two of the legs4 ,they are useful in lifting or in lowering material through a well or opening in the working platform1 as shown in fig4 #abe4 ,illustration3 ,,fig4 #abe ,illustration3 ,,fig4 #abf ,rails4--,scaffolds of a particularly strong construction have1 when necessary1 rails laid upon them1 in order that light trucks may be moved freely from place to place4 ,sack trucks are also used on platforms to carry cement1 c41 where required4 ,other accessories for carrying purposes1 the uses of which are obvious1 are described in the chapter on ,scaffolding ,accessories4 ,the attachment of material to the transporting power is within the province of the scaffolder4 ,to take each class of material separately3-- ,ironwork4--,ironwork is principally used in the form of girders and columns4 ,these are sometimes slung by a chain round the middle1 and as evenly balanced as possible4 ,there is considerable danger of the chain slipping1 however well balanced2 more especially is this the case if the load is tilted when swinging4 ,this may happen by the load receiving a jar through touching some part of the erection1 and thus allowing the material to fall4 ,to prevent this 'softeners'--i4e4 old bags1 sacks1 or even pieces of wood--are placed between the chain and load4 ,then1 with the chain turned twice round the whole tightly1 the danger is minimised4 ,an extra chain may also be run from each end of the load to a point some distance up the supporting chain1 as shown on fig4 #abf4 ,timber4--,timber in lengths can be carried in the same manner as ironwork1 but1 owing to the greater friction set up1 it is not so likely to slip as the former4 ,the same precautions should be taken4 ,to carry timber or ironwork vertically1 the supporting chain is given a timber hitch round one end of the pole1 and a half hitch round the end which is meant to rise first4 ,it is sometimes advantageous to substitute a cord lashing for the half hitch4 ,then1 when the highest end of the pole reaches the platform1 the lashing can be removed and the pole received horizontally4 ,this method is useful where the load has to be passed through a window4 ,bricks1 slates1 c41 are slung in crates and baskets1 and on small jobs are carried in hods by labourers4 ,these accessories are described in ,chapter ,,vi4 ,note should be taken that these fittings are in the first instance strongly made1 kept in proper repair1 not overloaded1 and that spring hooks are used on the slings4 ,stone4--,stone-work can be slung by means of the lewis1 slings1 cramps1 clips1 or shears4 ,another method is to pass the chain several times round the material1 as for girder lifting4 ,it is only suitable for rough work1 as any finished edges or chamfers may be flushed even if 'softeners' are used4 ,,chapter ,,viii ,,the ,,stability ,,of ,a ,,scaffold ,a scaffold1 considered as a whole1 is in a stable condition when1 under the forces that may act upon it1 it remains in a state of rest or equilibrium4 ,two forces which tend to create a loss of equilibrium are3 the pressure of wind which acts from any direction in a horizontal plane1 and the force of gravity due to the weight of the scaffold and that of attendant loads4 ,wind ,pressures4--,the effect of wind upon a pole scaffold3 ,the effect of wind acting on a single scaffold pole1 erected as a standard1 can be first considered4 ,for this purpose the pole shall be taken as #cb feet long1 #b feet of which are below ground level4 ,the force of wind depends upon its velocity1 and it is measured by the pressure it exerts on a square foot of surface normal to its direction4 ,if a point in a body is fixed1 so that the body cannot move out of its place1 but may rotate about that point2 a force which acts at any other point1 but in a direction that does not pass through the fixed point1 will produce rotation4 ,in applying this principle to the effect of wind on the scaffold pole1 the ground level will be the fixed point about which the standard may rotate4 ,the wind acting upon the exposed surface of the pole may be likened to a series of parallel forces that1 not acting through the fixed point1 tend to produce rotation4 ,an advantage is gained if1 instead of taking the wind as a series of parallel forces1 it is considered as a resultant force of proportionate magnitude exerting a pressure upon the centre of the exposed surface4 ,in practice it will be sufficiently correct to take the centre of surface of the pole at a point at half its height4 ,the tendency of a force to produce rotation about a fixed point is termed its moment about that point4 ,it is measured by multiplying the units of force exerted by the units of the distance between its point of application and the fixed point4 ,example3 ,if at the centre of surface of the pole under consideration1 that is at #ae feet above the fixed point1 the resultant force of the wind is equal to a pressure of #ajj lbs41 the moment about the fixed point will be #ae by #ajj #aejj4 ,in like manner the moment of resistance due to the weight of earth packed round that portion of the pole below ground can be estimated4 ,for the pole to remain in equilibrium it will be necessary for the moment of resistance to equal the moment of the overturning force1 assuming that the fixed point is stable4 ,no practical good can result by pursuing this calculation further4 ,it may be taken for granted that as the wind occasionally exerts a pressure of over #ej lbs4 per square foot1 and a pressure of #dj lbs4 per square foot is the least for which calculations should be made1 it will always be necessary when scaffolding to any height to adopt special measures to preserve stability4 ,when the ledgers are added to the standards they have some effect upon the equilibrium of the erection1 and this must now be considered4 ,the wind can be taken as acting from two directions1 first directly along the scaffold1 and secondly across the scaffold4 ,when at any other angle to the structure it will have effect in both of these directions1 being greatest in the one with which it most nearly corresponds4 ,when blowing along the scaffold4--,the standards and ledgers form with the ground level a series of rectangular parallelograms4 ,the connections between the sides of the parallelograms are not rigid4 ,they most nearly approach cup and ball joints1 and as such1 it will be wise to regard them as entirely loose to a rotating force4 ,the shape of a parallelogram with loose joints can be altered by a force acting in the plane of its surface1 and this alteration of shape can take place without creating any strain on its joints or members4 ,from this it will be seen that the tyings and ledgers of the erection may be considered as offering no resistance to a force tending to rotate the standards about their fixed points2 but by adding to the surface upon which the force can act1 the ledgers increase the overturning moment about the fixed point4 ,in practice1 although the scaffold may not entirely fail1 any change from regularity of structure due to wind pressure would cause the members of the erection to offer a less effective resistance to the other forces acting upon it4 ,this being so1 means must be taken to give that rigidity to the standards1 without which the scaffold may collapse4 ,although a parallelogram with loose joints will alter its shape under pressure1 a triangle under similar conditions cannot do so4 ,advantage is taken of this fact to obtain the rigidity which is necessary4 ,taking a standard1 and one of the ledgers1 or the ground level as forming two sides of a triangle1 a pole1 termed a brace1 is fixed to form the third side4 ,the triangle thus formed is a rigid figure offering resistance to any force acting upon it in the same plane as its surface1 and it will remain rigid until the destruction of one of its joints or members4 ,it follows1 therefore1 that the standard forming one side of the triangle becomes a sufficiently rigid body to withstand any pressure of wind that may act upon it4 ,the other standards in the erection1 if not tied to the brace1 gain rigidity from the triangulated standard because of their connection thereto by the ledgers4 ,when the wind is blowing across the scaffold4--,if the erection is of the dependent type1 the standards1 putlogs1 wall of building1 and ground level form a series of parallelograms which differ from those previously noted in that a sufficiently rigid angle is formed between the wall and ground level4 ,the effect of this inflexibility is to create rigidity throughout the parallelogram1 always providing that the other sides are firmly connected at their points of juncture4 ,in practice this is not so2 the putlogs1 if tied to the ledgers1 which for this purpose is the same as being tied to the standards1 have no fixed connection to the wall of the building2 but if they are supplemented by poles tied from the standards to within the building1 they can be regarded as having1 in effect1 fixed joints4 ,if it be impossible to tie the standards within the building1 the same effect can be gained by strutting from the ground level4 ,this scaffold1 if so treated1 is sufficiently rigid to withstand any wind force that tends to overturn the standard1 either towards or from the building4 ,if the erection is of the independent type1 the cross section also shows a series of parallelograms with loose joints1 and so similar conditions exist as in the first example1 except that the overturning force is acting in a different direction4 ,any of the methods of gaining rigidity already given1 and shown on figs4 #ba and #bd1 can be applied in this instance4 ,guard boards1 rails1 face boards1 c41 have no other effect than that of increasing the surface upon which the wind can act4 ,in consequence1 the overturning moment of the standards about their fixed point is also greater4 ,gantries form parallelograms with fixed joints with sufficient strength--unless carried to a great height--to withstand any wind pressure4 ,if necessary1 they can be braced in the same manner as the pole scaffold4 ,scotch derricks are so strongly built that1 unless a wind force exerting great pressure acted upon them1 they could be considered safe from destruction by that means4 ,the four pillars standing square to form each leg are crossed at right angles by transoms which are bolted to the uprights4 ,the parallelograms thus formed have joints which allow of rotation2 but the cross braces fitted in each bay give rigidity in two ways4 ,besides triangulating the frame1 they offer a definite resistance to movement on the bolt by butting against the transom1 as will be seen by reference to fig4 #a4 ,this resistance to movement is to some extent due to the resistance of the timber to crushing4 ,the larger parallelograms formed by any two legs1 the trussed beam and the ground level1 have joints that can only be destroyed by very great force4 ,as the highest pressures noted in this country have equalled #hj lbs4 per square foot1 and therefore have to be guarded against1 it is wise to triangulate the sides as shown on ,frontispiece4 ,the ,force of ,weight or ,gravity4--,the weight of a body equals the force with which that body is drawn towards the earth's centre4 ,the weight of a scaffold may thus be considered as a force acting vertically downwards4 ,the point at which the force acts is known as the centre of weight or the centre of gravity4 ,as a first example1 the effect of the forces of gravity may be considered when acting upon an independent unloaded scaffold in its simplest form1 consisting of four standards1 erected square on plan1 with ledgers and braces on each side4 ,this form of scaffold having regular sides1 and its weight being equally distributed throughout1 may be considered as a single1 evenly disposed1 rigid1 rectangular body4 ,the centre of such a body will coincide with its geometrical centre1 and may be found thus3-- ,draw a diagonal from ,a to ,b and from ,c to ,d 7see fig4 #abg74 ,the point of intersection will represent the centre of gravity required4 ,illustration3 ,,fig4 #abg ,in practice1 it will be best to consider the scaffold as a regular body1 comprised as to height within the top and bottom ledgers4 ,the extra length of standards in this connection can safely be ignored4 ,if a body rests on a hard surface1 it will stand or fall according as to whether a vertical line1 drawn from the centre of gravity1 falls within or without its base4 ,the base of a body is within a line drawn round the points of support4 ,it will therefore be seen that so long as the scaffold is not acted upon by any other force it will remain in equilibrium4 ,but a scaffold is erected to carry weights1 and the effect of these weights upon the stability must now be considered4 ,the effect of a load upon the scaffold is to alter the position of its centre of gravity4 ,illustration3 ,,fig4 #abh ,considering the scaffold and its load as two separate bodies1 the point or centre of gravity about which the two combined weights would act is found as follows3-- ,let ,a and ,b1 fig4 #abh1 represent two heavy bodies4 ,join the centre of ,a to centre of gravity of ,b2 divide this line into as many parts as there are units of weights in ,a and ,b together4 ,then mark off from ,a the number of units there are in ,b1 and the point thus found is the point about which the combined weights act1 i4e4 the required centre of gravity of the bodies4 ,the scaffold may1 however1 have several loads to carry1 one or more of which may be materials slung on the hoist4 ,to find the ,centre of ,gravity of a number of ,bodies4--,find the centre of gravity of two of the bodies ,a and ,b 7fig4 #abi74 ,from the point thus found1 take a line to the centre of gravity of a third1 ,c4 ,divide the line into as many parts as there are units of weight in all three bodies4 ,then from the centre of gravity of ,a and ,b divide off a number of units of distance equal to the number of units of weight in ,c4 ,the point thus found is the required centre of gravity4 ,this process is continued until all the bodies have been considered1 care being taken that all the units of weight in the bodies which have been considered are added to the units of weight in the body under consideration when dividing the line in which the centre of gravity is found4 ,the final centre of gravity found is the centre of gravity of the entire mass4 ,if the vertical line taken from it falls within the base1 the scaffold is in equilibrium and therefore stable4 ,illustration3 ,,fig4 #abi ,when boards are laid on a scaffold1 they may be treated as a load4 ,if1 however1 they are evenly distributed over the entire top of a scaffold1 their comparatively light weight may be usually neglected1 as1 their centre of gravity occurring immediately above the centre of gravity of the scaffold itself1 would have no other effect than to slightly raise the centre of gravity of the structure4 ,to find the ,centre of ,gravity of ,scaffold ,boards laid to form a ,platform4--,a scaffolding platform1 being of a slight depth in comparison with its length and breadth1 may be treated as a surface usually rectangular4 ,illustration3 ,,fig4 #acj ,the centre of gravity of a rectangular surface is the point of intersection of its diagonals 7fig4 #acj74 ,to find the ,centre of ,gravity of a ,dependent ,scaffold and the ,effect of ,loads upon it4--,a dependent scaffold1 having only one frame of standards and ledgers1 to which are attached the putlogs1 cannot be considered as an evenly disposed regular body4 ,nevertheless1 the rule that the scaffold will not be in equilibrium unless a line from the centre of gravity fall within the base still holds good4 ,in the case under consideration1 as the wall of the building to which the scaffold is securely attached by the putlogs and ties1 carries its share of the weight of the loads and putlogs1 it must be taken as forming an integral portion of the scaffold itself4 ,therefore the centre of gravity of a dependent scaffold will be the resultant centre of gravity of the outer frame1 the putlogs1 and the wall1 considered as separate bodies4 ,the centre of gravity of the frame may be found by taking it as a rectangular surface4 ,if necessary1 the boards may be treated in like manner4 ,the system of putlogs1 if they are regularly placed1 may be treated as a regular body1 and the centre of gravity found by the method already given2 but in practice their weight would have no effect towards loss of equilibrium4 ,the wall may also be treated in like manner if of even thickness4 ,if of varying thickness1 the centre of gravity of each portion of even thickness should be found4 ,the resultant will be found by the method already given for finding the centre of gravity of a number of bodies4 ,the base of the erection in this case should include the base of the wall4 ,the effect of ordinary loads upon the stability of a scaffold of this type is practically nil4 ,no weight that the scaffold was capable of carrying in itself could bring the resultant centre of gravity of the scaffold and wall outside of the base2 so that unless the scaffold failed from rupture of its members or connections1 it may be considered safe from collapse due to instability4 ,to find the ,centre of ,gravity of a ,gantry4--,this can be found by the method given for independent pole scaffolds4 ,to find the ,centre of ,gravity of a ,scotch ,derrick4--,owing to the unevenly distributed weights about these scaffolds1 they cannot be taken as regular bodies4 ,it will therefore be necessary to take each part of the erection separately1 and after finding the centre of gravity of each1 to find the resultant centre of gravity of the mass by the method already given4 ,to find the ,centre of ,gravity of each ,part4--,each leg can be treated as an evenly disposed rigid body4 ,the mass of brickwork that is placed at the foot of the legs may be treated similarly4 ,the platform may be considered as a surface4 ,if triangular1 the centre of gravity is found by the following method3-- ,bisect the base and join the point of bisection to the opposite angle4 ,the centre of gravity is at a point one-third of the length of the line measured from the side divided 7fig4 #aca74 ,illustration3 ,,fig4 #aca ,the centre of gravity of the joists supporting the platform can be taken with that of the platform itself1 providing that the weights of each are added together and the centre of gravity of the platform only lowered to half the depth of the joists4 ,the trussed girders supporting the platform may be treated as rectangular surfaces4 ,the centre of gravity of the guys1 sleepers1 and jib will be at a point in the centre of their length4 ,the centre of gravity of the engine may be somewhat difficult to find1 but it will be sufficient to treat it as a cylinder4 ,the centre of gravity of a cylinder is the middle of its axis4 ,loads may be of various forms1 but the centre of gravity will be found on a line drawn downwards through the load immediately under the supporting chain4 ,in actual practice no load1 the centre of gravity of which1 considered separately1 falls within the base of the scaffold which supports it1 will cause instability4 ,the greatest effect it can have is to bring the centre of gravity of the entire mass nearly to the edge of the base1 so that a comparatively light load acting from without may cause loss of equilibrium4 ,it has been so far assumed that1 owing to the use of braces1 ties1 struts1 c41 the scaffolds considered have been rigid bodies1 and where this is so the principles given hold good4 ,in practice1 however1 owing to the lack of1 or only partial use of1 the members just mentioned1 scaffolds are often more or less flexible bodies4 ,where this is the case1 the lack of rigidity greatly increases the danger of collapse1 as the timbers1 through yielding by flexure to the loads that act upon them1 allow such an alteration of the shape of the scaffold that the centre of gravity may be carried outside the base4 ,even where this does not occur1 the racking movement allowed is dangerous1 as the connections are strained and become loose1 creating an element of risk that the otherwise careful scaffolder cannot altogether remove4 ,for the scaffolder the lesson to be learned is--that1 whether the force he is dealing with arises from the wind1 loads1 or a combination of both1 he must triangulate--,,triangulate4 ,it will be necessary to know the weight of material in working out these problems4 ,these have been given in the ,appendix4 ,,chapter ,,ix ,,the ,,strength ,,of ,a ,,scaffold ,the strength of a scaffold equals the resistance that its members and their connections can offer to the strains that act upon it4 ,the timbers used may fail in various ways4 ,first4--,as beams1 they may fail to resist a cross strain4 ,secondly4--,as pillars and struts1 they may fail to resist compression in the direction of their length4 ,thirdly4--,as ties and braces1 they may fail to resist tension2 that is1 a strain tending to pull a beam asunder by stretching4 ,the loads that act upon a scaffold may be dead1 that is to say1 they do not create a shock2 or live1 which means they are not stationary1 and may cause shock and vibration4 ,a live load causes nearly double the strain that a dead load produces4 ,if1 therefore1 both are of equal weight1 the timber under strain will carry as a live load only one half of what it would carry as a dead load4 ,the breaking weight is the load that will cause fracture in the material4 ,the safe load is the greatest weight that should be allowed in practice4 ,it is in proportion to the breaking load1 and that proportion is termed the factor of safety4 ,experiments have been made to determine the resistance of timber to fracture under the various forces that act upon it4 ,the result of these experiments is expressed by a given number1 termed a constant1 which varies with the different growths of timber and the different strains to which they are subjected4 ,the constants 7,c7 for the strength of different kinds of timber under a cross strain are as follows3 ,,table ,i4 ---------------------------------------- ------- ,c in lbs4 for ,material rectangular beams ,authority supported at both ends ---------------------------------------- ------- ,spruce #djc ,larch #cib ,fir1 ,northern ,fir1 ,dantzic #ddh ,fir1 ,memel ,fir1 ,riga #cib ,hurst ,elm #ccf ,birch #ddh ,ash1 ,english #fgb ,oak1 ,english #efj ,oak1 ,baltic #dha ---------------------------------------- ------- ,the factor of safety for beams under a cross strain is one-fifth4 ,,table ,,ii4--,constants 7,d7 for compression4 ---------------------------------------- ------------------------ ,d#c in lbs4 for ,d#d in lbs4 for ,material crushing only ,material flexure for long pillars ---------------------------------------- ------------------------ ,wet ,dry ,spruce #f1dii to #f1hai ,spruce -- ,larch 7fallen two ,larch #a1fde months7 #c1bja to #e1efh ,fir1 ,riga #b1jce ,fir 7white deal7 #f1gha to #g1bic ,fir1 ,memel #b1cfa ,elm #aj1cca ,elm #a1fbj ,birch1 ,english #c1big to #f1djb ,birch -- ,birch1 ,american #aa1ffc ,ash #h1fhc to #i1cfc ,ash #a1hdj ,oak1 ,english #f1dhd to #aj1jeh ,oak1 ,english #b1jfh ,oak1 ,dantzic ,oak1 ,dantzic #b1daj 7very dry7 #g1gca ,pillars of medium length--the constant for bending is taken at #bi for all timbers4 ---------------------------------------- ------------------------ ,the working load on pillars should not be greater than one-tenth of the breaking weight2 but if the pillars are used for temporary purposes1 and are over #ae and under #cj diameters one-eighth1 and under #ae diameters one-fifth may be taken as the factor of safety4 ,,table ,,iii4--,the ,constants 7,e7 for ,breaking ,weight under tensional stress4 ---------------------------------------- --------------- ,material ,e in lbs4 per unit of #a sq4 inch ,authority ---------------------------------------- --------------- ,spruce #c1cfj ,larch #c1cfj ,fir #c1cfj ,hurst ,elm #d1dhj ,ash #d1dhj ,oak #f1gbj ---------------------------------------- --------------- ,the working load should not exceed one-fifth of the weight that would cause rupture4 ,beams subject to a ,transverse ,strain4--,the loads that act upon a beam may be concentrated1 that is1 acting at one point1 or distributed1 which means that the load is evenly placed over the entire length of the beam or a portion of the beam4 ,an evenly distributed load is considered to act at a point immediately below its centre of gravity4 ,if a beam carries several loads they are considered to act at a point immediately below the resultant centre of gravity of the whole4 ,beams may be fixed1 loose1 or continuous4 ,when fixed they are built into the structure2 if loose they are supported only2 and are continuous when they have more than two points of support in their length4 ,for practical purposes1 a continuous beam may be considered one-half stronger than when supported at two points only4 ,the strength of a solid rectangular beam varies directly as its breadth1 the square of its depth1 and inversely as its length4 ,the formula for finding the breaking weight 7,b4,w47 of a solid rectangular beam supported at each end and loaded at its centre is as follows3 ,b4,w4 7bd#b7_/l c where b breadth in inches2 d#b depth multiplied by itself in inches2 l length of beam between supports in feet2 c the constant found by experiment on the timber in use4 ,example4--,find the ,b4,w4 of a solid rectangular beam of ,northern fir1 #i in4 by #i in41 and #aj feet between supports1 loaded at its centre4 ,the constant for ,northern fir 7,table ,i47 is #ddh4 ,b4,w4 7#i #ib7_/aj #ddh 7#i #i x #i x #ddh7_/aj #ad tons #aa;cwt4 #bqrs4 #aa-a_/e lbs4 ,one-fifth of this must be taken as a safe load1 say #b tons #ah cwt4 99 99 99 99 99 ,the strength of a solid cylindrical beam varies directly as its diameter cubed1 and inversely as its length4 ,the formula for finding the breaking weight 7,b4,w47 of a solid cylindrical beam supported at each end and loaded at its centre is as follows3 ,b4,w4 d#c_/l c #aj_/ag where d#c least diameter in inches cubed2 l length of beam between supports in feet2 c the constant found by experiment on rectangular beams2 #aj_/ag the proportion that cylindrical beams bear to square beams1 ,example4--,find the ,b4,w4 of a solid cylindrical beam of spruce fir #f inches in diameter and #d feet between supports4 ,the constant ,c for spruce fir is 7,table ,i47 #djc4 ,b4,w4 7#f #f #f #djc #aj7_/7d #ag7 #ab1hja-c_/ag lbs4 #e tons #ad cwt4 #aqr4 #e-c_/aglbs4 ,one-fifth of this must be taken as a safe load1 say #a ton #b cwt4 #c qrs4 ,illustration3 ,,fig4 #acb ,the above diagram 7fig4 #acb7 illustrates the supports and loading of the beams just considered4 ,the following diagrams show beams variously supported and loaded1 and their relative strength to the first4 ,by adding to the formul already given1 the proportion that these following bear to the first1 the same formul can be used for all4 ,illustration3 ,,fig4 #acc ,beam supported at both ends and load equally distributed bears double of fig4 #acb4 ,illustration3 ,,fig4 #acd ,beam fixed1 load in centre1 bears half more than fig4 #acb4 ,illustration3 ,,fig4 #ace ,beam fixed1 load evenly distributed1 bears triple of fig4 #acb4 ,illustration3 ,,fig4 #acf ,beam fixed one end only1 load on free end1 bears a quarter of fig4 #acb4 ,illustration3 ,,fig4 #acg ,beam fixed one end only1 load evenly distributed1 bears half of fig4 #acb4 ,to find the effective length of a beam supported at both ends when the position of the load is varied3 ,rule4--,divide four times the product of the distances of the load from both supports by the whole span1 in feet4 ,example4--,find the effective length of a beam the supports of which are #f feet apart1 the load acting at a point #a foot from its centre4 ,the distances of the load from each support in this case are #b feet and #d feet4 ,therefore 7#b #d #d7_/f #e-a_/c feet1 effective length of beam4 ,posts and ,struts subject to ,compression4#e--,posts and struts1 when above #cj diameters in length1 tend to fail by bending and subsequent cross breaking4 ,when below #cj and above #e diameters in length1 their weakness may partly be in their bending and partly by crushing1 and when below #e diameters in length by crushing alone2 but1 as these latter are rarely met with in scaffolding1 they need not be considered4 ,on the resistance of long posts4--,to find the greatest weight1 ,w1 that a square post of #cj diameters and upwards will carry3 ,multiply the fourth power of the side of the post in inches by the value of ,d 7,table ,,ii471 and divide by the square of the length in feet4 ,the quotient will be the weight required in pounds4 ,the formula is as follows3 ,w 7d#d ,d7_/,l#b weight in lbs4 for square posts to resist bending1 where d depth in inches1 ,d constant in pounds1 for flexure1 ,l length in feet4 ,example4--,find the weight that may be placed upon a post of elm #ab feet long and #d inches square4 ,the value of ,d 7,table ,,ii47 being #a1fbj1 7#dd #a1fbj7_/abb 7#bef #a1fbj7_/add #b1hhj lbs4 ,one-tenth of this must be taken as a safe working load #bhh lbs4 99 99 99 99 99 ,the strength of cylindrical posts is to square ones as #aj is to #ag1 the rest of the formula remaining the same1 except that d diameter of post in inches4 99 99 99 99 99 ,when the pillar is rectangular4--,multiply the greater side by the cube of the lesser in inches1 and divide by the square of the length in feet4 ,the quotient multiplied by the value of ,d 7,table ,,ii47 will give the weight which the post will carry in pounds4 ,the formula is as follows3 ,w 7,,bt#c ,d7_/,l#b1 where ,b breadth of post in inches2 ,t least thickness in inches1 and the rest of notation as before4 ,example4--,find the weight that may be placed on a rectangular post of ,dantzic oak #h in4 by #f in4 and #ah feet long4 ,the value of ,d 7,table ,,ii47 being #b1daj lbs41 7#h #fc #b1daj7_/ahb 7#h #baf #b1daj7_/cbd #ab1hec lbs4 ,the safe working load say1 #a1bhe lbs4 ,on the strength of posts of medium length4--,when a post is less than #cj1 but over #e1 diameters in length1 and therefore tending to fail by crushing as well as by bending1 the resistance to crushing is a considerable proportion of the strength4 ,this must1 in consequence1 be allowed for in any calculation for the breaking weight4 ,to find the weight that would break a square or rectangular post of between #e and #cj diameters in length3 ,multiply the area of the cross section of the post in square inches by the weight in pounds that would crush a short prism of #a inch square 7,table ,,ii471 and divide the product by #aa added to the square of the length in feet1 divided by #bi times the square of the least thickness in inches4 ,the formula is as follows3 ,w ,,ds_/7#aa ,l#b_/,t#b #bi7 where ,d the constant for the resistance to crushing4 ,s the area of the cross section of the post in square inches4 #aa is a modification introduced in order that the result may be in accord with the result of experiments4 ,l the length of the post in feet4 ,t the least thickness in inches4 #bi the constant for the resistance to bending1 and which is taken at that figure for all timbers 7,table ,,ii474 ,example4--,find the breaking weight of a post of ,dantzic oak #aj feet long and #f inches square4 ,the constant for ,dantzic oak 7,table ,,ii47 is #g1gca4 ,w 7#g1gca #cf7_/7aa #ajj_/7bi #cf77 #bgh1caf_/bje #ace1gfc lbs4 ,the factor safety is #a_/h4 ,therefore the safe load will be #af1igj lbs4 ,the strength of cylindrical pillars is to square ones as #aj is to #ag4 ,braces and ,ties subject to a ,tensional ,strain4--,the weight that will produce fracture in a beam strained in the direction of its length1 is in proportion to the area of the cross section of the beam multiplied by the weight that would fracture a unit of that area4 ,the formula is as follows3 ,b4,w4 ,e ,s where ,e the cohesive force in lbs4 per unit of #a square inch1 as in ,table ,,iii4 ,s the sectional area of the beam in square inches4 ,example4--,find the ,b4,w4 of a rectangular elm brace #i in4 by #c in4 under a tensional strain4 ,the value of ,e 7,table ,,iii47 is #d1dhj4 ,b4,w4 #d1dhj #i #c #abj1ifj lbs4 ,one-fifth of this should be taken as a safe load1 #bd1aib lbs4 #aj tons #af cwt4 which is the safe load required4 ,to find the sectional area of a cylindrical beam square its diameter and multiply by #ghed4 ,the effect of fracture of a member of a scaffold depends upon its cause and upon the importance of the member destroyed4 ,if the fracture is caused by a live load1 say a heavy stone being suddenly placed over a putlog1 it is probable that the suspending rope1 if still attached1 would prevent more damage being done4 ,if the fracture arose from an increasing dead load1 say a stack of bricks being gradually built up by labourers1 the mass would probably tear its way through all obstructions4 ,nevertheless1 the entire scaffold1 if well braced and strutted1 should not come down1 the damage remaining local4 ,the result of fracture of a standard under direct crushing would be somewhat different1 as1 providing that the scaffold is rigid1 the greater strain thrown upon the ledgers1 due to the increased distance between supports1 would probably cause them to fracture4 ,in this case the damage would probably still remain local4 ,if1 owing to the fracture1 the effect of the bracing were lost1 the whole scaffold would probably fail1 as shown in the chapter on ,stability4 ,it should be noted that the ledgers1 together with the putlogs when fixed at both ends1 apart from carrying the loads1 have an important effect upon the standards1 as1 when securely connected1 they divide the uprights into a series of short posts1 thus dispelling any likelihood of failing by flexure4 ,,chapter ,x ,,the ,,prevention ,,of ,,accidents ,the safety of workmen depends not altogether upon the stability and strength of a scaffold1 but also upon the use of certain precautions which1 while not requisite for the progress of the work1 are most necessary for the prevention of accidents4 ,illustration3 ,,fig4 #ach ,put briefly1 the principal of these precautions are3 ,ladders should rise at least #f feet #f inches above the top platform they serve4 ,if the ladder is too short for this height to be allowed1 a ,t piece as fig4 #ach should be fixed across the top of the ladder to give warning to the workman that he has no higher hand hold4 ,ladders above #be feet in length between foot and rest should be stayed in the centre to prevent sagging4 ,the stay should be a wooden shaft with an iron clip4 ,by clipping the rung as shown in fig4 #aci they do not meet the workman's hands and feet when climbing4 ,the same effect is gained when the top of the ladder rises considerably above the point of rest1 by staying as shown on fig4 #adj4 ,illustration3 ,,fig4 #aci ,illustration3 ,,fig4 #adj ,ladders should have a level footing and be firmly tied to the point of rest4 ,working platforms should be fitted with guard rails along the outside and at the ends1 at a height of #c feet #f inches from the platform4 ,they may be temporarily removed for the landing of the workmen and material1 although it is not always necessary to do so in the latter case4 ,illustration3 ,,fig4 #ada ,if a well is left in the working platform through which to hoist material1 the opening should be guarded with rails as for the outside and ends4 ,a well hole1 if likely to be of permanent use1 should be fitted with a hinged flap door1 that can be shut down as required4 ,boards on edge should be fitted on the outside and ends of working platforms1 and should rise above the platform at least #g inches4 ,this will allow of a #i-;inch board being used standing on the putlogs4 ,they should not be fixed near ladders where the workmen land4 ,additional boards should be placed at the back of any stack of bricks or other material in order to prevent it falling off the scaffold4 ,illustration3 ,,fig4 #adb ,edge boards are usually nailed to the standards4 ,on exposed situations it is better to tie them1 as the wind1 continually acting on their surface1 will in time draw the nails4 ,platform boards1 when lapping1 frequently lose their place1 being kicked by the workmen during their progress about the scaffold4 ,when this happens the boards assume the position shown on fig4 #ada1 and what is known as a trap is formed4 ,the danger of a trap is shown on fig4 #adb4 ,illustration3 ,,fig4 #adc ,platform boards to be safe from tilting1 should not project more than #f inches beyond the putlogs4 ,at this distance the weight of the workman is most over the putlog1 and even if he stood on the extreme edge1 experiments have shown that his weight is more than counterbalanced by the weight and length of an ordinary board4 ,where scaffold boards are used as a means of communication between one part of the scaffold and another they should be laid in pairs1 so as to form 'runs' at least #ah inches wide4 ,to prevent unequal sagging they should be strapped on the under side4 ,it would be better to have properly constructed gangways and most decidedly safer4 ',bridging runs' for barrows are usually three boards wide4 ,five boards wide is better1 and1 as previously shown1 they should be joined to prevent unequal sagging4 ,centering should be carried on supports which rise from a solid foundation 7fig4 #adc74 ,the practice of trusting the supports to keep their position under pressure from the stay ,a 7fig4 #add71 or by being spiked to the new work1 is to be regretted1 as the only reason for its use is to effect a very slight saving of timber4 ,illustration3 ,,fig4 #add ,illustration3 ,,fig4 #ade ,the various knots1 tyings1 marryings1 c41 should be carefully watched1 as1 if used in a damp condition1 the cordage relaxes considerably when drying4 ,the scaffolder should have instructions to examine carefully all cordage in use and tighten the same as required4 ,the use of sound plant should be insisted upon4 ,defective plant should be at once marked1 so that its use cannot be unknowingly continued4 ,only the scaffolder or his assistant should be allowed to erect1 alter or adapt the scaffolding for its different purposes4 ,many accidents1 again1 occur owing to the scaffolding having been altered during a temporary absence of the mechanic1 and the reconstruction not having been made safe by his return4 ,this most frequently happens when the scaffolding is not under the charge of one responsible person4 ,no working platform should be used by the mechanic until its construction is complete4 ,sufficient plant should be on the job to enable this to be done without disturbing the platform already in use4 ,scaffolds should not be heavily loaded4 ,apart from the risk of the timbers failing1 the weight1 in the case of the bricklayers' scaffold1 has a bad effect upon the new work4 ,fan guards1 as shown on fig4 #ade1 are usually erected in urban districts to safeguard the public from falling material4 ,there is no reason why1 for the safety of the workmen1 they should not be always fixed4 ,due care should be exercised by the workmen themselves1 and observance made to the unwritten rules of experience4 ,the following instance is given as an illustration of what is meant4 ,illustration3 ,,fig4 #adf ,a scaffolder requiring a pole carried it from point ,a on fig4 #adf to point ,b4 ,he carelessly carried it upon his right shoulder1 and in turning the corner the pole hit against the standard ,c1 the recoil knocking him off the scaffold4 ,if he had carried the pole on his left shoulder he would have fallen inwardly on the boards1 and his life would not have been lost4 ,,chapter ,,xi ,,legal ,,matters ,,affecting ,,scaffolding4 ,,local ,,bye-,,laws ,regulations governing the erection of scaffolding have been made by many of the principal ,local ,authorities in the ,kingdom4 ,their purpose is to safeguard the public using the thoroughfares near which the structures are built4 ,those issued by the ,city ,corporation of ,london are summarised as follows3-- ,,corporation ,,of ,,london ,,regulations ,,for ,,scaffolds ,,applications ,each application for a scaffold is to be entered in a book1 with headings for the following information3-- ,name of street or place1 and number of house4 ,nature of work to be executed4 ,area of ground level of new premises to be built1 or old premises largely altered4 ,number of storeys1 including ground floor1 if new premises are to be built or old premises altered4 ,length of scaffolding needed4 ,time for which license is requested4 ,name and address of ,owner4 ,name and address of ,architect4 ,name and address of ,builder4 ,date of ,application4 ,signature of ,applicant4 ,,regulations ,the ,inspector of ,pavements is to report in the application book the time he thinks needful for the scaffold to be licensed2 the license is then to be made out1 and the conditions entered in the book by the ,engineer's ,clerk4 ,if there is disagreement between the applicant and the ,inspector1 as to the time needed1 the ,engineer will decide4 ,no scaffold is to project beyond the foot-way pavement where it is narrow1 nor more than #f feet where it is wide enough to admit of such projection2 any deviation on account of special reasons is to be stated upon the license4 ,no scaffold is to be enclosed so as to prevent passengers passing under it4 ,the lower stages of scaffolds are to be close or doubly planked2 each stage to have fan and edge boards1 and such other precautions to be taken as the ,inspector of ,pavements requires1 to prevent dirt or wet falling upon the public1 or for the public safety4 ,no materials are to be deposited below any scaffold4 ,where practicable or needed1 a boarded platform1 #d feet wide1 and as much wider as may be necessary for the traffic1 with stout post rails1 and wheel kerbs on the outside of it1 are to be constructed outside the scaffold1 as the ,inspector may direct4 ,where it is necessary in the public interest1 applicants shall form a gantry1 stage1 or bridge over the public-way1 if required1 so as to allow the foot passengers to pass beneath it4 ,the gantry is to be double planked1 and so constructed as to prevent dust1 rubbish1 or water falling upon the foot passengers1 and the licensee shall keep the public-way beneath it clean to the satisfaction of the ,inspector4 ,scaffolds are to be watched and lighted at night4 ,all fire hydrants must be left unenclosed in recesses formed of such size and in such manner as may enable the hydrant to be easily got at and used4 ,public lamps are not to be enclosed without the permission of the ,engineer4 ,when such enclosure is permitted1 the applicant shall put a lamp or lamps temporarily outside the scaffold1 so that the public-way may be properly lighted4 ,the licensee shall undertake to employ and pay the ,contractors to the ,corporation to make good the pavements1 lamps1 and all works disturbed1 to the satisfaction of the ,engineer4 ,licenses are not allowed to be transferred4 ,other cities have similar regulations1 but are not generally so complete in detail4 ,scaffoldings4--,the ,burgh ,police 7,scotland7 ,act of #aijc 7#c ,edw4 ,,vii41 ch4 #cc7 contains among its general clauses the following3-- ,sec4 #cb4--,the dean of guild court shall on the application of the burgh surveyor have power to prohibit and stop the erection1 use1 or employment1 and to order the alteration or removal of any crane1 scaffolding1 staging1 or shoring in or connected with the construction and erection1 or the demolition1 alteration1 repair1 or securing of any new or existing building1 or in or connected with any excavation for the purpose of any work authorised by the dean of guild court1 where such crane1 scaffolding1 staging or shoring is1 or is likely to be1 in the judgment of the burgh surveyor1 a source of danger4 ,sec4 #ajc4--';,dean of guild court' shall1 in this ,act1 as regards burghs where there is no dean of guild court1 mean the town council4 ,the above ,act applies to ,scotland only1 and the section mentioned first is carried out only so far as it affects the safety of the public at large4 ,,factory ,,and ,,workshop ,,act1 #aija ,section #aje of the above ,act1 so far as it relates to buildings1 reads as follows3-- ,,buildings #aje4--7a74 ,the provisions of this ,act with respect to-- 7#a7 power to make orders as to dangerous machines 7section #ag72 7#b7 accidents 7sections #ai-bb72 7#c7 regulations for dangerous trades 7sections #gi-hf72 7#d7 powers of inspection 7section #aai72 and 7#e7 fines in case of death or injury 7section #acf7 shall have effect as if any premises on which machinery worked by steam1 water1 or other mechanical power1 is temporarily used for the purpose of the construction of a building or any structural work in connection with a building were included in the word 'factory1' and the purpose for which the machinery is used were a manufacturing process1 and as if the person who1 by himself1 his agents1 or workmen1 temporarily uses any such machinery for the before-mentioned purpose were the occupier of the said premises2 and for the purpose of the enforcement of those provisions the person so using any such machinery shall be deemed to be the occupier of a factory4 7#b74 ,the provisions of this ,act with respect to notice of accidents1 and the formal investigation of accidents1 shall have effect as if any building which exceeds #cj feet in height1 and which is being constructed or repaired by means of a scaffolding 444 were included in the word 'factory1' and as if 444 the employer of the persons engaged in the construction or repair 444 were the occupier of a factory4 ,it will be noticed that the provisions of the ,act are more stringent for buildings which are being constructed or repaired by machinery1 and that these buildings come within the provisions of the ,act whether or not they exceed the limit of #cj feet4 ,the provisions of the ,act as mentioned in the beginning of this section have been embodied in the following abstract1 issued from the ,home ,office1 ,january #aijb4 ,form #eg4f ,january #aijb4 ,,factory ,,and ,,workshop ,,act1 #aija ,abstract of the provisions of the ,act as to ,,buildings ,,in ,,course ,,of ,,construction ,,or ,,repair ,h4,m4 ,,inspector ,,of ,,factories1 ,to whom ,communications and ,notices should be addressed ,h4,m4 ,,superintending ,,inspector ,,of ,,factories ,h4,m4 ,,chief ,,inspector ,,of ,,arthur ,,whitelegge1 ,,factories ,,esq41 ,m4,d41 ,home ,office1 ,london1 ,s4 ,w4 ,,certifying ,,surgeon ,certain provisions of the ,factory and ,workshop ,act1 including those which are stated below1 apply as if any premises on which machinery worked by mechanical power is temporarily used in the construction of a building1 or in structural work in connection with a building1 were a factory1 and as if the purpose for which the machinery is used were a manufacturing process4 ,for the purpose of the enforcement of those provisions1 the person so using 7by himself1 his agents1 or workmen7 any such machinery is deemed to be the occupier of a factory4 ,in the case of buildings over #cj feet in height1 which are being constructed or repaired by means of scaffolding1 paragraphs #d and #f apply in like manner1 whether machinery be used or not2 and for the purpose of their enforcement the employer of the persons engaged in the construction or repair is deemed to be the occupier of a factory4 ,the provisions stated below apply also to any private line or siding used in connection with a building in course of construction or repair as above4 ,sidenote3 ,dangerous ,machinery or ,plant4 #a4--;,if any part of the ways1 works1 machinery1 or plant 7including a steam boiler7 is in such condition that it cannot be used without danger to life or limb1 a ,court of ,summary ,jurisdiction may1 on complaint of an ,inspector1 make an order prohibiting it from being used1 absolutely or until it is duly repaired or altered4 ,sidenote3 ,dangerous ,processes4 #b4--;,if any machinery1 plant1 process1 or description of manual labour is dangerous or injurious to health1 or dangerous to life or limb1 regulations may be made by the ,secretary of ,state4 ,sidenote3 ,steam ,boilers4 #c4--;,every steam boiler must 7a7 be maintained in proper condition1 and 7b7 have a proper safety-valve1 steam-gauge1 and water-gauge1 all maintained in proper condition1 and 7c7 be thoroughly examined by a competent person every #ad months4 ,a signed report of the result of the examination must be entered within #ad days in a ,register to be kept for the purpose in the premises 7,form #gcg74 ,sidenote3 ,accidents4 #gd4--,when there occurs in the premises any accident which causes to a person employed therein such injury as to prevent him on any one of the three working days next after the occurrence of the accident from being employed for five hours on his ordinary work1 written ,notice 7,form #dcg7 must be sent forthwith to ,h4,m4 ,inspector for the district4 #e4--;,every such accident must also be entered in a ,register to be kept for the purpose in the premises 7,form #gcg74 #f4--;,if the accident is fatal1 or is produced by machinery moved by power1 or by a vat or pan containing hot liquid1 or by explosion1 or by escape of gas or steam1 written ,notice 7,form #dcg7 must also be sent forthwith to the ,certifying ,surgeon for the district4 ,sidenote3 ,returns4 #g4--;,if so required by the ,secretary of ,state1 a return of the persons employed must be sent to ,h4,m4 ,chief ,inspector of ,factories at such times and with such particulars as may be directed4 ,sidenote3 ,powers of ,inspectors4 #h4--;,h4,m4 ,inspectors have power to inspect every part of the premises by day or by night4 ,they may require the production of registers1 certificates1 and other papers4 ,they may examine any person found in the premises either alone or in the presence of any other person as they think fit1 and may require him to sign a declaration of the truth of the matters about which he is examined4 ,they may also exercise such other powers as may be necessary for carrying the ,act into effect4 ,every person obstructing an ,inspector1 or refusing to answer his questions1 is liable to a penalty4 ,the limiting height of #cj feet has been inserted for the reason1 apparently1 that it was not considered desirable to bring those minor accidents which might reasonably be expected to occur on the smaller buildings into notice4 ,,notice ,,of ,,accidents ,,act1 #aijf ,certain provisions of the ,factory and ,workshop ,act1 #aija1 have recently been repealed1 viz4 ,sec4 #ai1 which deals with the notification of accidents4 ,the repealing ,act1 and which contains clauses replacing the section1 is known as ,notice of ,accidents ,act1 #aijf1 which came into operation on the first day of ,january #aijg4 ,the fourth section1 which applies to buildings1 reads as follows3-- ,sec4 #d4--7a7 ,where any accident occurs in a factory or workshop which is either-- 7a7 an accident causing loss of life to a person employed in the factory or workshop2 or 7b7 an accident due to any machinery moved by mechanical power1 or to molten metal1 hot liquid explosion1 escape of gas or steam1 or to electricity1 and so disabling any person employed in the factory or workshop as to cause him to be absent throughout at least one whole day from his ordinary work2 or 7c7 an accident due to any other special cause which the ,secretary of ,state may specify by order1 and causing such disablement as aforesaid2 or 7d7 an accident disabling for more than seven days a person employed in the factory or workshop from working at his ordinary work1 written notice of the accident1 in such form and accompanied by such particulars as the ,secretary of ,state prescribes1 shall forthwith be sent to the inspector of the district and also in the case of the accidents mentioned in paragraphs 7a7 and 7b7 of this subsection1 and 7if the order of the ,secretary of ,state specifying the special cause so requires7 of accidents mentioned in paragraph 7c71 to the certifying surgeon of the district4 7#b7 ,if any accident causing disablement is notified under this section1 and after notification thereof results in the death of the person disabled1 notice in writing of the death shall be sent to the inspector as soon as the death comes to the knowledge of the occupier of the factory or workshop4 7#c7 ,if any notice with respect to an accident in a factory or workshop required to be sent by this section is not sent as so required1 the occupier of the factory or workshop shall be liable to a fine not exceeding ten pounds4 7#d7 ,if any accident to which this section applies occurs to a person employed in a factory or workshop the occupier of which is not the actual employer of the person killed or injured1 the actual employer shall immediately report the same to the occupier1 and in default shall be liable to a fine not exceeding five pounds4 7#e7 ,the foregoing provisions of this section shall be substituted for section nineteen of the ,factory and ,workshop ,act1 #aija4h ,this amendment1 as before stated1 renders ,part #d of the ,abstract inoperative4 ,the ,notice of ,accidents ,act also imposes new duties upon employers4 ,section #e reads as follows3-- ,sec4 #e4--7a7 ,if the ,secretary of ,state considers that1 by reason of the risk of serious injury to persons employed1 it is expedient that notice should be given under this ,act in every case of any special class of explosion1 fire1 collapse of buildings1 accidents to machinery or plant1 or other occurrences in a mine or quarry1 or in a factory or workshop1 including any place which for the purpose of the provisions of the ,factory and ,workshop ,act1 #aija1 with respect to accidents is a factory or workshop1 or is included in the word 'factory' or 'workshop1' or is part of a factory or workshop1 the ,secretary of ,state may by order extend the provisions of this ,act requiring notice of accidents to be given to an inspector to any class of occurrences1 whether personal injury or disablement is caused or not1 and1 where any such order is made1 the provisions of this ,act shall have effect as extended by the order4 7#b7 ,the ,secretary of ,state may by any such order allow the required notice of any occurrence to which the order relates1 instead of being sent forthwith1 to be sent within the time limited by the order4 ,the ,secretary of ,state1 acting under this section1 issued an order in ,december #aijf which stipulates that such an occurrence as the breaking of a rope1 chain1 or other appliance used for raising or lowering persons or goods by means of mechanical power should be forthwith notified on ,form #dc by the occupier of the factory to the ,inspector for the district4 ,,report ,,by ,,an ,,inspector ,,of ,,the ,,home ,,office ,,on ,,building ,,accidents ,under ,sections #gi-he of the ,factory and ,workshop ,act the ,secretary of ,state is empowered to make regulations for any description of manual labour that is dangerous or injurious to health1 or dangerous to life or limb4 ,no regulations for the building trade have as yet been made1 but in the ,chief ,inspector of ,factories' ,annual ,report for #aije a number of suggestions made by a member of the factory department were printed for the guidance of those engaged in building operations4 ,they are as follows3-- #a4 ,all working platforms from which it is possible for a workman or material1 tools1 and plant to fall a distance of more than #h feet should1 before employment takes place thereon1 be provided throughout their entire length both on the inside and outside1 and at the ends-- 7a7 with a guard-rail fixed at a height of #c feet #f inches above the scaffold boards2 7b7 with boards fixed so that their bottom edges rest on or abut to the scaffold boards4 ,the boards so fixed shall rise above the working platform not less than #g inches4 ,always providing-- 7i7 that where the working platform is fixed within a distance of #ab inches from the buildings1 the guard-rail and boards need not be supplied to the inward side2 7ii7 that where it is necessary to deposit upon the working platform material which could not be deposited thereon if the guard-rail and boards were fixed1 the guard-rail and boards may be removed for this purpose2 7iii7 that the guard-rail and boards need not be fixed within a reasonable distance of each side of any ladder which provides a means of access to the working platform2 7iv7 that the guard-rail and boards may be removed between any two standards between which material is being landed2 7v7 that the guard-rail may be considered unnecessary where additional boards on edge are fixed to a height of #c feet #f inches4 ,the reason for the limit of #h feet is as follows3-- ,the first platform is generally #e to #f feet above the ground and the material required on that platform can be placed upon it from the ground level4 ,if this is done safeguards are in the way4 ,but on the second platform about #aj feet high this would not hold good1 and from that point safeguards should be provided4 ,guard-rails should be rigid1 and not movable as would be the case if a rope or chain were fixed4 ,workmen are used to rigidity in their surroundings1 and their sense of safety is increased by the use of rigid rails4 ,it would also be difficult to keep ropes at the required height as they lengthen in dry weather4 ,boards to be placed on edge are usually #i inches wide2 therefore a rise of #g inches can easily be provided1 even when the boards butt to the platform by resting on the putlogs4 ,in exposed situations they are better tied into position than nailed as nails draw under wind pressure4 ,a scaffold is usually within a few inches of the building1 except where breaks in the wall of the erection occur1 so that rails and edge boards are not usually necessary on the inside of the platform4 ,in allowing a reasonable distance on each side of a ladder1 consideration must be given not only for the landing of workmen but also for material being carried2 #d or #e feet should be sufficient4 #b4 ,all bridging runs between different portions of a scaffold or building1 and from which a workman could fall a distance of more than #h feet1 should be not less than #ah inches wide4 ,if composed of two or more boards they should be fastened together in such a manner as to prevent unequal sagging4 ,the word 'bridging' is used to differentiate from those runs which are continuously supported along the top of a wall or in other ways4 ,some discretion should be used as to the prevention of unequal sagging4 ,if the runs have frequent supports1 say every #c feet1 the sagging would be so slight as to be negligible4 ,where necessary1 in lieu of a properly constructed gangway1 wooden straps screwed on the under side and at right angles to the run would be satisfactory4 #c4 ,scaffold boards forming part of a working platform or run should be carried at each end by a putlog or similar support and should not project more than #f inches beyond it unless lapped by other boards which should rest partly on or over the same putlog and partly upon putlogs other than those upon which the supported board rests4 ,always providing3--,that this suggestion should not apply to any projection at the ends of the working platform and similar places effectively guarded4 ,this suggestion is intended to prevent the formation of traps1 that is3 boards so laid upon the putlogs that they would tilt under pressure4 ,traps are the cause of accidents from which the victims have little chance of escape1 for when on a platform it is not easy to ascertain how the platform is supported4 ,also1 it must be remembered that workmen do not always note the position of the putlogs which support them4 ,even when originally well laid1 boards often lose their position unless they are butted1 and this means that constant supervision should be given to their position by the scaffolder4 ,when butted1 the putlogs at the board ends should be within #ab inches of each other and the boards given an equal projection1 otherwise they may tilt4 ,although this may not result in such a serious accident as when the boards lap each other1 it still remains a danger to be avoided4 #d4 ,ladders used as a means of communication in1 on1 or about a scaffold or building under construction or repair should rise at least #f feet above the place they give access to4 ,when climbing a ladder a man's arms are at about right angles to his body1 but to land it is easier and therefore safer to raise them somewhat higher4 ,therefore the limit of #f feet would be safe except to a tall man4 ,a piece of wood or rope nailed at the top of a short ladder would however give notice that there was no higher hand hold4 #e4 ,ladders used as a means of communication in1 on1 or about a scaffold or building under construction or repair should have a level and solid footing and be securely fixed at the top point of rest4 ,a firmly fixed wedge will usually supply a level-footing4 ,a sloping pavement generally causes this danger when the ladder is not standing at right angles to the incline4 ,a solid footing is also most necessary4 ,ladders are sometimes seen raised upon a stack of loose bricks or other similar material1 which is a most dangerous practice4 ,ladders can be fixed in various ways3-- 7a7 by lodgment on a suitable part of the building1 say within an embrasure2 7b7 by tying to the highest point of rest2 7c7 by the use of guy ropes to adjacent parts of the building4 ,as to-- 7a7 ,this is a fairly satisfactory method and is safer with long and therefore heavy ladders1 the weight being helpful to keep the proper position4 7b7 is the most secure but not always possible4 7c7 allows of considerable play1 but is fairly safe if the ladder has a fixed footing4 #f4 ,no ladder serving as a means of communication in1 on1 or about a scaffold or building in course of construction or repair should have an additional smaller ladder attached to or spliced on to it for the purpose of obtaining extra length4 ,ladders are often spliced especially for light work4 ,the danger arises from the displacement of the usual handhold and also foothold1 if the tying slips or gives sufficiently1 so that the rungs1 where the lap takes place1 are not on the same level4 #g4 ,openings within the working platforms through which workmen could fall a distance greater than #h feet should be surrounded with a guard-rail fixed at a height of #c feet #f inches above the working platform4 ,a guard-rail may at times interfere with the free use of the platform1 and where this occurs an alternative is to fit the well hole with trap doors which can be closed when the well is out of use4 #h4 ,no loose putlogs or other timbers should be allowed to remain projecting from the face of the scaffold where hoisting or lowering of material or plant is carried on4 ,the danger from any projecting timbers is a real one4 ,if loose the transport of material may disturb it by contact1 or the material itself may fall4 ,the face of the scaffold would be an imaginary line drawn from standard to standard on their outside4 #i4 ,baskets when loaded should not be slung from the handles only1 but the sling should be passed round the bottom of the basket4 ,provided always that if means have been taken in the construction of the basket to prevent its handles and bottom breaking out1 this suggestion need not apply4 ,several baskets are now on the market with wire ropes c4 used in their construction1 and which prevent the handles c4 breaking away4 ,the life of an ordinary basket in constant use averages about a fortnight1 but much depends upon the material carried1 slates1 for instance1 having a particularly wearing effect4 #aj4 ,all poles before being used in the construction of the scaffold should be barked4 ,this is generally done1 but is imperative when the poles are to be used as standards4 ,if not ripped off the bark acts as a sheath to the pole1 and having little adhesion thereto will slip under pressure such as is exerted by the ledgers4 #aa4 ,no work should take place on a working platform until its construction is complete1 unless the portion incomplete is effectively guarded from the men using it4 ,in the course of building1 the working platforms have to be raised as the work progresses4 ,it is at these times that the dangers arise which the above suggestion is intended to prevent4 ,as a rule only one platform is completely sheeted 7i4e41 boarded7 at a time1 and in the transition stage of raising the platform the workmen are tempted to proceed with their work before it is completed and safeguarded4 ,the remedy is for the use of additional timber4 #ab4 ,no alteration of or interference with the construction of the scaffold should be made except with the authority of a responsible person4 ,on small jobs the general foreman should take responsibility in this connection4 ,on large works1 where a foreman scaffolder is engaged1 it should be his business to superintend all alterations4 #ac4 ,all plant should be constantly examined1 and if any be found defective it should be disposed of in such a manner that its use cannot be continued unknowingly4 ,many builders have no objection to the total destruction of minor details of plant found defective when the same is ordered by the foreman4 ,no general system of marking defective plant is in use1 but a good plan is to arrange for its removal from the building1 care being taken that its return to the yard as defective should be made known to those concerned4 #ad4 ,in such places where the scaffolding has not been erected by the direct employer of the men using it1 or where its management has not been under his personal or deputed control or supervision1 he should satisfy himself either personally or by his agents before allowing his employees to work thereon that the foregoing suggestions are kept in force on that portion of the scaffold and building with which he is concerned4 ,this suggestion has a similar intention to the following clause often embodied in building contracts4 ,it reads as follows3-- ',the sub-contractor shall have the use in common with the workmen of the contractors and of other sub-contractors of existing scaffolding only4 ,the sub-contractor shall1 however1 satisfy himself that any scaffolding used for the purpose of this contract is fit and proper for his purpose and shall be solely responsible for any accidents which may result from the user of such scaffolding or plant to himself or men in his employ4' ,it is of course unnecessary to add that accidents will occur even when the greatest attention and care are exercised4 ,there is frequently no other reason for mishaps than overwork1 rushing1 misdirected economy in plant1 and1 it may be added1 intoxicating liquors4 ,much depends upon the foreman in these matters4 ,they are often first-rate managers of machinery1 have an excellent knowledge of the best means of carrying out work1 and not content with their existing reputations attempt to be also successful drivers of men4 ,this is1 perhaps1 more likely to occur when the job is not paying3 a hint from the employer to that effect will almost certainly result in an effort being made to retrieve matters4 ,this is only natural and praiseworthy1 if to gain the desired end the safety of the workmen is not jeopardised4 ,the cost of properly safeguarding a scaffold is certainly an item1 especially on large works1 but should not be difficult to calculate4 ,it is an expenditure that will not be in proportion to the cost of the building1 but would be a direct charge upon the scaffolding required4 ,i have made some calculations1 and in estimating it would probably be found not to exceed an increase of #e per cent4 upon the amount devoted to the cost of the scaffold4 ,,the ,,workmen',s ,,compensation ,,act1 #aijf ,in this ,act1 which came into force on ,july #a1 #aijg1 no mention is made of the limitations included in the superseded ,act of #ahig1 and which specially mentioned that compensation should only be paid for accidents occurring in1 on1 or about buildings which exceeded #cj feet in height and were either being constructed or repaired by means of a scaffolding1 or being demolished1 or on which machinery driven by steam1 water1 or other mechanical power was used for the purpose of the construction1 repair1 or demolition thereof4 ,in the new ,act the liability of employers to workmen for injuries is expressed in ,sec4 #a as follows3-- 7#a7 ,if in any employment#i personal injury#aj by accident arising out of and in the course of his employment is caused to a workman1 his employer shall1 subject as hereinafter mentioned1 be liable to pay compensation in accordance with the first schedule to this ,act4 ,provided that-- 7a7 the employer shall not be liable under this ,act in respect of any injury which does not disable the workman for a period of at least one week#aa from earning full wages at the work at which he was employed2 7b7 when the injury was caused by the personal negligence or wilful act of the employer or of some person for whose act or default the employer is responsible1 nothing in this ,act shall affect any civil liability of the employer1 but in that case the workman may at his option either claim compensation under this ,act1 or take proceedings independently of this ,act#ab2 but the employer shall not be liable to pay compensation for injury to a workman by accident arising out of and in the course of the employment both independently of and also under this ,act1 and shall not be liable to any proceedings independently of this ,act1 except in case of such personal negligence or wilful act as aforesaid2 7c7 if it is proved that the injury to a workman is attributable to the serious and wilful misconduct of that workman1 any compensation claimed in respect of that injury shall1 unless that injury results in death or serious and permanent disablement1#ac be disallowed4 ,,definition ,,of ,,employer ,,and ,,workman ,sec4 #ac4--;,in this ,act1 unless the context otherwise requires1-- ',employer' includes any body of persons corporate or incorporate and the legal personal representative of a deceased employer1 and1 where the services of a workman are temporarily lent or let on hire to another person by the person with whom the workman has entered into a contract of service or apprenticeship1 the latter shall1 for the purposes of this ,act1 be deemed to continue to be the employer of the workman whilst he is working for that other person2 ',workman' does not include any person employed otherwise than by way of manual labour whose remuneration exceeds two hundred and fifty pounds a year1 or a person whose employment is of a casual nature and who is employed otherwise than for the purposes of the employer's trade or business1 or a member of a police force1 or an out worker1 or a member of the employer's family dwelling in his house1 but1 save as aforesaid1 means any person who has entered into or works under a contract of service or apprenticeship with an employer1 whether by way of manual labour1 clerical work1 or otherwise1 and whether the contract is expressed or implied1 is oral or in writing2 ,any reference to a workman who has been injured shall1 where the workman is dead1 include a reference to his legal personal representative or to his dependants or other person to whom or for whose benefit compensation is payable4 ,both of these definitions have been altered from those given in the ,act of #ahig4 ,the definition of employer has been extended from the words 'deceased employer4' ,the definition of workman is much more definite1 and does not allow of much theorising4 ,with the few exceptions mentioned it covers all classes of service1 and should certainly cover any persons whose duties are connected with scaffolding4 ,,appendix ,,weight ,,of ,,material lbs4 per cubic foot ,asphalte 7gritted7 #aefjj ,brick 7common7 from #igca ,brick 7common7 to #abejj ,brick 7red7 #aceej ,brick 7pale red7 #acjca ,brick 7,common ,london ,stock7 #aaejj ,brick paving 7,english clinker7 #ajcca ,brick paving 7,dutch clinker7 #ibfb ,brickwork in mortar1 about #aajjj ,cement 7,roman7 and sand 7equal parts7 #aacef ,cement alone 7cast7 #ajjjj ,chalk from #abejj ,chalk to #affjj ,chalk 7,dorking7 #aafha ,clay 7common7 #aaiic ,clay 7with gravel7 #afjjj ,concrete 7lime7 #acjjj ,concrete 7cement7 #acfjj ,earth 7common7 from #iejj ,earth 7common7 from #abdjj ,earth 7loamy7 #abfjj ,earth 7rammed7 #iijj ,earth 7loose or sandy7 #iejj ,firestone #aabjj ,flint from #afabe ,flint to #afdcg ,granite from #aehfb ,granite to #ahgdg ,gravel #ajicb ,iron 7bar7 from #dgejj ,iron 7bar7 to #dhgej ,iron 7hammered7 #dheah ,iron 7not hammered7 #dgejj ,iron 7cast7 from #dejjj ,iron 7cast7 to #dgejj ,lead 7milled7 #gabic ,lead 7cast7 #gjiej ,lime 7quick7 #ebfh ,marble from #afabe ,marble to #aggej ,mortar 7,new7 #aajjj ,mortar 7of river sand #c parts1 of lime in paste #b parts7 #ajjic ,mortar well beaten together #aahca ,mortar 7of pit sand7 #iibe ,mortar well beaten together #aahic ,mortar 7common of chalk1 lime and sand1 dry7 #ifhg ,mortar 7lime1 sand1 and hair for plastering dry7 #hfej ,sand 7pure quartz7 #agahg ,sand 7river7 #aaghg ,sand 7,river ,thames best7 #ajbcg ,sand 7pit1 clean but coarse7 #ajjfb ,sand 7pit1 but fine grained7 #ibej ,sand 7road grit7 #iccg ,sand 7,river ,thames inferior7 #ijhg ,slate1 ,welsh #ahjej ,slate1 ,anglesea #agige ,slate1 ,westmoreland 7pale blue7 #agdgc ,slate1 ,westmoreland 7fine-grained pale blue7 #agjge ,slate1 ,westmoreland 7dark blue7 #agcdc ,slate1 ,westmoreland 7pale greenish blue7 #agcjj ,slate1 ,westmoreland 7black blue for floors7 #agbcg ,slate1 ,welsh rag #agbjj ,slate1 ,cornwall 7greyish blue7 #aegjj ,snow from #hjj ,snow to #adjj ,shingle #iejj ,steel from #dhfbe ,steel to #dijjj ,stone1 ,bath 7roe stone7 #aeehg ,stone1 ,bath #abcdc ,stone1 blue lias 7limestone7 #edah ,stone1 ,bramley ,fall 7sandstone7 #effb ,stone1 ,bristol #efhg ,stone1 ,caen #cage ,stone1 ,clitheroe 7limestone7 #fghg ,stone1 ,derbyshire 7red friable sandstone7 #dffb ,stone1 ,dundee #ehab ,stone1 ,hilton 7sandstone7 #cfjf ,stone1 ,kentish rag #ffjj ,stone1 ,ketton 7roe stone7 #eehg ,stone1 ,kincardine 7sandstone7 #ecjj ,stone1 ,penarth 7limestone7 #feha ,stone1 ,portland 7roe stone7 #echa ,stone1 ,portland #aeadc ,stone1 ,purbeck #fgej ,stone1 ,woodstock 7flagstone7 #fccg ,stone1 ,yorkshire 7paving7 #effh ,tile 7common plain7 #afae ,water 7sea7 #fdah ,water 7rain7 #fbej ,wood 7ash7 #ejjj ,wood 7birch7 #dejj ,wood 7beech7 #dejj ,wood 7elm1 common1 dry7 #cdjj ,wood 7fir1 ,memel dry7 #cdjj ,wood 7fir1 ,norway spruce7 #cbjj ,wood 7fir1 ,riga dry7 #biab ,wood 7fir1 ,scotch dry7 #bfhj ,wood 7larch1 white wood seasoned7 #bbge ,wood 7larch1 dry7 #chca ,wood 7oak1 ,english seasoned7 #dhef ,wood 7oak1 ,dantzic seasoned7 #dgbd ,wood 7oak1 ,riga dry7 #dcjj ,zinc #dejjj ,,footnotes3 ,footnote #a3 ,a ,treatise on ,shoring and ,underpinning1 and generally dealing with ,dangerous ,structures4 ,by ,cecil ,haden ,stock4 ,third edition1 revised by ,f4 ,r4 ,farrow4 7,b4 ,t4 ,batsford47 ,footnote #b3 ,as derived from tests made by ,messrs4 ,frost ,bros41 ,ltd41 rope manufacturers1 ,london1 ,e4 ,footnote #c3 ,authority1 ,hodgkinson4 ,footnote #d3 ,these constants1 in the absence of experiments1 are assumed to vary according to the modulus of elasticity of the wood4 7,tredgold1 from ,dr4 ,young's ,nat4 ,philos41 vol4 ii47 ,footnote #e3 ,tredgold's ,carpentry4 ,footnote #f3 ,these forms are to be obtained from ,messrs4 ,wyman ,sons1 ,ltd41 ,fetter ,lane1 ,e4,c4 ,footnote #g3 ,,note4--,part #d is now inoperative4 ,see p4 #afg4 ,footnote #h3 #a ,edw4 ,,vii41 c4 #bb4 ,footnote #i3 ,this brings about the inclusion of any workmen who are defined as such in ,sec4 #ac of this ,act4 7,see post1 page #agh;,c47 ,footnote #aj3 ,these words may bring an injury due to nervous shock within the provisions of the ,act4 ,footnote #aa3 ,this is an alteration from the ,act of #ahig1 in which two weeks was the period of disablement necessary before compensation could be claimed4 ,footnote #ab3 ,there is a slight alteration in drafting here from the ,act of #ahig1 but in no way is the substance affected4 ,footnote #ac3 ,the words 'unless that injury results in death or serious and permanent disablement' are new and considerably enlarge the scope of the section4 ,,index ,accidents ,act1 notice of1 #afg ,accidents1 report on1 by ,home ,office ,inspector1 #agj ,ash1 #gj ,ashlar shears1 #ajj ,attachment for hoisting1 #abi ,balks1 #gd ,barrows1 #ig -- hand1 #ig ,baskets1 #ie ,beams1 strength of1 #adc1 #ade -- stiffest1 #ff -- strongest1 #ff ,birch1 #gj ,blocks and tackle1 #abj ,boards1 #b1 #bf -- cutting of1 #fg ,boatswains' boats1 #de ,bogies1 stone1 #ig ,bolts1 #ajh ,braces1 #b1 #bf -- strength of1 #adc1 #aea ,buckets1 #ic ,bye-laws1 scaffolding1 ,london1 #afa ,centering1 supports to1 #aeh ,centre of gravity1 to find1 #acf ,chain lashings1 #ajc ,chains1 #i1 #aaj ,chimney climbing1 #cc ,cleats1 #ea ,connections1 #bi ,constants1 #adc ,cordage1 #gf -- danger from damp1 #aeh -- strength of1 #gf ,coupling links1 #i1 #aje ,crabs1 #af ,cradles1 #dc ,crane1 #aaf ,crates1 #ii ,cripples1 #ic ,dangerous occurrences1 notice of1 #afi ,dead shores1 #eh ,derrick platform1 #f -- staging for traveller1 #aj -- stagings1 #c -- travelling1 #aj ,dog irons1 #ajg -- -- fixing of1 #ajg ,duck runs1 #aab ,edge boards1 #aef ,effect of weight1 #acf -- of wind pressure1 #aca ,elm1 #gj ,employer1 definition of1 #agh;,b ,engines1 #aae ,face boards1 #bh ,factory ,act1 abstract of1 #afe -- -- repeal of ,sec4 #ai1 #afg -- -- application of1 #afd ,fan guards1 #aei ,flying shores1 #ej ,footing blocks1 #ad1 #ag -- piece1 #ee ,gantries1 #ab1 #af ,gin1 #abh ,guys1 #i ,hatchet1 #aac ,height of building under ,factory ,act1 #afd ,hods1 #ig ,horizontal shores1 #ej ,jibs1 #abe -- masons'1 #abg ,joggles1 #ej ,king legs1 #c ,kites1 #cc ,knots1 #gh ,ladders1 #ij -- accidents from1 #aed -- fixing of1 #h ,landing stages1 #bh ,larch1 #fi ,ledgers1 #b -- connections between1 #bb ,levers1 #ajf ,lewises1 #ajb ,masons' jibs1 #abg ,materials1 weight of1 ,appendix ,mortar boards1 #aab ,nails1 #aac ,needles1 #cj -- for shoring1 #ej ,notice of accidents1 #afg -- -- dangerous occurrences1 #afi ,oak1 #gj ,painters' boats1 #dc ,pine1 #fi ,plant1 danger from unsound1 #aeh -- danger from insufficient1 #aei ,platforms1 #f1 #ab -- for traveller1 #ae ,poles1 #gd ,posts1 strength of1 #adc1 #adi ,pulleys1 #aah -- differential1 #aba ,puncheons1 #bj ,putlogs1 #b1 #gd -- fixing of1 #bc ,queen legs1 #c ,raking shores1 #eb -- -- scantlings for1 #ed -- struts1 #ea ,repeal of ,sec4 #ai ,factory ,act1 #aija1 #afg ,report by ,home ,office ,inspector on building accidents1 #agj ,rider shore1 #eg ,rollers1 #ajf ,runners1 #b ,runs1 #aeg ,scaffolders' hatchet1 #aac ,scaffolding1 definition of1 #a -- foundations1 #c -- application ,burgh ,police ,scotland ,act1 #afc ,scaffolding needle1 #cj -- proper control of1 #aeh -- system of1 #b ,scaffolds1 bricklayers'1 #ai -- for chimneys1 #ca1 #cg -- for domes and arches1 #db -- ladder1 #df -- masons'1 #bg -- for steeples1 #db -- swinging1 #dc -- for towers1 #da ,shakes1 cup1 #fb -- radial1 #fb -- weather1 #fi ,shear legs1 #abg ,shears1 ashlar1 #ajj ,shore1 preparation of1 #ee ,shores1 #b ,shoring1 #di ,skips1 #ic ,slater's truss1 #aaa ,sleepers1 #i ,sole piece1 #ee ,spikes1 #aac ,spruce1 #fi ,stagings1 #ag ,standards1 #b -- fixing of rising1 #ba ,stone clips1 #aja -- cramps1 #ajc -- slings1 #aja ,straining pieces1 #ea ,straps1 #aji ,struts1 #b -- strength of1 #adi -- to shoring1 #ef ,system1 ,north country1 #b -- ,south country1 #ab ,ties1 #b -- strength of1 #adc1 #aea ,timber1 branding1 #ga ,timber1 classification and structure1 #fb -- conversion1 #fe -- decay of1 #gb -- defects in living tree1 #fb -- description1 #fi -- durability of1 #gd -- felling1 #fd -- preservation1 #gc -- scantlings1 #fe -- seasoning1 #fg -- selection1 #gj -- stacking1 #fg -- testing1 #ga -- use of scaffolding1 #gd ,tossles1 #ej ,transoms1 #b ,traps1 danger from1 #aeg ,trestles1 #ib ,trucks1 sack1 #ii -- timber1 #ii ,underpinning1 #eg ,wall plates1 #ej ,wedge driving1 #eg1 #fj ,wedges1 #aab ,weight1 effect of1 #acf -- of materials1 ,appendix ,wells1 safeguards1 #aef ,winch1 #abc ,wind pressures1 #aca ,window strutting1 #eh ,wire lashings1 #ajc -- ropes1 #aji ,workman1 definition of1 #agh;,c ,workmen's ,compensation ,act1 #agh;,a -- -- -- liability of employers #agh;,a ,,printed ,,by ,,spottiswoode ,,and ,,co4 ,,ltd41 ,,new-,,street ,,square ,,london 99