Cyclopedia of mechanical engineering; a general reference work Editor-in-chief Howard Monroe Raymond Assisted by a corps of mechanical engineers, technical experts, and designers of the highest professional standing . e motor throughthe pulley to the belt, but both cases are the same as far as theloading of the pulleys is concerned. The only other force theoretically acting is the centrifugalforce due to the speed of the pulley. This produces tension iuthe rim and arms, but for the low value of 1,300 feet per minuteperipheral velocity in this case may be disregarded. Considering the arms as be
Cyclopedia of mechanical engineering; a general reference work Editor-in-chief Howard Monroe Raymond Assisted by a corps of mechanical engineers, technical experts, and designers of the highest professional standing . e motor throughthe pulley to the belt, but both cases are the same as far as theloading of the pulleys is concerned. The only other force theoretically acting is the centrifugalforce due to the speed of the pulley. This produces tension iuthe rim and arms, but for the low value of 1,300 feet per minuteperipheral velocity in this case may be disregarded. Considering the arms as beams loaded at the ends, and thatone-half the whole number of arms take the load, and for , figuring the size of the arms at the center of the pulleygives the following calculation for the large pulley: ^X21=^^=.0393X2,500XA» Let S=2,500 fc=breadth of ovalh»= *^^^.=46 .47i=tliicknessofoval 4,515 lk=l/l6= (say ) .4h=.ix5 5= (say ) This is about all the theoretical figuring necessary on this pulley. The rim is made as thin as experience judges it capable of being cast; the arms are tapered to suit the eye, thus giving iiiuple fastening to the rim to provide against shearing off the run. Fig. IL MACHINE DESIGN 43 from the arms; generous fillets join the arms to both rim and hub; nud the hub is given thickness to carry the key, and length enough to prevent tendency to rock on the shaft. Uncertain strains due to unequal cooling in the foundry mold may be set up in the arms and rim, but with careful pouring of the metal they should not be serious, and the low value chosen for the fibre stress allows considerable margin for strength. The small pulley has the same forces to withstand as the large pulley, but on account of its small dianu^ter there is not room enough for arms between the rim and the hub, hence it is made with a web. The web cannot be given any bending by the belt ]>ull, the only tendency which exists in this case being a shearing where the
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