70 LEATHER BELTING 



the angle ebd, which is the angle whose sine is de+db. It can 

 readily be seen from the figure that de is the difference be- 

 tween the radius of the larger pulley and that of the smaller 

 one, and that db is the center line distance of the pulleys 

 themselves. If then we denote the radius of the larger 

 pulley by R and that of the smaller one by r, and the distance 

 between their centers by L, all being in the same unit, as 



FIG. 1 8. METHOD OF DETERMINING ARC or CONTACT OF BELT ON 



PULLEY. 



inches or feet, the arc of contact, in degrees, of the belt on 

 the smaller of a pair of pulleys will be 



/ R-r 



1 80 21 angle whose sine is 



L 



The angle of contact on the larger pulley will be 



/ T> ' 



1 80+ 2 1 angle whose sine is 

 \ 



The length of belt in contact with the larger pulley is 



R r 

 found by multiplying the angle whose sine is =r- as above by 



