288 



APPLIED SCIENCE 



length. It may be measured in the coil in the following 

 manner : To the diameter of the coil in inches, add the diameter 

 of the hole in inches; multiply by the number of coils in the belt 

 and multiply the resulting figure by .1309. The product will be 

 the length of the belt in feet. 



EXAMPLE. How many feet of belt are there in a coil that is 22 

 in. in diameter? The hole is 4 in. in diameter and there are 48 coils. 



22 + 4 = 26 

 26 X 48 = 1248 

 1248 X .1309 = 163.36, the number of feet of belting in the coil. 



If exact measurements are desired, it is necessary to get the average 

 diameter of the coil and the hole, and also any fractional parts of a 

 turn the belt makes in the coil. 



331. Pulleys and Their Management. Pulleys are made 

 of wood or steel (Figs. 143 and 144). They are measured by 

 their diameter and by the distance across the face or rim. 



(a) Taper Cone Pulleys (6) Step Cone Pulleys 



FIG. 143. Wood Split Pulleys. 



As the tendency of the belt on a pulley is to run to its highest 

 portion, the highest part of the face should be in the center 

 of the pulley, towards which the face should taper or crown. 

 It is the practice to crown pulleys with a taper of % in. per 

 foot or 1 in. per foot. 



