EARTH'S STUDIES ON BELTING 



43 



in which C is the center line 

 distance of the pulleys in 

 inches, the notation otherwise 

 being as before. In making 

 use of formula (12) p is first 

 determined by formula (7) or 

 (8), and then t\ and /2 are 

 evaluated by formulae (10) and 



(n). 



The use of the formulae is 

 simple. The number of sepa- 

 rate computations involved in 

 determining the values of p, 

 t t m and the horsepower for a 

 given velocity, however, is 

 large, and for a large number 

 of belts the operation would 

 be exceedingly tedious, if not 

 prohibitive from the stand- 

 point of time alone. To facil- 

 itate the application of the 

 formulae to belts which fall 

 within the usual shop range, 

 Mr. Earth has constructed the 

 slide rule illustrated in Fig. 7. 

 This rule embodies all the 

 above formulae except (12), 

 and by means of it, practically 

 every problem in belt driving 

 that may arise in the ordinary 

 factory can be solved. The 

 tables on pages 91 to no em- 

 body the same information, 

 and may to some prove of 

 easier application. 



