28 



MECHANICS. 



Fig. 5. 



Where there is a rapid succession of forces required 

 in practice, the fly-wheel 

 is usually of great advan- 

 tage. Hence its use in all 

 revolving straw - cutters, 

 where the knives make 

 quickly-repeated strokes 

 {Fig. 5). More recently 

 it has been applied to the 



Straw-cutter with fly-wheel. dasher - ohum {Fig. 6), 



where the rapid upright strokes 

 are so well known to be very fa- 

 tiguing for the amount of force 

 applied. 



By thus regulating motion, 

 the fly-wheel frequently enables 

 an irregular force to accomplish 

 work which otherwise it could 

 not perform. Thus a man may 

 exert a force equal to raising a 

 hundred pounds, yet, when he 

 turns a crank, there is one part 

 of the revolution where he 

 works to great disadvantage, and where his utmost 

 force will not balance forty pounds. Hence, if the 

 work is heavy, he may not be able to turn the crank, 

 nor to do any work at all. If, however, a fly-wheel be 

 applied, by gathering force at the most favorable part 

 of the turning, it carries the crank through the other 

 part. 



An error is sometimes committed by supposing the 

 fly-wheel actually creates power, for as much force is 



Chum with a fly-ivheel, far-equal- 

 izing the motion. 



