IXERTIA. THE FLY-WHEEL. 



17 



knives make quickly-repeated strokes (fig. 5). More re- 

 cently it has been applied to the dasher-churn (fig. 6), 

 where the rapid upright strokes are so well known to be 

 very fatiguing for the amount of force applied. 



By thus regulating motion, the fly-wheel frequently 

 enables an irregular force to accomplish work which other- 

 wise it could not perform. Thus a man may exert a force 

 equal to raising a hundred pounds, Fig. 6. 



yet, Avhen he turns a crank, there /^^/^^^'-v^)^ 

 is one part of the revolution where // lr<^'i^ 

 he works to great disadvantage, 

 and where his utmost force will 

 not balance forty pounds. Hence, 

 if the work is hea\ y, he may not 

 be able to turn the crank, nor to 

 do any work at all. If, however, 

 a fly-wheel be applied, by gather- 

 ing force at the most favorable 

 part of the turning, it carries the 

 crank throus^h the other part. ^, . . . , , . 



Y . . Chumwithajly-wheel, for equal' 



An error is sometunes commit- ^^i^g the motion. 



ted by supposing the fly-wheel actually creates power, for 

 as much force is required to give it momentum as it 

 afterward imparts to the machine ; it consequently only 

 accumulates and regulates power. 



On rough roads, the force of inertia causes a severe 

 strain to a loaded wagon when it strikes a stone. The 

 horses are chafed, the wagon and harness endangered, and 

 the load jarred from its place. This inconvenience is 

 avoided in part by placing the box upon springs, which, by 

 yielding to the blow, gradually lessen the effects of the 

 shock. For carts and slowly moving lumber-wagons 

 springs are useful, but more so as the velocity and 

 momentum increase. Even on so smooth a surface as a 

 rail-road, it was found by experiments made some years 

 ago, that when the machinery of a locomotive was placed 



