THE WHEEL AND AXLE. 



ECTfON II. 



THE WHEEL AND AXLE AND WHEEL-WORK. 



179. The Wheel and Axle. The wheel and 

 axle consists of a wheel united to a cylinder in 

 such a way that they may revolve together about 

 a common axis. It is a modified lever of the first 

 class. 



ISO. Advantages of the Wheel and Axle. 



The ordinary range of action of a lever of the first class 



is very small. In order to raise the 



load higher than the vertical distance 



through which the weight end of the 



lever passes, it is necessary to support 



the load and re-adjust the fulcrum. 



This occasions an internlittent action 



and loss of time, difficulties which are 



obviated by using the wheel and axle. 



FIG. 46. 



181. A Modified Lever. Considered as a lever 

 of the first class, the fulcrum is at 

 the common axis, while the arms of 

 the lever are the radii of the wheel 

 and of the axle. If a c, the radius 

 of the wheel, be used as the power- 

 arm, velocity or time is exchanged 

 for intensity of power. This is the 

 usual arrangement. If be, the radius 

 FIG. 47. of the axle, be used as the power- 



