THE WHEEL AND AXLE. 



99 



FIG. 49. 



as in the case of the windlass (Fig. 48) or capstan (Fig. 49). 



In all such cases, the radius being 



given, the diameter or circumference 



of the wheel may be easily computed. 



In one of the most common forms, 



the power is applied by means of a 



rope wound around the circumference 



of the wheel. When this rope is 



unwound by the action of the power, another rope is wound 



up by the axle,. and the weight thus raised. 



185. Wheel- work. Another method of securing 



a great difference in the in- 

 tensities of balancing forces, 

 is to use a combination of 

 wheels and axles of moder- 

 ate size. Such a combination 

 constitutes a train. The wheel 

 that imparts the motion is 

 called the driver ; that which 

 receives it, the follower. An 

 axle with teeth upon it is 

 called a pinion. The teeth or 

 cogs of a pinion are called leaves. 



186. Law of Wheel-work. A train of wheel- 

 work is clearly analogous to a compound lever ; the statical 

 law, given in 178, may be adapted to our present pur- 

 poses as follows : TJie continued product of the power 

 and the radii of the ivheels equals the continued 

 product of the weight and the radii of the axles. 



187. Another Law of Wheel-work. By 



examination of Fig. 50, it will be seen that while the axle 



FIG. 50. 



