SIMPLE MACHINES 



345 



that the capstan bar is 10 feet long and the horse at its end is 

 exerting a pull of a ton and a half; suppose, further, that the radius 

 of the cylinder is 6 inches: then the rope winding on the cylinder 

 is exerting a pull of 30 tons minus whatever power is used in over- 

 coming the friction of the machine. 

 The form of capstan in Figure 184 is 

 much used on shipboard for raising the 

 anchor or for similar heavy tasks. 



The wheel and axle is evidently like 

 the windlass except that the crank at- 

 taching to the cylinder is replaced by a 

 wheel. Several such simple machines may be combined in the 

 train of gear wheels so as to develop immense mechanical advan- 

 tage. Suppose in Figure 185 the power is applied as a weight on 



FIG. 185. A train of gear 

 wheels. 



FIG. 1 86. A hand derrick 



a rope that winds on the axle of the right-hand wheel. This 

 wheel has cogs that play into those of the small middle 

 wheel which is firmly fixed to the large wheel on the same 

 axis. The cogs of this play into those of the small left-hand 

 wheel, which turns the large left-hand cylinder. As the weight 



