344 



OUR PHYSICAL WORLD 



estimated to weigh 15,000 tons, was moved to its new location 

 by two teams of horses operating capstans. The wheel and axle 

 is commonly used in moving a rudder to steer a boat (Fig. 182). 



The city child who watches 

 the construction of a building 

 or the country lad who sees a 

 well dug will likely see the 

 windlass used. 



In this last contrivance, a 

 crank is firmly fixed to a hori- 

 zontal cylinder of wood or 

 metal, the axis of which is sup- 

 ported on uprights (Fig. 183). 

 A rope winds about this cyl- 

 inder, bearing at its free end 

 the bucket of earth, water, or 

 other substances it is desired 



to raise. Water was drawn out of the old-fashioned well by 

 such a windlass. A man turning the crank is applying power 

 to one end of a lever of the first class. The fulcrum is the 

 center of the axle, and the weight is the rope and bucket. Sup- 

 pose the distance from the center of 

 the axle to the end of the crank is 2 

 feet and the radius of the cylinder is 

 3 inches. Evidently a pressure of 10 

 pounds exerted to turn the crank will 

 lift a weight of 80 pounds, leaving 

 friction out of consideration. 



The capstan (Fig. 184) is like 

 the windlass except that the cyl- 



FIG. 184. A capstan 



inder is set vertically, and the capstan has a bar or bars which 

 turn in a horizontal plane, the equivalent of the crank on the 

 windlass. When a horse attached to the end of this bar is 

 driven around in a circle, the rope is wound on the cylinders, 

 and the power of the horse is tremendously multiplied. Suppose 



