100 



WELLS'S NATURAL PHILOSOPHY. 



Fig. 12. 



Fig. 72 represents a section of the wheel and axle, showing the radius 

 of the axle, b c, and the radius of the Avheel, a c. The two being in a 

 straight line, the weights hanging in opposition are 

 always as if they were connected by a horizontal lever, 

 a c b, turning on a fulcrum at c. If the radius of tho 

 wheel, or tho length of the longer arm of the lever, a c, 

 bo 24 inches, and the radius of the axle, or the length 

 of the shorter arm, c 6, be 3 inches, then the advantage 

 gained would be 24-=-3 = 8, and a power of 100 pounds 

 applied to the wheel would balance a weight of 800 ap- 

 plied to the axle. 



„ . 217. The methods of applying power 



How do we ap- ^^ •' " *^ 



ply power in in the Wheel and axle are very various, 



axle^f '''^'^' ^^^ ^* ^°^ being essential that the power should be applied by a 

 rope. Tlie axle is sometimes placed in a vertical or upright 

 position, and the power applied by means of levers, or bars, inserted into holes 

 FiCt, 73. in one end of the axle. A capstan of a ship, Fig. 



73, is an example of this. 

 ^'*'*%s>^^^^,^*'****^ In the windlass, a handle, or winch, is sub- 



stituted in the place of a wheel. (See Fig. 74.) 

 In this case, tho advantage gained is equal to 

 tho number of times that the length of handle i3 

 greater than the radius of the axle. Thus, if the 

 handle is 20 inches and the radius of the axle 

 is 2 inches, then the advantage would be 10, and 

 a power of 50 pounds applied at the handle would 

 just raise a weight of 10 times 50, or 500 pounds. 



When a weight, or resistance, of comparatively great amount is to be raised 

 by a very small power, by means of the simple wheel and axle, cither of two 

 inconveniences would ensue ; either the diameter of the axle would become 

 too small to support the weight, or the diameter of the wheel would becorao 

 BO great as to be unwieldy. This has been remedied by a very simple ar- 

 FlG. 74, rangement, called the double axle. Fig. 74. 



The axle of the windlass hero consists of 

 two parts of unequal diameters, and the 

 rope winds around them in different direc- 

 tions ; tlierefore, every turn of the wind- 

 lass, cr handle, winds up a portion equal 

 to the circumference of the one, but un- 

 winds a portion equal to the circumference 

 of tlie other, and if the two be nearly equal, 

 tho weiglit moves very slow. If the weight 

 rise 1 inch while the handle describes 100 

 inches, 1 pound at the handle will balance 100 attached to the rope. 



In this arrangement space and time are exchanged for power in a most 

 convenient manner. 



