Fig. 20. Wheel and axle
"The fulcrum is at C, the centre. The arm of the weight is W W, and the arm of the power is A C. In [Fig. 20] the arm of the power is the spoke of the wheel, while the arm of the weight is the radius of the axle. [Fig. 19] shows the ordinary winch, often used in well-digging for hauling up dirt and rock, and also for raising planks, shingles, rafters, and other light stuff, to the roofs and upper floors of buildings. Often it is made more powerful by adding spur or geared wheels to the end of the shaft, consisting of a pinion and a larger spurred wheel. The crank or handle is attached to the pinion, and the power is increased according to the difference in diameters of the spur wheels. The machine is then called a 'crab' and it is often used for lifting safes and other heavy weights to elevated situations. In [Fig. 20] the length of the crank (in a straight line) is the arm of the power.
"The mechanical advantage of the wheel and axle equals the ratio between the diameter of the wheel and of the axle.
Fig. 21. Capstan and hand bars
"It is not necessary that an entire wheel be present. In the case of the windlass and the capstan ([Fig. 21]), the power may be applied to a single arm or to a number of arms placed in the holes shown. The cable or rope on the barrel of the capstan is hauled in by turning the capstan on its axis, with handspikes or bars. The capstan is prevented from turning back by a pawl attached to its lower part, working in a circular ratchet on the base.
Fig. 22. Compensating fusee