. A textbook on the locomotive and the air brake . Fig. 4, the weight W isbetween the fulcrum F andpower P. This class is repre-sented in Fig. 8, as appliedto a car-truck wheel. In levers of the third class,Fig. 8. Fig_ 5^ the power P is between the fulcrum F and the weight W. This class is representedin Fig. 9, as applied to a car-truck wheel. 57. The Weight Sustained by the Fulcrum.—The force exerted on the fulcrum of a lever can be calculated by 46 THE NEW YORlv AIR BRAKE. §17 assuming that the fulcrum has changed places with either thepower P or the weight W, and then using the proper equa
. A textbook on the locomotive and the air brake . Fig. 4, the weight W isbetween the fulcrum F andpower P. This class is repre-sented in Fig. 8, as appliedto a car-truck wheel. In levers of the third class,Fig. 8. Fig_ 5^ the power P is between the fulcrum F and the weight W. This class is representedin Fig. 9, as applied to a car-truck wheel. 57. The Weight Sustained by the Fulcrum.—The force exerted on the fulcrum of a lever can be calculated by 46 THE NEW YORlv AIR BRAKE. §17 assuming that the fulcrum has changed places with either thepower P or the weight W, and then using the proper equation.^^^^ For instance, in example 1, ^•-^^ Art. 54, it was found thata force of 500 pounds at Pwould balance 1,000 poundsat Tf, the lever arms being20 inches and 10 inches,respectively. Now, to findthe force sustained at F,assume the fulcrum to havechanged places with power arm in this casewould be 20+10 = 30^^° ^ inches long, while the weight arm Avould remain the same as before, or 10 this case, PX Fc _ 500 X 30Fb~ ~ ^10. TT = 1,500 pounds. This, it will be noticed, is equal to the sum of the power Pand the weight W. If this method is applied to the three classes of levers, it willbe found that (1) the c pressure on the fulcrum ,- \ of a lever of the first ,-- \ class is equal to the v- \ sum of the power andthe weight, (2) the pres-sure on the fulcrum ofa lever of the second i class is equal to the /^ difference between the — weight and the power, while (3) the pressure on the fulcrum of a lever of the thirdclass is equal to the difference between the power and the weight. 58. Bent Tjevers.—All rules and equations that apply tothe straight lever apply equally well to the bent lever, if care is §17 THE NEW YORK AIR BRAKE. 47 taken to determine the true or virtual lengths of the lever arms. In the case of a straight lever with the forces acting at right angles to it, the arms may be measured along the lever itself; in all other cases [such as when (
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