HYDRAULIC LEVERAGE
However, we must remember that in mechanics, as in all walks of life, we cannot get “something for nothing.” If we multiply the pressure or force, we must pay for it in some way, otherwise we should be getting more work out of the press than we put in it, which is what the perpetual motion crank is ever trying to do. As the cross-sectional area of the plunger D is only 1/30th of that of the ram, the plunger must descend thirty inches to raise the ram one inch. We need not consider the difference in the head of water because it would not amount to more than a few ounces at most, nor need we consider frictional losses. The case is parallel to that of the lever. In fact, we may consider the hydraulic press as a fluid lever with the water in tube C as the effort arm and that in cylinder A as the weight arm. The two arms are here so proportioned that the power arm must move thirty times as far as the weight arm. The work put into the press is exactly balanced by that we get out of it. An effort of 100 pounds exerted through a distance of thirty inches is exactly balanced by the moving of 3,000 pounds through a distance of one inch.
It is a decided disadvantage to have to move the plunger so far and in actual commercial practice hand-operated hydraulic presses are not worked in that way. A pump is used to force water into the cylinder so that a great many short strokes may be taken in place of one long one, and the pump handle provides an added leverage, enabling a man with little effort to exert an enormous lift. The water enters the ram cylinder through a valve, and the pressure is maintained on the ram until relieved by the opening of an outlet port.