HYDRAULIC RAM 



HYDRAULICS 



the area of the larger piston will be 576 square 

 inches, each single square inch of which will 

 receive pressure equal to that exerted on the 

 square inch of water by the smaller piston. 

 Thus, if the smaller piston exerts (a force of 

 100 pounds, the larger piston will receive a 

 pressure sufficient to lift 576 times 100 pounds, 

 or 57,600 pounds. If the handle of the small 

 piston is made a lever with a mechanical ad- 

 vantage of four (see LEVER) a man exerting a 

 force of 100 pounds can lift four times 57,600 

 pounds, or 230,400 pounds, which is 115% tons. 



Of course the hydraulic press does not lift 

 its load the entire distance in a single move- 

 ment of the hand lever. If the small piston 

 moves downward six inches it displaces six 

 cubic inches of water, but this amount spread 

 beneath the 576 square inches of the larger 

 piston will raise the latter only y^Q of six 

 inches, or 0.010 inch. As soon as the stroke 

 is completed, the valve w closes; when the 

 handle is drawn up more water enters through 

 the valve v, and a second stroke can then be 

 made. C.H.H. 



HYDRAULIC RAM, a machine to use the 

 momentum of falling water to lift water. higher 

 than the source of supply. In the diagram, 

 water from the reservoir r flows through the 

 pipe p and out through the valve cv . As the 



HYDRAULIC RAM 



The letters which serve to explain its operation 

 are referred to in the text. 



flow becomes faster the pressure closes the valve 

 cv, suddenly checking the momentum of the 

 water, as when the water from a hydrant is sud- 

 denly shut off. There is a back pressure which 

 forces the water through valve b into the air 

 chamber a. The air is compressed and by its 

 pressure closes valve b and forces the water in 

 the chamber up through the pipe e. Since only 

 a small part of the total water flowing through 

 pipe p is forced up through pipe e, the machine 

 is not of practical value unless the source of 

 supply is much greater than the amount 

 needed. If the machine were perfectly effi- 

 cient, one-fifth of the water in p would be 



raised five feet in e; but, as there is much loss 

 by friction and waste, an efficiency of fifty 

 per cent is high, and even that is rapidly 

 diminished if the ratio of the fall to the height 

 raised becomes greater than one to twelve. 



HYDRAULICS, hi drawl' iks. When we open 

 a faucet in our house to get a glass of water; 

 when we see the embankments and levees 

 which protect the lands along the banks of 

 many rivers from disastrous floods; when we 

 think of the great canals that have been built 

 for improving communication by water; when 

 we read of the great irrigation works which 

 transform arid places into fertile plains or 

 smiling gardens, we must remember that men 

 have been able to accomplish all these works 

 as the result of the knowledge they have 

 gained about the natural laws that govern 

 liquids in motion. The branch of physics 

 which deals with the laws of liquids in motion 

 or of flowing liquids is known as hydraulics, a 

 name which is derived from the Greek, and 

 means pertaining to water. The practical ap- 

 plication of the laws of hydraulics has given 

 rise to the science of hydraulic engineering, to 

 which we are indebted for all the benefits 

 named above. 



Laws of Flowing Liquids. In this article 

 can be given only a few of the fundamental 

 laws to which liquids in motion are subjected. 

 When water descends or flows it is subjected 

 in theory to the same laws as all falling bodies 

 (which see). If a hole be made in the side 

 of a vessel containing water, the water flows 

 out of the hole, or orifice, forming a jet. One 

 important physical law regarding a jet of water 

 is the following: the velocity with which a 

 jet of water issues from the orifice is equal to 

 that of a body falling from the surface of the 

 water to the orifice. A descending jet of water 

 will therefore acquire the same velocity that a 

 stone would acquire in falling from the high 

 level of the descending jet to the ground. A 

 jet which issues from a dam through an orifice 

 made ten feet below the surface of the water 

 will have the same velocity as a stone which 

 has fallen ten feet. It follows that the velocity 

 with which a jet flows depends on the height 

 of the liquid above the orifice. 



Another important law is the following: a 

 jet of water will rise to the level of its source. 

 If a cistern is on a support twenty-five feet 

 high, and a pipe leading to the ground and 

 having the lower end bent upward is attached 

 to it, a jet issuing from the pipe will rise theo- 

 retically as high as the surface of the water in 



