SHOP TOOLS.

12 r

them as they descend upon the forging, when tlie high-pressurepumps starfc, and autornatically cut off the low-pressure. Therelative areas of the lifting and pressing rams are as 16 to 1.The pumps at each revolution depress the cross-head half aninch, whilst the lift is 8 inches. The rapidity of the pressingand return stroke can be made considerable by running thepumps quicker. The tool is raised at each Operation about 6inches above the forging, to allow it to be moved. This clear-ance is taken up at the rate of 2 feet per second, by connectingthe main ram cases with the low-pressure Service. There aretwo main-pressure rams 36 inches in diameter, and fwo liftingrams 9 inches in diameter, the ram cases being made of wroughtSteel. The stroke of all the rams is 7 feet. The maximumhydraulic pressure is 4500 lbs. to the square inch, and this isobtained from a set of three single-acting ram pumps 6 inchesin diameter and 12-inch stroke, which are driven from thecrank-shaft of a steam-engine.

In the Bessemer and Siemens processes for the manufactureof steel, the ingot cranes have to be quickly and easily con-trolled, with a freedom from gearing, and for this purposehydraulic power has been adopted as the most convenient.The cranes which are required for the purpose of manufac-turing steel have to deal with a different load, and with adifferent condition of things, to that which formerly existed, asthe modern Converters produce at each “ blow ” as much as 12to 15 tons, compared with a quarter of that weight which wasobtained previously. In steel-making, the centre crane isrelied on to receive, and distribute, the molten steel in the pro-cess, and it has to move a ladle, which must be capable ofinotion in several directions, in Order to accommodate itself tothe tipping motion of the Converter, which involves a verticaland horizontal motion of a few feet. It must also command aconsiderable horizontal radius, so as to deliver into the variousingot moulds. The vertical motion is capable of being accom-plished by employing a hydraulic ram working vertically in acylinder, and having a jib or beam resting on the top of, and