The Locomotive Of Today

114 The Engine : Steam Reversing Gear. means of a handle above, which has a cavity below wide enough and sufficiently upon one side of the vertical centre to cover one steam and the exhaust port, putting them into free communication with each other; upon the side of the disc oppo- site to the cavity is a hole through the valve itself, through which steam is admitted from above to the port below the disc, so that when the disc is turned, as shown, steam is admitted to the left port and the right port is open to the exhaust. When turned through half a revolution steam is admitted at the other port, and when turned a quarter of a revolution both ports are closed. The cylinder on the left is filled with oil or water, and instead of the disc valve has a bye pass cock, and no exhaust port ; opening the bye pass, which is done by giving the handle a partial revolution, allows the liquid to flow from one end of the cylinder to the other, as the steam pressure in the other cylinder may force it. Closing the valve separates the liquid in each end and locks the piston in its position. Ihe steam cock upon the cylinder is coupled to the bye pass cock and opens and closes with it. The piston in the steam cylinder is fitted with the ordinary spring ring, but that in the other cylinder is fitted with two cup leathers, as shown ; a cup is also provided upon the bye pass cock, so that any loss, due to leakage, etc., may be made up and all slack kept properly taken up. The movement ot the piston rod is transmitted to the reversing shaft through a long lever, shown broken at the left of the sketch, and is coupled to a rod which connects it to the arm projecting' clown from the shaft. This gear is also fitted in other positions upon engines, often being arranged vertically as at the front end of the side tanks of tank ■engines. The marks upon the scale indicating the gear and point ■of cut-off are founcl on the engine after it has been coupled up and had the valves set. Thus the cut-off points for the ports upon one side of the engine are determined as has been before described, and marks made upon the valve spindle, the crank is then set at the point in its stroke at which it is required to •cut-off, this point being found on the slide bar, and the reversing gear moved until th.e valvs ©xactly closes the front port, the point upon the scale that the pointer indicates is marked, and the wheels turned, with the reversing gear still in this position, until the back port closes and the position ot the crosshead noted. The crank is then set at the next position for which the cut-off point is required, and the lever moved as before and the scale marked, and so on for all points in the