The Locomotive Of Today

66 The Engine : Stuffing Boxes, Drain Cocks y Pistons. Large ports are to be recommended, as the steam will not then be wiredrawn in entering, or choked in leaving the cylinders and a free running engine will be secured. The valve never completely opens the port to the admission of steam, but allows the exhaust, after the piston has done its stroke, the full area to escape and thus reduce back-pressure. At C one cylinder is represented detached from its fellow, and the ports are plainly seen. The valve is not shown, but the steam entrances will be noticed at the top on either side of the exhaust outlet. D is a front elevation of one cylinder and half the steam chest, showing one method of making the joint of the two covers where they intersect each other; another is to divide the covers in a straight line, so that half the holes through which some of the studs pass may be in each cover, one nut then holds both to the face; this, however, requires the two covers to be of exactly the same thickness, otherwise there will be a tendency for one to blow and even the flange to break off the thickest cover. E is a back end elevation, showing the giands and stuffing boxes for the piston rod and valve spindle, and also the place for attachment of the slide bar. The ledges shown on the top of the casting at each end are where the front tube-plate of the boiler and front smokebox plate take their bearings, these being bolted to the casting to form a joint. Round the barrel of the cylinder, ribs are cast for strength, and the whole is attached to the frames by bolts, as shown on A. When the diameter of the cylinders is more than 18-in. it is a common expedient to place the valves and steam chest above or below the cylinders, whilst some designers have placed them on the outside of the frames. The best, perhaps, is to have them below, as then they are better drained of all condensed water, and further, the valves drop from the faces when steam is shut off whilst running and thus reduce wear. Drain cocks are fitted at either end of each cylinder and on the steam chest, controlled by rods from the cab, so that the driver may open them to allow water to escape, they are screwed into the bosses shown on the sketches at B, D and E. The nozzles of these cocks usually turn toward the front of the 'engine and upwarcl, so that issuing steam and water shall not ,-strike the ballast and throw it up into the motion. I'ig- gives views of one of a pair of outside cylinders having their steam chests placed between the frames for the valves to be operated by direct valve gear without the inter- vention of rocking shafts. With cylinders of this type it is customary to form on the casting a face and projection,