The Locomotive Of Today

The Engine : Valve Buckles, Slide Valves. 83 or “ motion,” usually by a taper end fitting into a socket, and held by a cotter passed through. At B a buckle suitable for engines with valve chest between the cylinders is shown; if the chest were either above or below, the spindles or shanks could be made straight, but when between, the giands have to be pitched wider than the distance between the valves to get the stuffing boxes in, hence the necessity for setting the spindle as shown. When the valves are placed below they drop away from the faces when steam is shut off, and so wear is reduced ; but, to prevent them from falling too far away, and possibly allowing’ a layer of steam to get between them and the face, or when worn thin from being lifted up so sharply as to break them, small coiled springs are inserted into sockets in the buckle to hold the valve more or less near the face. As the steam exerts its pressure upon the back of the whole valve it presses it upon the face with considerable force and causes it to require a large percentage of the power of the engine to move it, and various contrivances have been employed with a view of remedying this. At C a device known as the “Trick” or “Allan” valve is shown; it has the flange and cavity as before, but in addition a channel passes round above the cavity from one face to the other, so that the valve has to travel a smaller distance for the same port opening, as the edge of the flange opens the port a little, and at the same time the channel opens at the reverse end beyond the face, and steam enters and passes over into the port opened. This device does not lessen the pressure upon the valve, but reduces the travel and conse- quently the total friction to be overcome. At D a section through a typical American steam chest is shown, the valve in this case being balanced upon the “ Richardson ” system : four strips are let into four planed grooves on the back of the valve, and projecting upwards bear upon a planed plate held so as to be parallel to the valve face, the strips being pressed up by means of springs ; the area enclosed is under exhaust pressure only, as a hole through the crown of the valve places the back in free com- munication with the biast pipe; from this it will be seen that even should the strips leak it is not possible for pressure to accumulate at the back of the valve. At E is shown a plan of the valve, showing the strips and method of making the corner joints, this being to a slightly larger scale than the sectional arrangement. Continuous bands, both rectangular and circular, have also been used for balancing, but the four independent strips seem to answer best, as they can adapt