The Locomotive Of Today

36 The Boiler : Regulators. end of the above-mentioned connecting rod is attached. To open the regulator the handle in the cab is moved, this raises the connecting rod, and the pin being a fit in the small valve it is lifted at once and uncovers the small port allowing the steam to pass through the large valve into the pipe, admitting pressure to the inside of the large valve, and thus tending to a State of equilibrium, so that when the pin has travelled to the top of the slotted hole, it will lift the large valve more easily than would be the case if no pilot valve were fitted. It will be observed that the large valve has a lug cast upon its upper end, which overhangs the head, so that should any of the mechanism be disconnected or broken the valve will drop until the lip catches, and this is the position when both ports are covered; the small valve is also sometimes provided with a similar lip, but this practice is by no means universal. It should also be noticed that two plate springs pass across the backs of the valves and hold them to the faces, so that should the engine be subjected to any sudden jolt they cannot fali back and leave the ports open to steam. The head is arranged so that it is not exactly vertical but slightly inclined, to allow the crank on the rod below to be always working in an advan- tageous position. In the next example, at C, the regulator as before is located in the dorne, and the ports, four in number, are arranged around a centre, upon a pin at the centre a butterfly valve is made to revolve, and is provided with four similar ports and blanks between them, sufficiently large to cover the ports in the head. The valve has two lugs cast upon it at opposite sides for connecting rods from the horizontal rod from the cab ; to open it the valves are turned until the holes uncover the ports. The design shown is that for small engines, but larger engines have similar ones with a pilot valve so fixed as to allow steam gradual admittance to the steam chest. D shows a section of the usual design used in America, in which the head has two holes, one at the top and one at the bottom, and two valves upon a common spindle, and as the top valve is made of a larger diameter than the lower one the amount of work necessary to overcome in opening them, is only equal to the difference in the area of the two. It is general with this design of regulator to have the rod from the cab of the “pull out” type, and connected to a bell crank, as clearly shown in the sketch. The usual position of the driver on American engines being at the side of the firebox, and not, as here, at the back, this form of handle is more convenient. The handle is worked upon a sector with notches as in