. Science of railways . Fig 3Homestead Straight-Way Valve. which it is placed, and the plug will be free to be easilymoved. A quarter of a turn in the direction forclosing it causes the cam to rise and take a bearing onthe upper surface of the chamber, and the only effectof further effort to turn the stem in that direction is toforce the plug more firmly to its seat. A slight motionin the other direction immediately releases the camand the plug turns easily, being arrested at its properopen position by contact of the fingers of the cam atthe other end of its travel. E, D, D, are balancingparts
. Science of railways . Fig 3Homestead Straight-Way Valve. which it is placed, and the plug will be free to be easilymoved. A quarter of a turn in the direction forclosing it causes the cam to rise and take a bearing onthe upper surface of the chamber, and the only effectof further effort to turn the stem in that direction is toforce the plug more firmly to its seat. A slight motionin the other direction immediately releases the camand the plug turns easily, being arrested at its properopen position by contact of the fingers of the cam atthe other end of its travel. E, D, D, are balancingparts. This valve forms a very efficient blow-off LOCOMOTIVE APPLIANCES. 577 valve where an automatic valve is not desirable(see chapter on Boiler Cleaners.) THE MULTIPLATE VALVE ^^ftii. Multiplate Globe Valve. The trade mark Multiplate means many plates and appliesto the multiplicity of thin metal plates of rolled metal thatcompose the head and seat surfaces of the valves. The plates are made of any metal best suited to the con-ditions of service to which the valves are applied, and areabout the thickness of metal that would ordinarily be refacedor reground off the contacting parts of the valve surfacesordinarily used, when they are worn from continuous service. The plates are applied compactly together to the head andto the seat, forming a solid wearing surface to the parts, andproduce with ease a tight metal seated valve. 578 L0C02I0TIVE APPLIANCES. When this wearing surface becomes worn or cut, a platemay be taken off the head of the valve, and one off the seat,and thrown away. The succeeding plate on each part willpresent a new true surface; this is all that is necessary tomake a tight valve. This simple operation entirely eliminatesrefacing or regrinding, which
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