Model in brass (scale 1:8) of Silvers patent slide valve

Model in brass (scale 1:8) of Silvers patent 1864 slide valve and variable expansion reversing gear for steam engines

This represents the form of slide valve and operating gear patented by Mr. Silver in 1864. The valve is elongated and has portions of its ends cut away so that the port area for steam admission is restricted, while the whole area is available for exhaust. Motion is given to the valve by a disc oscillated by an eccentric, the point of attachment of the valve rod being adjustable so that variable expansion and reversing are obtainable. Adjustment is effected by attaching the valve rod to the middle point of a link which slides upon two pins fixed in the face of the disc; a rack is formed on the back of the link and this gears with a pinion which is rotated by a worm and worm wheel.