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The Walschaerts valve gear on a steam locomotive (a PRR E6s). The valve gear of a steam engine is the mechanism that operates the inlet and exhaust valves to admit steam into the cylinder and allow exhaust steam to escape, respectively, at the correct points in the cycle. It can also serve as a reversing gear. It is sometimes referred to as the ...
The Bulleid chain-driven valve gear is a type of steam locomotive valve gear designed by Oliver Bulleid during the Second World War for use on his Pacific (4-6-2) designs. It was peculiar to the Southern Railway in Britain , and borrowed from motor-vehicle practice in an attempt to create a compact and efficient design with a minimum of service ...
In mechanical engineering, backlash, sometimes called lash, play, or slop, is a clearance or lost motion in a mechanism caused by gaps between the parts. It can be defined as "the maximum distance or angle through which any part of a mechanical system may be moved in one direction without applying appreciable force or motion to the next part in mechanical sequence."
The valve gear operation combines two motions; one is the primary lead motion which is imparted at the bottom of the combination lever (12). The secondary is the directional/amplitude motion which is imparted at the top. Consider that the driver has adjusted the reversing lever such that the die block is at mid-gear. In this position the ...
During the 1830s, the most popular valve drive for steam locomotives was known as gab motion in the United Kingdom and V-hook motion in the United States. [3] The gab motion incorporated two sets of eccentrics and rods for each cylinder; one eccentric was set to give forward and the other backwards motion to the engine and one or the other could accordingly engage with a pin driving the ...
Some of the Union Pacific 9000 class locomotives were converted to a "double Walschaerts" valve gear, while later examples were built with roller bearings for the moving parts of the Gresley mechanism. In Australia, the VR S class Pacifics avoided many of the middle cylinder problems that beset Gresley by placing a 'set' in the axle of the ...
The Hackworth valve gear is a design of valve gear used to regulate the flow of steam to the pistons in steam engines. It is a radial gear , with an actuating lever driven from the crank. The drive may be taken directly from the crank or indirectly via a return crank (as in all pictures).
This entails controlling the admission and exhaust of steam to and from the cylinders with a valve linked to the motion of the piston. [3] For timing and dimensioning of slide or piston valves where the valve opens and closes the steam and exhaust ports, a consideration of the "lap" and "lead" is required.