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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.
The valve spindle is milled out to enable a better through-flow. The 4 piston rings on the valve heads are clearly visible. The valve on this locomotive has a diameter of 300mm. The Trofimoff valve (German: Trofimoff-Schieber) (also Trofimov, Troffimoff or Trofimof) is a springless pressure-compensation piston valve for steam locomotives.
In a steam engine, cutoff is the point in the piston stroke at which the inlet valve is closed. On a steam locomotive, the cutoff is controlled by the reversing gear.. The point at which the inlet valve closes and stops the entry of steam into the cylinder from the boiler plays a crucial role in the control of a steam engine.
Controls the supply of steam to the cylinders. The valve gear, actuated by connection to the driving wheels, ensures that steam is delivered to the piston with precision. Types are slide valves, piston valves or poppet valves. [2] [3]: 62 Valve chest / Steam chest Valve chamber next to the cylinder (24) containing passageways to distribute ...
LNER Class V2 4771 Green Arrow.Note Gresley conjugated valve gear located ahead of the piston valves, driven from the valve spindles. The Gresley conjugated valve gear is a valve gear for steam locomotives designed by Sir Nigel Gresley, chief mechanical engineer of the LNER, assisted by Harold Holcroft.
One is a steam piston to move the rod as required. The other, containing oil, holds the rod in a fixed position when the steam is turned off. Control is by a small three-way steam valve (“forward”, “stop”, “back”) and a separate indicator showing the position of the rod and thus the percentage of cutoff in use.
The valve closes automatically as the piston descends, and the steam is exhausted through the existing cylinder porting. The inertia of the flywheel then carries the piston back to the top of its stroke against the compression, as it does in the original form of the engine.
Cylinder, with slide valve removed to show ports A double-acting slide valve cylinder. Steam enters via the steam port SP, and is admitted by the slide valve SV through the upper passage S to push down the piston P. At the same time, exhaust steam from below the piston passes back up the lower passage S, via the valve cavity, to exhaust E. As ...