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The Stephenson valve gear or Stephenson link or shifting link [1] is a simple design of valve gear that was widely used throughout the world for various kinds of steam engines. It is named after Robert Stephenson [ 2 ] but was invented by his employees.
Stephenson valve gear - most common valve gear in the 19th century, normally inside the locomotive frame. William T. James valve gear 1832, used first by Baltimore and Ohio Railroad, United States. Allan valve gear, a straight-link valve gear. It is fitted to 0-4-0WT "Dolgoch", preserved on the Talyllyn Railway.
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 steam to the cylinders. [6]: 41 [3]: 75 Firebox
Developments after the separate expansion valve led to more sophisticated valve gears that could achieve the same goal of varying inlet lap with a single valve. The first of these were the link valve gears, particularly the Stephenson link valve gear. This uses a pair of eccentrics with a sliding link mechanism between them that acts as a ...
The discrepancy may be explained by the missing numbers having been allocated to some steam ... Valve gear: Stephenson: Valve type: Vertical-face slide valves: Train ...
The Stephenson valve gear remained the most commonly used valve gear on 19th-century locomotives. However, the Walschaerts valve gear had the advantage that it could be mounted entirely on the outside of the locomotives, leaving the space between the frames clear and allowing easy access for service and adjustment, which resulted in it being ...
On locomotives fitted with Westinghouse air brake equipment and Stephenson valve gear, it was common to use the screw housing as an air cylinder, with the nut extended to form a piston. Compressed air from the brake reservoirs was applied to one side of the piston to reduce the effort required to lift the heavy expansion link, with gravity ...
In British practice, inside valve gear is usually of the Stephenson type while outside valve gear is usually of the Walschaerts type. However, this is not a rigid rule and most types of valve gear are capable of being used either inside or outside. Joy valve gear was once popular, e.g. on the LNWR G Class.