Walschaerts Valve Gear
The Walschaerts valve gear is a type of steam engine valve gear invented by Belgian railway mechanical engineer Egide Walschaerts (1820-1901) in 1844. His name is given both with and without the final "s" in the literature - it is said the gear was incorrectly patented without the "s"; it is also said that before 1830 the 2 forms were interchanegable.
The gear was extensively used in steam locomotives from the late 19th century until the end of the steam era.
The Walschaerts valve gear was slow to gain popularity. The Stephenson valve gear remained the most popularly used valve gear on 19th-century locomotives. The Walschaerts gear had the advantage that it could be mounted entirely on the outside of the locomotives, leaving the space between the frames clear; this caused adoption first among some articulated locomotives. The Mason Bogie locomotive type was the first to use the Walschaerts gear in North America.
The first application in Britain was on a Single Fairlie 0-4-4T, exhibited in Paris in 1878 and purchased by the Swindon, Marlborough and Andover Railway in 1883. According to Ahrons, the locomotive saw very little service as nobody seems to have known how to set the valves and this led to enormous coal consumption.
In the 20th century, the Walschaerts valve gear was the most commonly used type, especially on larger locomotives. In Europe, its use was almost universal, whilst in North America, the Walschaerts gear outnumbered its closest competitor, the Baker valve gear, by a wide margin.
In Germany, the Walschaerts gear is often named the Heusinger valve gear after Edmund Heusinger von Waldegg, who invented the mechanism independently in 1849. Heusinger's gear was closer to the form generally adopted, but most authorities accept Walschaerts' invention as sufficiently close to the final form.
See Also
Sources of Information
- [1] Wikipedia