The Walschaert valve gear was a type of steam engine valve gear invented by Belgian railway mechanical engineer Egide Walschaerts in 1844. The gear is properly named without the "s", since it was patented under that name, but both forms are commonly used.
History
It was slow to gain popularity. The Stephenson valve gear remained the most popularly used valve gear on 19th Century locomotives. The Walschaert gear had the advantage that it could be mounted entirely on the outside of the locomotives, leaving the space between the wheels and frames clear; this caused adoption first among some articulated locomotives. The Mason bogie locomotive type was the first to use the Walschaert gear in North America.
In the 20th Century, the Walschaert valve gear was the most commonly used gear, especially on larger locomotives. In Europe, its use was almost universal, while in North America, the Walschaerts gear outnumbered its closest competitor, the Baker valve gear , by a wide margin.
In Germany, the Walschaert 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.
Technical details
