Egide Walschaerts
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Egide Walschaerts (21 January 1820 - 1901) was a Belgian mechanical engineer, best known as the inventor of the Walschaert valve gear for use in steam engines.
Born in Mechelen, Belgium, Walschaerts studied at Liège, and in 1842 joined the Belgian State Railway workshops. In 1844 he invented a type of valve gear that came to be used in the majority of steam engines. The gear, known as the Walschaert Gear in his honor, allows for adjustment of the timing of the inlet and exhaust valves on the drive cylinders, enabling a steam locomotive to be put into reverse. He invented several other improvements to steam engines, and was awarded a gold medal at the 1878 Exposition Universelle in Paris.
The following image illustrates the working of the Walschaerts gear, click on it for a technical explanation.