The Walschaerts valve gear, known as Heusinger valve gear in parts of Europe, is a type of valve gear used to regulate the flow of steam to the pistons in steam locomotives, invented by Belgian railway engineer Egide Walschaerts in 1844. The gear is sometimes named without the final "s", since it was incorrectly patented under that name. It was extensively used in steam locomotives from the late 19th century until the end of the steam era.
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Walschaerts valve gear in the context of Nigel Gresley
Sir Herbert Nigel Gresley CBE (19 June 1876 – 5 April 1941) was a British railway engineer. He was one of Britain's most famous steam locomotive engineers, who rose to become Chief Mechanical Engineer (CME) of the London and North Eastern Railway (LNER). He was the designer of some of the most famous steam locomotives in Britain, including the LNER Class A1 and LNER Class A4 4-6-2 Pacific engines. An A1 Pacific, Flying Scotsman, was the first steam locomotive officially recorded over 100 mph in passenger service, and an A4, No. 4468 Mallard, still holds the record for being the fastest steam locomotive in the world (126 mph).
Gresley's engines were considered elegant, both aesthetically and mechanically. His invention of a three-cylinder design with only two sets of Walschaerts valve gear, the Gresley conjugated valve gear, produced smooth running and power at lower cost than would have been achieved with a more conventional three sets of Walschaerts gear.
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