Caprotti, Arturo

SUBJECT AREA: Land transport, Railways and locomotives, Steam and internal combustion engines

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b. 22 March 1881 Cremona, Italy

d. 9 February 1938 Milan, Italy

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Italian engineer, inventor of Caprotti poppet valve gear for steam locomotives.

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Caprotti graduated as a mechanical engineer at Turin Royal Polytechnic College and spent some years in the motor car industry. After researching the application of poppet valves to railway locomotives, he invented his rotary cam valve gear for poppet valves in 1915. Compared with usual slide and piston valves and valve gears, it offered independent timing of inlet and exhaust valves and a saving in weight. Valve gear to Caprotti's design was first fitted in 1920 to a 2−6−0 locomotive of the Italian State Railways, and was subsequently widely used there and elsewhere. Caprotti valve gear was first applied in Britain in 1926 to a Claughton class 4−6−0 of the London, Midland \& Scottish Railway, resulting in substantial fuel savings compared with a similar locomotive fitted with Walschaert's valve gear and piston valves. Others of the class were then fitted similarly. Caprotti valve gear never came into general use in Britain and its final application was in 1954 to British Railways class 8 4−6−2 no. 71000; this was intended as the prototype of a class of standard locomotives for express trains, but the class was never built, because diesel and electric locomotives took their place. Some components survived scrapping, and a reconstruction of the locomotive is in working order.

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Further Reading

John Marshall, 1978, A Biographical Dictionary of Railway Engineers, Newton Abbot: David \& Charles.

P.Ransome-Wallis (ed.), 1959, The Concise Encyclopaedia of World Railway Locomotives, London: Hutchinson (contains a note about Caprotti (p. 497) and a description of the valve gear (p. 301).

PJGR