Chapelon, André

SUBJECT AREA: Land transport, Railways and locomotives

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b. 26 October 1892 Saint-Paul-en-Cornillon, Loire, France

d. 29 June 1978 Paris, France

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French locomotive engineer who developed high-performance steam locomotives.

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Chapelon's technical education at the Ecole Centrale des Arts et Manufactures, Paris, was interrupted by extended military service during the First World War. From experience of observing artillery from the basket of a captive balloon, he developed a method of artillery fire control which was more accurate than that in use and which was adopted by the French army.

In 1925 he joined the motive-power and rolling-stock department of the Paris-Orléans Railway under Chief Mechanical Engineer Maurice Lacoin and was given the task of improving the performance of its main-line 4–6–2 locomotives, most of them compounds. He had already made an intensive study of steam locomotive design and in 1926 introduced his Kylchap exhaust system, based in part on the earlier work of the Finnish engineer Kyläla. Chapelon improved the entrainment of the hot gases in the smokebox by the exhaust steam and so minimized back pressure in the cylinders, increasing the power of a locomotive substantially. He also greatly increased the cross-sectional area of steam passages, used poppet valves instead of piston valves and increased superheating of steam. PO (Paris-Orléans) 4–6–2s rebuilt on these principles from 1929 onwards proved able to haul 800-ton trains, in place of the previous 500-ton trains, and to do so to accelerated schedules with reduced coal consumption. Commencing in 1932, some were converted, at the time of rebuilding, into 4–8–0s to increase adhesive weight for hauling heavy trains over the steeply graded Paris-Toulouse line.

Chapelon's principles were quickly adopted on other French railways and elsewhere.

H.N. Gresley was particularly influenced by them. After formation of the French National Railways (SNCF) in 1938, Chapelon produced in 1941 a prototype rebuilt PO 2–10–0 freight locomotive as a six-cylinder compound, with four low-pressure cylinders to maximize expansive use of steam and with all cylinders steam-jacketed to minimize heat loss by condensation and radiation. War conditions delayed extended testing until 1948–52. Meanwhile Chapelon had, by rebuilding, produced in 1946 a high-powered, three-cylinder, compound 4–8–4 intended as a stage in development of a proposed range of powerful and thermally efficient steam locomotives for the postwar SNCF: a high-speed 4–6–4 in this range was to run at sustained speeds of 125 mph (200 km/h). However, plans for improved steam locomotives were then overtaken in France by electriflcation and dieselization, though the performance of the 4–8–4, which produced 4,000 hp (3,000 kW) at the drawbar for the first time in Europe, prompted modification of electric locomotives, already on order, to increase their power.

Chapelon retired from the SNCF in 1953, but continued to act as a consultant. His principles were incorporated into steam locomotives built in France for export to South America, and even after the energy crisis of 1973 he was consulted on projects to build improved, high-powered steam locomotives for countries with reserves of cheap coal. The eventual fall in oil prices brought these to an end.

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Bibliography

1938, La Locomotive à vapeur, Paris: J.B.Bailière (a comprehensive summary of contemporary knowledge of every function of the locomotive).

Further Reading

H.C.B.Rogers, 1972, Chapelon, Genius of French Steam, Shepperton: Ian Allan.

1986, "André Chapelon, locomotive engineer: a survey of his work", Transactions of the Newcomen Society 58 (a symposium on Chapelon's work).

Obituary, 1978, Railway Engineer (September/October) (makes reference to the technical significance of Chapelon's work).

PJGR