Andre Xavier Chapelon
Regarded by many as the greatest locomotive engineer since Stephenson, was born in St Paul en Cornillon, Loire on 26 October 1892 (Rogers). Chapelon joined the French P.O. Railway in 1924 and retired as engineer-in-chief of the SNCF in 1953. By making relatively inexpensive but well-thought-out changes to the steam passages, draughting systems, and superheaters he was able to obtain great increases in power output, sometimes as much as fifty per cent. His reconstruction of a P.O. Pacific in 1929 was the beginning of a new wave in locomotive design which was felt also outside France.
His enthusiasm for steam locomotives developed early. After achieving distinction in mathematics and science he served as an artillery officer during WWl. During 1919-21 he completed his education at the Ecole Centrale, Paris, and graduated as Ingenieur des Arts et Manufactures. His first appointment was on the PLM as a probationer in the rolling stock and motive power section under Etienne Tribolet at Lyon-Mouche depot. Seeing little hope of promotion, he left locomotive work in 1924 and joined the Société Industrielle des Telephones, soon becoming assistant manager.
On 1 December 1925 Chapelon returned to railway work at the research and development section of the Paris Orléans Railway. In conjunction with Kylälä, a Finnish engineer who had designed a steam and gas exhaust device in 1919, Chapelon. designed a new exhaust system which he named the Kylchap, in 1926, producing an adequate draught with minimum back pressure. This was applied to the 4500 and 3500 class compound Pacifics and the 3591 class simple Pacifics and other PO locos and the results were highly encouraging. By redesigning and enlarging steam passages he reduced throttling losses. The first rebuild, No 3566, emerged from Tours works in 1929-11 and was an outstanding success. Until then Chapelon's ideas been regarded with scepticism; with success faith in his principles was established. His next success was the rebuilding of one of the 4500 class Pacifies, No 4521, as a 4-8-0, completed in August.1932. Its performance excelled that of the rebuilt pacific 3566, and eleven more were rebuilt renumbered 4701-2 and later 240 701-12.
In 1936 he began a new 6-cylinder 4-12-0 rebuilt from a PO6000 class 2-10-0. It had two high pressure cylinders inside between the second and third coupled axles and four lp cylinders in line in front. The hp cyls drove the fourth coupled axle, the outside lp cylinders the third and the inside lp cyls the 2nd. His greatest achievement was the 3-cylinder compound 4-8-4 No 242 A.1 rebuilt in 1942-6 from 4-8-2 3-cyl simple No 241.101. It is arguably the greatest steam locomotive ever built. it could maintain continuous 4000 hp at the tender drawbar at 44-62mph (70-100km/h) and 3800 hp at 74mph (120km/h). The triple Kylchap exhaust resulted in a high steaming rate at all speeds. The hp cylinders had Trick valves with double admission and the lp cylinders had Willoteaux valves with double admission and double exhaust. At 62.4mph (100km/h) and developing a drawbar hp of 4000 coal consumption was 2.641b/hr (1.197kg/h) and water 14.31b/hp/hr (6.486kg/hp/h). For a Stanier Pacific on BR at 60mph (96.6km/h) developing 825dbhp the amounts were 3.031b/hr (1.375kg/h) and 251b/hp/hr (11.34kg/hp/h). The failure to preserve 242 A.1 was one of the greatest tragedies in locomotive history: it was scrapped in 1960.
Many honours were awarded to Chapelon.: in July.1934 he was appointed Chevalier of the Legion of Honour and in the same year was awarded the Plumey Prize of the Academie des Sciences and the Gold Medal of the Société d'Encouragement pour l'Industrie Nationale. Various other medals and awards followed, in 1938 he published his great book La Locomotive d Vapeur (revised edn 1952). Chapelon's principles influenced other steam locomotive engineerss throughout the world, particularly Gresley on the LNER, and engineers in Brazil and Argentina. He died on 22 July 1978..
Book: originally published in 1938
La locomotive à vapeur with preface by
Édouard Sauvage. 2nd French ed;. translated into English by George
W. Carpenter. Bath: Camden Miniature Steam Services, 2000. x, 631 p., 
p. plates : illus. (some col.)
Details from BLPC
Article by or about in Rly Gaz., 1937 (May)
Mentions Willoteaux valves
Patents (United Kingdom only)
683,976. Improvements in steam distributors for steam engines. Applied 17 July 1950. Published 10 December 1952.
276,369. An improved device for increasing the draught in steam boilers. Applied 22 July 1927. Published 22 November 1928.
276,368. An improved device for increasing the draught in steam boilers. Applied 22 July 1927. Published 16 February 1928
H.C.B., Chapelon, Genius of French Steam, 1972.
Cox, E. S., World Steam in the Twentieth Century 1969;
H.M. Le Fleming (Concise encyclopaedia).
van Riemsdijk, J.T. Compound locomotives: an International survey. Penryn: Atlantic Press, 1994. 140pp.
Chapter 12: Chapelon begins: "Chapelon was the most influential thinker in the field of locomotive design in the twentieth century and produced designs were unsurpassed anywhere."
Glancey, Jonathan. Giants of steam. 2012.
A good journalist's book and by someone capable of seeking out information from the right people: in the case of Chapelon nobody could have been better than George Carpenter, surely the steam locomotive's last oracle.
Vuillet, Gerard, R Reminiscences of three Continents 1968;
SLS Journal 7/9/11.1970
Livesey, E. H. 'Andre Chapelon and the steam loco', Engineer, 200 1955 p 140
Andre Chapelon. H.C.B. Rogers. Rly Wld, 1978, 39, 488
Obituary, Born in St Paul en Cornillon on 26 October 1892. Died 29 June 1978. As well as outlining his enginneering achievements notes that André Chapelon was modest, kindly, humourous and very religious.
Rutherford, Michael. Express eight coupled
some notes on the Gresley 2-8-2 and Chapelon 4-8-0. (Railway Reflections
No.126). Backtrack, 2005,
"The most remarkable British express locomotive introduced in the period was undoubtedly the London & North Eastern Railway 2-8-2 No. 2001 Cock o' the North and in France (and perhaps the world) André Chapelon's 4-8- No. 4521 for the Paris-Orléans system..." In the case of the British design, the author also considers Gresley's two P1 freight 2-8-2s which were based upon the A1 Pacific boiler and front end and No. 10000 (mainly from the point of view of styling, and of Chapelon's Kylchap exhaust system which reduced back pressure in the cylinders. Sometime between 1941 and 1943 Kevin watched in awe as the streamlined Cock o' the North pulled into Dundee Tay Bridge: it remains his most memorable experience of any steam locomotive. Thus this abstract is bound to be biased, although he is well aware that Norman McKillop, who drove the mighty beasts, had reservations about them, but they matched the mighty Forth Bridge in a way that most of the buses on steel wheels fail to do. Illus.: first Chapelon 4-8-0, rebuild of PO Pacific No 4521; second P2 No 2002 Earl Marischal; weight diagrams of Chapelon 4521 4-8-0 and Cock o' the North; 240P.4-8-3 locomotives with greater style. Sequel in Volume 21 page 44 et seq.
Rutherford, Michael The twentieth century steam
locomotive. Was there any progress? Part 3. Railway Reflections No. 82.
Backtrack, 2001, 15,
Part 1 was on page 468; Part 2 page 494: Further evidence for progress: André Chapelon's contributions: Kylchap double chimney reduced back pressue in exhaust, higher superheat could be achieved with Houlet elements given better lubricants and poppet valves. Enlarged steam pipes reduced throttling. Thermic syphons increased circulation and evaporation. These features were applied to a Paris Orleans Pacific 3566 and vastly improved performance. Many of the ideas were incoroprated in Cock o' the North which Rutherford regarded as a near miss. In 1910 SLM manufactured Pacifics for the 3ft 6in line in Java between what was then Batavia and Surabaya and these four-cylinder compounds and 29ft2 grates enabled journey times to be halved. Very high speeds for the gauge were attained. Rutherford correctly queries why such designs could not have been constructed in the 1920s for railways in Britain. Super power in the USA originated under William E. Woodward. A 2-8-2 No. 8000 was built for the Michigan Central in 1922: it featured a booster, a very large superheater, feed-water heater, mechanical stoker, free steaming and light reciprocating parts. Alco's eventual response was the 2-8-4 Berkshire type with 100 ft2 grate and vanadium steel cyclinders to save weight. The development of the trailing truck enables the 4-6-4 and 4-8-4 types to be constructed. Gresley derived motion was used on some of Alco's output. Timken had to fight hard to get roller bearings installed and this was achieved via Alco demonstrator No. 1111. This led the way for the high speed Mallets developed on the Union Pacific by Otto Jabelmann. Rutherford argues that the Duplex 4-4-4-4 on the Pennsylvania Railroad were the "fastest steam locomotives of all time". In Britain the Castles were "little more than Churchward's Stars slighly enlarged", but they influenced the output from all the other companies. The great success of the Duchess Pacific class is noted, and especially its lack of major components in common with the Princess Royals.