Léon Serpollet

Léon Serpollet was born in Culoz, in the Ain department of France in 1859, son of the carpenter Auguste Serpollet. He went into the family business with his brother Henri (1848–1915) producing circular saws and wood working machines. It was when seeking to power their workshops that Henri came up with the idea of flash steam generation, with a patent applied for on 25 October 1879.

Leon went to Paris to study engineering at the Conservatoire national des arts et métiers, and at the same time he continued to develop the flash steam concept with his brother by post. In 1886 the two brothers arrived at their best design of flash steam boiler, and then shortly afterwards they went into business building flash steam boilers, initially small scale to power lighting systems and pumps, but soon to power tricycles and steam boats, and eventually to cars, trams, and buses.

Not only was Léon Serpollet a talented engineer, but he also drove his own cars in various races and rallies, for in the first years of the 20th century his steam cars were faster than any internal combustion engine cars, as he proved when he took the world land speed record in 1902 at Nice promenade at 120.80 km/h.

Serpollet's steam cars meant he had contact with many distinguished customers, including the future King Edward VII, the Maharajah of Mysore, and the Shah of Persia - Mozaffar ad-Din Shah Qajar, who in 1900 conferred on him the Order of the Lion and the Sun. In 1900 he was made a Chevalier of the Legion of Honour.

Leon Serpollet died aged 48 of a 'malignant disease', and with his passing the interest in steam cars seemed to wane, especially in France, there were no steam cars on show at the Paris Salon automobile show of 1908. His influence on the automotive industry had been substantial as stated in many obituaries, for example "The death of M. Leon Serpollet has removed from our midst a pioneer in the motor industry, whose genius in the cause of automobilism can only be compared to that of Stephenson for the locomotive"...."The death of M. Serpollet is a heavy loss to the industry." In another obituary "M. Serpollet's name has been for a score of years as well known in the world of the steam motor-car as is that of Marquis de Dion in the region of internal combustion vehicles".

Léon Serpollet is commemorated by a statue by Jean Boucher at the Place Saint-Ferdinand (48°52′41″N 2°17′17″E / 48.877969°N 2.288112°E) in Paris' 17th arrondissement, and the Parc Léon Serpollet (48°53′32″N 2°20′18″E / 48.89228°N 2.33831°E) in its 18th arrondissement.

Serpollet frères et Cie

In 1886 Leon teamed up with an industrialist, Larsonneau, an enthusiastic partner who helps him to create "Serpollet frères et Cie" and to open workshops on rue des Cloÿs in Paris, in the 18th district, a location that has become the Parc Léon Serpollet today. Léon continued to revise and develop the flash steam boiler design changing it from flat plates to tubes, which led to further patents (e.g. CH1038 1889, CH7958 1894, CH12280 1896). Léon's engineering talents had been spotted by Armand Peugeot who provided the firm with financial support. Serpollet then used his flash boiler to create a steam powered tricycle, which was exhibited by Peugeot at the 1889 World's Fair in Paris. Peugeot produced several of the steam tricycles under licence, now known as the Peugeot Type 1.

In the 1890s Léon Serpollet was involved in applying his flash steam boiler to tramcars. In January 1897 he entertained a deputation from Aberdeen at his depot in Willesden, London, where he displayed a 4-seater Phaeton, and a double-decker steam tramcar for 50 people running on a test track. A report in 1897 on the Paris Tramway system stated that 60 Serpollet trams were in use, and another 40 were to be added over the next few months.

The key characteristics of flash steam boilers stem from the fact that there is very little water in the boiler at any moment, which leads to fast startup, and minimal explosion risk - they also provide high steam pressures and temperatures which can give high thermal efficiency, but were not ideal for the steam engines of the time. In addition flash boilers needed a sophisticated control system to ensure the water injected to the boiler and the heat from the burner matched, and that the steam produced matched the demand of the engine. In addition to the control system, Léon also had to devise a better steam engine design suited to very high pressure steam, using poppet valves the actuation of which presents a problem with providing the variable cut-off needed to allow steam to work expansively. Numerous Serpollet patents in different countries cover the inventions designed to overcome these difficulties (e.g. CH12280 30 May 1896, GB190005128 17 Mar 1900, US680000 6 Aug 1901). The solution was to use a form of variable valve timing, where the camshaft moved along its axis and so changed the cam profile driving the valve movements - this arrangement also allowing the Serpollet engine to be reversed.