Steam Train Engines
31, Jul, 2010

French National Railways No. 232.U1

Written by steamtrainengines.com   

Shortly before the outbreak of war in 1939, the Northern Region of the French National Railways (S.N.C.F.) placed in service seven 4-6-4 express locomotives designed by Monsieur de Caso and designated Classes ' R ' and ' S.' The eighth engine was to have been a Lungstrom turbine, but due to the war this was never carried out and the locomotive entered service after the war as a modified Class ' S ' 4-cylinder compound numbered 232.U1.

Ul may be regarded as the last word in French steam locomotive design, and probably the most advanced steam engine in the world. Basically it is a de Glehn compound with the difference that the high-pressure cylinders are between the frames; for ease of maintenance the Dabeg poppet valves of the other 4-cylinder compounds were omitted and Walschaerts valve gear, with a conjugated drive to the inside cylinders, was employed.

French National Railways No. 232.U1Also, unlike most compound engines in France, the respective cut-offs were not independently variable; they remained at a fixed ratio. However, through a system of servomotors and air-operated regulators, the locomotive started as a 4-cylinder simple and automatically changeg over to compound working as speed was gained.

Other refinements included a Standard 3-jet stoker, feed water heater, roller bearings on all axles, brakes on bogie and trailing wheels, and self-adjusting axleboxes; the latter, combined with equalized springing, assured magnificently smooth riding.

232.Ul spent her entire life based at La Chapelle depot in Paris, working high-speed expresses north to Aulnoye and Lille; after these services were taken over by electric traction, Ul was scheduled for museum preservation.