French State Railway 232 U

The 232 U 1 was one of the eight streamlined 4-6-4 locomotives designed by Marc de Caso from 1938 for the Nord. While the others were built with conventional cylinders, the eighth one was originally planned to be powered by a steam turbine. Its construction was started by SACM at Graffenstaden, but interrupted by World War II. After the war, the design was changed to a four-cylinder compound and the frames were passed on to Corpet-Louvet for further assembly. It was only completed in 1949 and assigned to the new class 232 U due to changes compared to the 232 S.

The diameter of the high pressure cylinders was nine millimeters less and instead of rotating cam shafts, it had conventional Walschaerts valve gear. Additionally, all axles ran in SKF roller bearings. The boilers of all three types were basically the same. They were operated at 20 bars and featured a ACFI feed water heater and two Thermix injectors. As six-axle tenders would have been too long, they had tenders with four axles, equipped with a stoker and carrying 36 m³ of water and 11.5 tonnes of coal. Indicated power is usually been given as 3,400 hp, but there are also claims of 4,000 hp. 

The 232 U 1 was nicknamed “la Divine” and used in express service on the Paris-Lille line, together with the three 232 R and four 232 S. There it managed to haul 576 tonnes with an average speed of 114.25 km/h. All were approved for 140 km/h, although more would have been technically possible. Like the others, the 232 U 1 had an axle load of 23 tonnes, prohibiting the use on many lines. Like its sisters, it was withdrawn in 1961 and replaced by electric locomotives. Today it is on display at the Cité du Train in Mulhouse, Alsace.