French State Railway 232 R

In the 1930s, the Nord was planning a new express locomotive that, due to its size, should achieve lower operating costs with longer trains and should also ideally be suitable for the speed range between 160 and 200 km/h. In order to be able to determine the ideal cylinder arrangement, Marc de Caso developed the 232 R with a simple three-cylinder engine and the 232 S with a four-cylinder compound engine. Due to the founding of the SNCF, the program was postponed and the three 232 R were therefore only delivered in 1940.

The wheel arrangement chosen was 4-6-4 since it was possible to use a boiler of the same size as a 4-8-2 and at the same time take over large chassis parts from a 4-6-2 and replace the trailing axle with a bogie. A streamlined fairing was necessary in order to be able to reach the required speeds. The boiler was operated at a relatively high pressure of 20 bars. Otherwise, the locomotives had a Lemaître blast pipe, an ACFI feed water heater and modern injectors. The tender was basically designed for 38 m³ of water, but could only hold 36 m³ with the built-in stoker. On an incline of 0.4 percent, they could haul 685 tonnes at 113.5 km/h, which corresponded to an output at the drawbar of 2,615 hp. 

The tractive effort calculated from the cylinders is more of a theoretical value that could only hardly be achieved under real conditions. The practical factor of adhesion for three-cylinder locomotives is usually given as 3.5, but it is 2.65 here. Thus, depending on the condition of the rails, there will have been a strong tendency to slip. If one takes the value 3.5 as a basis, one gets a realistic tractive effort of 193 kN or 43,400 pounds. The three locomotives were tested on the Paris-Lille line with regular trains. Due to the war, their power could not be fully exploited and they were only approved for 140 km/h. Two locomotives were retired in 1958 and the third in 1961.