Paris-Lyon-Mediterrannee 2-10-2 Locomotives in France

Class Class 151.A (Locobase 2503)

Data from MRS French Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange and Reder (1974).

Compound tractive effort given in specs based on 1924 ARA formula.

Unusual valve gear highlights this big compound-expansion freight locomotive. All four cylinders were fitted outside, the large LP cylinders just behind the pony truck and driving the second axle, the HP cylinders farther back driving the last axle. This arrangement has sometimes been described in Whyte terms as a 2-4-6-2, but, unlike the Pennsy duplexes or traditional Mallets, the two engine sets were coupled between the 2 and 3 axles. Each of these axles was cranked and joined by a coupling rod inside the frames. Thus, from the outside, they looked like duplexes, but all five driving axles were synchronized.

The Dabeg poppet valves were operated by slender shafts driven off the second axle. Also fitted with a Kylchap blast pipe.

Trials included a 2,599-ton train pull between Lens and Le Bourget at 33.5 mph (53.5 km/h) . Clearly, that was a maximum effort because in normal service they were rated at 1,250 ton at 31 mph (50 km/h) between Laroche and Dijon.

This design was not repeated after the SNCF was formed, although the class remained in service after World War II.