In 1932, the Belgian firm of Ateliers Métallurgiques in Tubize built the world's only Quadruplex locomotive with the assistance of the Italian Attilo Franco. Its special design was not only to increase power, but also to increase efficiency. It was much larger than anything the Belgian Railways needed, but was used as a prototype for a planned compound hexaplex locomotive for the Soviet Railways that was even larger, but never realized.
The locomotive consisted of three sections called A, B and C. The middle B section housed a special double boiler that had two central fireboxes. These were located side by side, were each fired by one fireman and had their own coal bunker. Each end of this section had a cab since the locomotive was way too long to use turntables.
Locomotive Magazine, August 1933
The A and C sections contained large Franco feedwater heaters which were encased by the water tanks. The chimneys were on the extreme ends of these sections since the hot gases only escaped to the atmosphere after passing through the feedwater heater. A part of the hot gases was ducted to the grates to mix with the cold air.
A total of ten driving axles were powered by four pairs of two cylinders each. The B section had two pairs of two driving axles, with carrying axles at the ends and one in the middle. The A and C sections had three driving axles and one trailing axle. This led to the wheel arrangement 0-6-2+2-4-2-4-2+2-6-0T. With this arrangement, the locomotive could pull 1,200 tonnes on an incline of 1.6 percent. Additionally, it was found to have a low specific consumption.
After the trials, the locomotive with the builder's number 2096 was shown on the Brussels exhibition in 1935 and then withdrawn. In 1943, it was split in half and rebuilt to two 0-6-2+2-6-2T locomotives by adding an additional driving axle below the half of the old B section. After getting to Germany in 1944, they were used in a shipyard. When the war ended, the Soviets brought them to two different locations in Poland where they were used for a few years.