German Reichsbahn E 21⁰

The E 21⁰ included two of the five electric express locomotives that were procured between 1926 and 1928 to test the single-axle drive (see E 15). In contrast to the E 15 and E 16, these, like the E 21 51, had seven axles. It was the asymmetrical wheel arrangement 2-D-1 and also an asymmetrical body. Each of the four axles mounted directly in the main frame was driven by two motors, which passed on their power via a helical-spring gear. This was a form of quill drive in which the spokes were cushioned relative to the hollow shaft. This reduced both the bumps from the tracks and the jerky changes in torque when starting off.

At one end of the locomotive, the body formed a flush finish and underneath was a two-axle bogie. At the other end there was a half-height hood in front of the cab and a single carrying axle. On the E 21 01 this was still designed as an individually movable Bissel axle, but on the E 21 02 it was combined with the adjacent driving axle to form a Krauss-Helmholtz bogie, which improved the running characteristics in curves.

Test drives showed that even the first locomotive was significantly more powerful than the specifications had envisaged. A speed of 95 km/h could be reached on the flat with express trains of up to 1,905 tonnes, which was more than three times the required weight. It could reach its top speed of 110 km/h with trains of up to 1,050 tonnes, which was still much heavier than most express trains.

The second was ordered while the first model was being tested. After testing, both went into regular service in the Giant Mountains and stayed there until the end of the war. They then came to the Soviet Union as reparations until they returned in 1952 and 1953 and were temporarily parked. After around seven years of service, they were refurbished by the Reichsbahn, but were only used occasionally in the years that followed. A few years later, enough new electric locomotives had been delivered, which meant that not only the old machines with rod drives became superfluous, but also small classes with single-axle drives. Both were parked again in 1965, officially retired in 1966 and finally scrapped in 1967.