The T 26 was a rack tank locomotive that was used in various regions of Prussia. It was intended for routes such as those found on the slopes of the Rhine or in the Thuringian Forest. The gradients of sometimes more than 6 percent could only be overcome with the help of a rack. The first three pieces came from the Esslingen machine factory, but the remaining 32 were built by Borsig on their own territory.
The Abt rack system was used on these routes, which used two racks with offset teeth for better guidance and smooth running. Thus, the locomotives also had gears with two rows that were toothed alternately. This ensured that a tooth was engaged in the rack at all times.
In adhesion operation, the T 26 had three coupled axles and a trailing axle and could thus reach 45 km/h. When operating on the rack, two gear axles were used, the drive of which was separate from the coupled axles. The wheels were driven by two outer cylinders and the gears by two inner cylinders. Due to the reduced speed in rack operation to 15 or 20 km/h, the inner drive could be designed differently in order to achieve more traction.
Production of the T 26 ran until 1921 and two years later the locomotives were classified as class 970 when they were taken over by the Reichsbahn. During this time, however, the T 16.1 (class 945-17) and T 20 (class 95) were already being procured. Due to the cheaper operation of these two new locomotives, the last 970 were retired from the Reichsbahn in 1932. Seven pieces were sold to private and works railways and remained in service until the 1960s, but with the cogwheel drive removed.
