Prussian T 15

The T 15 was developed to replace the six-coupled locomotives that had reached their limits on the mountain lines in Thuringia and Silesia. The list of requirements included that a load of 200 tonnes could still be hauled at a speed of at least 15 km/h on inclines of 3.3 percent and curve radii of 200 meters. Significantly more power was required in the tight corners than would have been necessary for the same incline on the straight.

In order to achieve the necessary ability to negotiate curves, an unusual, split chassis with only one common pair of cylinders was used. The front three coupled axles sat firmly in the frame and were driven like a conventional six-coupled. The two rear axles sat in a bogie and were driven by the front coupling rods via a lever system. Although this design involved greater maintenance, the locomotives were able to live up to expectations.

The design came from the Christian Hagans machine factory in Erfurt and was ready for series production in 1897. Since they usually produced smaller locomotives there and did not have the sufficient capacity for larger numbers of a locomotive of these dimensions, production was handed over to Henschel. Thus, between 1897 and 1905, a total of 92 locomotives of this type were created. At about the same time, 29 of the four-axle T 13 of the Hagans design were also manufactured by Henschel.

With the idea of simplifying the engine, Professor Otto Koechy later developed the design named after him, which reduced the number of components through a design with rocker arms. Despite the practical approach, only one example of this design was made, since the more powerful T 16 with the much simpler chassis of the Gölsdorf design was already being produced from 1905.

Due to the superiority of the T 16, the T 15 could not achieve a very long service life. None of them received a Reichsbahn number, as they were all retired by 1923. The one-off continued to be used, but was withdrawn in 1922 at about the same time as its sisters.