Prussian tank locomotive 78 510

The class 78 was a versatile steam locomotive used for both freight and passenger services, including express trains.

The locomotives, almost all of which were built by the Vulcan works in Stettin (now Szczecin, Poland), had a special technical feature: their axle load was adjustable. For routes with steep gradients, where greater friction between rail and locomotive was desirable, load on the drive axles could be increased to 17 tonnes. For lines with a maximum axle load of 16 tonnes, the locomotive could be adjusted accordingly. This was achieved by transferring the weight using adjustable springs on the non-driving wheelsets.

Their versatility made the class T 18s very popular. Originally, they were only requested by the Mainz and Stettin railway divisions. Soon, however, other divisions began to procure the locomotives. Between 1912 and 1927, the Vulcan works delivered no fewer than 458 class T 18 tank engines to the Prussian state railway and Deutsche Reichsbahn.