Einheitsdampflokomotive
This considerably hindered the flexible employment of locomotives within the railway network, and servicing and maintenance was very costly as a result of the large number of different spare parts that had to be stocked.
On top of that, substantial reparations as a result of the First World War, 1914–18, considerably reduced the rolling stock of the German railways without regard to the variety of classes.
Initially the question was posed as to whether proven state railway classes should continue to be built or whether new, modern locomotives should be developed and ordered.
The Prussian G 12 (Class 58.10), which was not developed until 1917, effectively counted as the first German Einheitslok, because it was employed by almost all the state railways and built by several locomotive factories across the whole Reich.
Technical and economic factors, as well as the Reichsbahn's aim of improving main lines to handle a standard axle load of 20 tons, led to the decision to develop new types of locomotive.
Playing a decisive role in these discussions was the head of the Grunewald Locomotive Research Office at that time, Richard Paul Wagner.
In fact the production of engines in the desired quantities could not be achieved at first, both for economic reasons and due to delays in the improvement of routes to take the higher axle loads.
In spite of the Deutsche Reichsbahn's ambitious plans, their actual acquisition of locomotives, even from 1925 onwards, only reached about one tenth of the average procurement quantities for the years 1914-1920 and it remained at this level until 1938.
To meet the increasing demands in performance on the newer engines, a larger boiler was required, for which there was not enough room for the high-sided plate frame.
The use of individual components or systems such as, for example, the boiler, the carrying bogies, etc., for as many classes as possible, enabled considerable savings to be achieved in construction, in repair and in the stocks of spares parts needed.
The Reichsbahn tried to have the fewest possible number of locomotive classes in operation and to make maximum use of the permitted axle loads, which were dependent on the type of track bed.
As a result, after 1925, the DRG Class 01, two-cylinder, express train locomotive emerged first, with a power of about 2,200 PS and 4-6-2 wheel arrangement.
It was intended to relieve the DRG Class 17s, that consisted mainly of Prussian S 10s, Saxon XII Hs and Bavarian S 3/5s with their four-cylinder, superheated, compound configuration and 4-6-0 wheel arrangement.
For branch line operations, the 2-6-0 Class 24 passenger train locomotive was developed in 1926 with an axle load of 15 tons and 920 PS.
That put it within the range of light express train duties, for which it was often used e.g. on the Thuringian Forest lines (e.g. to Meiningen from Arnstadt and Eisenach).
Other engines built to standard designs, albeit in smaller numbers, appeared from 1936 in the shape of the heavy and especially powerful 2-10-2 Class 45 goods train locomotives.
The ten-coupled Class 87 engines with their two Luttermöller cogwheel axles were built for operations on the very tight curves of Hamburg Harbour's railways.
The construction principles used for standard locomotives were also used for newly built narrow gauge engines in order to reduce the cost of servicing and maintenance.
