For the cost-effective use of passenger trains on routes with low passenger volumes, the Royal Bavarian State Railways developed a locomotive that reached sufficient speed in both directions and could be operated by one man. The solution was a tank locomotive with a 2-4-2T wheel arrangement, which had a tipping device for loading the firebox with coal.
Second variant (No. 5011 to 5012)
Die Lokomotive, October 1908
Thanks to superheated steam, it achieved adequate power and the coupling wheel diameter of 1,546 mm ensured a good compromise between tractive power and speed. There was a gangway from the driver's cab to the train and the front platform could also be reached via running boards with railings. The water tanks were designed to be narrower than the locomotive so as not to block the way.
Schematical drawing of the first version
Die Lokomotive, September 1906
A special feature of the chassis was that the first coupled axle was in a Krauss-Helmholtz bogie together with the leading axle, although there were only two coupled axles. This resulted in a fixed wheelbase of zero with very good curve guidance at the same time. The top speed was initially set at 75 km/h and later increased to 80 km/h. According to reports, however, they regularly ran in both directions at up to 90 km/h.
Twelve pieces were made, some of which differed from one another in several aspects. The Reichsbahn took over all of these and classified them as class 712. Some examples survived the Second World War and were used until 1948.