The express locomotives of the class 01 were the first standard locomotives that the Reichsbahn purchased from 1925. These were two-cylinder Pacific locomotives. In contrast to the sister class 03 developed later, it had an axle load of 20 tonnes. This made a greater output possible, but limited service to the few lines which had already been upgraded at the time. Before series production began, a comparison was made with the otherwise almost identical class 02 with a four-cylinder compound engine, which the 01 was able to win.
Here, the features which all standard locomotives later had in common could be found for the first time. In part, modern advances in steam locomotive design were ignored to allow for a simpler, standardized design. These included the abandonment of a combustion chamber and using two- and three-cylinder engines with simple steam expansion instead of compound engines. Due to the boiler without a combustion chamber, the tubes were 6,800 mm long, which led to stresses in the material under heavy loads. These problems were also encountered with other large standard locomotives and they were only solved after the war when new boilers with a combustion chamber and thus shorter tubes were installed.
At the front, the large Wagner smoke deflectors and skirts were used, which led to a characteristic appearance. The top speed was initially 120 km/h, but was increased from 01 102 to 130 km/h by increasing the diameter of the front wheels from 850 to 1,000 mm and strengthening the brakes. The first batch used the shorter 2'2 T 30 tender with ten tonnes of coal and 30 cubic meters of water as a tender. Later the 2'2 T 32 was used with the same amount of coal and 32 cubic meters of water and over the years many machines were given the 2'2 T 34 from the class 44.
Series production in larger numbers did not begin until 1930, but a total of 231 had been built by 1938 and another ten were created from the rebuilding of the prototypes of the class 02. After the war, the 01 remained a very important flagship for express trains for both German railways for a long time. However, their condition made some modifications necessary, which were carried out on both sides. At the Bundesbahn they mainly received welded boilers with a combustion chamber, and at the Reichsbahn the changes were much more extensive. The resulting class 015 will be described in a separate article. The latter remained in use until 1982, while the withdrawal in the Bundesbahn was completed in 1973.
