When "Heinrich" / "Henry" was still smaller ... Coal is a bulk freight that has traditionally been conveyed by rail. In the Thirties it was domestic coal that had to be transported from the coalfields in Germany. To the extent that the areas of demand were not on the major main lines, the axle loads for transport on branch lines were limited. For that reason small, short freight cars were used for a long time – similar to in England – that spread the load over many axles. This meant that the black gold could be brought with trans-loading from the sidings for the coal mine to the industrial siding at the boiler house or to the siding for the fuel dealer. Typical for these cars were the car types "Schwerin" and "Nürnberg" with a load limit each of 15 metric tons. Around 40,000 of these cars were available for use on the DRG around 1930. The locomotives had to fulfill corresponding requirements for this work: powerful motive power with a low axle load. This was exactly the design of the class 50 as a lightweight freight locomotive. With an axle load of 15 metric tons and 5 powered axles, this locomotive reached a starting tractive effort of around 16 metric tons (160 kilonewtons). On flat terrain it could confidently master a typical heavy coal train with 30 cars and 700 metric tons. The track network had to be expanded first before the "Lange Heinrich" / "Long Henry" could grow to its full size: load capacity, block length, and safety equipment were not sufficient for a 4,000 metric ton train until the DB era.