Diesel locomotive Therefore, diesel traction became economical for shunting before it became economical for hauling trains. The construction of diesel shunters began in 1920 in France, in 1925 in Denmark, in 1926 in the Netherlands, and in 1927 in Germany. After few years of testing, hundreds of units were produced within a decade. Diesel-powered or "oil-engined" railcars, generally diesel–mechanical, were developed by various European manufacturers in the 1930s, e.g. by William Beardmore and Company for the Canadian National Railways (the Beardmore Tornado engine was subsequently used in the R101 airship). Some of those series for regional traffic were begun with gasoline motors
Diesel locomotive accounted for 25% of the initial purchase price. Spare parts were cast from wooden masters for specific locomotives. The sheer number of unique steam locomotives meant that there was no feasible way for spare-part inventories to be maintained. With diesel locomotives spare parts could be mass-produced and held in stock ready for use and many parts and sub-assemblies could be standardized across an operator's fleet using different models of locomotive from the same builder. Modern diesel locomotives are designed to allow the power assemblies the be replaced, which greatly reduces the time that a locomotive is out of revenue-generating service