Drewry 1936 0-4-0 diesel mechanical shunting locomotive, providing good motive power for site shunting and works trains. 40 horse-power. Powered by a 4-cylinder General Motors Detroit 2-stroke diesel engine, model 4081, unit number 4A 100246 with a maximum RPM No Load of 1920. An example of the smallest diesel mechanical locomotive, commonly used in various railway yards throughout New Zealand.
Tr 21 was built by The English Electric Company at its Dick Kerr Works in Preston and exported to New Zealand through their agents, The Drewry Car Company Limited. It was received by New Zealand Railways on the 31st of March 1939 and went into service in June/July of that year. Records show that the locomotive was allocated to Dunedin's Way & Works branch and it was one of two used on the re-alignment of the South Island Main Trunk around Sawyers Bay, before being stationed at Blenheim in January 1950. It was then loaned Frankton Goods from 1955 to 1958, and then withdrawn from service due to the condition of the original petrol engine which was obsolete and generally run down. The engine was subsequently sent to Plant Zone, East Town where it was replaced with a GM 4081 diesel engine and an Alison torque converter. It reentered service and was in Greymouth in 1960 at Elmer Lane - Roundhouse and then moved to Paeroa in November 1969 where it ran No.27 shunting service to Thames. The last allocation was with the Station Master at Mangapehi, as at September 1972. It was re-numbered Tr 85 under the TMS system. It is typical of many small diesel and petrol shunting locomotives used extensively throughout the country from the 1920s and was known as a "Baby Drewry". It is operational on the Western Springs Railway.
The Drewry Car Company Limited. 1938. Locomotive [Diesel (Tr 21)], F1002.2002. The Museum of Transport and Technology (MOTAT).