NZR RM class (Leyland diesel)
| NZR RM class Midland |
|
|---|---|
| In service | 1936–1941 |
| Manufacturer | New Zealand Railways |
| Built at | Hutt Workshops |
| Constructed | 1936 |
| Entered service | 3 August 1936 |
| Scrapped | 1942 |
| Number built | 2 |
| Number in service | None |
| Number preserved | None |
| Fleet numbers | RM 20 and RM 21 |
| Capacity | 19 passengers; or 8 passengers and 1 ton newspapers |
| Operator(s) | New Zealand Railways |
| Line(s) served | Midland Line, Hokitika Branch, Stillwater–Westport Line |
| Specifications | |
| Car length | 26 ft 1 in (7.95 m) overall |
| Width | 8 ft 9.5 in (2.68 m) |
| Maximum speed | 60 mph (97 km/h) |
| Weight | 7.81 long tons (7.94 tonnes; 8.75 short tons) |
| Prime mover(s) |
Leyland 8.6 litre (525 cu) 6-cylinder diesel engine |
| Power output | 98 hp (73 kW) |
| Transmission | Lysholm-Smith Fluid Torque Converter |
| UIC classification | 1-A |
| Track gauge | 3 ft 6 in (1,067 mm) |
The NZR RM class Midland rail motor (or Leyland diesel railcar) was the first successful rail motor, and first diesel-powered vehicle, to enter revenue service in New Zealand. Two were built, RM 20 and RM 21, and they ran for five years from 1936 to 1941 before being replaced by larger Vulcan railcars. Due to their diminutive and lightweight design, they are sometimes called "railbuses" rather than railcars. They operated primarily on the Midland Line and the Greymouth-Hokitika portion of the Ross Branch.
The New Zealand Railways Department (NZR) had been looking for an economic means of handling regional and rural passenger traffic for over two decades. Branch lines in rural New Zealand were typically operated by mixed trains that carried both passengers and goods, and their schedules were usually slow due to the loading and unloading of freight that occurred during the journey. This slowness made them unpopular with travellers, but insufficient demand existed to justify a dedicated passenger service. Secondary main lines in regional districts often had their own passenger trains, but these were often uneconomic, especially as car ownership and bus competition rose in the 1920s and 1930s. Thus, NZR investigated railcars as an alternate means of providing an attractive passenger service without the expenditure and costs associated with a locomotive-hauled carriage train.
The first experiment with railcars took place in 1912 with a MacEwan-Pratt petrol railcar, and while it was not a success, further research and development was undertaken in the following years. By 1936, no design had proven successful enough to warrant construction of a whole class, though an Edison battery-electric railcar built in 1926 had proved efficient and popular until it was destroyed by fire in 1934.
In 1936, NZR and a newspaper company were looking into the development of a railcar to provide quick conveyance of both passengers and Christchurch Press newspapers from Christchurch to Westland: although long-term prospects for large railcars existed, a more immediate solution was required. For this experiment, NZR utilised a diesel-engined Leyland bus chassis to create a small railbus. Two were built at Hutt Workshops in Petone and entered revenue service in the South Island.
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