The NZR RM class Midland railcar (or Leyland diesel railcar) was the first successful railcar, 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. They operated primarily on the Midland Line and the Greymouth-Hokitika portion of the Ross Branch
These kinds of vehicles were known in some other countries by a variety of other names, including "railbuses" and "railmotors". However, such self-propelled passenger vehicles were known in New Zealand as "railcars" from the late-1920s onwards.
Background
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.
Technical specifications
The Midland railcar used the chassis of a Leyland Tiger bus, though once its body was constructed it did not look like a bus. It had four wheels, was long, and weighed unladen. Power was provided by a Leyland diesel engine that could produce up to at 1,950 rpm and propel the railbus at speeds of up to . Electric lighting and thermostatically controlled hot air radiators were both fitted. Up to 19 passengers could be carried, though with a full load of of newspapers this was reduced to 8 passengers.
Initially, the two railcars had one technical difference: RM 20 was built with a four-speed manual gearbox, while RM 21 utilised a fluid torque converter. Three months after services began, RM 20 was also fitted with a fluid torque converter.
Trials
A 320 km (200-mile) trial run of RM 20 was undertaken in the Wellington area on Saturday 25 July 1936 and included a climb up to Pukerua Bay on the 1 in 57 grade. Its performance was considered "exceptionally good" and the car "flew like a bird" up the steepest grades. The all-round view that passengers had of the surrounding countryside from the front half of the railcar was favourably commented on by passengers, as was the very quiet running of the engine.
The first of the two railcars, RM 20, was taken from Wellington to Lyttelton on the deck of the steamer Waipiata on 29 July 1936.
The first trial run of RM 20 in the South Island was on 30 July 1936 from Christchurch to Hokitika and return – a distance of 547 km (340 miles) in 9 hours 26 minutes running time (an average speed of 58 km/h (36 mph)), despite the motor not having been run in. Another trial run from Christchurch to Timaru on 31 July 1936 demonstrated that the railcars could cover a distance of 164 km (102 miles) in 2 hours 8 minutes at an average speed of 77 km/h (48 mph). The speed of the vehicle surpassed the expectations of all Railways Department experts, according to the general manager, Garnet Mackley.
RM 20 entered service on Wednesday 5 August 1936, two days later than earlier announcements but less than two weeks after its first trial run.