In 1933, Leyland Motors Ltd were asked to construct a diesel rail coach by the London Midland and Scottish Railway Company. Three four wheeled rail cars numbered 29950 , 29951 , 29952 were built to lot number 760. Their appearance gave away their bus heritage and the lightweight construction mirrored bus construction of the same era.
The rail coach had an overall length of 41 ft 1 in., a width of 9 ft, and a height of 10 ft 7 in. The tare weight was 10.5 tons with a fully laden weight of 13.1 tons. The two-axle coach had one axle power driven from a high speed Leyland diesel engine which developed 130 horse power operating through a torque converter.
The engine was mounted in the middle part of the underframe, and the torque converter was built integrally with the engine. The torque converter consisted of a centrifugal pump, mounted in a single casing, with a three stage hydraulic turbine.
This unit multiplied the engine torque and varied it automatically in accordance with the speed required by the operational conditions. The driver, therefore, was only concerned with regulating the speed of the unit. The torque converter replaced the convential gearbox, all speeds required being automatically given.
From the torque convertor the power was transmitted via a propeller shaft through a reversing gear, which was mounted in the casing of the drive axle, spiral bevel pinion wheels being used to take the drive from the propeller shaft to the axle.
The reversing gear mechanism was actuated through a double-acting vacuum cylinder, controlled by magnetic valves, which were operated from a switch on the driver's control panel.
The units were relatively smooth running with good acceleration, and could attain a speed of 20 m.p.h. from stationary in 11 seconds, reaching 50 m.p.h. in 49 seconds.
They had a top speed of 56 m.p.h.. and could operate for around 200 miles before refuelling.
Unit 29952 was modified to attain a top speed of 63 m.p.h.
Fuel consumption stood at 13 miles per gallon.
The units cost the London Midland and Scottish Railway Company £1850 each.
The Railbus seated 40 3rd Class passengers, all in pairs of seats, either side of the centre gangway, in two saloons, both sides of the centre-passenger entrance doors.
The driver sat in an enclosed compartment on the left hand side of the unit, which was very compact having a driver's control column, which was duplicated at each end of this unit.
This control column contained two small levers for controlling the engine throttle and power brake.