Development of the Scammell Mechanical Horses
In the late 1920ís the railway companies were looking for a suitable vehicle to use on their town parcels delivery traffic, which was predominately horse drawn. The London Midland & Scottish Railway experimented with various ideas and in late 1930 announced, jointly with Karrier Motors, a tractor unit for this purpose. The vehicle, the Karrier Cob, was powered by a twin cylinder Jowett engine and utilized a mechanism to couple existing horse trailers to the tractor unit. Meanwhile the London and North Eastern Railway had approached Napier's, the quality car and aero-engine makers for an answer to the same problem. They came up with some ideas, but didnít wish to develop the concept and sold the project to Scammell Lorries. Their designer, O. D. North, refined and further developed the concept of the three wheel tractor unit which automatically coupled and un-coupled trailers, and in 1934 announced the introduction of the Mechanical Horse.
Scammell Mechanical Horse
This was a very simple and sturdy vehicle which was constructed on a steel channel frame and fitted with a wooden cab, the early versions having canvas doors. The Mechanical Horse came in two sizes, capable of carrying loads of three tons and six tons. These were powered by Scammell's own side valve petrol engine of 1125cc (3-ton) and 2043cc (6-ton), the engine being offset to the left of the cab. The vehicles are very manoeuvrable (with a 16 foot trailer they can turn through 360O in 19 feet), have a road speed of about 20 mph, and do between 10 and 20 mpg. In addition to the railway companies, they were also used by quite a number of private companies and the armed forces, who used them in stores and on aircraft carriers. The 6-ton coupling was also fitted to popular makes of light trucks such as Bedfords.
After the end of the Second World War, Scammell Lorries looked at the Mechanical Horse, which was basically unchanged from its 1934 design, realised that something more modern was called for and set about re-designing the vehicle. The successful automatic coupling was retained, but the rest of the tractor was completely new. The frame was cranked downwards, the engine, gear box and rear axle were built as one unit and fitted low down in the frame behind the cab. The radiator was fitted in the back wall of the cab, drawing cooling air from a duct behind the driverís door. The side valve petrol engine of 2090cc was used for both the 3 and 6-ton models. Later Scammell offered diesel engines, these were the Perkins 4-199 for 3-ton and P4 and P4203 for 6-ton models. The low mounting of the engine and other design changes made the Scarab more stable and its rounded all steel cab was more comfortable for drivers. The Scarab lasted in production until 1967.
The Scammell Townsman three wheeler replaced the 3-ton Scarab in the Railway industry. It closely followed the Scarab in its basic design at the front. The futuristic lines of the fibreglass cab hid a great many new developments, such as vacuum-assisted hydraulic brakes. Fitted equipment included a heater-demister, two rear view mirrors, interior sun-visors, totally enclosed oil-immersed coil spring front suspension and dual rate mounting of semi-elliptic leaf springs at the rear. An unusual feature of the day was provision on the steering column for a Waso lock. The frame was of a welded construction and had integral coupling ramps fitted with Scammell Mechanical Horse automatic coupling. A vacuum operated release mechanism replaced the hand lever in the Scarab. The engine, gearbox and driving axle formed a rigid assembly pivoted at the front end in a large rubber bush. Later a larger engine was supplied and fitted; the Leyland OE160, but even with its better driver controls and faster road speed (50mph) the main customer was still British Rail. A few however did find employment with other operators including The Royal Mail. Production ended in 1968.