Requirements
The first vehicle was built as an experimental prototype, but its success was so great that plans were made to produce them commercially. The specification of requirements was thus drawn up in October 1923, after the prototype had been trialled. These were:
- Engine power of at least 80 bhp
- Winch capacity of 5 tons
- Ability to cope with a 1 in 4 gradient, whilst towing a trailer load of 5 tons
- Ability to stop and start under control on a 1 in 5 gradient
- Average speed of 22 mph over two hours.
- 20 inches ground clearance in general, with at least 10 inches beneath the axles. The vehicle otherwise to be low in overall silhouette.
- Turning circle of 55 feet. This required a short wheelbase, but the ditch and bank climbing requirements also limited the vehicle's overhang beyond its wheels. Together with the weight limit, this required an extremely compact vehicle.
- Maximum weight of 5 tons.
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