The Hathi prototype was developed by a team of P Company under Professor (honorary Colonel) Herbert Niblett of the Royal Army Service Corps Training College, Aldershot, using parts of a German Erhardt tractor. Production models were built by Thornycroft, 25 being built in 1924.
Although capable for its day, the Hathi was a complex and expensive vehicle that required regular maintenance if the front axle was to remain reliable. For most purposes it was soon replaced by 6×4 lorries with just as many driven wheels, but without the need for the complex combined driving and steering axle. Even half-tracks, particularly the Kégresse system, were more popular in this period.
Bodywork of the Hathi was typical for the time with a wide bench-seated open cab and not even a windscreen. The only weather protection was a folding canvas roof.
As for other Thornycrofts the radiator surround was a massive casting (in aluminium, to save weight) topped by a brass header tank with the "Thornycroft" name prominently cast into it. A distinctive feature of the Hathi, appropriately giving its elephantine appearance, was the extreme width of the bonnet. The top panels of the bonnet cover were also noticeably concave and are recognisable in photos.
Prominent spare wheels were mounted high up, on each side of the rear bodywork.
Four wheel drive for heavy vehicles in this period was difficult and the Hathi used a complex arrangement of bevel gears to transmit drive through the steering joints of the front axle. Rather than the common system of articulated drive shafts to the front hubs (the shaft either inside an axle casing or external), fixed shafts were used. Shafts inside the axle casing carried power to the ends of the axle, then a bevel gear drove a short shaft running through the steering kingpin. A further bevel on the outer part of the hub carrier (the part moving with the steering) drove the hub itself.
The constant velocity joint used to make modern articulated drive shafts was unheard of as yet and even the simpler Hooke-type universal joint wasn't yet in common use. Thornycroft's usual practice for prop shafts at the time was to use a flexible leather disk joint. To save weight, the axle casings were cast in aluminium.
The engine was a Thornycroft GB6 11.3 litre straight-six petrol engine. As was common for the period, the cylinders were cast in two blocks of three. Valves used the "IOE" or "Inlet over Exhaust" arrangement, with overhead valves (in the head) for the inlets and side-valves (in the cylinder block) for the exhaust. Dry sump lubrication was used, to avoid problems when tilted off-road.
Use as a breakdown recovery vehicle
In 1926, at least one Hathi was converted as a breakdown recovery vehicle. A fixed jib with a small hand-operated winch was mounted on the rear deck, with the frame for a canvas tilt over it. Other examples were converted for the RAF and the Royal Navy, a naval example from Portsmouth Dockyard being the survivor today.
Some time in the early 1930s a number of Hathi, possibly seven, were transferred to Australia.
Hathi were still in reserve service in Australia in 1945.
- "The Elephant - experimental Hathi tractor". Old Motor and Vintage Commercial 3 (6). December 1964.
- Fletcher, David (1998). British Military Transport. HMSO, for The Tank Museum. p. 67. ISBN 0-11-290570-6.
- Baxter, Brian S. (1989). Breakdown: A History of Recovery Vehicles in the British Army. HMSO, for REME Museum. pp. 13–14. ISBN 0-11-290456-4.
- "Type A1 RSW". Hants gov, Thornycroft.
- "Thornycroft Hathi (Acc 1988.3253)". REME Museum.
- "Type QC lorry". Hants gov, Thornycroft.
- "Two 30cwt Ford trucks are hitched side by side in front of a Thornycroft Hathi tractor" (photo). Australian War Memorial. 15 September 1934.
- "Australian 3rd Ordnance vehicle park in 1945, showing rows of Hathi" (photo). Australian War Memorial.
- "Thornycroft Hathi". Classic Military Vehicle (20): 33. January 2003.
- "Museum of the Month: Hathi at the REME museum" (Good quality photo). October 2004.