A T the instigation of -the Forestry Commission; : Roadless •
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Traction,' Ltd., Hounslow, Middx, have • modified two Land-Rover long -wheelbase chassis to carry 10 X. 28 tractor tyres: The first converted vehicle; with fire-fighting bodywork, is being used experimentally by the Commission., whilst the second prototype is undergoing tests which shoUld result in its being offered .in a commercial version towards the' end of 1960.
The fitting J:If large . tyres • increases the Land-Rover's ability to surmount certain types of obstacle—deep drainage gullies in the case of the Forestry Commission. When the unladen vehicle was demonstrated to The Commercial Motor last week, it was obvious that none of the standard Land-Rover's cross-country capabilities had been lost, whilst the ground clearance between the axles allowed the vehicle to get over sharpcrested ridges on which the conventional vehicle -would have see-sawed.
It showed also a remarkable aptitude for getting in and out of steep-sided holes, proceeding steadily through these hazards at a low throttle opening.
For the large wheels the standard axles are replaced by Kirkstall spiral-bevel units of 7.2-to-1 ratio. This gearing is too high for the Rover oil engine fitted to the prototype vehicle as it does not permit top gear ro be used, and restricts maximum speed to about 24 m.p.h.
Axles with ratios of 13 to 1 will be fitted, when they become available, to give a maximum speed of about 35 m.p.h. and impressive gradient ability. The Kirkstall axles provide front and rear tracks of 6 ft. 3 in. and 5 ft. respectively. The wider front track is required to give adequate steering lock.
No modifications are made to the standard transmission for the Roadless conversion, but the original road springs are replaced by stronger units. Brake drums are at present 14 in. in diameter.
c48 This is not sufficient and larger units will • be incorporated later. , 'Although the tyres are inflated to only 7 p.s.i. and have deep lugged treads, the steering is not; heavy unladen. On the road there are no untoward effects from the tyres, which Roadless consider to be capable of sustained running at speeds
in the order of 40. m.p.h.
With such large section tyres, the Land-Rover exerts low ground pressure and has possibilities as a swamp vehicle. In this capacity it is being 'considered by an oil company for exploration work.