Scammell 6 x 6 Vehicles for Army
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1iTlL1TARV six-wheel-drive vehicles 1V1 with petrol engines of 200 b.11,p. are being made by Scammell Lorries, Ltd. The machines provide a tractive effort of 18,000 lb., are equipped for tropical operation and can run through water 6 ft. deep.
Mr. L. D. Watts, chief engineer of the company, made this statement in a paper read to the north-eastern centre of the Institute of Road Transport Engineers. Referring to the uses made of the four-wheel-drive dumper, he said that in Saudi Arabia these vehicles, each drawing a 10-ton trailer, carried poisoned locust-bait across open country to sites on which swarms were spotted by aeroplanes. The bait was laid at night and when the locusts woke in the morning, they ate the bran and died.
The Scammell concern fitted its 6-ton coupling to fourwheeled tractors as it recognized that these usefully supplemented the Scarab threewheeler. The combination of threeand fourwheeled tractors, all capable of being hitched to the same semitrailers, greatly increased the versatility of a fleet.
During the discussion, Mr. Watts said that 12 years' experience had proved the good wearing qualities of cast-iron crankshafts . fitted in the engine 6f the Scarab. " We have tried the ordinary hardened crankshaft," he said, "but we get far better results from the iron shaft."
Turning to deal with rubber suspension, used for the rear axles of the Scammell rigid eight-wheeler, he said there was insufficient room on the front bogie for such equipment and laminated springs were used. Weight for weight, rubber was a better medium than steel, but the use of rubber in compression necessitated the provision of a balance link which offset the advantage.
A system introduced in America in which the rubber was in torsion was even more economical, than the use of rubber in compression. Rubber was better for independent suspension, but if it were employed with twin tyres, bush loading would be too high, Mr. Watts added.