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A Hands Semi-trailer with Novel Features
Page 90
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A NEW semi-trailer, with many novel features, is being marketed by Hands (Leteliworth), Ltd., of Letch
worth. A singe-axle type and a doublebogie-axle type are available, various models being intended for pay-loads of from 5 to 15 tons. A special feature of this new semi-trailer is the novel frame construction, in which a central box girder forms the backbone, cross-members being electrically welded to the centre member. The lifting gear is of the hydraulic type and is of ingenious design, as, in. addition to lifting the trailer, it automatically controls the coupling gear and braking system.
When the trailer is lifted clear of the turntable by means of the hydraulic mechanism, the rear brakes are automatically applied and the rear light adapter is disconnected. Recoupling may be effected from any angle, and the range of lift provided is ample, the control being arranged so that the trailer may be lifted or dropped a small amount to mate with the turntable should any alteration in levels have taken place while the trailer was detached.
Low-periodicity semi-elliptic springs are employed at the rear, the springs having fixed anchorage points, no shackles being used. In the case of the double-bogie machine, the springs are transversely mounted, the axle bearers being carried on large bearings fitted in the spring bosses.
Brakes operated by air pressure or by vacuum may be used, the vacuum type being the standard system for use with petrol-engined tractor units. The braking effort is derived from compression springs of predetermined strength, c48 which are incorporated in the brake cylinders, and the desired braking force is obtained by controlling the pressure exerted by the springs. The trailer brakes are independently connected with the foot and hand brakes of the tractor unit, and a mechanical control is provided to operate the trailer brakes separately when required.
An ingenious feature of the double-bogie-type trailer is that the brake-operating sear is accommodated within the axle bearer, upon which the wheels are mounted on stub axles. Furthermore, to enable the tyres of the inner wheels to be changed, or to inspect the brakes on the hubs, the axle bearers can be revolved upon their own axes, so that the inside wheels can quickly be brought to the outside positions.