Clever Features in a
Page 54
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NEW SIX-TON TRAILER
BESIDES its particularly robust construction, there are several distinctly novel features in a new 6-ton trailer which has been produced by Fredk. Braby and Co., Ltd., Ashton Gate Works. Winterstoke Road, Bristol.
The square-section axles of Siemens Martin steel have spring pads forged integrally and are provided at each end with SKF taper-roller bearings, the hubs being also steel forging& Here is, perhaps, the first point of interest, for all the wheels are canted outwards slightly. This, amongst other things, is claimed to improve the wagon's trailing qualities.
An advantage of the use of suitable roller bearings, in conjunction with giant Dunlop tyres of 36-in. by &in. section, is a marked reduction in the rolling resistance of the complete trailer.
The method of carrying the spare wheel is interesting, inasmuch as a complete wheel and tyre of this size represent a considerable weight, and one which cannot easily be man-handled. In order to meet the difficulty a light tubular framework is hinged to the chassis of the Braby trailer and its "free " end is adapted to carry the wheel. At this point, however, there is a large nut fitting over a square-threaded shaft de pending from one of the side members. The nut itself can be rotated by means of bevel gearing and a handle which is inserted in the centre of the wheel hub.
As a result, the wheel can be attached to its mounting while its weight is still resting on the ground, and then by means of the handle the whole assembly is lifted up.
Probably the most novel feature of the whole design is in the arrangement of the forecarriage and turntable. A large rectangular pressing is carried on two half-elliptic springs which are pivoted at their front ends and are provided with sliding blocks at the rear. Over the .centre of this pressing is mounted a steel forging which might be described as a circular plate with a shallow cylinder upon it.
Inside this cylinder are eight pockets arranged in a circle and in each of them there is a stiff helical spring. Upon these eight springs there rests a steel plate carrying a Skefko thrust bearing on a spherical seating. Above this ball race there is a second steel casting consisting of a square plate adapted to 'fit in two channel cross-members of the chassis.
This casting has a shallow cylinder formed on its lower surface, it being, machined so as to fit over the first-mentioned cylinder, allowing suitable clearances. Passing through the centre of the assembly there is a hollow king-pin which serves simply to prevent the various parts from being jolted out of position. The drawbar load is. however. not transmitted through the king-pin, but is taken on the cylindrical faces of the two steel castings already described. It is thus distributed over a large area.
Another feature of the Brahv trailer calls for special mention. The various leaves of each of the road springs are not held together in the conventional manner by means of clips. Instead, each spring is longitudinally ribbed on its lower surface and is grooved on the upper one, so that, in effect, each leaf is keyed to the one below it
The rear wheels carry internal-expanding brakes operating in drums of 17-in, diameter, the facing width being 2i ins. In addition to a hand-controlled lever, there is a cable which passes down through the hollow king-pin of the turntable and can be connected to any suitable operating device on the towing vehicle.
It might be mentioned that the trailer incorporates a device whereby the brakes are automatically applied should the trailer become accidentally disconnected at the drawbar.
As regards the general dimensions of the Braby trailer, the wheelbase is 9 ft. 9 ins, and the track is 5 ft. Overall the body measures 16 ft. 3 ins. long and ?7 ft. wide, the loading level being approximately 4 ft. above the ground. The unladen weight is 2 tons 4 cwt. 1 gr.