A New Eight-wheeled Trailer
Page 56
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An Interesting Dyson Design which Enables a 16-ton Pay load to be Legally and Safely Carried
COR operation in conjunction with specialized types of haulage vehicle, such as the Latil Traulier and certain kinds of tractor, R. A. Dyson and Co., Ltd., 76-80, Grafton Street, Liverpool, has just produced a well-designed trailer, having a normal length of 18 ft. and a width of 7 ft., a tare'weight with bodywork of only 3i tons, and a load capacity of about 16 tons.
If such a trailer be hauled behind a motive unit working 2I-3 tons, it will be capable of carrying 15i-16 tons without exceeding the legal gross weight of 22 tons. Also, as the law permits a maximum weight of.10 tons to be transmitted to the road through four wheels in line, making 20 tons for the laden trailer, a fair margin for uneven load distribution is afforded.
We recently examined one of these trailers, which has been supplied to Mr. I. Lel tley, of 86, North Street, Barking, Essex, and noticed that the weight saving is, in the main, obtained by the use of shaped pressed-steel chassis members.
Fourshort axles are used, each being bolted to a Woodhead trunnion-ended spring, which allows the axle to oscillate so that the wheels set themselves for road camber, etc. Under load the axis of oscillation passes through the axle. This is necessary for stability and it prevents the wheels from swinging outside the chassis.
To obtain this feature, the springs have, of course, to be underslung, and their brackets are, therefore, very deep. Tubular cross-members between them take the side thrust, and the rear crossmember is arched for access to wheels.
The foreearriage consists of a pressedsteel ring to which are fixed the pressed spring brackets. A corresponding channel-section ring is fitted to the chassis, and 34-in, rollers are inserted between the rings and separated by distance pieces, thus forming a complete roller race in which neither rollers nor distance pieces are fixed. Free rollers
cause wear of the race to occur evenly. The pull is taken on spigoted bolster plates, which relieve the king-pin of all shear stress. We found it an easy matter to man-handle this forecarriage, which, by the way, has one of the new Dyson channel-steel drawbars with drop-forged ends.
A heavy trailer controlled from a ,comparatively light motive unit must have excellent braking. In this case, 16-in. by 4-in, drums are fitted to the four rear wheels, giving about 600 sq. ins. of friction area. The brakes are coupled in pairs with a compensating link and easy individual adjustment.
The main cross-shaft is carried on two self-aligning ball bearings, and application is by a special Westinghouse vacuum system with a storage cylinder fitted to the trailer, which allows the brakes to be applied even when the engine is not running. This arrangement reduces time lag. There is a special break-away valve, which automatically applies the brakes should the trailer become detached accidentally from the motive unit.
The, brakes can be cable operated when the trailer is used with a vehicle not equipped with the Westinghouse system ; also the brakes can be applied when two empty trailers are being pulled in tandem. The standard model has 36-in. by 8-in. tyres.