New Features in Dyson 100-ton Trailer
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ABUILT-IN hydraulic jacking system having its own petrol engine, a centre bed mounted on eccentrically bushed pins to enable it to be lowered or raised, and a chassis which can be adjusted for width, are among the interesting features of a 16wheeled, 100-ton trailer recently built by R. A. Dyson and Co., Ltd., 76-80, Grafton Street, Liverpool, 8.
Two girders, suitably braced with cross-members, form the bed, which is secured to the cranked extensions by two 6-in.-diameter high-tensile steel pins. To alter the width of the chassis, one set of cross-members is replaced by another. The minimum centre of the chassis beams is 3 ft. 4 ins., and the maximum 7 ft: 1 in. In making this change the bogie bolsters, to which the girders are bolted, are not disturbed.
Cross-bolster Construction
The cross-bolsters are built up of heavy-section girders, and in the centre af each bolster there is a sphericalshaped king-pin fitting into a steel casting, with a bronze liner in the centre of each bogie frame. To prevent the bogie parting from the main frame there is a locking collar fitted to each housing.
Both the main cross-bolsters are provided with stabilizers, and at the rear end circular rubber discs, interposed with steel plates, are employed as shock absorbers in respect of side sway.
Each bogie consists of a complete frame fabricated from steel plate and channel by electric welding. Semielliptic springs, by Jonas Woodbead and Sons, Ltd., are used on all eight axles. Each bogie is provided with self-con
tamed mechanical and air-pressure braking, with a safety device which applies the brakes should the cbm • pressed-air supply fail.
The cast-steel wheels are equipped with Henley 771 by 15 solid tyres, each of which is rated to carry 8 tons.
The drums of the Girling two-leadingshoe brakes measure 164 ins. by 5 ins., and all 16 wheels are similarly equipped. The air-pressure system was supplied by the Clayton Dewandre Co., Ltd.
A heavy-duty winch, with a worm and worm wheel enables the rear bogie to be steered by hand. On the shaft taking the wheel is a sprocket which is connected to the spider ring on the carriage by a Renolds roller chain. The rear bogie can be hand-steered by the winch, manipulated by the rear drawbar, or locked for straight travel.
By means of inbuilt jacks, the chassis bed can be made to assume one of two positions when travelling. The lowest position gives a ground clearance of 10 ins, laden, and the highest 15.1 ins. laden. As the jacking system is incorporated in the bed of the trailer, the loading space is not obstructed.
The principle of using the hinged cranks is still followed, but the rear hinge-pins are located in eccentric housings having two positions. The eccentricity is magnified by the large arm of the crank, thus a difference of 61 ins, can be obtained by 1-in. eccentricity of the hinge pins.
In making use of the jacking system, the self-contained petrol engine is started, and the hydraulic fluid circulated. There are four jacks, two at the front and two at the rear, which can be operated either singly or in groups. The securing pins are first relieved of their load by using all four, when the pins can be driven out by hand. Both carriages, complete with their cranked portions, can be drawn away separately, a small hand-operated jack and wheel being fitted behind the cranks to facilitate handling.
Independent Control of Jacks The jacking controls are then released to lower the centre bed to the ground. If required, either end can be lowered separately by using the relevant jacks. Incidentally, as the pump gear is mounted on a sub-frame it can be mounted at the rear or the front of the trailer.
An adjustable dolly, mounted on th; trailer bed, is used under the cab of the drag-line excavator which the trailer . was designed to carry. The jacking system, complete with motor and pump. is of Tangye make.
The overall length of the outfit, with 80-ton Scammell tractor, is 50 ft. 11 ins., the loading space on the trailer bed being 20 ft. 6 ins.
The design was evolved by the trailer maker in co-operation with Charnley and Davidson, Ltd., of Blackburn. Sir Lindsay Parkinson and Co., Ltd., of London, is the operator.