New Ideas in an Extensible Chassis
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WHILST equipped for the haulage of long indivisible VV loads_ the tractor-trailer outfit illustrated on this page can also be used for general purposes as a normal vehicle not exceeding 22 ft. in the length of the trailing portion and laden up to 22 tons gross.
Made to the order of Samuel Williams and Sons, Ltd., Dagenham, and designed and built by Multiwheelers (Commercial Vehicles), Ltd_, 3, Grosvenor Gardens, London, SAVA., the machine was primarily constructed for the transport of ferro-concrete piles, which are made in lengths up to 50 ft. and must be supported during transit at only certain points clearly marked upon them. The distances between these supporting points depend upon the length of the piles, but, normally, do not vary by more than 9 ft.
Accordingly, the trailer is constructed so that it can be extended or contracted in 1-ft. stages, the greatest distance between the front gantry and the rear bolster, which can also he set in any of four positions to give a fine adjustment, being 30 ft. The wheelbase varies in accordance, the maximum length being 26 ft. 10i ins. As can be seen from the pictures, the vehicle is not of the pole type, but has a boarded floor ; thus, when contracted, there is nothing abnormal about it. One of the general purposes for which it will be employed is the transport of stone slabs.
It is noteworthy in this connection that both piles and slabs are fragile goods, and we are informed that when, in the past, rail transport was tried, it proved quite unsatisfactory, as piles frequently arrived broken at their destination. Very careful handling is also necessary in the case' of slabs, for chipping of the corners renders them useless.
Coupled to a normal Multiwheeler Meadows-engined
tractor by means of the concern's well-known automatically variable weight-superimposing drawbar, the trailer chassis is constructed with two frames. The longitudinals of the front portion rest upon those of the rear which, at their front ends, are provided with rollers, these running on the upper sides of the lower flanges of the front channels. Pads of friction fabric are interposed between the side members.
There is a pair of hook-like fittings attached to the forward ends of the rear .part of the frame, which engage with a pair of pegs that can be inserted in any opposite two of a series of holes in the upper members. Thus, to extend the trailer, the pegs are inserted in the suitable holes and the tractor driven forwards with the front part of the trailer until the pegs are picked up by the hooks.
At the rear of the upper longitudinals two further rollers are mounted on eccentric spindles, which are incorporated in a clamping device. The spindles can be turned by accessible levers, the action being either to raise the upper member on the roller, which can then run on the lower, or to lift the roller clear and pull up the clamp, which then holds the top channel down on the bottom one. The pegs are of the screw-in type also serving as locking devices.
The gantry, which is 3 ft. 10i ins, high, is mounted 2 ft. forward of the front-axle centre, whilst the detachable rear bolster is 2 ft. 91 ins, behind the back axle. The object is to concentrate the load at the extreme ends of the trailer when it is extended. To give stability when cornering, the turntable centre is 4 ins, in front of the forward trailer axle. In addition, a stop, for use when the vehicle is laden, limits the angular movement of the turntable. Having. a platform height of 4 ft. 61 ins., the trailer is equipped with 12.00 by 20 tyres.
Dewanclre double-acting vacuum brakes operate on the four rearmost wheels, which run on rocking half axles. Because of the variable trailer wheelbase, provisien has to he made for altering the length of the vacuum Accordingly, the main supply pipe, which runs down beside the near-side o'hannel of the front part, has a number of tapping points, to any of which the flexible connection on the back part can be coupled, Westinghouse joints being used. There is a hand control on the trailer also.
For the tail lamp a neatly coiled extension lead is provided. It has sufficient flex to reach the extremity of the load, lamp and number plate being detachably mounted. .
There are other similar practical details, such as the numbering of the peg holes with inter-gantry length figure which show the careful thought that has been given to the design. The outfit will be licensed as an articulated vehicle and weighs unladen under 8 tons. This interesting vehicle appears to represent an advance on conventional practice, being, we believe, the first of its type. Its perfortriance in operation will, no doubt, be watched closely, because, whilst built for the efficient accomplishment of a special and delicate job, it is an economic solution to the problem of keeping the specialpurpose machine in full-time employment.