A New Semi-Trailer for maximum loads
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THE machine depicted in an accompanying illustration comprises an A.E.C. Mammoth towing unit and a Vtiebco detachable semitrailer, built to carry 13-14ton pay-loads. The semitrailer is a new product of Arthur H. Webber and Sons, Ltd., Cobholm Engine Works and Garage, Great Yarmouth, and incorporates a number of noteworthy features, whilst the motive unit follows—so far as the chassis is concerned—the standard specification of the Associated Equipment Co., Ltd.,
Southall, Middlesex, except for the fact that it has a wheelbase of only 10,ft. 6 ins. The cab—an ash-framed, steelpanelled structure—was built and de signed by the maker of the attachment.
This, as is clearly seen, is of the dropped-frame type, the downsWept longitudinals being 26 ft. long and having a section, throughout their length, of 8 ins. by 4 ins. by 5-16 in. They are braced by six cross-members of the same dimensions, and, at their upper level, have five outrigger brackets on each side to obviate the need for crossbearers above the frame and a consequent increase in floor level.
Forged high-tensile-steel axles aro used, the combined spring seats and brake brackets being shrunk on. Caststeel strongly webbed hubs, running on Skefko tapered-roller bearings, carry
twin wheels which are interchangeable with those of the A-.E.c. and are shod with 40-in. by 8-in. tyres.
Straightforward in layout and of sturdy construction, the suspension system embodies a rocking beam on each side, to which the adjacent springends are shackled. These two beams are mounted on a cress-shaft carried by two substantial brackets bolted to the main frame. Similar but longer brackets, which are deeply webbed for rigidity, support the remote ends of the four rear springs, to' which they are pinned. NewaIls high-tensile bolts are employed to secure all six brackets to the longitudinals.
The turntable follows orthodox practice, having a large-diameter ring and a fabric-faced damping device. PrOVision is made for lack of horizontal alignment between the two units, and kit facilitating coupling and uncoupling; for the concern, in the service of which the outfit is operating, wishing to take full advantage of the scope of this type of vehicle, employs two semitrailers with one tractive unit.
To support the weight of the front end when the two units are uncoupled, a pair of tubular telescopic legs is pro
vided. These are extended hydraulically, by Skyhi lifting apparatus, and can be operated, we are informed, by one man when the vehicle is fully laden. The legs swing back out of the way when the machine is on the road.
Of Dewandre design, the brakes are of unusual interest. The system incorporates two Dewandre vacuum cylinders, set one on each side, within the frame IongitudinaIs. They exert a
pull on two rods pinned to arms on the ends of a cm-ninon brake cross-shaft. The arms are double ended and carry four further rods hinged to levers on two individual cross-shafts, whence. another four rods transmit the pull to the four brake camshaft arms.
The arrangement may sound a little complicated, but actually it is quite straightforward, and appears to afford equal distribution of braking effort. whilst eliminating torsional stresses in the shafts and permitting the use of light parts.
Messrs. Tom Scotney, St. Ives, were the builders of the bodies of these two vehicles. They are of steel and timber construction with aluminium panelling, and contribute towards keeping the unladen weight of the complete articulated outfit well below 9 tons.