Simplicity and Strength in
Page 41
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New Semi-trailers
ASIMPLE layout, embodying parts of generous size, is the leading characteristic of the new semi-trailer which is announced this week by Flexion Extensions, Ltd., The Hyde, Hendon, London, N.W.9. A stout fullwidth frame, powerful vacuum brakes, and a stable turntable arrangement have been concentrated upon, yet with the Bedford 2-ton short-wheelbase chassis as a motive unit and a trailer of 18-ft. body length with 18-in, drop sides, also the standasd Bedford cab, the unladen weight comes just within the 3-ton class. This is with truck-type 32-in. by 6-in, twin trailing-wheel tyres, and in this form the semi-trailer chassis costs £130, the drop-side body 6 ft. 6 ins. wide costing £40:
The main frame consists of roiledsteel channels, with full-width front and rear cross-members, these carrying a bowed angle-iron front and straight angle-iron side longitudinals. The 18-ft. models, which represent the standard size, have the frame trussed by means of a tie-bar with turnbuckle adjustment. The brake layout is simplicity itself, and should be quite unaffected by spring flexing, steering, etc. Standard BendixPerrot two-shoe brakes in 16-in, drums are operated by a Dewandre vacuum cylinder, and as the brake pedal carries a lightly acting hinged pad to control the vacuum, it is quite certain that the trailer brakes will always come on before the motive-unit brakes take effect. The Dewandre cylinder is rigidly mounted in the centre of the trailer flame. on two angle-iron cross-members, and pulls a bushed pin from which two rods extend obliquely towards the rear wheels.
The final stage from chassis frame to brake-cam levers is by I3endix flexibly enclosed cables, which remove all fear of spring flexing interference, just as the hose vacuum coupling to the semitrailer obviates all chance of steering interference. A lost-motion device adjacent to the bushed pin referred to above is provided for a ratchet-type parking brake lever, operated from the side of the trailer. It can be seen in the left hand illustration at the foot of this page.
Semi-elliptic rear-shackled springs convey the load to a high-tensile tubular trailing axle, carrying standard Bedford hubs and ball races.
As to the turntable, its main feature is that the ring is mounted on the motive-unit frame and not on the trailer, for this means that the trailer front is supported, no Matter what its angular position in relation to the motive unit. The turntable is not mounted on the existing cross-members, two extra members being provided. The centre block has conical and cylindrical faces, which take the vertical and towing stresses, so that the centre bolt is relieved of any sheer stress. A lubrication groove fed by a nipple is machined in the conical face. The pads are free to oscillate in phosphor-'bronze bushes in brackets beneath the main Iongitudinals of the trailer frame. Every nut and bolt throughout the chassis is of the Newell's high-tensile type.