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Flexibility an Advantage in Body Construction

25th November 1949
Page 56
Page 56, 25th November 1949 — Flexibility an Advantage in Body Construction
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Which of the following most accurately describes the problem?

THETHE value of using aluminium in the of insulated van bodies was referred to by Mr. T. G. Griffiths, B.Sc. (Eng.), A.F.R.Ae.S.. development engineer of the Northern Aluminium Co., Ltd., in a paper whic.h he read to members of the Institute of Road Transport Engineers, in London, last week.

Polished aluminium, he said, was not only a most efficient reflector of heat, but it possessed the converse property of low emissivity. and was a poor radiator. The exterior panelling should, if possible. be polished, and the inside surfaces left bright.

Of aluminium foil in the capacity of an insulator, Mr. Griffiths said that it was both light arid efficient. Weighing only 3 Oz. per cubic ft., it had the same thermal conductivity as glass fibre, with a density of 3 lb. per cubic ft.

Conflicting Forces

Some operators, he said, viewed the light-alloy platform body with some distrust, because of its flexibility. This was in no way detrimental, but was, on the contrary, advantageous. He pointed out that the chassis itself was relatively flexible, and that if the body were stiff and rigidly attached to the chassis, it would restrain chassis movement.

'This would have the further effect of setting up high stresses in both the chassis and body, which were avoided if the body possessed a degree of

flexibility. His retnaAsconcerning body cross-bearers also touched on the matter of ,flexibility.

A cast bearer, in light alloy, if secured rigidlyto the chassis, developed cracks as the result of severe local stresses. One way of overcoming the trouble was to use a composite cross bearer — a flexible cross-member attached to a pair of cast pedestals.

It might not be generally realized that a high proportion of the total weight of a body was in the floor, a typical example chosen showing this figure to be as high as 40 per cent. in the case of a platform bodY built in light alloy.

The flooring was of corrugated section, which material was less than half the weight of wodd performing the same duly.

The .speaker said that whilst there was much in favour of chassisless construction, there were possible disadvantages which could not be overloOked.

The discussion was animated and interesting. Asked whether tubes would not be more satisfactory than other sections, the author said that whilst individually stronger, double-skin construction gave almost the same effect, also the width and height of most bodies were not so great as to require tubular construction.

Replying to another query on costs. he said that aluminium was considerably More . expensive, being about Is. 9d. per lb. against steel at say, 3d. a _lb., but it was advisable to ,consider the matter in. terms of volume. not weight. You obtained three times More volume of aluminium than steel for the same weight. .

. Other answers were_ that galvanic action between steel and aluminium was almost, negligible. Steel bolts removed after years showed little effect from this cause, but there was considerable corrosion if brass and aluminium were in metallic contact. Underframes should preferably be protected by bituminous paint. One member said that he had had aluminium bodies working near the sea for four years, and they were quite unaffected.

The author added that acids, and particularly alkalis, were bad for aluminium, also that a chassisless vehicle in aluminium could be produced much.more cheaply than a chassis and body built separately in steel_

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People: T. G. Griffiths
Locations: London

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