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MARCH OF THE LIGHT BRIGADE

8th October 1987, Page 40
8th October 1987
Page 40
Page 41
Page 40, 8th October 1987 — MARCH OF THE LIGHT BRIGADE
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Aluminium has become one of the most popular metals in the UK bodybuilding industry. it is lightweight, durable and flexible enough to be extruded into all sorts of shapes and sizes. Leyland's futuristic TX450 gives a clue to its future potential.

MI Aluminium is playing an increasingly important role in the automotive industry. The aluminium industry, seeking new markets for its metal, has developed lighter and stronger alloys, new joining techniques in brazing, welding and adhesive bonding, and improved rolling, extruding, casting and forming production techniques.

Economic, environmental and other considerations have resulted in a worldwide drive to conserve materials and fossil fuels, and to reduce pollution and wastage. The benefits of aluminium include its high strength-to-weight ratio, its durability and its ability to be formed into shapes inconceivable in steel. These assets have put aluminium in the forefront of the materials now being considered by automotive engineers, because reduced weight equals lower fuel consumption and higher payloads, so the replacement of steel by aluminium makes good economic sense.

This is precisely what Leyland has done with its revolutionary TX450 truck, which has a monocoque box-girder chassis, constructed of aluminium alloy extrusions, that is significantly stiffer and lighter than the traditional steel ladder-frame design it replaces.

JOINING METHOD

Another vital design ingredient is the joining method. Welding is out, and adhesive bonding — the gluing technique developed and proved over many years in the aircraft industry — is in. The use of adhesives eliminates the localised softening, or annealing, that takes place on welding aluminium, so much stronger structures are obtained. The weight savings attributable to using aluminium can also have a knockon effect: by saving weight in certain areas it is also possible to reduce weight in many secondary areas of construction.

The ease of producing complex shapes in extruded aluminium has led to the development of many ranges of side raves, cant rails, corner pillars, side-boards and flooring.

Richard Nicholls, managing director of Ingimex, the biggest aluminium user in the side-board system business, says: "It would be impossible to make our range of CV products in any other way than with aluminium extrusions. The design possibilities they offer are unbeatable."

The durability of unpainted, 'mill-finish' aluminium means that it does not need to be protected against corrosion, so while aluminium can be painted or anodised, for many applications such treatment is unnecessary.

Extrusions are particularly beneficial to the body designer and builder. The cost of producing a steel die to produce any required section is relatively low, and can be measured in a few hundreds rather than many thousands of pounds. The shape complexity that is so easily obtained by extrusion enables fabricators to reduce the fabricating and joining operations needed to make and assemble a unit, and adhesive bonding enables different materials to be joined together easily.

VEHICLE SIDES

The use of aluminium sheet also has its attractions for vehicle sides and roofs. There has been a move away from sheet aluminium in recent years towards glassreinforced plastics, but this may be re versed, because in the passenger car section of the industry sheet aluminium body shells are now being actively developed. Audi, the West German manufacturer, has produced an aluminium body shell which, weighing only 149kg, is 131kg lighter than its steel counterpart.

The aluminium alloy shell was successfully deep-drawn using a special alloy that possessed good ductility and strength under load. Other benefits of the aluminium shell are high energy absorption, good buckling resistance and a high standard of surface finish. Audi, like Leyland with the TX450, opted for adhesive bonding as the main joining method, combined with a selective rather than extensive use of rivetting.

Another major 'under the bonnet' revolution in the use of aluminium has occurred with radiators. Many European manufacturers are turning to radiators constructed of aluminium sheet and foil instead of copper and brass. The development of acceptable brazing techniques and of alternative mechanically-assembled components has been at the heart of this materials switch. Once again, the reasoning is straightforward.

The use of aluminium results in useful weight savings without loss of heat exchange efficiency, and tests have shown the aluminium constructions to be more durable under corrosive atmospheric and road conditions than the copper radiators they have replaced.

CV manufacturers are also making increasing use of aluminium castings, particularly for engine parts such as cylinder heads and blocks, sumps and pistons, to take advantage of the lower weight and better heat conductivity of aluminium compared with steel.

JOINT DEVELOPMENT

Over the next few years continued cooperative development between aluminium producers and vehicle manufacturers is likely to result in a much greater use of aluminium as a factor in the quest for improved vehicle performance.

Not only is aluminium the most abundant metal available on earth, it is easily recycled with only a low energy requirement, so designers and producers can have confidence in the material's continued availability, and the conservationists and environmentalists can have confidence that the metal in a vehicle at the end of its life cycle can be reclaimed and put to good use again.

E by John Lane

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