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Light alloys are key to motoring that's fuel savvy

By unknown | Aug 20, 2008 | COMMENTS [ 0 ]

The looming oil shortage has given extra impetus to the quest for lighter cars and engineers have turned increasingly to lighter materials, both metals and plastics.

Let's look at two metals that are important in this regard: aluminium and magnesium.

Aluminium, once regarded as a precious metal more valuable than gold, is corrosion-resistant, easily machined, non-magnetic, and it has about one-third the density, and stiffness, of steel.

That means an aluminium bar will have only one-third the weight of an identical steel bar.

The use of aluminium alloys started picking up in cars about 30 years ago when the swing from cast iron to aluminium cylinder heads got under way. This was followed by aluminium radiators and engine blocks. On the latest passenger cars an all-aluminium engine - both block and cylinder head made from aluminium - is commonplace. As always, there are no gains without pains, and the pains of an aluminium engine include the danger of stripping the relatively soft threads when installing things such as spark plugs and bolts. Use a torque wrench and don't exceed the prescribed torque.

You also have to pay more attention to the correct type and concentration of antifreeze in the coolant.

Magnesium is known as the lightweight champion of the metals. It's the lightest of all metals used in general engineering, having two-thirds the density of aluminium.

An alloy of it was used for the engine block of the VW Beetle, because the air-cooled engine design was ideally suited for ultra-light alloy.

The last decade has seen a renewed interest in magnesium among car manufacturers because of a decrease in its cost, brought about by the rapid growth of magnesium production in China.

Magnesium can be cast more readily into complex parts of very thin section than aluminium, and no metal can be cut, filed, drilled or shaped as easily as magnesium.

Cast magnesium instrument panels, steering wheel cores, seat frames, tappet covers, and intake manifolds are appearing on cars, and "mag" wheel rims have long been popular on sports cars. - Motoring Reporter


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