MOTORING

King Country Chronicle, Volume XXXIII, Issue 4817, 31 July 1939, Page 3

MOTORING

HEADLIGHT FAILURE. If one headlight bulb burns out frequently, the trouble is practically certain to be due to an intemrittent short circuit in the wire to that bulb. This can be caused by a chafing of the rubber insulation surrounding the wire. The most likely place for this to occur is inside the lamp shell, just behind the reflector. If the trouble is not here, it will be somewhere along the wire before it makes a junction with the wire from the other lamp. If there is on intermittent short after this junction, both lamps will be affected. Once found, the faulty section is easily repaired by putting a few turns of black insulating tape round the broken rubber covering. GROWING USE OF RUBBER. One of the features of the modern chassis is the liberal use of rubber, not only in mounting the engine, but for many components and minor fittings. The results obtained have been so good that still further use will no'doubt be made of it in bushings and mountings throughout the chassis. Some very interesting results have been obtained from tests using a system by which rubber can, as it were, be welded to metal, almost as though the two were chemically combined. That the rubber does, in fact, combine with the metal has been demonstrated by a special testing machine. A test piece, consisting of two metal faces, connected by rubber, had to be subjected to a very high stress before the rubber itself could be persuaded to break, and even then, rubber was left on each metal face.

An example of where such components can be used is the rubber for the damper employed on the crankshaft of multi-cylinder engines, for the damper thus constructed consists very simply of a heavy rim connected to a centre through rubber, so that when it is once right, the damper remains a permanent fixing, requiring no adjustment.

The flexible centre of a disc clutch is another instance, and a universal joint a third, having, incidentally, the advantage that there are no wearing parts. THE LIGHT METAL. MODERN INNOVATION. SOURCE OF ALUMINIUM. Commercially unknown less than 100 years ago, aluminium, so familiar in every household to-day, was a product of no apparent importance until well within the last 50 years. It is derived from bauxite, an ore that occurs in many parts of the world. It has the appearance of clay, but is much harder, and its colour ranges from grey to brown, and even red to pink. Rock-like in substance, it is quarried, methods ranging with the nature of the deposit. In the reduction of the clay to aluminium great heat—about 1000 degrees centigrade—is required, and as ample electric power must be available, accessibility to such a supply is often the deciding factor in the location of plants. Aluminium in its "straight" condition is little used in engineering, its constitution being such that though lightness is abundantly present, strength is absent. Consequently it is always alloyed with some other metal—mostly copper—the alloys going under various trade names. Some of them give roughly the strength of steel while retaining approximately one-third of the weight. Pure aluminium has a specific gravity of 2.7 as compared with the figures of 7.8 for mild steel. Besides its advantage of lightness aluminium and the aluminium alloys are wonderful conductors of heat, giving a decided advantage in such engine parts as the cylinder head, pistons and crankcases, etc., Both aluminium and its alloys are easily machined.

There is no danger of aluminium ever running short. It is abundant, being computed at 31.9 per cent, as compared with iron 19.9 per cent, in the earth's make-up to a depth of 10 miles. There is no fear of ever burning up the aluminium supply.