New Type Spark Plugs

Hawera Star, Volume LIV, 2 March 1935, Page 15

New Type Spark Plugs

Patent Obviates Short= Circuiting of Points

One of the commonest troubles with even the best of spark plugs is partial or complete failure due to oiling nip, or "the short, circuiting of the points through carbon or moisture. Ordinarily- the fault tends to become aggravated in that if the charges in the cy-linder do not explode there may be a gradual pumping up of the. oil which accumulates in the combustion chamber. The immediate cure is to remove and clean the plugs, and then to look for the cause of their having become fouled.

But if the claims made for a new type of plug which was recently- patented abroad, but has not y-et been produced in commercial quantities, are vindicated, many- cases of bad running and "missing” and of roadside stoppages should be avoidable. The principle of construction is that the "earthed” electrode of the plug, that is to say-, the one attached to the metal shell, is so designed that it vibrates constantly, although its degree of movement is not great enough to cause any- serious variation in the width of the plug gap. Various designs have, it is said, been tested, with most satisfactory- results. One make has the outer eleetrod in the form of a loose ring, which is carried in guides, so that although it is free to vibrate an accurate gap is maintained, while in another the "earthed” electrode is a small rod, which is supported transversely- in the shell of the plug, after the manner of a gudgeon pin in its piston, and has a small tolerance which permits an effective but not excessive degree of movement.

It will be apparent that if the electrode is constantly- moving and vibrating the formation of an accumulation of oil or carbon is discouraged', and it is reported that w-hen such plugs were immersed first in dirty- oil and then in water, and at once replaced in the cylinders, the engine fired easily- after a few turns of the self-starter, and thereafter ran perfectly- smoothly-.