SPARKING PLUGS

Ashburton Guardian, Volume 59, Issue 22, 5 November 1938, Page 9

SPARKING PLUGS

“HOT” AND “COLD” TYPES. ENGINE EFFICIENCY. The sparking plugs usually provide evidence of how the engine is functioning. They also indicate if Hie right type of plug for the engine is in use. For average driving, one cannot do better than follow the automobile manufacturer’s .recommendation as to the most suitable type of pfhg to fit. Generally speaking, there are two types of plugs, one for “hot” engines, and the other for power units that run relatively cooler.

A “hot” ping is one in which the heat has to travel a, relatively long distance before reaching thje water jacket; the heat path on a “cold” plug is relatively short. If two plugs, one “hot” and one “cold,” arc placed in the same engine, the electrode and, insulator of the “hot” plug will obtain a. considerably higher temperature than the “cold” plug.

If the operating temperature of a spark plug is too high, pre-ignition will usually result, while small blisters are likely to form on the insulator if the plug is too hot for the engine. In addition, the electrodes will wear rapidly. On the other hand, if the operating temperature is too low, i.e., the plugs too cold for the engine, carbon will accumulate. on the insulator, and the plugs will soon foul. Short circuiting is then likely, resulting ih misfiring. When one finds that plugs arc running too hot, generally rccognisabje by the pock-marked blistered appearance, of the insulator and excessive wear of the gap-points and absence oi all traces of carbon, “cold” plugs should be tried.

When plugs are overheated they frequently function satisfactorily until high speed is attained, or when climbing a long hill on full throttle. Under these conditions, the engine starts to lose power and has a tendency to misfire and fir® back into the carburettor.

Dirty plugs, on the other hand, generally indicate that the plugs used are too cold for that particular engine. There are two types of fouling—caused either'by carbon or oil. In the former, the insulator and plug become coviered with dry sooty caifbon. When a, plug is fouled with; oil, as the result of excessive oil in the combustion chamber, the deposit on the plug will be a wet, oily carbon, generally the result of worn piston rings, etc. When plugs consistently get into this condition, hotter plugs will invariably help to overcome the trouble.

An incorrect sparking plug gap will also cause a, plug to foul. Too wide a gap may cause missing at high speeds, allowing unburnt fuel and oil spray to he deposited on the plug. When the plug fires this deposit is burned to carbon and so fouling of the plug begins. In a. similar manner, if the points of the electrodes are set too close, missing may occur at low speeds. A point about the cave of sparking plugs is never to attempt to bend the central electrode. The insulator is likely to be chipped or cracked, if this is attempted. Gaps should be adjusted by bending the side electrode only. THE FIRST RUBBER TYRE. FRENCH INVENTION OF SOLID RUBBER. A great many people have wondered how and when the first rubber tyre was made, and also who was responsible for the invention. The use of rubber tyres looks perfectly simple to us, because they have been in general use for so many years. I do not speak now of the pneumatic tyres, but rather of the solid rubber tyres that were first used on carriages and wagons (says a publication of the Firestone Company). The history of the industry is not very clear on this subject, but it appears that the first rubber tyre was invented, by a Frenchman about the year 1835. According to Ins plan, a layer of crude rubber was used between the rim of the wheel and the outer steel band. It did not prove to be very practical, however, and little use. was made of it.

The name that seems to stand out most conspicuously in connection with the first successful rubber tyre is that of Thomas Hancock, an English inventor and business man. Hancock was a contemporary of Charles Mackintosh, who invented the rainproof coat that came to he known as the “mackintosh.” Hancock was the inventive typo and was a tireless worker. Mackintosh was more of the business type, although some important Inventions are traced to his genius. Thomas Hancock and Charles Mackintosh were two of the greatest names in the pioueqr days of the rubber industry about one hundred years ago. Mackintosh had a. small factory. As early as 1846' we know that he was producing there a. solid rubber tyre for horse-drawn vehicles, of which it is likely that Thomas Hancock was the inventor, because in a hook he wrote ten years later, giving personal reminiscences of the pioneer rubber business, Hancock says: '“These tyres are about one and one-half inches wide, and one and one-fourth inches thick. Wheels shod with them make no noise and they greatly relieve concussion of pavements and rough roads; they have lately been patronised by ‘Her Majesty.’ ” The use of “Her Majesty” in this ■ case referred to Queen Victoria who had ascended the throne in 1837.

Just imagine what the invention of rubber tyres must have meant to the Queen of England in her frequent journeys. Consider for a- moment the situation prior to this discovery. Her ]iower and wealth made it possible for her to have every convenience and luxury that human genius could, produce. And yet for the Royal coach she had only won tyres that had to travel on rough cobblestone pavements. Even the springs could not keep the Queen's

carriage from bumping as it travelled over the uneven streets. And what a clank and noise it must have made as the iron, tyres hit against the stones in the roadway! That kind of trstvel could not have been very pleasant nr best. It was attractive only because nothing better had as yet been producedl to take its place.

Then came the solid rubber tyres. They wore crude, but they provided a cushion between the wheels and tho rough pavement No 'wlonder they were patronised by Her Majesty.