IGNITION VOLTAGES.

Timaru Herald, Volume CXXV, Issue 18203, 2 March 1929, Page 16

IGNITION VOLTAGES.

Modern ignition systems are so reliable that the average car owner rarely gives his battery set or magneto a thought, and ony realises its existence when something goes wrong. This attitude on the part of motorists is a tribute to designers and manufacturers of automobile electrical equipment, who are never contented to rest on their laurels of past achievements. They are continually striving to better their products. No aspect is deemed too small to merit very careful researecr*. For instance, in a paper read to members of the Institution of Automobile Engineers (London), Mr E. A. Watson discussed the electrical characteristics of spark gaps and sparking plugs, and arrived at some very interesting conclusion. Mr Watson pointed out that magnetoes, working as they do up to 10.000 or 12,000 volts and furnishing up to 200 sparks per second, function under conditions in which the factor of safety is far less than is usual in other engineering pro* lems, either mechanical or electrical. Describing the tests made on a 9 h.p. Rover car on the road t,v determine the voltage at the plug points under various conditions, he stated that one unexpected was “that higher voltages are reached with a car driven gently and occasionally accelerated than with one which is driven really hard and it would seem that the cautious driver, who in addition is hot expert in the use of his gearbox, will demand more from his ignition apparatus than the driver who indulges in high speeds and makes full use of his intermediate gears.” Mr Watson found that when negotiating fairly dense traffic voltages up to 10,000 were frequently observed when accelerating to pass other vehicles, while on the open road, where a steady speed could be maintained, the voltage never rose above 6000, even when the lirottle was opened wide for hill climbing. He condemned the practice of enclosing high tension cables in metal tubing or casing, for “this has the effect of considerably increasing the capacity to earth of the. high-tension

system, and* affects the ignition system adversely in two ways—firstly, in that it (in the case of a magneto) increases the speed necessary to produce a spark, and hence adversely affects the starting of the car; and, secondly, in that it increases the amount of oscillating energy in the high-tension circuit.”