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Platinum Points for K.L.G. Plugs

24th April 1936, Page 44
24th April 1936
Page 44
Page 44, 24th April 1936 — Platinum Points for K.L.G. Plugs
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-rim fitting of platinum points to

K.L.G. sparking plugs was an experiment carried out in the course of ordinary research work, and the company was quite surprised to find the distinct improvement which they effected, the outstanding being a great reduction in the working voltage and a remarkable decrease in the burning of the points.

Further investigation was carried out by means of loops of wire fitted into two-pole plugs and arranged so that these could be heated to any required temperature by low-tension current. The loops were inserted in the place of standard sparking plugs, and the engine driven by a separate motor at its normal speed, while the loops B30' were gradually heated until auto-ignition took place.

From this it was found that a wire about 0.1-in. diameter—the size of a normal plug electrode—caused autoignition when it reached a temperature of 700 degrees C., but a platinum wire only 0.02-in, diameter could be raised to 1,200 degrees C.

Full advantage is taken of this fact in the new plugs equipped with platinum points. Undoubtedly the platinum operates at a very high temperature, thereby requiring a low working voltage, but owing to its nature and size it does not cause pre-ignition.

This feature can be used in two ways, either the normal gap may be maintained, when the Stresses on the coil and ignition will be reduced ; or the ap may be widened so that the voltage is brought up to the normal. The wide gap, however, gives marked improvement in slow running. The best arrangement, in the opinion of the maker, is a compromise, using a gap of between 0.020 in. and 0,025 in.

The resistance to point burning, although not absolute, is much greater than with other metals, so that not only does the gap remain unaltered for a long time, but even when it widens this can go on to a greater extent than with an ordinary type plug.

There also appears to be no tendency to condensation on the fine point, and owing to the low-voltage feature a plug with a platinum point will continue to run satisfactorily when its insulator is so dirty that, -with a normal point, short-circuiting wouldoccur. •

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