Machine to Clean and Test Plugs A NEW sparking-plug cleaner and
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tester, made by the A.C.-Sphinx Sparking Plug Co., Ltd., was demonstrated in London last week. Known as the Plug Doctor, the machine is likely
to appeal mostly to the garage proprietor, but operators of large fleets could put it to good use.
The Plug Doctor has two independent units. The first cleans a plug rapidly by bombardment by a cleanser compound, a blast of clean air clearing away any residue. The second unit is the tester, which .operates at a voltage of 20,000.
Soundness of a plug is determined by opening the points so that a spark cannot be made. A current is then applied to the insulator which, if sound, forces the current to take an alternative path, where it jumps across a test gap. Absence of a spark here indicates a faulty plug.
If the plug passes this test, it is then necessary to find out whether it would function in an engine. The points are adjusted to the correct gap and inserted in the socket of the tester. Air is then applied at a pressure, the figure for which is obtained from the manufacturer of the engine.
In the demonstration,.a plug from a Bedford engine was tested and the air pressure Was 50 lb. per sq. in., as recommended by Vauxhall Motors, Ltd. When a current is passed a spark reflected in a mirror shows that the plug is sound.
Three Bedford vans are touring the country demonstrating the Plug Doctor, which is likely to cost 'between £20 and £25.