The Supply Department.
Page 23
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Selected Information which is likely to be of Interest to Makers, Owners, and their Buyers.
Some New Sparking Plugs.
We illustrate on this page some sparking plugs which have recently been introduced on the market. The first of these, the invention of Mr. R. F. Hall, is of extremely simple yet robust construction, and should give good results in the hard service to which many commercial vehicles are subjected. We have had a set fitted to the engine of a two-cylinder 3ocwt. van, and intend to test them to failure. The plug has been designed with a view to make the most effective use of the explosions within each cylinder to the end that agas-tight joint shall be maintained. If gas can escape through any part of a sparking plug, it is pretty certain that oil from the cylinder will be induced to follow the path, resulting in the formation of soot and the commencement of shortcircuiting troubles. The Hall plug is certainly well calculated to continue gas tight, so long as the insulator remains undamaged by fracture. The simplicity of construction is well shown in the sectional drawing. Neglecting such parts as nuts and washers, the plug con sists of but three loose parts : (1), the steel body; (a), the insulator with its metal sleeve cemented on; and (3), the pin, or central electrode. Surface leakage is almost in] possible, because of the great distance which separates the two electrodes, the centre one of which is of pure nickel. These plugs are supplied in metal cases, each containing three plugs, as shown in one of our illustrations. In addition to the plugs, the case also contains a spare nickel electrode, and a special spanner. Another interesting plug, sold by Messrs. Eyquem's Patents, of 31, Duke Street, St. Mary Axe, E.C., is also • illustrated. It is a combination of sparking plug and compression cock. By the opening of the relief cock, the high-tension current is short-circuited, through the contact with the body of the plug of a wire that is attached to the spindle of the relief cock, as may be seen in the illustration. At the same time that the current is diverted from the sparking points, the escaping gases effectively clear the points of all deposits of oil or soot. The relief-cock spindle is of course, provided with an insulated knob.
The second plug shown in the same illustration as that which is provided with the test cock is made according to another of Eyquem's patents. Both patterns are provided with a patented form of wire terminal, the use of which obviates the need for nuts and spanners.