The Editor ponders about plugs
Accessories and components are taken very much for granted, however much the cars themselves are discussed and dissected by enthusiasts. So I thought it was time to ponder about some of them.
I started by visiting the Champion Sparking Plug Co. at Feltham, a splendidly spacious factory with tasteful office block right on the fringe of London Airport. At one time Champion plugs, originated in Boston in 1906, the factory transferring to Toledo, Ohio, by 1910, were better known in America than in Britain. That was changed when a sales office was opened in 1922 in Pall Mall to sell Champions imported from the Canadian factory. The demand was so encouraging that the Feltham factory was built in 1937, Tom Gorst coming from Ford to run it. Champion plugs were fitted as original equipment in those days by Morris, Ford, Standard, Humber, Triumph, Singer, Riley, and other British manufacturers.
During the war Champion, with A.C. was commissioned to supply plugs for the vehicles of all our Armed Forces, and the Civil Defence services.
Today, in spite of ever-rising costs, Champion plug output has risen so tremendously that the price of what is a very high-quality product has been held at 5s. Champion plugs are fitted as standard by Austin, Morris, Wolseley, M.G., Riley, Austin Healey, Bentley, Rolls-Royce, Rover, Aston Martin and Jaguar.
I was interested to learn that four sizes, as distinct from types, of Champion plug are available. These are the 22 mm., mainly for industrial engines, the 18 mm., well-known to vintage-car owners, the popular 14 mm., and the 10-mm. racing plugs. The demands of racing engines have proved that the 10-mm. size is 100% dependable if properly handled, but it proved too frail for general usage. Before the war Fiat of Italy introduced the 12-mm. size for their Fiat 500 but it was short-lived. Today the 14-mm. plug is almost universal.
As engine design has progressed, it has been possible to reduce the number of types of plug and still meet every known requirement. Thus in 1962 the Champion N5 sufficed for 90% of the cars in current production, although a wide selection of types was needed for the remaining 10%. Before that the Champion L10 half-inch reach plug was specified for the majority of car engines, and three types covered 80% of all cars on the road, old models as well as new. Another three types looked after another 10%, and the rest of the Champion range met the requirements of the remaining 10%. After the L10 the Champion N8 was in most general use but increasing engine compression-ratios called for the cooler N5 plug.
In very early days Champion introduced the projected core-nose plug, in which the electrode protrudes beyond the insulator, and perfected it, but it showed small benefits in the prevailing woolly power units. Modern engines, however, can use it to advantage, carbon burning off the more exposed electrodes, and the introduction of these projecting-nose plugs has somewhat increased the type-range.
Champion now recommend plug-cleaning at 5,000-mile intervals and renewal at 10,000 miles.
Their existing range of normal plugs covers the 22-mm., 18-mm., 14-mm. and 10-mm. sizes, of which the types made number 12, 13, 26 and 2 respectively, the two 10-mm. types covering certain Velocette and B.S.A. motorcycle requirements. These Champion products are further augmented by resistor, suppression, full-suppression (shielded) and marine variants. Nor must the glow-plugs and aviation plugs be overlooked.
So far as racing plugs are concerned, Champion are in the proud position of supplying the sparking plugs used in Lotus, Cooper, B.R.M. and Brabham G.P. cars, while the majority of successful rally cars—Mini-Coopers, Saab, Austin Healey 3000, etc.—rely on them.
Champion racing plugs are made in i8-mm. (12 types), 14-mm. (23 types—3/8 in., 1/2 in. and 3/4 in. reach) and 10-mm. The last named, as used in the race-winning Coventry-Climax and B.R.M. V8 engines, are in three types—G-54R, G-56R and G-59R.
The technique of deciding on the design of a sparking plug to meet given heat-range requirements has been enormously simplified since the Champion Company developed the thermo-couple method of measuring the heat distribution of experimental plugs and were thereby able to decide on the correct shape and size of the insulator below the lower gasket seat, which is the vital factor in the “heat” characteristics of a sparking plug. Apart from this method, a 17.6 cu. in. single-cylinder Waukesha variable-induction-manifold-pressure engine is used to measure the i.m.e.p. obtainable from any given plug prior to detonation by pre-ignition, thus forming another means of accurately grading different types of plug.
A quick tour of the Feltham factory is a revelation in the complexity and precision of plug manufacture to Champion standards. A battery of B.S.A.-Acme Gridley machines produce the plug body from steel bar, all cutting fluid afterwards being separated from the swarf and used again in the complex machining processes. Terminal studs and terminals are produced on batches of 5-spindle Davenport automatics, and the “shells,” as the plug bodies are called, are weighed and washed before passing to the assembly bays.
The central electrodes of copper-coated nickel-alloy steel are “headed” to locate them in the insulator and welded together, and the side electrode is welded to the plug body, after it has been through a process of preparation in cleansing and plating vats.
Assembly is a highly ingenious automation process on automatic machines specially designed by Champion for the task. These machines measure and ram home the powder which forms the internal sillment seal between the insulator and central electrode and shell, these seals, incidentally, being capable of resisting a pull of 2 cwt., amongst other complex assembly processes, and each of these machines represents 24 hand-assembly stations.
In this light, spacious factory entirely devoted to sparking plug manufacture, female labour represents a considerable proportion of the 350-400 workers employed. Even the cartons and containers for the plugs are made by Champion, and their stores cover an area in which the entire spare-parts stocks of a major car manufacturer could easily be mislaid! I was interested to see that steel washers are fitted permanently and last the life of a plug.
From this factory beside the Great South-West Road out of London come the plugs which last year helped Britain to win the Monaco, Dutch, European, Belgian, French, U.S.A. and Mexican G.P. races, which were in the Sheraton Special with which Foyt won the 1964 Indianapolis 500, and which are favoured by Bentley and Rolls-Royce for their production engines. Champion!—W.B.