From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Letter detailing the features and ongoing tests of a new H-T sparking plug design.
Identifier | ExFiles\Box 58\2\ Scan022 | |
Date | 7th December 1931 | |
- 3 - A.J. Rowledge, Esq., (contd) 7th. December, 1931. conductivity of copper, can use a center electrode - without welds - of the highest type of special non-burning alloy, which in turn means that the sparking plug is so balanced that the center electrode, and the copper sleeve, has a greater expansion than the shell of the plug itself, which in turn means that the hotter the plugs get, the more gas tight it gets. Still another feature of the H-T sparking plug is the use of a closed-end shell in which the combined area of the vent holes is greater than that of the gap hole surrounding the center electrode, yet sufficiently restricted so that on the compression stroke some of the fresh gas is sure to be forced through the spark gap hole. This effectively prevents gas lock at that point, which is so often responsible for a momentary miss in quick acceleration. I would call your attention to this closed-end of the shell which not only gives maximum burning surface, but by its restricted perforations secures a charging effect so that any particle of moisture which might have gathered between the electrodes when the engine is left overnight, is blown out at the first compression stroke. As I stated in my previous letter, it is our intention, should the plug prove satisfactory, to ultimately manufacture this plug in England, and it is primarily my intention, by the present, to interest you in making some tests on this plug in order to appreciate its suitability for your engines. At the present moment we are only making the one type I sent you for high compression engines, as that type has proven itself entirely suitable and satisfactory for American engines, but it is possible that certain modification may be necessary for your engines, such as the reach of the plug, and such minor details as the terminal nut, etc. However, if you would care to make some tests, for example on a single cylinder unit, it would be greatly appreciated, and I should be delighted to supply you with any further information you may care to have, and be extremely pleased to see you on my next visit to England. For your personal information, the British Air Ministry are now conducting exhaustive tests at Farnborough, the preliminary tests having been quite satisfactory, and in their own words they say 'Generally the plug is well made and is considered to be worth pursuing.' Confidentially, Mr. Fedden has conducted some tests at Bristol, and an extract from his report reads as follows; | ||