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).
Translation of a patent description for C.F. Sparking Plugs by Dr. A. Tebaldi.
| Identifier | ExFiles\Box 58\2\ Scan098 | |
| Date | 31th May 1934 guessed | |
| Translation. 8/12a Hs{Lord Ernest Hives - Chair} thought you had written to the By X1812 C.F. SPARKING PLUGS patent Dr.A.Tebaldi. Engineer. DESCRIPTION ----------- It has been observed, especially in these last years, in the course of which car and aero engines have reached extremely high speeds, that the problem of constructing sparking plugs has become a very arduous one while that of its working is of equal interest for the constructor of the engine and the users of same. The ideal sparking-plug should possess as its characteristic the possibility of working at the various speeds of the engine, maintaining all the time the electrode at an almost constant temperature, that is to say, a temperature at which the oil deposited on the electrode burns off and, on the other hand, not so high as to produce premature ignition and consequent undue wear of the electrode itself. The sparking-plug used at present, having a constant degree of heat transmission, determined by the various elements constituting the sparking-plug itself, the aim of the constructors is to produce for every type of engine such type of sparking-plug which sufficiently answers the extreme running conditions of the given engine, that is to say, at slow running and at full power. It appears at once obvious that under such conditions, the action of the sparking-plug is limited by these two extreme speeds, viz. it is too cold at slow running and has therefore a tendency to get dirty while at full power, it becomes too hot, with consequent rapid wear, and may cause premature ignition. As already said, this state of things has created the necessity for designing, as can be seen in practice, various types of sparking-plugs for the various types of engines. The principle on which the invention of the C.F. sparking plug is based, was that of creating a state of things such that the coefficient of heat transmission should vary proportionally with the temperature of the electrode itself, and in such a way that, when the temperature of the electrode is low, its coefficient of heat transmission is small, whereas, when its temperature is high, that coefficient is the highest possible. A sparking-plug would thus be obtained, which would be "very hot" at low engine speed and "very cold" at high engine speed. This principle has now been applied in the construction | ||