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).
Ministry's instructions for the type testing of sparking plugs.
| Identifier | ExFiles\Box 58\2\ Scan097 | |
| Date | 31th May 1934 | |
| WST r1812a Mr. Loxford. c to Mr. Hives./West c to Mr. Robbins. R/B/s 31-5-34 Type Test of Sparking Plugs Instructions have been received from the Ministry that before any sparking plugs are finally approved for general use on any particular type of Service engine, at least 75% of a half engine set shall have completed satisfactorily a service type test, with the exception of the power curves and detonation test. The erosion of the electrodes after each ten hour period is to be recorded in the type test report, together with electrical tests specified in respect of the internal flash over dielectric strength test of the central electrode and sparking test under air pressure. It is to be noted that prior to effecting these electrical tests, the sparking plug gaps may be adjusted, and further, that the above conditions seem to me to permit that type test of the sparking plug will not require the self same plugs to be used on the power curves and the last ten hour period of the detonation test, as well as the remaining curves and 90 hour periods. Apparently on the one hand the use of doped fuel for the curves and the nature of the detonation test on the other is considered to be outside the type test requirement for the sparking plugs. Details of the electrical tests are contained in R.D.E. Specification 31 issue 1 dated April 1934, which it is believed Mr. West is already familiar with. The above requirements particularly refer to the standard 18 m/m long or short reach sparking plugs for Service engines, and it is understood that further specifications are being prepared by R.T.D. for other types of Service sparking plugs, and sparking plugs for civil aircraft engines. A Daynes Inspector-in-Charge. A.I.D J/HB{C. E. Harcombe} | ||