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).
Disagreeing with the alteration of the 'H' engine safety gap from 7.7 to 8.5 m/m.
| Identifier | ExFiles\Box 43\4\ Scan263 | |
| Date | 4th March 1930 | |
| X4021 14 MR. PLATFORD: MR. ROWLEDGE MR. COVERLEY. E.A.C. MARCH 4/30 J/HB{C. E. Harcombe}/B16 I am returning herewith memo EFC/2/AD/28/2/30. I do not agree that it was at all desirable to alter the "H" engine safety gap from 7.7 to 8.5 m/m because it means that if a lead should become detached from the engine, an excessive potential is put upon the instulation of the winding over and above what the magneto is designed for up to the stafe of the breaking down potential of the air gap. The memo states that the reason for altering the safety gap was that sparking was occurring there with the 7.7 gap when the magneto was run on a 5 1/2 m/m test gap. but it does not say what the 5 1/2 m/m test gap consists of. I rather think you are still using the 3 point test gap which has long ago been substituted by a ball gap. I think it is very undesirable for this alteration to have been made to the type test magneto without A.I.D. being informed, and I certainly think that it constitutes a somewhat unfair loan on the magneto, but I do not think that it will, unless the magneto breaks down, raise any question of the invalidation of the magneto as the result of a satisfactory type test. A.I. For D.A.I. | ||