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 from North & Sons, Ltd. regarding magneto specifications, cam angles, and clearances.
| Identifier | ExFiles\Box 65\3\ scan0144 | |
| Date | 16th December 1927 | |
| X 7791 THE BRITISH MADE Watford SPEEDOMETERS & MAGNETOS. NORTH & SONS, LTD. WHIPPENDELL ROAD, WATFORD. TELEPHONES: LONDON 1346 GERRARD WORKS: 622 & 623 WATFORD. TELEGRAMS: AEROMAGS WESTCENT LONDON. AEROMAGS WATFORD. CONTRACTORS TO THE ADMIRALTY, WAR OFFICE CROWN AGENTS FOR THE COLONIES, INDIA OFFICE. Governing Director: R.B.North EFC3/T Director & Works Manager: C.K.Kirby. CHK/DEW.18 Secretary F.Stockwell 16th December, 1927. Messrs. Rolls-Royce Ltd., DERBY. Dear Sirs, We thank you for your letters of the 12th and 13th instant and beg to say that the F.W.6. Magneto No.100080 was fitted with cams intended to give the conditions called for but as, pending the final decision as to the actual form of the cam, grinding fixtures have not yet been made, the actual conditions were slightly different, the angle through which the points were kept open being 69º on one cam and 72º on the other. The Magneto No.100081 was fitted with cams ground more accurately to shape and the points were kept open for 73.5º on each cam. With regard to the tunnel clearance, we beg to say that this has not been reduced as compared with that of our other models, the dimensions allowing for a clearance of .004" to .006" while both the pole shoes and the armature are ground. We do not think the clearance should be greater than this but shall be pleased to carry out tests with a greater clearance if you consider, in view of these figures, that it is desirable. Yours faithfully, FOR AND ON BEHALF OF NORTH & SONS, LTD. DIRECTOR | ||