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).
Safety gaps of Watford Aero Magnetos Type IS.12, noting they are too small and comparing them to B.T.H. magnetos.
| Identifier | ExFiles\Box 43\4\ Scan028 | |
| Date | 10th December 1926 | |
| X4021 To Wd.{Mr Wood/Mr Whitehead} from EFC. EFC5/T10.12.26. X.4021 - WATFORD AERO MAGNETOS TYPE IS.12. The safety gaps of these magnetos are not accessible for measurement with removal of the armature cover. We generally include the specification of the length of the safety gap in our Specification of the Production Inspection & Test. This will not, however, be expedient in the case of these magnetos. We have measured the safety gap of one magneto and find it to be only 7.8 mm. This we consider to be too small for a jump spark magneto of this type, as there should be no difficulty in regard to insulation of this type of magneto with stationary armature. The safety gaps of the B.T.H. magnetos of the SCE12-A and SC12-7 types are 8.5 to 9.0 mm. and we consider the Watford safety gaps should be of similar length. We should be pleased to hear what Messrs. Norths have to say on this point. EFC. | ||