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).
Analysis of noise reported from a Watford E06 (d) Magneto, No.73972, off test.
| Identifier | ExFiles\Box 48\2\ Scan234 | |
| Date | 6th February 1925 | |
| EFC. {E. Fowler Clarke - Electrical Engineer} WA. {Mr Wallis} 108. 6th Feb. 1925. X.4181d. WATFORD E06 (d) MAGNETO No.73972 REPORTED NOISY OFF TEST. This magneto has now been carefully run to analyse the noise emanating from the various rotating etc. units. We find that the noise is almpst entirely caused by the contact breaker and sleeve mechanism. This noise appears to be lack of rigidity of the cam ring and the sleeves, in the case of the sleeves especially, allowing them to vibrate or oscillate with a frequency dependent upon the magnetic reactions imposed upon them as medium to the permanet magnet and the armature core. These vibrations vary considerably therefore with the speed, causing a knocking sound at low speeds and a hum very much akin to the sound of A.C., at high speeds, more especially in the advanced position of the hand lever. This vibration could be demonstrated, by applying pressure with the finger, on the portion of the sleeve visible in the armature tunnel (magneto running) which immediately damped out the oscillation considerably. It is considered that the brass locating ring at the rear end of the sleeves should be made a good sliding fit in the driving end bearing, circular location, provided. It is further suggested that if the whole system of cam ring and sleeves were more accurately and firmly located to the main body of the magneto, noise would be | ||