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).
Investigation into the sources of noise on a Scintilla AM-8-A magneto at various speeds.
| Identifier | WestWitteringFiles\L\2April1924-June1924\ Scan53 | |
| Date | 6th March 1934 | |
| EFC. COPY. 6.3.34. WA.{Mr Wallis}11. X.4183 - INVESTIGATION OF NOISE ON SCINTILLA AM-8-A MAGNETO To facilitate the analysis of the noise emanating from this magneto, the distributor and contact breaker was removed, and the noise investigated first with the magneto minus the H.T. distributor and contact breaker, secondly with the H.T. distributor in position , and lastly in a completely assembled condition. The percentage noise in the first case at all speeds above 500 R.P.M. was considered to be Rattling gears 50% Governor. Bearings. etc. 50%. In the second case it was observed that at slow speeds the tracking of the H.T. carbon brushes on the rotor, caused a whistling noise. This developed into a hissing sound at high speeds. The contact breaker was then put into position and the magneto run at 1000 R.P.M. and 3000 R.P.M. and the noise investigated at each speed (primary gap .016") The percentage noise was as follows :- 1000 R.P.M. Contact breaker. 15% Gears, governor, etc. 70% Distributor. 15% 3000 R.P.M. Contact breaker 25% Gears, governor etc. 70% Distributor. 5% It will be seen from the preceding investigations that the majority of noise is caused by the rotating elements. It was noticed that the noise from the gears was uniformly distributed, i.e. there was no knocking. The contact breaker was exceptionally quiet in comparison with KDG Watford, probably due to the fact that the noise is muffled to a greater extent. On the whole the magneto can be considered to be reasonably quiet. EFC/H.E.West. | ||