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).
The testing of four EW6 magnetos and the causes of the noise they produced.
| Identifier | ExFiles\Box 65\3\ scan0184 | |
| Date | 3rd March 1928 | |
| EFC. from Hs{Lord Ernest Hives - Chair}/AJL. X7791 3.3.28. EW6. MAGNETOS. We have tested the four magnetos which you handed to us with the following results. Only one of these (No.100094) was considered acceptable with regard to quietness as compared with the present EO6 type. The make and break noise is the chief complaint although two of the magnetos tested had squeaky H.T. distributor brushes. It was found that in the present design the magnitude of the noise depended upon the following causes :- (1) Size of gap between contact points. (2) Strength of contact breaker spring. (3) Bedding of contact points. In (1) it was found that the size of the gap between the contact points of the EW6 type magneto fitted 31.10.27 (3168 miles) had increased from .012 to .025". In case (3), if the contact points were only touching on one edge the magneto was considerably quieter. We also found that the fitting of the cam sleeve varied, making it impossible for the return spring to retard the magneto in one case (100094). In addition to the above, one of the suggested modified type of contact breaker lever was tried on each of two of the above machines in turn, in order to see if noisiness was affected by such change. No appreciable difference was observed. Sgd. E.Butler. | ||