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).
Test report comparing the sparking performance of Mea and Eisemann magnetos.
| Identifier | ExFiles\Box 4\5\ 05-page296 | |
| Date | 20th August 1924 | |
| EFC. WA.{Mr Wallis}69. X.430 20.8.24. RE MEA MAGNETO AND EISEMANN MAGNETO. X.177 X430 X.178 Both these magnetos were tested using a 3.5 mm. H.T. gap, as neither of them appeared capable of sparking regularly over a larger gap. (N.B. In the production test of the R.O.1 Watford magneto, a 4.5 mm. gap was used, and the minimum speed for regular firing in the fully retarded position was specified as 275 R.P.M.). not to exceed The high speed sparking of both magnetos was found to be O.K. on the 3.5 mm. gaps, but not on a 4.5. The low speed sparking on both magnetos on the 3.5 mm. gap is as follows :- Mea. Minimum speed for regular sparking in all positions of advance - 400 r.p.m. (On this magneto the magnets are advanced with the contact breaker). Eisemann. This magneto is very bad at low speed sparking and will not spark regularly at all on a 3.5 mm. gap until the speed is increased to about 1500 r.p.m. The Eisemann magneto has no hand advance but is fitted with an automatic advance arrangement, the characteristics of which have been obtained (see curve). It appears from the above that both magnetos are weak - possibly the magnets require re-magnetising. EFC/HSW. | ||