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).
Comparison table of technical data for various types of magnetos.
| Identifier | ExFiles\Box 4\5\ 05-page168 | |
| Date | 22th May 1921 guessed | |
| -3- A.{Mr Adams} Contd. Magneto. | (17) Contact breaker flinging speed (R.P.M.) | (18) Primary resistance (Ohms). | (19) Secondary resistance (Ohms). | (20) Secondary m.a. on 108 volts 50~ Hor. / Vert. | (24) Remarks. Watford. | | .54 at 19°C. | 3319 at 19°C. | - / - | " | | .535 at 18°C. | 3057 at 18°C. | 15.5 / 9.4 | " | | .51 at 14°C. | 2600 at 15°C. | 20.3 / 9.8 | " | | .49 at 16°C. | 2840 at 17°C. | 20.1 / 11.2 | R.Bosch. | | .73 at 15°C. | 2849 at 16°C. | 9.4 / 5.3 | U.S.A. Bosch. | | .935 at 20°C. | 3106 at 21°C. | 8.4 / 6.7 | U.S.A. Bosch. | | -- | -- | -- / -- | Low speed sparking characteristics taken before endurance test on which test magneto broke down on H.T. brush. Dixie. | | .68 at 16°C. | 3458 at 16°C. | 12.8 / 8.4 | Conner. | | .51 at 18°C. | 2400 at 19°C. | 13.6 / 8.1 | B.T.H. | | .76 at 14°C. | 2690 at 16°C. | 22.4 / 16.3 | Gap had to be increased to obtain slow speed figures owing to distortion produced on endurance test. Handwritten note (vertical): Not cleared | ||