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 performance data, specifically lowest speeds, for different models of magnetos.
| Identifier | ExFiles\Box 4\5\ 05-page165 | |
| Date | 1st December 1920 | |
| -2- Contd. | Magneto. | Type and number. | X. No. | Lowest speeds. | Remarks. | |---|---|---|---|---| | | | | Adv. | Cent. | Retd. | | | R.{Sir Henry Royce} Bosch. | Z.R.6 | 427 | 260 | 170 | 246. | Advanced position same as maker's. Retarded position 2.5° earlier than maker's. | | | 2571556. | | | | | | | U.S.A. Bosch. | Z.R.6 | 3916 | 120 | 162 | 240. | Advanced position same as maker's. Retarded position 3.5° earlier than maker's. | | | 2998784 | | | | | | | Dixie. | Aero 648. | 3724 | 180 | 180 | 185. | Sparking speed unaltered by advancing or retarding, hence figures as first obtained on maker's range are representative | | | 718237. | | | | | | | Conner. | C.M.1 | 4210 | 350 | 260 | 170. | Retarded position same as maker's, this position giving minimum regular sparking speed. Further retard again increased speed rapidly. Advanced position 14.5° later than maker's. | | | | | (Accepted averages of two sets of figures). | | | | | B.T.H. | P.M.6. | 3516 | 244 | 192 | 220 | Advanced position 10° earlier than maker's. Further advance limited by fouling of timing lever, but apparently would further reduce the minimum sparking speed in retarded position. Retarded 21.5° earlier than maker's. | | | R.311941 | | (Retarded to stop by fouling of lever). | | | | | ||