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).
Table detailing the performance results of various magneto models.
| Identifier | ExFiles\Box 4\5\ 05-page166 | |
| Date | 23th March 1921 | |
| A.{Mr Adams} X.430. TABLE OF RESULTS OF MAGNETO PERFORMANCE. (L) Magneto. | Type & No. | X. No. | (1) Weight (lbs). | (3) Air gap ("). | (4) H.T. safety gap. (mm). | Platinum gap (inches). | (6) Range Make ratio. | (13) Utility test spark lengths (mm). (a) (b) (c) (d) ---|---|---|---|---|---|---|---|---|---|---|--- Watford. | E.6 40886 | 2375 | 11.7 | .006 | 6.85 | .020 | 30 .858 | 7.0 | 6.7 | 5.7 (Magneto No.45168). | 3.8 " | E.6 44258 | 2375 | 11.7 | .006 | 6.85 | .022 | 30 .861 | -- | -- | -- | -- " | E.O.6a 46993 | 4181a. | 12.7 | .006 (.003 between sleeve & pole shoe) | 7.2 | .009 | 32 .906 | 7.0 | 6.7 | 5.7 (Magneto No.46988). | 4.2 " | E.O.6b 48919 | 4181b. | 12.9 | .006* (.003 between sleeve & pole shoe). | 7.0 | .012 | 63 .888 | 6.3 | 6.3 | 6.3 | 5.0 R.{Sir Henry Royce} Bosch. | Z.R.6 2571556 | 427 | 18.25 | .006 | 9.9 | .014 | 36.5 .458 | 8.5 | 8.3 | 8.1 | 5.0 U.S.A.Bosch. | Z.R.6. 2998784 | 3916 | 15.1 | .005 | 8.7 | .026 | 37.5 .850 | 7.6 | 7.2 | 4.3 | 4.2 U.S.A.Bosch. | B.6 3002660 | 3917 | 11.0 | -- | -- | .027 | 35.5 .864 | -- | -- | -- | -- Dixie. | Aero 648 718237 | 3724 | 14.1 | -- | -- | .022 | 38 .407 | 8.0 | 6.5 | 4.0 | 2.0 Conner | C.M.1 | 4210 | 16.1 | .006 | 8.7 | .010 | 48.5 .433 | 9.5 | 8.6 | 5.4 | 3.6 B.T.H. | P.M.6 R311941 | 3515 | 10.25 | .003* (taken from another machine). | 7.6 | .012 | 45.5 .556 | 6.6 | 6.6 | 6.0 | 6.0 | ||