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 of results of magneto performance tests.
| Identifier | WestWitteringFiles\F\March1921\ Scan62 | |
| Date | 23th March 1921 | |
| A.{Mr Adams} X.430. TABLE OF RESULTS OF MAGNETO PERFORMANCE. 23.3.21. X.2375- X.4181 X.39/6 | Magneto. | Type & X. No. | (1) Weight (lbs) | (3) Air gap (") | (4) H.T. safety gap (mm) | Platinum gap (inches) | (6) Range | Make (a) ratio | (13) Utility test (a) | spark lengths (mm) (b) | (c) | (d) | |---|---|---|---|---|---|---|---|---|---|---|---| | Watford. | W.E.6 40886 | 2375 | 11.7 | .006 | 6.85 | .020 | 30 | .858 | 7.0 | 6.7 | 5.7 | 3.8 | | " | E.6 44258 | 2375 | 11.7 | .006 | 6.85 | .022 | 30 | .851 | (Magneto No.45168). | -- | -- | -- | | " | E.O.6a 46993 | 4181a. | 12.7 | .006 (.003 between sleeve & pole shoe) | 7.2 | .009 | 32 | .906 | 7.0 (Magneto No.46988). | 6.7 | 5.7 | 4.2 | | " | E.O.6b 48919. | 4181b. | 12.9 | .006" (.003 between sleeve & pole shoe) | 7.0 | .012 | 63 | .888 | 6.3 | 6.3 | 5.0 | | R.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 | 8.5 | 8.6 | 5.4 | 3.6 | | B.T.H. | F.M.6 R311941 | 3515 | 10.25 | .003" (taken from another machine) | 7.6 | .012 | 45.5 | .556 | 6.6 | 6.0 | 6.0 | 6.0 | | ||