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 magneto distributor dimensions, make ratios, and ranges.
| Identifier | ExFiles\Box 4\5\ 05-page266 | |
| Date | 8th May 1924 | |
| X 730 X.430. TABLE OF MAGNETO DISTRIBUTOR DIMENSIONS, MAKE RATIOS, AND RANGES EXPRESSED IN FRACTIONAL VALUES OF THE DISTRIBUTOR PITCH IN EACH CASE. X.800. | Magneto. | Type. | Width of carbon brush. | width of seg: | Sum of brush & seg. | Make ratio. | Sum of make ratio brush & segment. | Range. | Forward overlap at advance. | Forward overlap at retard. | Backward overlap at advance. | Backward overlap at retard. | Remarks. | | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- | | U.S.A. Bosch. | BRS. Ed.{J. L. Edwards}19. | .22 | .61 | .83 | .85 | 1.68 | .21 | .13 | .34 | .55 | .34 | Same as Ed{J. L. Edwards}18. but differently wound armature. | | Watford. | E06c | .15 | .64 | .79 | .88 | 1.67 | .18 | .19 | .37 | .48 | .30 | R.R. 40/50 standard. | | Watford. | EL06 | .14 | .68 | .82 | .88 | 1.70 | .34 | .12 | .46 | .58 | .24 | Large machine. | | R.Bosch. | Z.F.6. 2490573. | .16 | .56 | .72 | .90 | 1.62 | .17 | .13 | .30 | .49 | .32 | 20 H.P. size. | | Scintilla | AMG-A 34937. | .21 | .49 | .70 | .43 | 1.13 | .29 | .10 | .39 | .03 | -.26 | Stationary armature. Rotating Field | | Scintilla | AMG-A 26495. | .20 | .48 | .68 | .46 | 1.14 | .29 | .17 | .46 | -.03 | -.32 | Large cams. | | ||