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 ignition pitch values for different magneto types.
| Identifier | ExFiles\Box 4\5\ 05-page156 | |
| Date | 24th June 1921 | |
| CAP X.430. TABLE OF MAGNETO DISTRIBUTOR DIMENSIONS, MAKE RATIOS, AND RELATIVE POSITIONS OF PRACTICAL VALUES OF THE IGNITION 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 | ZR.6 Ed{J. L. Edwards}19 | .22 | .61 | .83 | .85/1.88 | 1.68 | .21 | .13 | .34 | .55 | .34 | Same as Ed{J. L. Edwards}18 but different wound armature | | Watford | ED{J. L. Edwards}6c | .15 | .64 | .79 | .88 | 1.67 | .18 | .19 | .40 | .48 | .30 | | | Watford | ELO.6 | .14 | .68 | .82 | .88 | 1.70 | .34 | .125 | .46 | .575 | .235 | | | ||