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 for various types.
| Identifier | ExFiles\Box 4\5\ 05-page160 | |
| Date | 24th June 1921 | |
| C.A.P. 24.6.21. X.430. TABLE OF MAGNETO DISTRIBUTOR DIMENSIONS, MAKE RATIOS, AND RANGES. X.500 EXPRESSED IN FRACTIONS, VALUES OF THE DISTRIBUTOR PITCH IN EACH CASE. Magneto. Type. | Width of carbon brush. | Width of segment. | 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. ---|---|---|---|---|---|---|---|---|---|---|--- Watford. E.S | .15 | .62 | .77 | .86 | 1.63 | .17 | .14 | .31 | .49 | .32 | Standard. " EO.6(a) | .16 | .61 | .76 | .91 | 1.67 | .18 | .15 | .33 | .52 | .34 | Extra long range (630). " ------ (b) | .16 | .62 | .78 | .89 | 1.67 | .30 | .08 | .43 | .59 | .24 | R.{Sir Henry Royce} Bosch. ZR.6 | .12 | .65 | .77 | .46 | 1.23 | .20 | .15 | .35 | .08 | -.12 | Long case. U.S.A. Bosch. ZR.6 | .22 | .61 | .83 | .85 | 1.68 | .21 | .13 | .34 | .55 | .34 | " B.6 | .25 | .18 | .43 | .86 | 1.29 | .20 | .03 | .23 | .26 | .06 | Jump spark distributor. " DUZ.6 | .20 | .61 | .81 | .87 | 1.68 | .19 | .13 | .32 | .55 | .36 | Scintilla. CN.{Mr Chamberain}1 | .10 | .62 | .72 | .43 | 1.15 | .27 | .10 | .37 | .05 | -.22 | Long case. B.T.H. PM.6 | .26 | .25 | .51 | .56 | 1.07 | .25 | .01 | .26 | .06 | -.19 | Jump spark distributor. Medium Cam. Eisemann. GN.6 | .18 | .55 | .73 | .84 | 1.57 | .17 | .22 | .39 | .35 | .18 | 6 Stationary carbon brushes, and one revolving metal segment. Dixie. Aero 648. | .18 | .54 | .72 | .41 | 1.13 | .21 | .12 | .33 | .01 | -.20 | Polar inductor machine. Long case | ||