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 data showing minimum sparking speeds for magnetos at various timing positions and cam angles.
| Identifier | ExFiles\Box 40\2\ Scan104 | |
| Date | 12th April 1926 guessed | |
| - 2 - MINIMUM OF SPARKING SPEEDS. Timing position. Angle of Make 84° " Break 96° Angle of Make 90° " Break 90° Angle of Make 110° " Break 70° Adv: 55 r.p.m. 60 r.p.m. 60 r.p.m. Ret: 30° 95 " 100 " 100 " " 60° 145 " 155 " 145 " 2. Magneto fitted with Magnet of 12 m/m thickness. Cam. Angle of Make 84°. Angle of Break - 96° Utility values with various cams. Timing position. 500 r.p.m. 700. 2100. 3000. Adv: 4.15. 4.35 5.0 6.25. Ret: 30° 5.90 6.25 8.35 10.0. " 60° 7.15 7.70 11.1 14.3. Cam. Angle of Make - 90° Angle of Break 90° Timing Position 500 r.p.m. 700 2100 3000. Adv: 5.0 5.0 5.25 5.9. Ret: 30° 6.25 4.75 10.0 11.1 " 60° 7.15 7.7 14.3. 14.3. Cam. Angle of Make - 110° Angle of Break 70° Timing Position 500 r.p.m. 700. 2100 3000. Adv: 4.17 4.35. 3.85 4.55. Ret: 30° 5.55 5.9 7.15 9.1. " 60° 9.10 8.3 14.3 20.0. | ||