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 dimensions for a jump spark distributor.
| Identifier | ExFiles\Box 43\4\ Scan244 | |
| Date | 18th February 1930 guessed | |
| -3- Distributor dimensions. | | Relative. | Absolute | | |---|---|---|---| | | | INCHES | DEGREES | | Pitch (P) = | 1.000 | .754 | 30 | | Make ratio (M) = | .462 | .348 | 13.9 | | Range (R) = | .338 | .255 | 10.2 | | Forward overlap at full advance (Fa) = | .111 | .084 | 3.3 | | Forward overlap at full retard (Fr) = | .450 | .339 | 13.5 | | Backward overlap at full advance (Ba) = | -.103 | -.078 | -3.0 | | Backward overlap at full retard (Br) = | -.442 | -.333 | -13.2 | | Width of brush (B) = | .298 | .225 | 8.9 | | Length of segment (S) = | .248 | .187 | 7.4 | | Distributor dia. (D) = | | 2.880 | | Jump spark distributor, contd. | ||