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).
Calculation of ignition timing parameters and conditions required for an engine starting spark.
| Identifier | ExFiles\Box 54\5\ Scan253 | |
| Date | 9th January 1924 guessed | |
| -2- Contd. Further, the fully advanced make will occur R + 120 r - d degrees before dead point. It is clear that in moving the ignition lever from full retard to full advance a make will occur if the stopping position S degrees of the engine lies some- where between 120 r-d degrees and R + 120 r-d degrees. Also that on the reverse motion of the lever, i.e. retarding the lever through its whole range, a break will occur, in the same circumstances, at the same point. Such a break causesa an igniting spark with which to start the engine, if the ignition is switched on. (The spark does not go to the cyliinder under consideration but to the one next in aevance of this). The difficulty that may prevent the realisation of this spark is that the engine stopping position may lie outside this range on the retard side; or algebraically that S may be less than 120 r-d. {John DeLooze - Company Secretary} The condition therefore that such a spark may be realised is that S >= 120 r -d e.g. if d = 10º and r = .55, in accordance with the production setting, then S must be >= 66º - 10º. i.e. >= 56 degrees. With equally good compressions and the engine quite free, S should of course be 60º. Contd. | ||