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).
Development of a formula to determine the ignition break position for starting the engine.
| Identifier | ExFiles\Box 54\5\ Scan308 | |
| Date | 30th October 1928 | |
| X.5680 30.10.28. BATTERY IGNITION. X.3949. Development of formula giving position of lever on quadrant, at which ignition break should take place on retarding lever, for starting engine. The position for which a formula is required depends upon four Quantities, each of which is represented by general symbols in the first instance. The Quantities are :- (1) The make ratio of the contact breaker which we will call r (usually .5 to .55). N.B. The make ratio is defined as the fraction Period of make ------------------------------------------------ Total period (period of make+period of break) (2) The fully retard ignition setting of the engine. (Usually about 5º to 10º A.D.P.) Let this be d degrees after dead point. (3) The available range of advance (hand advance only and reckoned on engine). This for the present 20 H.P. ignition is 40º, and for the present 40/50 ignition 30º. Call this R degrees. (4) The position in which the engine has stopped. Assume this to be Sº before dead point for some particular cylinder. (This will be in the neighbourhood of 65º - see below). Since fully retarded break is set to d degrees after dead point, the fully retarded make will be 120 r - d degrees before dead point. Contd. | ||