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).
Factors affecting the ignition lever position on Phantom and 20 HP models.
| Identifier | ExFiles\Box 32\5\ Scan080 | |
| Date | 25th October 1928 | |
| X6096. 25.10.28. BATTERY IGNITION ON PHANTOM AND 20 H.P. X5680 X2129. Items affecting position of ignition lever on quadrant at which ignition break should take place on retarding lever for starting engine. The position of this lever on the quadrant which gives a break of ignition current on retarding the lever with engine standing depends upon four quantities and should, for the normal values of these quantities, occur two-thirds of the way down the quadrant (Phantom), i.e. approximately opposite the letter E in 'LATE'. If this is not the case on the average of a number of positions in which the engine stops, there are three quantities, one, two or all of which are incorrectly arranged. The four quantities on which this position depends are :- (1) The number of degrees B.D.P. at which some particular cylinder stops. It is understood that this is usually not much different from 60°. (2) The full retard of the ignition, the normal value of which is 10° A.D.P. (3) The make ratio of the contact breaker, the normal value of which is .5 to .55, representing the ratio of the period on contact to the period between successive makes. (4) The total range of hand advance which is 30°. The above figures are for the Phantom. Contd. | ||