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).
Technical report page discussing the performance and issues of an ignition relay piston and advance curve.
| Identifier | WestWitteringFiles\O\2April1926-June1926\ Scan030 | |
| Date | 4th April 1926 guessed | |
| contd :- -2- efficient combination of leather and ring for the relay. We find that the most efficient piston requires a load of 6 lbs. to retard it and the controls and distributor (mag. disconnected) when the oil is warm. Unless we have at least double this load, the retardation of the ignition is very sluggish when the oil is cold. The spring we have been using on production since we got magneto with a sleeve friction of 3 lbs. only gives a load of 12 lbs. in the fully retarded position. The piston in these relays has not the latest arrangement of leather and ring, however, and is therefore a much easier fit in the bore of its chamber and consequently easier to retard. The trouble with these pistons has been that they do not maintain their efficiency as well as we could wish after prolonged service. With reference to the relay on 7-EX. This was tested to give standard advance curve as fitted up on the car. Unless therefore the oil pressure has been changed or the cup leather has in some way lost its efficiency, we are unable to see why its performance should have altered. If car speeds of 75 m.p.h. are attainable, the ignition advance must be adequate. The standard flywheel advance curve given by the relay is given in Graph 1. As will be seen from this curve we have always used a small initial advance to overcome lag due to over-load. The reason we did not use more initial advance, as we should have wished, was because the governor characteristics were such that had we done so we should have had excessive ignition advance at the higher speeds. contd :- | ||