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 explanation of the Synchro-Start system's operation and its influence on the ignition.
| Identifier | ExFiles\Box 62\1\ scan0361 | |
| Date | 4th February 1936 guessed | |
| is off. The electrical circuits are dead, of course, in these circumstances. When the ignition key is turned, and at starting speeds, the speed of the make and break interruptions is not sufficient to induce the current value necessary, in the secondary winding, to operate the relay. As soon as this speed rises to the pre-determined rpm the relay will operate to break the starter-switch control circuit, thus releasing the starter switch contact ram. Following the attached wiring diagram, 'A' indicates the transformer primary circuit, controlled by the ignition switch and timer contacts. The fine lines 'B' show the secondary circuit operating the relay (whose contacts 'C' on the beamare closed by gravity). Immediately the ignition is switched on at 'D', circuits 'A' and 'B' are alive, as also circuit 'E' and the starter operates. When the engine has attained the pre-determined speed, the value of the current in circuit 'B' will be such that the relay will be withdrawn, opening contacts 'C' and depriving circuit 'E' of the current energy necessary to operate the solenoid controlled starter switch. The spring on the latter will open the starting motor main circuit. This position is maintained as long as the engine speed does not fall below the desired idlingspeed. As soon as this occurs, there will be a loss in thevalue of the current induced in circuit 'B', the relay will close contacts 'C', circuit 'E' will be alive and the solenoid will at once close the starter switch. The above is the sequence of operation in the event of a threatened stall. WHAT IS THE INFLUENCE OF SYNCHRO-START ON THE IGNITION ? It will be noticed that two inductances 'F' and 'G' are included in the transformer primary and secondary circuits. They are responsible for the time factor change in the coil. When the breaker contacts make contact for the ignition coil, they also close the circuit to the transformer, building up a flux field and, when they break, this field breaks down causing the inductance in the secondary circuit to build up. These inductances break down at a time when the breaker points are open and cause a reversal of conditions in the transformer, which induces a current in the primary winding of this transformer the polarity of which is suchthat it tends to assist the ignition coil primary to charge and | ||