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).
Explanation of the electrical system's operation, detailing the function of various switch positions.
| Identifier | WestWitteringFiles\F\January1921\ Scan29 | |
| Date | 10th December 1920 | |
| R.R. 285A-(100 T) (S.H 798. 10-12-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2947 Contd. -2- EFC1/T21.1.21. (1) The battery is only connected to the system by the right hand switch when desired. (2) In the "off" position of the right hand switch, the main dynamo field is short circuited and no current is available for the lamps, even though the lamp switch on the left hand be put on. (3) In the B position of the right hand switch the battery is connected through the ammeter to the lamp switch and the lamps may then be switched on to the battery, the current from which is shown by a deflection of the ammeter needle to the left. The dynamo field is still short circuited by the switch in this B position. (4) In the D position of the switch, the battery is entirely disconnected from the system, but the dynamo is connected to feed the lamps through the ammeter giving an indication in the same direction as previously, the dynamo field having now been un-short-circuited so that the dynamo is allowed to excite. The field current, after traversing the main field winding from the live terminal 1 to terminal 2, passes down to earth through the regulator spring and spindle, via the carbon granule to the barrel of the regulator which is earthed. Thus it is possible to run the lights direct from the dynamo without any functioning of the battery. Further, the current supply to the lamps does not have to pass through the cut-out. (5) In the D and B position of the switch the current from the dynamo has to pass through the cut-out and back to the switch, then feeds direct to the lighting switch, missing the ammeter, but in order to get to the battery to charge it, has to pass back through the ammeter. It will be seen that the current delivered by the dynamo to the battery, when the battery is also connected to the system, has to pass the reverse way through the ammeter and therefore the indication when the battery is receiving charging current is to the right, although this current is proceeding from the dynamo as before. The ammeter is now entirely in the battery circuit, as with us. (6) The electrical scheme of the cut-out calls for no particular mention as it differs in no way from that of the ordinary article. (7) There is a point electrically about the regulator, however, which calls for mention. It will be seen from the diagram that the regulator is fed from the live terminal 1 of the dynamo, and it has been ascertained that the circuit passes through a low resistance series coil from the end of which a tapping is taken to an insulated ring which can be touched by the Contd. | ||