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).
Investigation into the green lamp scheme on car 18-EX in France, detailing the cause of a fault and the proposed solution.
| Identifier | ExFiles\Box 65\2\ scan0168 | |
| Date | 28th December 1928 | |
| X 7740 Extract from RJA1/C.28.12.28. X.7780. 18-EX IN FRANCE GREEN LAMP SCHEME. X.4040. X.7740. This was found to have the bulb burnt out and another was fitted. The operation of the device is reported by drivers to be very erratic. There is a good deal of side play in the pivot of the relay armature and since the adjustment is rather critical (as has been noted on the bench) this may account for the fact. On 14-G4 which has now arrived it was reported that the green lamp would come on with the switch in the ignition only position. It has been found possible to produce the same effect on 18-EX and we have traced this the cause as follows :- In the M & B position on these cars the battery is still connected to the dynamo armature, and as was found at Derby, feeds the green lamp coil via the dynamo armature and field in a reverse direction and giving rise to a reversal excitation of the dynamo. Then when the dynamo is speeded up an E.M.F. is generated in the armature, the greater portion of which is added to that of the battery thus raising the potential of the field terminal C and causing the relay to close. The dynamo polarity reverses nearly every time of switching charge off and on. We found at a moderately high speed with the switch in the M & B position a reversed E.M.F. of 7.0 volts across the dynamo main brushes. The cutout points are naturally showing signs of burning. To meet the above defects we propose to connect the green lamp relay coil to terminal B (armature). This will prevent the reversals and the switching on in the M & B position, although it will leave the lamp on after switching off charge. This has already been done on 14-G4. | ||