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).
Cost, functionality, and potential simplification of the J.III and Parching starter motor main and relay switch.
| Identifier | ExFiles\Box 179\3\ img050 | |
| Date | 1st March 1932 | |
| SECRET. To R.{Sir Henry Royce} From He/Wst. c. SG.{Arthur F. Sidgreaves - MD} c. WCR. c. Hy.{Tom Haldenby - Plant Engineer} Cx.{Major Len W. Cox - Advertising Manager} c. PM. DD. ORIGINAL He/Wst.1/ADG.3.32. X6121 J.III AND PARCHING STARTER MOTOR MAIN AND RELAY SWITCH. The automatic starter switch intended for these chassis is the same one as used on P.2. This switch is an expensive item compared with the simple starting switch used by Bosch and our existing 20/25 oil switch. The cost of the present P.2. sequence starter motor switch is £3.13.6. as compared with the 20/25 price of £1.9.0. The switch is expensive when it is considered that only one advantage is gained and other disadvantages remain. The only advantage gained is that should the starter button be depressed and held down after the engine has started, the switch will automatically switch off the motor. There is no protection, however, of our engagement should the button be depressed whilst the engine is running. We think there is very little risk of the starter button being continued to be pressed after the engine has started, and before we duplicate this scheme on future cars we think it is a point which should be re-considered. We have been carefully considering the electrical arrangement of the starter motor circuits and we can see that if the auxiliary relay portion of the switch, incorporating the hold off coil feature preventing re-engagement or starting, was deleted, the main switch would be considerably simplified and the cost reduced at a rough estimate by 50%. In assembling this automatic switch the assembly and adjustment time has always been lengthened owing to the fact that the mechanical interlocking of the two switches complicates the adjustment and makes it critical, whereas with a simple heavy current relay the adjustment is straightforward. We are now going to suggest that this hold off switch is really an unnecessary refinement for the following reasons. | ||