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).
Modification to the P.2. starter's auxiliary switch by removing the carbon contacts.
| Identifier | WestWitteringFiles\V\December1930-February1931\ Scan018 | |
| Date | 1st December 1930 | |
| ORIGINAL R.{Sir Henry Royce} from EFC. c. Sg.{Arthur F. Sidgreaves - MD} c. Ry. Wor.{Arthur Wormald - General Works Manager} EFCL/ADL1.12.30. X.6048. AUXILIARY SWITCH OF P.2. STARTER X.7655. SWITCH UNIT WITHOUT CARBON CONTACTS. We have observed that on the present standard P.2. auxiliary switch of the starter switch unit the break does not occur first on the silver contacts, but, due to inertia lag of the carbon contacts, the final break is taken by the silver contacts. The result in effect is that since the teazer circuit is broken before the main motor circuit is completely made, a spark occurs on the auxiliary switch silver contacts at break. When the mechanical interconnection of auxiliary switch to main switch was originally conceived it was the intention that the auxiliary switch should completely break before the main switch began to make -- a slight overlapping of these functions led us into difficulties with the single push button switch. The push button switch was therefore made duplex and permitted overlapping of the switch functions of the auxiliary and main switch without any bad result. As the switches are set to our production instructions at present, the carbon contact only of the main switch makes prior to the breaking of the teazer circuit by the auxiliary switch. There is no reason in principle why the overlapping should not be greater, and why in fact, the copper contacts of the main switch should not make before the teazer circuit is broken. It is only a question of modifying the various gap settings. If this were done then it would be the case that no protection to the teazer circuit break is necessary for the whole portion of the teazer circuit from the battery positive through the push button switch, auxiliary switch and motor teazer winding to main switch terminal becomes actually short-circuited by the closure of the copper contacts of the main switch. The teazer current is thus suppressed before the teazer circuit break takes place. We propose to arrange a switch in this way for experimental test. This suggested modification together with that of deletion of the carbon contacts of the push button switch would reduce the production cost of the apparatus by a worthy amount. EFC. | ||