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).
New scheme for an electrical switchbox to avoid destructive sparking.
| Identifier | ExFiles\Box 65\2\ scan0136 | |
| Date | 25th September 1928 | |
| EFC. )from E.{Mr Elliott - Chief Engineer} Hs.{Lord Ernest Hives - Chair}EY) c. to BJ. Wor.{Arthur Wormald - General Works Manager} XTT 40 RL/M25.9.28. EAC.10 ELECTRICAL SWITCHES. X.7736/40. Your remarks in EFC/21.9.28 pointing out that if we break the exciting circuit of the dynamo before disconnecting the brush from the battery no destructive sparking takes place, has caused us to consider still another scheme, which is as follows: The switchbox is used for all ordinary operations, and a small auxiliary single way tumbler switch is used to cut out the magneto for the purpose of testing if the battery is working efficiently. The following are the novelties: The metal segment of the ignition and charge switch is arranged so that in the 'off' position it is still in contact with the battery ignition wire, then the next position, the same segment picks up battery and dynamo wires, and so gives "battery and magneto ignition on" (and also magneto earth is broken) but the magneto earthing segment, although it has left the direct earth, has picked up a contact from the auxiliary magneto earthing switch, so that in this position we can have M.{Mr Moon / Mr Moore}& B. or B. only, and so testing B. with C. off. The next movement of the switch the same segments picks up the dynamo exciting wire contact, and so starts the charge M.B.& C., or B.& C. (according to the tumbler switch). In the next position we drop the battery ignition contact and also drop the contact leading to the tumbler switch (electrical interlock) so that we have M.{Mr Moon / Mr Moore} & C. whatever the position of the tumbler switch. E.{Mr Elliott - Chief Engineer} pointed out that it was undesirable to run into the 3rd. position (M.{Mr Moon / Mr Moore}& C.) with the magneto accidentally turned off, and I suggested the electrical interlock. You suggested the absence of destructive spark if we break the exciting circuit (visible flash but not XXXXXXXXXXX destructive) first. We hope this will prove true, and the best scheme. It requires very little change to the present switchbox, and the changes can be made an improvement. E's drawing - LeC.2597 - explains. R.{Sir Henry Royce} | ||