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).
Material choices and issues like contact splashing for a condenser in a battery ignition system.
| Identifier | ExFiles\Box 34\1\ Scan061 | |
| Date | 27th May 1919 | |
| H.R. 285 A (100 T) S.P. 575. 16-4-19) (1. 2554. To R.{Sir Henry Royce} from EFC. c. to CJ. c. to E.{Mr Elliott - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} X.2512. EFC1/T27.5.19. X.3129 - RE CONDENSER FOR BATTERY IGNITION. Referring to LeC.1091, this would appear to satisfy our requirements except for the fact of the spring contact. We had previously stated (not however to you) that spring contacts should be avoided if possible. Perhaps, however, this is impossible and under the circumstances we would like to make a suggestion. As it stands at present, the contact would apparently be between a piece of brass and a piece of steel. We are not quite sure whether this will be invariably satisfactory. From our experience of condenser currents, we find such currents to possess rather peculiar properties. Owing to their being of the nature of a high frequency oscillation, they seem to have a sort of disruptive effect which has a tendency to cause splashing at a contact which is not thoroughly good. This might be explained as being due to very intense heat being generated very locally and suddenly, especially if there is any oxide, dust or dirt on the contact. A spring contact may be quite O.K. in passing several amperes of direct or alternating current of low frequency, but when called upon to pass a high frequency alternating current of the same value, it would appear to exhibit this phenomenon. What we would like to suggest is that the two points of contact be faced with silver, because being softer, the actual area of contact for the same pressure would be greater and there is not the tendency to oxidise. We have even found Contd. | ||