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 report into the failure of an L.H. Chassis Backing Light Switch, recommending silver or gold silver contact points over tungsten.
| Identifier | ExFiles\Box 168a\2\ img024 | |
| Date | 2nd February 1931 | |
| X6029 By Mr RD. from EFC. c. Sft.{Mr Swift}/Mr. Breck. EFC5/AD12.2.31 X.6029. L.H. CHASSIS BACKING LIGHT SWITCH. As a result of your By/RD14/N9.2.31, we have duly looked into the failure of this switch and my assistant's report AD.86 is given below. In spite of the failure having been due to some foreign substance on the contact points, it would still appear that contact points of silver or gold silver with cylindrical meeting surfaces (as on the cut out) would be better than the tungsten points. "On examining the switch we found that the dark coating on the points was not oxide but some foreign substance of a greasy or waxy nature. This could be removed by fairly hard rubbing with a cloth leaving the points bright and smooth as new. To test the switch we rigged it up on our automatic starter-rig and made it operate 10,000 times, lighting a 12 volt 24 watt lamp. This had no appreciable effect on the contacts and we think they are safe for use on production, provided they are kept clean during assembly. We suggest, however, that some less expensive form of contact could equally well be used. The tungsten contacts fitted are flat, but it will be difficult to ensure that they come flat together in production but merely touch on one corner as they do in the switch tested. This, however, is sufficient for the purpose, whence it follows that much smaller points having spherical surfaces and made of silver or gold silver would probably be quite suitable." We return the switch herewith. EFC. | ||