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).
The temperature effects on cut-out operating voltage and the materials for contact points.
| Identifier | WestWitteringFiles\D\March1920\ Scan43 | |
| Date | 13th March 1920 | |
| To R.{Sir Henry Royce} contd. -4- Ckl/T13.3.20. conjunction with their respective cut-outs, and in both cold and fully hot conditions. So far as we have gone at present, it would appear that the change in operating voltage of the cut-out between hot and cold is considerably more than is desirable. We think that a small temperature effect is not amis, as, when everything is not, the battery voltage is itself somewhat higher. It would appear, therefore, in answer to one of the points raised in Mr. Elliott's note E3/G9.9.19, that it really would be advisable to wind a cut-out with some portion of nontemperature coefficient wire so as to reduce its temperature coefficient to, say, 1/3 of its original value. This is not done on either the Smith cutout or the Lucas, but you may remember that we reported to you that this was done on the Bijur cutout which re unwound. The resistance was not external but formed part of the winding of the coil. In anwwer to another point raised in the same memo of Mr. Elliott's, the contact points on the Smith cutout which make first and break last, are of silver and not of platinum. It was considered by Messrs. Smith that silver was equally as good as platinum for the purpose as usually the current is broken at a value round about zero, and further that it is only broken in the almost non-inductive circuit of the battery and series coil. Contd. | ||