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).
Quoting a letter about ignition coils, comparing those with and without ballast resistance and armored casings.
| Identifier | WestWitteringFiles\R\2October1927-November-1927\ 128 | |
| Date | 9th November 1927 | |
| To R.{Sir Henry Royce} from EFC. C. BJ. ORIGINAL RE IGNITION. X5129 I have received a letter from Mr. Olley from which I quote the following three paragraphs :- "With regard to coils, we find that the coils without ballast and with "armored" casing, (American Bosch or DeJon) are far less liable to accidental damage than any others we have tried. We are going to make some tests on maximum temperature rise when left standing with ignition coil on. I will send you the results. I originally understood that a length of nickel or other similar wire was used in the low tension circuit to act as a resistance coil, but Mr. Nadin points out that on the American Bosch coil which we have cut open, there is nothing but copper wire." like We do not agree with the idea of running an ignition set without ballast resistance. We think that the levelling up at different speeds is a good feature, of the use of the ballast resistance. EFC. | ||