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).
Comparison and discussion of various spark plug types including Mercury, Champion, and Lodge.
| Identifier | WestWitteringFiles\F\February1921\ Scan45 | |
| Date | 17th February 1921 | |
| To HS.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} Copy to CJ. " " WGR. (Struck through) " " EP.{G. Eric Platford - Chief Quality Engineer} (Struck through) " " HM.{Capt. W. Hallam - Head Repairs} (Struck through) " " R.R. of America Inc. (Struck through) (For the attention of OY.) (Struck through) ORIGINAL (Stamped) 17 FEB 1921 (Stamped) RECEIVED (Stamped) R1/G16/2/21. X.1812 RE SPARKING PLUGS X. 4277 X.3413 X 4196 X.3905 X 4295 The Mercury plug from its appearance, one would expect to be superior to the Champion, although there is nothing about the Champion one could object to, except the single contact, which we found in the past when the petrol was good, was liable to oxidisation. Regarding the three-pointer Mercury plug, we think this is excellent for the purpose, since it satisfies your test, and appears with its detachable and heavy central electrode and three points, to fulfil the conditions we so desire. We are certain that the present ignition plugs you are sending out (Lodge) the porcelain and mica is very unsatisfactory, and I have personally always condemned them, and preached that we are wanting a porcelain of the form used in the Champion and Mercury plugs. I understand, however, that these were the best that could be obtained for the post-War cars at the time. With reference to the Mercury plug, the undercut on the thread is bad because it does not spigot the copper asbestos washer. These plugs seem very similar to the Basse/Michel and Pognon plugs which, in the old days, we used to take to pieces and pack up in much the same way, but having the advantages of modern improvements, central electrode etc. Is the central electrode of nickel in the Mercury plug ? The Bethlehem plug does not appear to me nearly so satisfactory. In conclusion, I agree (subject to further exhaustive tests confirming) to prepare for at once standardising the Champion (Canadian make) for U.S.A. and the Mercury (Birmingham make) for English made cars. R.{Sir Henry Royce} R R 339V (100 L) (2 H 198 11-9-20) C 3500 | ||