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).
Failure of Champion and Mercury ignition plugs during testing and proposing design modifications.
| Identifier | WestWitteringFiles\F\February1921\ Scan97 | |
| Date | 1st April 1921 | |
| To HS.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} Copy to CJ. [Strikethrough] " " ERO. [Strikethrough] ORIGINAL [Stamped] R6/G12/4/21. RE IGNITION PLUGS. Handwritten: X1812, X4196, X4095, X0635 The Champion plug you gave me to test in the little pump engine here soon broke its porcelain through expansion, and cracked off in a ring. I understand they have altered this pattern, but certainly it does not speak much for the porcelain of the Champion plug. Regarding the Mercury plug, you will remember my pump engine shewed this to pre-ignite. I do not know whether they are altering this plug at all, but I should like to suggest that if they get some experimental porcelains, we have one or two suggestions we should like to make to them. You will remember that our views are quite simply explained i.e. the recess for the central electrode is made less and less deep experimentally until it is of no depth at all, when it will be very similar in design (effectively) to the old four-pointer Bosch which I so favoured, and still favour. This four-pointer Bosch, however, may, owing to recent reduction in the quality of petrol, soot up too easily. I send you a sketch of my modifications to the Mercury plug which you should take up with the makers. The other point with reference to these plugs is the brass collar which renders them detachable. I think this would be better in steel, because when the brass gets hot it becomes very weak, that is, it soon loses its elasticity. In contradistinction to a tungsten steel, it remains hard and stiff to a red heat. I do not suggest tungsten steel for this purpose, but an ordinary steel is far different from yellow brass. R.{Sir Henry Royce} [Footer text: S & K' 330V (100 L) (2' H 126' II-8-20) C 3000] | ||