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).
Specified gap for Lodge sparking plugs, justifying the 15/1000 inch measurement.
| Identifier | ExFiles\Box 79\1\ scan0078 | |
| Date | 20th December 1916 | |
| To Wd.{Mr Wood/Mr Whitehead} from EFC. c. to EP.{G. Eric Platford - Chief Quality Engineer} EFC-1/T201216. December 20th 1916 X.601. RE - LODGE SPARKING PLUGS. In answer to your memo Wd{Mr Wood/Mr Whitehead}5/NJ/181216, we are still of the opinion that it will be advisable to specify the gap on the sparking plugs supplied to us from the Lodge Sparking Plug Company, to be 15/1000 of an inch, in spite of the possible variation of 5/1000 either way. The reason for this is that during the use, the metal of the plug is bound to be eaten away, to a greater or lesser extent and the tendency will be for the gap to be actually larger than that specified. Moreover, the gap at different points round the ring will tend to be equalised during working, because the spark will always take place approximately across the smallest distance. Therefore, if Mr. Platford agrees to this, please will you leave your order for the 15/1000 gap plugs unaltered. EFC. | ||