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).
Letter from The Lodge Sparking Plug Co. Ltd. discussing the manufacturing tolerances for aeroplane spark plug gaps.
| Identifier | ExFiles\Box 79\1\ scan0084 | |
| Date | 12th January 1917 | |
| COPY X.601. BH/HB{C. E. Harcombe} Wd{Mr Wood/Mr Whitehead}/EH17/E9117. Messrs Rolls-Royce Ltd., Nightingale Road, Derby. 12th Jan.1917. Dear Sirs, Further to your letter of the 9th inst. relative to gaps on aeroplane plugs, we note your instructions to make the theoretical gap .0175", the minimum to be .015" and the maximum .020", and we would again state that we cannot undertake to work to these limits. We beg to refer you to our letter of the 2nd. inst., in which we stated that with a theoretical gap of .0175" we could not work closer than a minimum of .0125" and a maximum of .0225"; that is to say we must have an out of centre tolerance of .005". Will you now kindly state the theoretical gap you wish us to work to, bearing in mind the above mentioned tolerance. Yours faithfully, The LODGE SPARKING PLUG CO.,LTD. | ||