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 North & Sons Ltd. discussing the requirements for a new magneto, including spark gaps and armature design.
| Identifier | ExFiles\Box 49\5\ Scan142 | |
| Date | 6th September 1920 | |
| X 4279 COPY. MESSRS. NORTH & SONS LTD., WHIPPENDALL ROAD., WATFORD. Your Ref. BY4/H1920. Our Ref. CHK/NS.{Norman Scott} 6th September 1920. Messrs. Rolls Royce Ltd., DERBY. Dear Sirs., X 2375 X 4279 X 4181 For the attention of Mr Harvey Bailey. We beg to acknowledge receipt of your letter of the 1st inst., from which we gather that you require a magneto with the safety spark gap set at 10 m/m, in order that you may run with your plug points set at a greater distance than the .012" for which the machine we are supplying to you is designed, and also that you prefer a machine in which there is provision for adjustment of the meshing of the gears. The first point is one which has only recently been raised, the fact of your wishing to run your engines with wider gaps at the plug points having been first mentioned on the occasion of our Mr Allen's recent call on you. The second is one which we have had under consideration for some time and to provide for which we have already designed a method of adjustment which we think you will agree is better than that in use in the Bosch machine, which you have had an opportunity of inspecting it. The important point therefore relates to the possibility of supplying a machine with a larger safety gap and capable of giving an efficient spark across a larger gap at the plug points. To fulfil these requirements it will be necessary to make a machine with a larger armature than any model we are now making, but we are quite prepared to undertake this and to provide a magneto for your next seasons cars which will not only permit of the safety spark gap being increased to 10 m/m, but by combining the larger armature with our recently introduced moveable pole shoes to give an efficient spark over gaps of .020 at the plug points over a range of advance of 55° on the magneto. contd. | ||