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 modifications and materials for a magneto, including slip rings, armature covers, and high-tension pick-ups.
| Identifier | ExFiles\Box 48\2\ Scan344 | |
| Date | 18th December 1925 | |
| COPY OF LETTER FROM:- NORTH & SONS LIMITED., WHIPPENDALL ROAD WATFORD. Our Ref. CHK/HC.20. Your Ref. Wd {Mr Wood / Mr Whitehead} 11/NJ171225. 18th December 1925. Messrs. Rolls-Royce Ltd., DERBY. Dear Sirs, We beg to acknowledge receipt of your letter of the 17th inst. and regret the delay in replying to your letter of the 30th ult., reference Wd {Mr Wood / Mr Whitehead} 17/NJ301125. The points raised have however been receiving consideration, but as there was no necessity to retain the armature a new slip ring was fitted and it was returned to you. We have looked into the question of thickening the flanges of the slip ring but find that this is not possible. The ring being made in Stabilite is much stronger than the usual ebonite ring but the space available does not admit of thickening the flanges. With regard to the question of a more rigid cover over the armature we beg to say that we made up a cast aluminium cover much thicker than the plate generally used, with ribs to increase its stiffness and this was fitted to Magneto No.87407 which our Mr North brought with him when he visited your works on the 8th inst., so that you might compare it with other magnetos recently delivered. The high tension pick-ups we are using are made from "Mouldensite" the reason for this being that the ebonite pick-ups were damaged by heat. Now that the magneto is fitted in a position where the temperature is lower we think it would be advisable to revert to ebonite and are making moulds for this material which will produce a mechanically stronger pick-up than the original one while retaining the advantage of this material as an insulator. Yours faithfully, FOR AND ON BEHALF OF NORTH & SONS, LTD. (Sgd) C.H. Kirby, DIRECTOR. | ||