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 discussing magneto requirements and engine specifications for two different engine sizes.
| Identifier | ExFiles\Box 48\2\ Scan017 | |
| Date | 5th December 1922 guessed | |
| R. {Sir Henry Royce} R. {Sir Henry Royce} Coy (Derby) (1920) 2500-1-27 M1328/A Contd. -2- EFC {E. Fowler Clarke - Electrical Engineer} 3/T. We prefer to run with rather wide sparking plug gaps, viz. .025" and we would like the magneto to be capable of supplying sufficient energy to overcome such gaps under all conditions of running, particularly retarded spark, full throttle, slow speed. The bore and stroke of the engine for which the magneto is required is 76 mm by 114 mm, maximum speed 3600 R.P.M. We would like you to tell us if you think this smallest magneto of the three would satisfy our requirements taking into account the fact that we very critically require perfect running at all speeds. We anticipate that you may advise us that you do not recommend this small magneto, but prefer us to experiment with the AM6 type. For our larger engine, bore 114 mm, stroke 121 mm, maximum speed 2500 we should also be interested to know if in the larger magneto you can provide exactly the same amount of automatic and hand advances, the same having been found to be suitable for both engines. Yours faithfully, FOR ROLLS-ROYCE LIMITED. | ||