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 F.H. Royce detailing requirements for magnetos for the Phantom and 20HP cars.
| Identifier | ExFiles\Box 57\2\ Scan181 | |
| Date | 26th April 1927 | |
| Copy to - BJ Copy to - GY Copy to - BY Copy to - EFC. X5790 "ELMSTEADHenry Royce's home in West Wittering" WEST WITTERINGHenry Royce's home town. CHICHESTER. R.{Sir Henry Royce} B. North Esq., at Messrs North & Sons Ltd. Whippendell Road. WATFORD. 26th. April 1927. Dear Mr. North, MAGNETOS FOR RR. CARS. X 7291 /X5790 In reply to your Mr. Kirby's letter of the 22nd inst. I do not want to trouble you to come here. If it is clear what we want there will be no necessity for us to meet at the moment. Later I hope to see you in London, or at Watford, but just now I am very busy indeed with aero engine and other design work. Referring to our magneto requirements I understand that what we want is a sleeveless magneto for our Phantom chassis, which is naturally easier to advance and retard automatically, or by hand. It is a simpler machine, less liable to suffer from wear, and should be less costly to build, and probably more silent. Regarding the range of advance, at present we want 55º advance on the magneto, which equals 38º on the crankshaft, for the Phantom, and we do not mind if the sparking speed when fully advanced is 300 revs. a minute, but when retarded it should be as slow as possible so as to facilitate starting with only hand turning. On the 20HP* the angular advance need not be so great, but it should not be less than 45º on the magneto, corresponding to 30º on the crankshaft. We should set both these magnetos so as to have about 10º crankshaft advance when retarded. This would not affect the requirements, but would give us the extra advance we want for high speed running, and it would not be too great for hand starting. X.5792 We notice from your diagram 603/1. referring to a 55m/m armature about 2" long, that the minimum speed for sparking occurs at 20º retarded. Would it not be possible for the minimum speed of sparking to occur when the magneto is retarded say 50º. We do not mind if the speed when fully advanced is over 300., the reason being that with our auto: advance the magneto is always fully retarded when the engine slows down. What can we hope to get at an early date. Yours sincerely, New prices required. (Sgd.) F.H. ROYCE. * is the one without distributor * This mag: should not burn a jump spark distributor. | ||