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 J.A. Stevens Ltd. concerning magneto specifications and test performance data.
| Identifier | ExFiles\Box 57\2\ Scan242 | |
| Date | 20th January 1928 | |
| COPY X5791 J.A. STEVENS, LTD., UPPER RATHBONE PLACE, LONDON, W.1. January 20th 1928. JWH/FW. Messrs. Rolls-Royce, Ltd. Derby. Ref. Roy{Sir Henry Royce}19/MG19.12.27. X5790 Dear Sirs, Adverting to our letter of the 21st December, to which we do not appear to have had a reply, we would advise you if this magneto is to be driven at three-quarter engine speed, then we would suggest sending you for test a GF6 magneto, and as before mentioned this will be similar in dimensions to the GF12 magneto we have already supplied to you. If the magneto is to be driven at 1 1/2 engine speed, we should be glad to send you our FU6 magneto for test. This magneto has a range of advance of 54° measured on the armature spindle, and the functioning of the magneto is as follows :- TABLE DATA: Column 1: 6 mm. standard gap. Column 2: 3 mm. std. gap shunted with 200,000 ohms resis. Row 1: Timing lever fully advanced (54°) - 6mm Gap: First spark 30 r.p.m., Regular sparking 55 r.p.m. - 3mm Gap: First spark 70 rpm., Regular sparking 90 rpm. Row 2: Timing lever fully retarded. - 6mm Gap: First spark 125", Regular sparking 200" - 3mm Gap: First spark 190", Regular sparking 240" Awaiting your reply, we are, Yours truly, J.A. Stevens LIMITED. | ||