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).
The low-speed performance and cold-start issues of Watford EW6 and EC6 type magnetos.
| Identifier | ExFiles\Box 48\2\ Scan373 | |
| Date | 26th March 1928 | |
| EFC. {E. Fowler Clarke - Electrical Engineer} WC.91. X8796 26.3.28. X.8796. X.7791. LOW SPEED PERFORMANCE OF WATFORD EW6 AND EC6 TYPE MAGNETOS. A number of the latest Watford type EW6 magnetos have been rejected by the Test Dept. owing to their inability to start the engine from cold. A case of this kind has been demonstrated to us by Mx. {John H Maddocks - Chief Proving Officer} on a test chassis and we were satisfied that the particular magneto on that chassis would not start up the engine cold, everything else being in order. We obtained one of these magnetos No.105321 and tested it in the laboratory to our production specification which it passed O.K. The std. leak and test gap was then used and the low speed figures with and without the leak were as follows :- Minimum speed for regular sparking on 5.5 mm. gaps in air :- Advance 60 r.p.m. Retard 170 r.p.m. with the std. 2.5 micromhs leak and std. test gap the retarded figure was 350 r.p.m. Our production specification limits for low speed performance are :- Advance 120 r.p.m. )on 5.5 mm. gaps Retard 190 r.p.m. ) in air. We then obtained a std. EC6 magneto No.98251 which the Test Dept. assured us was quite O.K. and tested it similarly. The low speed figures with and without the leak were as follows :- Minimum speed for regular sparking on 5.5 mm. gaps in air :- Advance 135 r.p.m. Retard 120 r.p.m. With the std. leak and annular test gap the minimum retarded figure was 250 r.p.m. Contd. | ||