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).
Magneto performance tests, detailing firing speeds, operational noise, and comparison with other models.
| Identifier | WestWitteringFiles\R\2October1927-November-1927\ 75 | |
| Date | 2nd November 1921 guessed | |
| -3- Contd. (12) The highest speed at which the magneto is capable of firing regularly in sequence six 5.5 mm. third point unshunted spark gaps in air in the fully advanced position was observed and found to be over 5000 r.p.m. - our General Specification gives 3500 r.p.m. (13) The lowest speeds at which the magneto is capable of firing regularly in sequence six unshunted 5.5 mm. third point spark gaps in air in each of the three positions (a) advanced, (b) central, and (c) retarded, was observed and found to be 70 r.p.m., 165 r.p.m., 205 r.p.m. respectively. Our General Specification speed for the fully retarded position is 190 r.p.m., so that this does not quite meet the specification in this particular. It may be remembered that both the recent EW6 Watfords have satisfied us in this respect, the figures being 140 and 145 r.p.m. (15) In accordance with our General Specification it was ascertained that the average variation of break consequent upon a variation of the length of primary point gap of .004" did not exceed ± 3º. (16) Remarks re Silence of Operation. Gears and contact breaker were rather noisy. The magneto was not as quiet as the sleeveless Watford, or the Lucas. (17) The tangential force required to advance or retard the contact breaker cam ring is 1.0 lbs. wt. This is similar to the Watford EW6 and meets the specification. General Remarks. Although the range of this magneto is only 54º the results compare very favourably with the Lucas ER6 and the Watford EW6, and especially in the utility test performance. The magneto passes the specification with two exceptions, viz. the range and low speed sparking, but we are of the opinion that the use of longer cams, giving a smaller make ratio, would remedy this. The outstanding points about this magneto are :- Contd. | ||