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).
Performance comparison of Watford and Lucas magnetos detailing their firing capabilities at various speeds and settings.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 174 | |
| Date | 13th June 1927 guessed | |
| -7- Contd. the central position from 900 to 4000 r.p.m. but in the advanced position it was incapable of firing the gap. N.B. It had been previously arrived at that the amount of leak on this test is perhaps too big, as in neither case does the machine comply with our specified requirements of being able to fire this special test gap regularly for any position of the hand range lever over a speed range of 700 to 2100 r.p.m. (length of H.T. leads assumed always to be 2 ft.). It certainly, however, does give a comparison. We have had magnetos of sufficient output energy to be capable of firing such a gap over a range of speeds in the fully advanced position, in fact one of the earlier Lucas' was quite easily capable of so doing. (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 was found to be 3400 r.p.m. for the Watford and over 4000 r.p.m. for the Lucas. Our General Specification gives 3500 r.p.m. for this. Therefore the Watford does not quite meet it. (13) The lowest speed 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 for the Watford and Lucas respectively :- Watford. Lucas. Advanced. 165 115 Central. 150 170 Retarded. 160 205 Contd. | ||