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 between Watford and Lucas magnetos against general specification criteria.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 175 | |
| Date | 13th June 1927 guessed | |
| -8- Contd. Our General Specification speed for the fully retarded position is 190 r.p.m. so that this is just missed by the Lucas machine, though previous machines we have had have satisfied the specification in this respect. Initial sparking speeds for the present standard Watford magneto in the retarded position might be (from analyses of a number of observations) anything from 140 to 240 r.p.m. with new magnetos. (14) The maximum and minimum milliamperes taken by the secondary winding at 108 volts 50~ A.C. were :- Watford. Lucas. Maximum. 11.0 15.0 Minimum. 5.3 4.2 (15) In accordance with our General Specification it was ascertained that the average variation of break consequent upon a length of primary point gap of .004" did not exceed ± 3º with both magnetos. (16) Remarks re silence. The Watford machine was found to be very quiet - just a slight contact breaker noise was xxxx noticeable. The Lucas machine was found to be equally quiet at low speeds, the contact breaker being actually quieter than that of the Watford. (17) The tangential force required to advance or retard the contact breaker cam ring is 1.0 lbs. wt. for the Watford and 1.25 lbs. wt. for the Lucas. The limit given in our Specification is 2.0 lbs. Contd. | ||