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).
Comparison report on the performance of Watford sleeveless type and Lucas type E.H6 magnetos.
| Identifier | ExFiles\Box 40\2\ Scan210 | |
| Date | 13th June 1927 guessed | |
| -9- Contd. (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 General specification is 2.0 lbs. General remarks re comparison of Watford sleeveless type magneto and Lucas type E.H6 magneto. It would appear that the Lucas is the more normally arranged of the two machines electrically, i.e. its contact breaker and distributor timing are more like what would be expected on principle for the best general operation. It appears that this is possible because the capacity of the Lucas armature is greater than that of the Watford. The good low speed sparking result of the Watford in the retarded position (range 50° only) has been obtained by the use of very extended pole shoes and by improving the low speed retarded sparking at the expense of the high speed advanced sparking. Further, by (1) Having the centre of the variable range more advanced than in the Lucas, (2) Providing a smaller range (50° in place of 60°). The Lucas machine just misses our specification of low speed performance in the fully retarded position, but the Watford machine very much misses our specification of high speed and utility performance in the fully advanced position. It appears to us that the performance of the machine as it stands has largely been obtained by nursing, and that the more ordinary conditions obtaining in the Lucas magneto would be an advantage in the long run. | ||