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 performance and improvements of the latest Watford IS12 aero magnetos, with a comparison to B.T.H. models.
| Identifier | ExFiles\Box 43\4\ Scan142 | |
| Date | 10th September 1928 | |
| To R.{Sir Henry Royce} from EFC. c. BJ. RG.{Mr Rowledge} c. BY.{R.W. Bailey - Chief Engineer} X4021 EFC3/T10.9.28. X.4021. WATFORD TYPE IS12. MAGNETOS- AERO. -LATEST MODELS- We recently received two of the latest and considerably improved Watford IS12.aero magnetos, in which the screening and general outline of the magneto are modified, the screening being considerably improved, also the working range is increased to 30°. These magnetos have been duly tested and have now been handed over for engine test on a development engine. The bench performance of these magnetos is also considerably improved, particularly in regard to the high speed operation. Concerning these machines my assistant reports as follows :- "Our general impression of these magnetos is that they are exceptionally good at high speeds, i.e. better than the B.T.H., but at low speeds fully retarded the B.T.H. is generally better, although one of the Watfords No.98033 was equally as good as one of the B.T.H. magnetos recently tested. The B.T.H. gives a better leaky gap performance and an inspection of the o.c. volt and s.c. ampere-speed curves rather confirms this, the Watford s.c. amperes being much lower for a given speed than the B.T.H., and they do not rise to their approx. final value so rapidly as the B.T.H. There was observed a slight difference in the contact breaker timing between the two Watford magnetos, and the effect of this could be discerned in the subsequent | ||