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).
Vacuum feed performance on the 20 HP and New Phantom models, and suggesting carburetter improvements.
| Identifier | ExFiles\Box 56\1\ Scan003 | |
| Date | 11th August 1925 | |
| To hs.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} c. to OJ. BJ. PN.{Mr Northey} c. to BY.{R.W. Bailey - Chief Engineer} EP.{G. Eric Platford - Chief Quality Engineer} K5510 NEW PHANTOMCodename for PHANTOM I & 20 HP. VACUUM FEED. R2/M11.8.25. X. 8510 E.{Mr Elliott - Chief Engineer} 5510 We have carefully observed the behaviour of both the 20 HP. and the New PhantomCodename for PHANTOM I as regards the effect of the vacuum feed on slow running, but we cannot detect any practical difference when the temperature under the bonnet is normal. The water and jacket were hot, but the petrol tank, float chamber, and carburetter were cool. It remains to be proved whether there is any difference due to increased temperature of the vacuum chamber or the carburetter. We believe however that neither of the above engines are so good for slow running as the old 40/50. but since it is not now necessary to run the engine light without load, they are quite satisfactory in this respect. Regarding the 20 HP. please test a lighter air valve piston, and I am inclined to think that the present carburetter spring made from semi-hardened wire, and one turn more or less tucked into a groove, is not sufficiently exact and permanent, especially as regards length, because it seems indefinite how much of a convolution is tucked into the groove. A really hard spring, and precise attachment like we formerly had is to be preferred. E.{Mr Elliott - Chief Engineer} will send one or two suggestions for trial. I believe the present arrangement was adopted in Derby from the American practice, who were unwisely out for cheapness in a very important piece. R.{Sir Henry Royce} | ||