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 of carburettor fuel flow, level variation, and float design for Falcon, Condor, and Supercharged F engines.
| Identifier | WestWitteringFiles\S\March1928-May1928\ Scan102 | |
| Date | 16th April 1928 guessed | |
| contd :- -2- desirable that the maximum fuel flow through the carburetter should be considerably in excess of the demand of the engine in order that there shall be a plentiful reserve of fuel in the float chamber to take care of engine operation during such manoeuvres as may temporarily interrupt the fuel feed. Therefore for ground boosting it would appear desirable and necessary for the float chamber to provide a fuel supply equal to that of the Condor carburetter and for this reason we have made a comparison of the Falcon and Condor carburetters shewing the principal differences accounting for the variation in operation between these two. The supercharged F.{Mr Friese} carburetter used was fitted with a larger needle valve and seat - .344 dia, - as described in a previous report. The appended table gives a comparison of the two carburetters. Increasing the size of the needle valve resulted in a greater variation of fuel level between the maximum head of 12 ft. and the minimum head of 18 ins., due to the greater float submersion necessary to exert the required pressure on the needle valve. The difference in fuel level between the maximum and min. fuel heads amounted to .43". We have previously found it undesirable to have a large variation in level because to ensure good 'opening up' from low speeds we require the fuel as near the top of the diffusers as possible. Larger floats, or rather floats having a large sectional area at the fuel level, naturally reduce the variation of the level with variation of the fuel head, because the submerged volume of the floats increases rapidly contd :- | ||