Design notes on the float chamber, needle seating, and external finish for a carburettor.
| Identifier | ExFiles\Box 123\1\ scan0029 | |
| Date | 19th February 1940 | |
| - 3 - (5) Float Chamber. The floats and supports are made of particularly light gauge material, and we have had instances where the floats themselves fouled the sides of the floatchamber. This however, has only happened when the float mechanism has been disturbed, during development tests. We record this as we may have to do something about it later as we consider the floats to be rather flimsy. However, we may get away with it. (6) Needle Seating. (Float Chamber.) As the size of the needle seating depends upon the pressure exe(Aero Engine)rted on the needle valve we have to cater for two versions of needle seating. 8-cylinder engines are to have electrical petrol pumps and 6-cylinder engines will have mechanical; the reason for this is a design problem. We have had considerable correspondence with the Zenith Carburettor Co., on this subject, because they apparently do not agree with our reasoning. The facts are as follows:- (a) In order to get an adjacent fuel delivery into the float chamber on the 8-cylinder unit, to maintain maximum power at top speeds, we have to use a .140 diameter needle seating in conjunction with the S.U. electrical pump. This we do quite successfully and we say that the factor of safety is greater than with the standard seating for this carburettor of .101 working with the mechanical pump. Rm {William Robotham - Chief Engineer} /JBD {John B. Dixon - Fuel Systems} has dealt with this matter in his letter dated 20th. July 1939. (copy attached.) (7) External Finish. (Appearance.) This should be also specified for the last production series of Wraith with the addition that the embossed figuring relating to American origin should be removed and the usual Zenith cum R.R. plate put on to the float chamber lid. {A. J. Lidsey} Rm {William Robotham - Chief Engineer} /CTS. {C. Trot Salt - Carburation} | ||
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).