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).
Modification to the Phantom II semi-expanding carburetter to prevent flooding on inclines.
| Identifier | ExFiles\Box 13\4\ 04-page165 | |
| Date | 30th June 1933 | |
| X 7080 To E.{Mr Elliott - Chief Engineer}) from Hs{Lord Ernest Hives - Chair}/Wyman " BY) & Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell} c. to Slt. c. to EP.{G. Eric Platford - Chief Quality Engineer} c. to Mx.{John H Maddocks - Chief Proving Officer} Hs{Lord Ernest Hives - Chair}/Wymn.2/KT.30.6.33. PHANTOM II SEMI-EXPANDING CARBURRETTER. Trouble has been experienced on this type of carburetter with regard to flooding, when standing on an incline (ascending direction) in excess of 5º or 1 in 11.5. By lowering the petrol level in the floatchamber from 1.050 (present standard level) to 1.375 below the floatchamber parting surface under a 1 foot petrol head, it is possible to station the car on an incline of 1 in 5+ before flooding occurs. The fact of lowering the level to 1.375 reduces the needle valve movement from .125 to .060, which is insufficient to pass the necessary petrol for high speed work. In order to recover the needle valve movement it is necessary to reduce the effective float weight by the use of a lighter float. Satisfactory results have been obtained by using a 26 S.W.G. (.018) float which permits a needle movement of .125 with the 1.375 level. When assembled to E.83420 the complete assembly weighs 71 grams, or 2.5 ozs. as against 84 grams, or 3 ozs. which is the assembled weight of the 24 S.W.G. (.022) float now used in production. The lower level does not appear detrimental in any way to the performance and carburation either on the test bed or on the road, where comparative tests have been taken. These are tabulated on the attached sheets. The lighter float with the new level setting should go into production immediately under the following specification:- (a) The float halves to be of 26 S.W.G. (.018) material otherwise made to the drawings, E.83413 & E.83421. (b) When completely assembled to E.83420 the total weight of the float and its fittings should be - 71 grams = 2.5 ozs. (c) Under a 1 foot head of petrol the level should be | ||