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).
Carburetter petrol levels for the Phantom model, detailing float adjustments required for different fuels like benzol.
| Identifier | ExFiles\Box 66a\1\ scan0157 | |
| Date | 30th December 1926 | |
| To Hs.{Lord Ernest Hives - Chair} Carburetter Petrol Level (Phantom) Specific Gravities:- Petrol (Shell-Mex) = .740. Pure Benzol = .868. 50/50 S.M and Benzol = .807. Carburetter Levels. The carburetter level when using benzol in a carburetter fitted with a standard petrol float, is .250" lower than when petrol is used, with the same float. When 50/50 benzol mixture is used the level is slightly lower than petrol; but a reliable figure cannot be obtained owing to the variation in petrol level. The level varies up to .200" even when tests are carried out under apparently absolutely identical conditions. The cause can only be due to the lack of sensitiveness of the type of float mechanism employed. The carburetter is not sensitive to the petrol level, quite large variations are not detrimental to its correct functioning, hence the defect is not noticeable under normal conditions. Float Weights. Weight of standard float = 81 grams. Weight to be added to the standard float to produce the same level with benzol as when petrol is used = 8 grams. The small difference in level consequent upon using 50/50 mixture does not warrant the addition of any weight to the float; but if pure benzol is used the float should be increased in weight by 8 grams. The only method of doing this is to supply a specially shaped washer to be soldered on to the concave base of the float. If the weight is added at the top of the float it fouls the bob weight mechanism. [Drawing of a float base with an arrow pointing to the centre] Weight (8grams) should be added here. [Signature] | ||