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).
Page detailing carburetter needle valve settings, float drops, and fuel flow issues between front and rear float chambers.
| Identifier | WestWitteringFiles\S\March1928-May1928\ Scan104 | |
| Date | 16th April 1928 guessed | |
| contd :- -4- With the needle valve set so that the petrol level is just below flooding point with the maximum fuel head the needle valve has only .080" lift which means the floats fall .275". Further lift is prevented by the front float coming in contact with the bottom of the float chamber. If light floats are used and the needle valve re-adjusted to give the required level a greater float drop is obtained due to the floats being less submerged which results in a greater fuel flow. With the larger needle valve seat we require a maximum needle valve lift of not less than .150 in order to obtain a fuel flow giving a good margin over the maximum demand requirements. CONNECTING PASSAGE BETWEEN FRONT AND REAR FLOAT CHAMBERS We found the petrol flow through the carb. rapidly decreased when the carburetter was inclined in a diving position. The flow was reduced as low as 181 pts/hr. for a diving angle of 10°. The reason for this we found was due to the fuel which was trapped in the front float chamber and which raised the float thereby restricting the flow through the needle valve. The arrangement of the float chamber is such that the fuel is fed into the front chamber and reaches the rear chamber - from where the diffusers draw their supply - by flowing over the dividing partition or weir. This means that the front chamber contains more than its normal volume of fuel while the rear chamber is practically empty. This trouble occurs to a lesser extent when the carb. is level but could be overcome, as shewn by experiment, by | ||