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 float chamber design and fuel flow considerations.
| Identifier | WestWitteringFiles\S\March1928-May1928\ Scan103 | |
| Date | 16th April 1928 guessed | |
| contd :- -3- with rise in level. Large leverage ratio of the float to the needle valve is also conducive to small level variation. We have drawn up a table which shews how the fuel level would vary between the max, and min; heads for several different float needle valve leverage ratios assuming also that each float was increased in width by a quarter of an inch. From this we see with regard to obtaining the min. variation in level it is desirable to have floats of large sectional area at the fuel level and also a fairly large leverage on the needle valve. This latter factor - i.e. large leverage - has the disadvantage that greater float movement is required to give the desired needle valve lift for the required fuel flow with consequently greater fall in the fuel level when the carb. is working. This however, we should not consider a serious defect and any influence it exerted on the metering it should be possible to allow for by the proportioning ax of the diffuser unit. It is desirable to arrange the float chamber so that when the engine is using its maximum amount of fuel - and the fuel has fallen to its lowest level - the feed passages to the diffuser are well submerged so that in the event of violent manoeuvres of the machine the fuel is not 'swilled' away from these passages. For this reason it is desirable to reduce to the minimum any air spaces above the fuel level. FUEL FLOW THROUGH CARBURATTER. With regard to the fuel flow through the carb. we find with the larger valve seat used for these tests we can get an adequate supply providing we obtain greater needle valve lift than at present obtained. contd :- | ||