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).
The function of carburettor float chambers during fast cornering and tilt.
| Identifier | Morton\M19\ img065 | |
| Date | 7th May 1931 | |
| To R.{Sir Henry Royce} From Ha/Lov.{Mr Lovesey} c. to Sg.{Arthur F. Sidgreaves - MD} NOR. c. to Rg.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to Hy.{Tom Haldenby - Plant Engineer} ORIGINAL Ha/Lov.{Mr Lovesey}1/KT.7.5.31. x1053. x4529. CAR CARBURETTERS - FLOAT CHAMBERS. We have looked at several makes of carburettors to see how they would function during fast cornering and to see if the trouble encountered with our twin float carb. is usual. We have just stripped one of the latest Zenith twin choke carbs. (36 U.V.P. model) and examined its float chamber lay out. It is provided with a single cylindrical float located “outboard” from the engine, which in the case of the P.II. would be on the right hand side. A comparatively deep float chamber is employed and the petrol feed to the two chokes is taken from the base of this chamber. This allows a very abnormal angle of tilt (carburetter nearly on its side) before the jets are starved. The fuel level comes approx. half way up the float leaving as much volume above as below the petrol line. Tilting the carburetter through side angles does not appreciably lessen the load holding the needle valve closed. A condition when flooding over the diffusers occurs only when the float chamber is tilted towards the chokes and this takes place at an angle of 13°. The Zenith employs a comparatively low fuel level and depends upon its accelerating pump for snap acceleration. Now that we have gone to the accelerating pump it would appear to relieve the necessity for employing the max. petrol level and thereby give us a greater margin from flooding. On the Zenith, the accelerator pump is completely enclosed, the actuating shaft operating this passes inside the lid{A. J. Lidsey} of the float chamber. It will be remembered the place where the petrol was lost through the R.R. carb. was at the top of the accelerator pump. Although, as pointed out above, slight flooding takes place through the diffusers with tilt in one direction, we could not obtain the condition with any normal angle of tilt where the float pressure is relieved | ||