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).
Investigation into twin choke carburetter performance, comparing present and modified designs.
| Identifier | WestWitteringFiles\V\March1931-September1931\ Scan132 | |
| Date | 21th April 1931 | |
| R.{Sir Henry Royce} FROM E.{Mr Elliott - Chief Engineer} C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} C. to HS.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} ORIGINAL E1/M21.4.31. P. 2. TWIN CHOKE CARBURETTERS. 87080. Referring to HS{Lord Ernest Hives - Chair}/LOV{Mr Lovesey}3/KT17.4.31., the slope obtained on the petrol level when turning under normal conditions is surprising. On the design as made the main spray jets are in the ideal position in the centres of the float chambers and are therefore unaffected by angular changes of level of the fuel. As however all the features of the carburetter cannot occupy the central position there are certain of them that will flood or become cut off beyond a certain angle. We have made an investigation to see what improvement can be obtained in the design within the limitations imposed by the engine. We are anxious at the same time not to increase the distance between the choke tube and throttle valve. The following table gives all the figures for the carburetter at present being tested and also the improved figures we expect to get by modifying the design. Present angle. | Expected improvement by modified design. Petrol floods out of top of accelerator pump. | Plus 26° | Plus 40°. Accelerator pump begins to cut out. | Minus 6° | Minus 30°. Limit of correct balance of float immersion. | Plus ) Minus) 10° | OK. for any angle. Starvation - supply hole to main jet variable restriction begins to uncover. | Minus 25° | Minus 40°. Main jet variable restriction begins to flood at top. | Plus 30° | Plus 40°. Petrol floods out of top of low speed jet housing. | Plus 28° | Plus 40°. Petrol floods out of low speed air supply hole. | Plus 37° | Plus 55°. (1) HS{Lord Ernest Hives - Chair} RECEIVED | ||