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).
Test results for a Semi-Expanding Carburetter P.II, detailing efforts to prevent air leaks and balance float chamber depression.
| Identifier | ExFiles\Box 13\4\ 04-page088 | |
| Date | 9th January 1933 | |
| E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell} C. to Hy.{Tom Haldenby - Plant Engineer} 87080 Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}12/KT.9.1.33. SEMI-EXPANDING CARBURETTER P.II. We have tested the scheme to Lec.3334, the object being to prevent air leaking past the mixture control into the well below the main jet, by balancing the float chamber depression with that in the mixture control chamber. An external pipe .187 internal diameter was fitted between the float chamber and the mixture control chamber. In order to allow the full effect of the balance passage, the control nut was reduced to .300" diameter giving an all round clearance in the chamber of .040". The float chamber vent into the intake was opened out to .156" diameter throughout, this being as large as possible as to avoid running into other passages. The following figures give effect of varying air leaks between the control spindle and its gland nut on the float chamber depression. | RPM. | Float-chamber Dep'n Ins.H2O | Dep'n in well Below main jet. | Petrol Cons Pts/Hr. | | |---|---|---|---|---| | 3000 | 6.0 | 3.9 | 96 | Spindle .311 dia. Gland nut .313 dia. | | 3000 | 5.6 | 3.8 | 97 | Spindle .311 dia. Gland nut .315 dia. | | 3000 | 4.6 | 3.3 | 100 | Spindle .311 dia. Gland nut .318 dia. | From these figures it shows that with a diametrical clearance of .004, the float chamber depression is beginning to be effected, although with the balance in operation the consumption is practically unaltered. Unbalanced and running with the above clearance at the top and lower portions of the control spindle in its bushes, the consumption is weakened of from 97 pts/hr. to 80 pts/hr. In the later types of expanding carburetter, where we have a definite petrol | ||