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 carburetter flooding, identifying fine aluminium turnings from the filter assembly as the root cause.
Identifier | ExFiles\Box 135\2\ scan0163 | |
Date | 20th May 1937 | |
Hs.{Lord Ernest Hives - Chair} from Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux} E.{Mr Elliott - Chief Engineer} Rm.{William Robotham - Chief Engineer} Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux}7/R.20.5.37 P.III. CARBURETTERS - FLOODING. Mx.{John H Maddocks - Chief Proving Officer} E.{Mr Elliott - Chief Engineer} and myself have investigated the causes of carburetter flooding on Ph.III. Several cars in the Test Dept. were taken after the routine test and the carburetters dismantled and examined. It was observed that in several there was fine turnings of what was proved, aluminium, in the float chamber. A further investigation of filters were made and the fine turnings of aluminium were found in the filters. It was proved that these turnings did not come from any other source than the filter itself, and that these fine pieces of aluminium turnings were formed by the act of screwing the steel filter cap into position. The aluminium thread in the body of the filter when formed by the tap causes small burrs. The thread of the steel cap is left like a cutting tool by the absence of chamfering. The thread of the aluminium body being on the small side diametrically, the screwing down of the cap turns off fine pieces of the aluminium. The gauze of the filter has allowed these turnings to pass through, and in the cases of flooding a piece has become wedged on the needle valve seating. This could happen repeatedly by the re-fitting of the cap on to the filter after taking apart for cleaning. A comparison of the 25/30 and P.III filters was made, and it was found that we have been fitting a much coarser gauze, i.e., 60 mesh, to the P.III than to the 25/30 i.e. 100 mesh. It was explained that the gauze of the Bentley was taken as a sample when the design was being made for the 4 carburetters. The 25/30 fine gauze filter would not pass these fine turnings, and the size of the filters being practically identical, it was agreed that the finer gauze could be used if tests proved it to be suitable for the demand of P.III. Mx.{John H Maddocks - Chief Proving Officer} has carried out tests both on the engine bed and flow tests, using the fine gauze filter. The results are:- | ||