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).
Performance comparison and analysis of a Duplex Down Draught Carburetter for the Phantom III.
| Identifier | ExFiles\Box 20\9\ Scan074 | |
| Date | 7th January 1936 | |
| X1033 E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Swd.l.4/MA.7.1.36. DUPLEX DOWN DRAUGHT CARBURETTER PHANTOM III. Comparisons have been taken between the experimental mock-up scheme and Lec.4748 with the result that the latter is 10 BHP. down at the peak speed 3750 R.P.M., or 177 BHP. as against 187 BHP. This test will have to be repeated as between these comparisons a new dynamometer brake was fitted and the unit dismantled and reassembled with minor modifications, but strictly speaking the figures should be directly comparable. Of the 10 BHP. loss, 5 BHP. can be accounted for by the increased induction pipe depression from 3.0" Hg. to 3.6" Hg. at 3750 R.P.M., as taken in the main portion of the branch manifold. In the layout of the hot spot box of the mock up scheme, the riser portion and the branch manifolds are the same 2.000 centres as the carburetter which rendered the inlet spark plugs very inaccessible. To overcome this difficulty, the centres of the branch manifolds were increased to 4.500 in Lec.4748, which makes the plugs accessible but does not give such a free and direct flow from the carburetter to the branch manifolds. This offset in centres and indirect flow presumably accounts for the raised depression in the manifold from 3.0" to 3.6" Hg. It appears from the drawing that the outer radius of the riser, could be made more gradual from the carburetter flange into the hot spot box with advantage, as we suspect that there is considerable turbulence in the hot spot box with the present arrangement. Another feature which is different and may account for a further loss is that in Lec.4748, the centre branch pipes are taken sharply at right angles from the main pipe, whereas in the mock up scheme these are taken in with a very gradual radius. | ||