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).
Carburetter and silencer testing, including performance notes and proposed modifications.
| Identifier | ExFiles\Box 13\3\ 03-page376 | |
| Date | 12th December 1931 | |
| -5- Ha/Rm.{William Robotham - Chief Engineer}1/W.12.12.31 Cont'd.{John DeLooze - Company Secretary} power. On the road the single S.U. behaves exceedingly well It will slow run at 180 R.P.M. with 5.25 c/r and will accelerate without hesitation throughout the whole range. The metering of the twin R.R. carb. is so upset by its being made into a single carburetter that we cannot get a reasonable impression of its road performance until we have concluded our alterations to the diffusers. The two separate S.U's are also awaiting the correct needles before they can be fairly compared with the big single on the road, for snap opening up etc. We have tried both the 1 5/8 and 1 3/4 S.U. carbs on the common induction pipe (sketch 3) for slow running, but we cannot get them to function quite as well as the single (200 R.P.M.) The distribution of pipe, sketch 5, is the best we have so far attained, being good to 500 R.P.M. full throttle and free from loading up. The pipe (sketch 3) is also good for distribution. Either are better than the Weir. It is hardly fair to judge pipe sketch 4 as we have only patched it up temporarily, and it is difficult to tell with incorrect metering. We are, however, converting the existing twin carburetter pipe to a 'T' pipe with a proper hot spot which will give this carburetter a fair chance. In parallel with these tests on the 40/50 we have been developing the two carburetters to LeC.2924 on Japan 1, with a balanced induction pipe and these are now ready for the road and will be reported on shortly. In connection with silencing slow running, 'snivelling', and carburetter 'hiss', the 'Smith' type of silencer is worthy of mention, samples being illustrated in photographs 3 & 5. This is exceedingly simple, sketch 6, and very effective. Rather an interesting point is that when silencing the Big S.U. giving 180 B.H.P. we found that the casing of the silencer alone dropped the power 10 H.P., but when filled with fine wire (scrap armature windings) this was reduced to 2 H.P. only. In view of the power we lose silencing the standard carburetter we are taking an interest in this type. Ha/Rm.{William Robotham - Chief Engineer} [Diagram Text] FINE WIRE WHISTLE AND DEPRESSION INCREASES | ||