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).
The development and testing of an air silencer for a horizontal carburetter to reduce suction noise.
| Identifier | ExFiles\Box 102\1\ scan0189 | |
| Date | 30th June 1934 | |
| HS{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Sent to E X5060 Hs{Lord Ernest Hives - Chair}/FD.{Frank Dodd - Bodies}7/KW.30.6.34. Air Silencer for R.R. Horizontal Carburetter. On the new 25 HP. Horizontal Carburetter we are troubled with suction hiss, and whilst the large air silencer takes care of the induction roar, it hasno effect in reducing the suction noise from the carburetter. On the old type of carburetter the suction noise is greatly eliminated by the various passages, choke tubes, etc. etc. also the type of air valve used greatly affects the sound. We have proved that on the new horizontal carburetter all the objectionable noise comes from the throttle valve and the passage between the base of the piston and the bridge. We tried, though unsuccessfully, to cure the trouble at the source, by chambering the edges of the throttle valve, re-shaping the base of the piston over the bridge, removing all sharp corners etc., but none of these alterations made any improvement. We also tried taking the air into the carb. like the S.U. to omit passing round the piston casting, but this also was unsuccessful. Our next move was to make an additional air silencer, the print of which is attached. We have tried to fit this silencer as near to the source of the noise as possible. It therefore comes between the carburetter and the large air silencer. It will be seen from the print that the small silencer is made up of baffles and a ring of wire gauze. The result is entirely different if the baffling arrangement is fixed to the entrance to the large silencer. It must come next to the carburetter. | ||