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).
Modifications to exhaust silencers, fish-tails and lagging.
| Identifier | WestWitteringFiles\N\July1925-September1925\ Scan253 | |
| Date | 12th June 1925 | |
| EXPERIMENTAL REPORT. -2- Expl. No. The intermediate pipe (or cut out tube) is the same as standard with the exception that it is drilled at its rear end with 63 holes .312" dia. The second silencer tube is 5" dia. and is drilled at its front end with 60 holes .250" dia. The three silencer baffles are spaced longitudinally as in a standard silencer and they are drilled with 52 holes .312" dia. A Phantom type fish-tail is used. SILENCE. The modified standard silencer (A) is a decided improvement on the present standard; it is however necessary to use a Silver Ghost type fish-tail. This has the effect of producing a hissing noise at high engine speeds. If a Phantom type fish tail is used, the silencing is not sufficiently good. We find we cannot use holes in the silencer baffles of less dia. than .312" otherwise whistling occurs. The effect of opening out the holes in the intermediate pipe from .250" to .312" dia. is to reduce the exhaust boom considerably. The concentric tube silencer (B) is quieter than the above and does not necessitate the use of a Silver Ghost type fish tail; the addition of this certainly gives a slightly quieter exhaust at speed. LAGGING. There is no advantage gained by the use of asbestos lagging between the front expansion box and the silencer on either of these silencers. or intermediate pipe. contd :- | ||