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).
Technical memo discussing the design and testing of exhaust silencers to reduce fishtail noise.
| Identifier | ExFiles\Box 182\M18\ img002 | |
| Date | 9th July 1932 | |
| C.W. Hancock from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hotel de France, Chateauroux, Indre, France Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} 3/AD9. 7.32. EXHAUST SILENCERS On the P.2 silencer we have established the fact that if we want to get the fishtail noise quiet we have got to have a considerable amount of expansion room for the gas after it has left the resonant part of the silencer. The only way we can do this on the short type silencer is to increase the diameter, and the only way we can increase the diameter is to throw away the heat shield. We think that with the reduced back pressure and the fact that the hot gases are led along the outside of the silencer in the resonance type, it should be possible to get rid of the heat shield. Cadillacs have two silencers under the rear seats but no heat shield. Will you try running 19-EX with the cut out open and see if the heat in the back seats when you pull up after a fast run is very different with and without the heat shield. You can actually use a thermometer. The reason we are asking you to run with the cutout open is because the final resonance silencer will have very little more back pressure than you get at present with the cut out open. With the cutout closed we find that you lose something like 20 H.P. in the exit from the silencer to the fishtail and in the fishtail pipe, i.e. now that we have reduced the back pressure in the silencer itself, the fishtail is quite incapable of dealing with the quantity of gas. We should be much obliged if you would let us have this information as soon as possible as we have the whole of the 40/50 silencer under design at present. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||