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).
Test report on the Goshawk II silencer and cutout, detailing issues with noise levels and power output.
| Identifier | WestWitteringFiles\I\October1922\ Scan43 | |
| Date | 4th October 1922 | |
| ORIGINAL To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair} c. to CJ. c. to E.{Mr Elliott - Chief Engineer} c. to Do. c. to By.{R.W. Bailey - Chief Engineer} RE GOSHAWK II SILENCER AND CUTOUT. X4269 We have tested a silencer and cutout made to N. Sch. Lec.1304 both on a car and on the test bench. We find that this cutout and silencer has two features which require modification. With the cutout closed, it is not efficient as a silencer - there is considerably more noise than with the present standard silencer. The cutout open makes very little difference, either to the amount of noise or the HP. available. We consider that when we add the extra expense and complication of the cutout, with it shut we should not sacrifice any of the silence of the exhaust; also when the cutout is open it should make a marked difference in noise and should give us the maximum power of a free exhaust. Cutouts are used for the double purpose of increasing power and giving audible warning. If we attempt to exhaust through the tail pipe over the axle, the fish-tail outlet will restrict our power, and also give a stuffy note to the exhaust. We must have the fish-tail in order to get the required silence. No matter how many baffles we put inside, if we have a length of tail pipe without a fish-tail, it will give a hollow, drumming note. If the fish-tail is altered in depth from .25" to .3" the difference in note is noticeable. It therefore should be realised that if we use the tail pipe in connection with the cutout, we shall Contd. | ||