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).
Exhaust silencer boom, vibration, and cracking issues and the subsequent modifications.
| Identifier | ExFiles\Box 179b\3\ img384 | |
| Date | 10th May 1924 guessed | |
| - 12 - The exhaust silence at first was not good. There was a slight boom at approx 20 MPH, an objectionable boom at 30 MPH, and a general booming 65 and upwards. Over run booms were not so predominant. The swinging link anchorage at the rear end of the rear silencer was found to transmit the periods of exhaust vibrations to the body, and this type of body amplified the vibrations making them unpleasant, at the master period ie 30 MPH. The rear anchorage was removed, the silencer at this point being suspended by a wire band. This reduced the vibrations transmitted to the body, and the boom at 30 MPH was then not objectionable. We had considerable failures of the front resonance chamber. The welded joint of the down pipe cracked approx. during each 250 miles. The welding being built up around the joint, weakness then developed round the outer edge of the chamber, the metal cracking. Upon curing this end, the same failure developed at the rear end of the chamber, and the same procedure was carried out. The cause was due to excessive vibrations of the down pipe and chamber. A stay was fitted from the engine base to the front end of the silencer, which, although loosening the vibration did not stop the cracking of the end cover of the resonance chamber. The whole silencer had by this time come forward approx. two inches. This was caused by the straightening out of the bend of the front down pipe. This caused the link suspension at the front and of the rear silencer to foul the cross member and its usefulness was eliminated. The exhaust booms under these conditions were more pronounced, we therefore fitted a spring flexible mounting to the front end of the rear silencer. The fitting of this allowed the whole silencer system to vibrate more with worse results in the body. The link suspension at the front end of rear silencer was replaced making it clear the cross member. A stiffer stay was fitted to the resonance silencer. This considerably reduced the booms from the exhaust and a passable condition was obtained. | ||