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).
Investigation into exhaust noise and carburettor roar on the London Trials Car, with suggestions for sound absorption.
| Identifier | ExFiles\Box 18\4\ Scan008 | |
| Date | 19th January 1933 | |
| To PN.{Mr Northey} From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. Wor.{Arthur Wormald - General Works Manager} C. Cx.{Major Len W. Cox - Advertising Manager} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}2/KT.19.1.33. X7960 48-MS. LONDON TRIALS CAR. X-93 With reference to PN.{Mr Northey}10/WT.16.1.33. We have now carried out tests on this car. As far as we could determine, the influence of the exhaust system was confined to speeds below 40 m.p.h. We actually tried a resonance silencer on the car without being able to effect a material improvement. We therefore replaced its own exhaust system. We fitted the standard fishtail in conjunction with the original exhaust system and think this is definitely better than the long fishtail fitted, though not a cure. Although we do not know the exact conditions under which this car is mainly used, the worst feature appeared to us to be a carburetter roar which starts below 40 m.p.h. and does not disappear until about 60 m.p.h. This car is the worst example of this trouble we have encountered. As this has the old type carburetter fitted, there is no effective air intake silencer designed which can be utilised. Since there seems to be little doubt that this body, for some reason or other, accentuates engine and exhaust system noises, we should like to interest you in a process developed by Messrs. J.W.Roberts Limited of Armly, Leeds, whereby finely divided asbestos is sprayed on to the scuttle and panels of an automobile body, thereby absorbing sound. The increase in weight appears to be very little. Ferodo's are controllers of the Co. and have told us that good results have been obtained on various types of mass produced coachwork. The London Underground can give you further information, as they have spent a lot of money silencing a portion of their track utilising this scheme. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||