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).
Completion of tests on a resonance silencer for the 20/25 HP car, outlining modifications and results.
| Identifier | ExFiles\Box 179b\2\ img023 | |
| Date | 19th October 1932 | |
| ORIGINAL R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Lid.{A. J. Lidsey} C. Ss.{S. Smith} Wdf. C. E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} C. By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Lid.{A. J. Lidsey}1/KT.19.10.32. X5330. RESONANCE SILENCER FOR 20/25 HP. CAR. We have now completed our tests on the resonance silencer for the 20/25 HP. car. The final silencer differs from the first one (which was found unsatisfactory) in the manner shown in the attached print. It will be seen that the modifications from the original (Z.58990) consist solely of modified drilling of the baffles and central tube, and modified positioning of the baffles. Actually there is a good deal less drilling involved so that the silencer will be less costly to produce. It is necessary to use with this silencer, the present standard lagged downtake pipe, front expansion box and intermediate pipe. The present standard 1.50" diameter swan neck and fishtail is also used. The advantages to be gained are not so great as we originally hoped when we commenced working on this type of silencer. They are - (1) Slight reduction in weight, (2) Slight reduction in power loss to silencer, (3) Reduction in cost, (4) Improved silencing qualities. We hoped originally to be able to dispense with the standard type of front expansion box and use an unlagged mild steel straight through pipe. This, if it had been possible would have been responsible for a big saving in weight - 16 lbs, and also a big saving in cost. The reason we cannot use a straight through pipe is because the low speed exhaust noise is very vigorous when listened to from outside the car, and can only be damped out by using a front expansion box. We know that only a very small percentage of our customers would notice or take objection to it, but it is not quite up to our usual standard of silence, and we feel it would be false economy to use the straight through pipe. (1) | ||