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).
General report on the development and testing of carburettor intake silencers.
| Identifier | ExFiles\Box 179b\2\ img172 | |
| Date | 28th November 1932 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. Sg.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} c. E.{Mr Elliott - Chief Engineer} BY.{R.W. Bailey - Chief Engineer} c. Ds. HDY.{William Hardy} Hs{Lord Ernest Hives - Chair}/RmL/BE.28.11.32. x442. x7080. x5080. * CARBURETTOR INTAKE SILENCERS - GENERAL. We have now done sufficient work on intake silencers to be able to say that we can produce a quiet carburettor without loss of power on a 1600 BHP. engine, provided the size of the silencer is not necessarily limited to below 300 cu.ins. On the whole, we have been unable to confirm, in practice, the somewhat elaborate theory evolved by the Americans explaining the action of the 'double' resonance silencer. Actually, we have not succeeded in reducing very materially the resonance capacity needed by employing double chambers connected together. We have, however, found that a single chamber will suppress a 'roar' over quite an appreciable range, particularly at the highest speeds, and we have achieved successful results on the one carburetter so far dealt with, by employing two simple and separate chambers in various positions. The silencers produced do not depend in the slightest on restriction, 'air cleaning' or 'wire maze' air intake for their silence, in fact all the tests have been conducted throughout without any form of air cleaner being fitted, though some sort of thing is shown in the sketches. Such As will be deduced from the results, it is much easier to get silence if the intake is restricted, in fact for a power loss of about 4% the silencer size required can be halved. Naturally, the lower the note, the larger the resonance capacity required, and unfortunately we have a roar at 40 m.p.h. as well as 60 m.p.h. However, on reviewing the American efforts, we find our silencers are not unduly large. Sheet C. shows two samples. The Burgess we bought; it is far too restricted for the Phantom and drops the power over 10%. It is not very silent, yet is appreciably larger than our intermediate size and weighs twice as much (the 'steel wool' sound absorbing packing is very heavy). -continued- | ||