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).
Preliminary particulars of a modified exhaust system for the 20/25HP car, focusing on cost and weight reduction.
| Identifier | ExFiles\Box 104\2\ scan0020 | |
| Date | 2nd June 1932 | |
| E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Lid.{A. J. Lidsey} c. to Wor.{Arthur Wormald - General Works Manager} Y 5230 Hs{Lord Ernest Hives - Chair}/Lid.{A. J. Lidsey} 2/MA. 2.6.32. 20/25HP CAR EXHAUST SYSTEM. We are now able to give preliminary particulars of a modified exhaust system which we have been developing for the 20/25HP car. The main drawbacks in the present system are its cost and weight. The modified system has been evolved after extensive tests with varying combinations of baffles etc and aims to reduce weight, cost, and at the same time absorb less power. The present front expansion box is done away with and a plain downtake pipe from the manifold to the silencer is used. One inner tube only is used in the main silencer and a P.II swan neck and fish tail is used. There is only one actual baffle in the silencer, and although we have not yet tested it for HP loss there is every reason to expect that this will be less than in the standard system. The exhaust noises and booms are comparable with the standard system; a car was tested by PN{Mr Northey} with the modified silencer fitted and no fault was picked out. The test was short and carried out on a country road; to be completely satisfactory the test should include running in town between buildings, walls etc which tend to aggravate any noise or boom. We do not anticipate however that any test of this nature will show up any objectionable characteristics. Owing to the fact that the silencer is freer from back pressure it is bound to sound slightly more 'open' from the outsiders point of view even if it is free from noise and periods to anyone actually in the car. The only way of overcoming this is to increase the restrictions in the silencer which of course will result in increased back pressure. We do not anticipate however that this will be at all necessary. We feel that the results are sufficiently satisfactory to permit of design work going ahead; it is suggested that a cheapened method of construction could be obtained by inspecting the Cadillac silencer. The method of fixing the baffles is less costly than ours and would appear equally effective. We do not yet know what the material is that is used, but we are | ||