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).
Tests and alternatives for a semi-expanding carburetter air intake silencer.
| Identifier | ExFiles\Box 179b\2\ img174 | |
| Date | 28th November 1932 | |
| -3- Ha/Rml/BE28.11.32. P.II. SEMI-EXPANDING CARBURETTER AIR INTAKE SILENCER Tests on the Phantom semi-expanding carburetter have demonstrated that we require a certain minimum length of intake pipe and resonance capacity in order to get 100% elimination of induction roar. We have two alternatives:- (1) To have a considerable vertical intake length from the carburetter to the top of the induction pipe, and fit the silencer proper above the induction pipe. Samples of this arrangement are shewn on Sheets A and B. Figs 1. 2 and 3. The advantages are, that the plugs are accessible. The disadvantage, a length of intake that is not necessary for the purpose of silencing. (2) To fit the silencer as near as possible to the air intake. An example of this is shewn on Sheet B. Fig.4. The advantage is neatness and conservation of material. The disadvantage, that the silencer has to be removed before two of the sparking plugs are accessible. Scheme.1. We have done most work on scheme 1. The first silencer evolved is shewn on sheet A.{Mr Adams} Fig.1. This is considerably the smallest having a resonance volume of 140 cu.ins. It is not 100% efficient for silence but loses about 4% of power on the Phantom output of 160 BHP. It was therefore necessary to increase the diameter of the intake, which at the same time, our tests have shewn, means a slightly larger silencer. Silencer(2) on Sheet A loses no more than 1% at any speed and the resonance capacity is only about 20% larger than (1). A final test was made to see the dimensions required to cause no loss of power whatever. Silencer(3) fulfilled these requirements having 300 cu.ins. capacity, or slightly more than twice as large as the silencer causing 4% loss. -continued- | ||