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).
Test results for different straight-through exhaust pipe configurations and a cast iron expansion box.
| Identifier | ExFiles\Box 14\6\ Scan253 | |
| Date | 26th November 1931 | |
| -4- Straight through pipe reinforced with .040" thickness of metal, making total thickness .104" Result - Only 50% as good as standard system for quietness, and exhaust booms more pronounced. 30 - 33 m.p.h. Bad. 35 - 40 " " 50 - 52 " " 68 m.p.h. upwards bad. Weight of pipe .104" thick 20 lbs 9 ozs. 19.11.31. Straight through pipe reinforced with .080" thickness of metal, making total thickness .184" Result - as good as standard system for tittering, but the swishing noise is very apparent between 20 - 30 m.p.h. Weight of pipe .184" thick 34 lbs 8 ozs. EXHAUST booms are the same as on previous test. 26.11.31. A further test was carried out with the cast iron expansion box machined down to .062" but we found this was much too thin, the exhaust noises being much worse, and decided that we could not use a cast iron box less than .187" thick. G.H. Whyman. | ||