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).
Objectionable exhaust noise on the Phantom chassis.
| Identifier | WestWitteringFiles\N\2October1925-December1925\ Scan50 | |
| Date | 12th October 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. Expl. No. REF: Hs{Lord Ernest Hives - Chair}/AJL2/LG121025. To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/AJL; c.c. to C.J. BJ; c.c. to RG.{Mr Rowledge} E; c.c. to DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} c.c. to Wor.{Arthur Wormald - General Works Manager} ORIGINAL RE: 'PHANTOM' EXHAUST. Y8230 An objectionable exhaust noise has been noticed on numerous New PhantomCodename for PHANTOM I chassis. This noise takes the form of a chirp or detonation and can be cut out if No.6. cyl. is cut out. It was found that the noise only occurs at full throttle position at speeds over 15 m.p.h., below this speed it is hardly noticeable, above 25 m.p.h; it is still discernable but becomes somewhat amalgamated with other noises and does not stand out. If the exhaust choke valve in the rear down pipe be left closed, the noise does not occur. To cut out the noise it was found necessary to cut off the extension of the front down pipe into the front silencer so that gases coming down the rear down pipe do not impinge on to it. [Diagram of exhaust pipe modification] Pipe cut off here. By doing this we dispense with any advantage given by the ejector fitted in the front silencer. Comparison power curves before and after shortening the pipe, however, show no loss of power or other disadvantage. The actual result contd :- | ||