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).
Experiments to eliminate a 'boom' noise in Phantom II cars at 60 M.P.H.
| Identifier | ExFiles\Box 137\4\ scan0114 | |
| Date | 10th November 1930 | |
| To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/IAL. c. to Wor.{Arthur Wormald - General Works Manager} Sg.{Arthur F. Sidgreaves - MD} c. to E.{Mr Elliott - Chief Engineer} Ds. c. to By.{R.W. Bailey - Chief Engineer} BOOMS - PHANTOM II. Many Phantom II's have complaints of a 'boom' at 60 M.P.H. (i.e. 2250 R.P.M.) Experiments are being carried out on 24-EX., which is one of the worst examples we have tried for this complaint, in order to eliminate this 'boom'. We know there are other slight booms at certain engine speeds but we have decided at present only to work on that at 60 M.P.H. (2250 R.P.M.). It is expected that if this boom were eliminated the remaining booms would also disappear, as they are not nearly so bad. Several attempts have been made in order to lay down the actual cause of the boom but so far no definite cause has been recorded. In order to eliminate the exhaust system the car was towed with the push rods removed in second gear at 2250 R.P.M. The boom was still prominent. This left vibration the cause of the trouble, so we decided to make the torsional periods much worse by removing the slipper wheel and spring drive. The worst torsional period was at 50 M.P.H. (1875 R.P.M.). There was no boom at this speed, and the boom at 2250 R.P.M. was unchanged. It had been noticed from previous results that slacking off the front engine diabolo feet rubbers made a slight relief to the boom. We therefore decided to try central single point front engine mounting. The result | ||