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).
Crankshaft periods and engine vibration on the Bentley, quoting a letter from Hancock.
| Identifier | ExFiles\Box 82\3\ scan0309 | |
| Date | 20th May 1935 | |
| To E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} trova Ha/Rm.{William Robotham - Chief Engineer}S/KW.20.5.35. Crankshaft Periods on the Bentley. The following is an extract from one of Hancock's letters, dated May 17th :- "We had got the engine almost perfect with regard to periods, by getting a damper load of 27 lbs. There was only the slightest vibration at 3,600 and you had to keep the foot on the clutch pedal to feel that. We have got cork discs in the damper which are very good. We are however up against the softness of the cork which flattens out with the pressure. We shall get over this in some way." This bears out our original experience, that as we put up the maximum pressures by using a higher compression ratio we require a bigger crankshaft damper and higher friction load. It does not seem to be necessary to have a higher I.M.E.P. to produce greater amplitude of crankshaft torsional movement, the maximum pressure seems to be the dictating factor. This is why Diesels are running into trouble, see page 614 of the May 4th issue of Automotive Industries. Ha/Rm.{William Robotham - Chief Engineer} | ||