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).
Technical memorandum discussing flywheel vibrations, inertia, and crankshaft design modifications.
| Identifier | ExFiles\Box 13\7\ 07-page084 | |
| Date | 6th February 1931 | |
| E.{Mr Elliott - Chief Engineer} RG.{Mr Rowledge} ) FROM R.{Sir Henry Royce} HS.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer}) (At Le CanadelHenry Royce's French residence.) V7300 R1/M6.2.31. Copy to - SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} HY.{Tom Haldenby - Plant Engineer} Copy to - EP.{G. Eric Platford - Chief Quality Engineer} RHC.{R. H. Coverley - Production Engineer} ENGINES GENERALLY X.634. CARS IN PARTICULAR. X.7300. X.5300X P. 2. is the most important at the moment. London is most concerned by what we now know to be flywheel vibrations. We do not think this is an ordinary whirl, but is set in motion at its periodic speed by the deflection of the last crank, and perhaps the crankcase. No matter how much the flywheel was over the bearing we know that when struck on the side it would shiver sideways. This occurs at some particular speed and it is sufficient to know that we would like to raise this speed 30 to 50% until it was out of the speed range of the engine, say over 3000 revs. As the shiver occurs round the centre of the main bearing we cannot reduce the weight of the flywheel very much without reducing its flywheel value, and if we do this very much we shall get angular speed variations from impulses and inertia which may cause transmission vibrations or knocks, so we are very much limited in how much we can reduce the inertia of the flywheel. Some compensation will be obtained if we can use some balancing masses on the crankshaft and this is one of the 3 advantages that we can get from these. Also we need less flywheel if we keep to the longer con. rods. or lightest possible pistons, but there may not be much in this because one feels that our greatest angular speed variation is due to the gas pressures, and the maximum would be governed more by compression ratio. Having done all we can do lighten the flywheel we must next stiffen up the control. The back plate and flange is an easy matter and Derby have tested this on the 25HP. independant of the crankshaft and found considerable part of the deflection occurred in the flywheel itself on its connection with the crankshaft. This work is being carefully examined and improved and it is hoped that this alone would put up the vibratory speed 10%. Now the first crank undoubtedly contributes to the flexibility compared with the staight shaft because of its greater length - i.e. along each web and across the pin. I rather suspect the thin webs as the greatest source of flexibility and I have stated elsewhere that I am much afraid of thin webs for this reason. (1) | ||