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).
Engine vibration issues at various speeds, their potential causes like flywheel whirl, and proposed solutions.
| Identifier | ExFiles\Box 12\6\ 06-page014 | |
| Date | 16th April 1931 guessed | |
| (4) Item (2) is naturally the obvious way to improve this 65 to 70 MPH. vibration by putting up the natural period from 2700 complete vibrations per period, which if it could be raised to 3300 would never be in the speed range of the engine under even the best ordinary road conditions, but might be found with a streamline body. Item (3) might do some good by helping (2) to put up the period. Item (4) according to Mr. Goals calculations would have very little effect but item (5) might do good, but would not save the bearings, and therefore is inferior to item (1), but otherwise much the same in effect i.e. would not alter the periodicity, but lessen its intensity. Counting that the master crankshaft period is beyond our speed range as it naturally must be kept under any conditions we can adopt, my impression is that we have two items which are causing us trouble. (i) Torque reactions - low speed. ) Improved by mounting (ii)Over-run - medium speed. ) (iii)Flywheel whirl - high speed ) Improved by items (1) (2) (3). The results reported seem so very indefinite that one wonders if our conclusions are correct. To help prove this I had suggested that in addition to getting an indicator to register the periodicity so that we can better find the cause, or confirm our views, and also there may be others. One thinks that even at lower speeds the disturbing effect of the couples (centrifugal etc) may be rather worse than I imagine because though the forces are less the time is longer. The result seems that the deflection would be directly proportionate to the speed in revs. Our 18-EX. shews definite torque reaction in top gear, 18 to 25 MPH., then a smooth period with very slight vibrations, then at 65 MPH. commences the bad period, which is what all my anxiety is about and to which my suggestions refer, and which we have thought to to now is from the flywheel whirl, and this is the only vibration I think that is modified by items (1) (2) and (3) given on page 2. of this memo. I want you to let someone concentrate on this but I hope before you get this note the situation will have cleared itself. I believe that if you put in the diamond mounting without rubbers at the front and rear, but with very soft | ||