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 such as torque reaction, over-run, and flywheel whirl, and proposing potential solutions.
| Identifier | WestWitteringFiles\V\October1930-February1931\ Scan351 | |
| Date | 23th February 1931 guessed | |
| (4) Item (4) according to Mr. Grylls 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 so under any conditions we can adopt, my impression is that we have two items which are causing us trouble: (1) Torque reactions - low speed. ) Improved by mounting. (11) Over-run - medium speed. ) (111) 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 and thick rubber top and bottom at the side, no other metal touching, you will get much better results than at present for all torque vibrations, - i.e. torque reaction, over-run, and harmonic of crankshaft period. That if you tackle the flywheel you will be able to raise the 65 MPH. period to over 80. by the simple expedient of lightening, and less overhang, with stiffer back plate flange and fixing. Then also something can be done with rather larger pins, and when convenient 4 small balance weights as large as master period will allow. These should be like oil on troubled waters to main bearings and crankchamber deflections. I have said if only 30% they should be fitted. | ||