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).
High-speed engine vibration and crankshaft critical speed, noting bearing distortion.
| Identifier | WestWitteringFiles\R\2October1927-November-1927\ 109 | |
| Date | 4th November 1927 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to BJ. Wor.{Arthur Wormald - General Works Manager}✔ c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer}✔ c. to DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer}✔ c. to OY. ORIGINAL X634 V5010 X8010 HIGH SPEED ENGINE VIBRATION. We have recently, both on the 40/50 HP. and 20 HP been running the engine for long periods in the neighbourhood of the crankshaft criticial speed. In every case, we find that when treated in this manner, the engine gets progressively rougher in spite of the fact that nothing is altered i.e., the crankshaft vibration damper setting etc. remains the same. We have not sufficient experimental data as yet to definitely account for this phenomenon, but in view of the fact that the re-designing of the crankcase is now under consideration, we consider that it might be worth recording our impression. We have made various crankshaft models of wire. When we twist the crankshaft as occurs in torsional vibrations, the main bearings go out of line. When an engine is stripped after running on, or near, the critical speed, the main bearings are not worn, but have a peculiar bedding which does not retain the oil pressure well and would indicate local distortion in the main bearings. We have proved a number of times that bearing fits have a marked influence on crankshaft torsional vibrations. Therefore, at the moment we believe that the maximum possible local support of the main bearing is desirable in combating crankshaft periods. We have evidence that racing people do support | ||