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).
Vibration recorded on coil-ignition units for the Vulture II engine.
| Identifier | ExFiles\Box 142\1\ scan0273 | |
| Date | 14th November 1938 | |
| R.R. 306. 5T. 30966. 6/11/37. C.E. 1204 EXPERIMENTAL DEPARTMENT REPORT REFERENCE:- Lr{Mr Ellor}/HWS.9/GB.14.11.38. Subject of Report:- Vibration Recorded on Coil-Ignition Units. Vulture II, No.4 during 100 hour development test. (21.9.38 onwards) General Conclusion:— Following the series of failures of ignition units on the above engine during the 100 hours development test, wherein it appeared that these were the resultant of excessive vibration, an analysis was made of the failures. It appeared that airscrew running at 2850 r.p.m. was the least satisfactory condition. The engine in question incorporated a revised design of gear-drive and in order to ascertain whether this accentuated vibration a series of vibration diagrams were taken from the ignition-units during brake running and afterwards compared with a similar series for engine II - 2 of normal design. This latter engine subsequently completed 40 hours airscrew development without similar failures being recorded. It was found that no exceptional conditions obtained in engine II - 4 on the bed but the form of the vibrograms was interesting in that it revealed a sixth order vibration of relatively small amplitude modulated at first order or airscrew frequency, some normal addition effects also being noted. Similar waveforms were obtained from unit II - 2. The measured results are given on the accompanying print VM.I. From these results it is assumed that any special conditions existing on Vulture II - 4 were peculiar to airscrew running in the region of 2850 r.p.m. It is pointed out that it has been established that the 1 1/2 order critical speed exists close to 2850 r.p.m. and that the possible effects of the resulting gear case vibration must be considered. In this connection it is interesting to note that the strip examination revealed that the securing-nuts for two of the layshaft pinions (continued) Copies of Report Circulated to:— E.{Mr Elliott - Chief Engineer} Lr.{Mr Ellor} Bn.{W.O. Bentley / Mr Barrington} Lr{Mr Ellor}/Wst. Lr{Mr Ellor}/LBH.{Mr Hall - Aero Design Engineer} Rm.{William Robotham - Chief Engineer} Report to be noted for further action by:— Test carried out on:— By:— Lr{Mr Ellor}/HWS. Test No. Date:— | ||