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).
Analysis of gear failures and vibrations in Vulture II engines, specifically engines II-4 and II-2.
| Identifier | ExFiles\Box 142\1\ scan0279 | |
| Date | 21th October 1938 guessed | |
| (5) In the case of a geared engine the reactions between the gear shafts will of course be influenced by the presence of torque fluctuations and consequently the torsional oscillations will be capable of producing vibrations at corresponding frequency in the gear-housing. An examination of the gears of engine II - 4 has revealed several peculiarities which may enumerated :- (1) The airscrew-shaft gear showed marked indication of a heaving bearing at the forward end, which is dismissed as being due to the distortion of the gear-housing under load and not concerning us in the present matter. (2) A small piece of metal had broken away from the flank of one airscrew gear tooth. It is expected that the laboratory will indicate that this is due to a material defect and it is not considered important from our point of view. (3) It was found that on two layshafts the securing-but for the pinion had loosened and allowed some fretting of the gears on the splines, following the failure of the tab-washers. Such an occurrence might have resulted from prolonged running under vibration coupled with unsuitable material; and it is considered possible that following the loosening of the gears the vibration under critical speed running would become more serious. This would of course account for the hangar failures at 2850 R.P.M. on the engine in question. In view of the fact that the other engine investigated (i.e. II - 2) has now completed the whole of its 40 hours hangar running, including 20 hours at 2850 r.p.m. without ignition failure, there seems to be justification for asserting that some special vibration conditions resulting from the gear fitting in Vulture II - 4 occurred in a serious degree whilst running at the critical speed. Consequently, we are inclined to attribute the abnormal failures on engine II - 4 to the foregoing cause and recommend that further attention be given to the method of fitting and/ or material used in securing the layshaft nuts. ------------- Lr{Mr Ellor}/H.W.S. | ||