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).
Experimental investigations into crankshaft torsional characteristics and airscrew blade stress measurements.
| Identifier | ExFiles\Box 138\2\ scan0176 | |
| Date | 12th December 1938 guessed | |
| (2) Merlin airscrew development run. The advice of Dor{Mr Dorey}/Hks. will be sought in connection with the placing of the elements. (3) We should like, if possible, to obtain an Exe crankcase to investigate the bending-stresses in the regions where failure occurred on the earlier designs. (4) EXPERIMENTAL INVESTIGATION INTO TORSIONAL CHARACTERISTICS OF CRANKSHAFT SYSTEMS.- Arrangements have been made to carry out an electrical torsiograph investigation on the Vulture engine in parallel with the R.A.E. torsiograph for which Lr{Mr Ellor}/LBH{Mr Hall - Aero Design Engineer}/DCJ. is responsible. In this case the major difficulty lies in obtaining an engine for hangar running but it is hoped to obtain Vulture II No.5 which should follow the type-test engine already mentioned. The necessary modified drive will be assembled in a Vulture II gearcase which will be kept ready for fitting to the engine as soon as it is available. By conducting the tests in parallel with the R.A.E. torsiograph it is hoped to confirm the behaviour and calibration of the electrical apparatus and to establish confidence. It is pointed out that when this has been done it will be possible to carry out torsiograph investigations on the ramp at Hucknall and to relieve some of the difficulty of obtaining engines for this work owing to the reduced installation difficulties associated with the application of the electrical method. The matter has been discussed with Bn{W.O. Bentley / Mr Barrington}/TGFM. and it has been agreed that experimental data should be obtained for the torsional oscillation characteristics of all current engine types in view of the known discrepancies existing between calculated and measured performances. It was considered that as a result of extended tests under a wide range of engine conditions the necessary data could be adduced to enable the Stress Section to overhaul the present methods of calculating the amplitudes at critical speeds. Such work was considered to be of fundamental importance as a basic factor in undertaking new designs. We accordingly request that due consideration be given to obtaining the necessary tackle for modifying the airscrew drive and actuating the electrical torsiograph on Merlin, Peregrine and Exe engines. (5) AIRSCREW BLADE STRESS MEASUREMENTS.- The necessary equipment is available for testing Rotol airscrews for Vulture, Merlin and Peregrine engines. It is pointed out, however, that the recent trend towards the use of Schwarz blades has modified the position with regard to vibration-testing as at present we are unable to find a cement suitable for attaching strain-gauges to blades in rotation which does not involve the application of a considerable amount of heat. We intend to investigate the possibilities of some commercial cements of the acetate type, in the near future. | ||