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).
The De Havilland strain-gauge recording gear, its performance, and programme of work.
| Identifier | ExFiles\Box 138\2\ scan0175 | |
| Date | 12th December 1938 | |
| 4204# 1164 To - Hs.{Lord Ernest Hives - Chair} Copies to E.{Mr Elliott - Chief Engineer} Lr.{Mr Ellor} Rm.{William Robotham - Chief Engineer} Bn.{W.O. Bentley / Mr Barrington}x E/SGH.{Sir Stanley Hooker} Bn{W.O. Bentley / Mr Barrington}/TQFM. Dor{Mr Dorey}/Hks. CL Lr{Mr Ellor}/HWS.8/GB.12.12.38. DE HAVILLAND STRAIN-GAUGE RECORDING GEAR. The above equipment has now been delivered to us and we have received from Messrs. De Havilland a technical description and relevant calibration data, etc. We have also received a quantity of calibrated pick-up elements which should suffice until the necessary apparatus for calibration is available here. At present we are gaining the necessary experience in operating the gear which is being employed on the supercharger vibration investigation and at the same time are experimenting with photographic recording which forms an essential feature of the equipment. Our impressions of the apparatus todate are favourable, although some slight unsteadiness has been observed at high inputs (*), which however seems to be inevitable in view of the good low-frequency response. At the same time a small amount of stray pick-up of magnetic origin can be detected at the two positions of highest amplification but it is not expected that these defects will occur under the practical conditions of use. The photographic attachment appears to be satisfactory, negatives suitable for measurement being obtained at exposures of one trace at a sweep frequency of up to 200/second. The equipment was originally designed to work in conjunction with the Hamilton strain-gauge elements and was accordingly given an upper frequency limit of some 1500-2000 cycles for reasonable response but it now appears that the range must be extended to upwards of 8000 cycles for certain work in connection with supercharger vibration. However, the matter has been taken up with the De Havilland Company and we feel that the necessary modifications may be incorporated with ease at Derby. IMMEDIATE PROGRAMME OF WORK. - (1) As already mentioned, the equipment is now in use in connection with the measurement of vibrations existing in supercharger units on the rig. (2) Arrangements have been made to measure the stresses existing in the Vulture air-frame at Sinfin during the type-test running on Vulture II, No.4, which should be available in 10-14 days time. It is proposed to affix the strain-gauges to the frame during preceding (*) e.g. Abnormal transient output following a shock to the vibration pick-up, etc. | ||