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 vibration of a 4.2' bore single-cylinder liquid-cooled sleeve valve engine.
| Identifier | ExFiles\Box 134\1\ scan0105 | |
| Date | 17th October 1938 | |
| Lr{Mr Ellor}/HWS./SGL.6/GB.17.10.38. VIBRATION OF 4.2" BORE SINGLE CYLINDER LIQUID COOLED SLEEVE VALVE ENGINE. Vibration records have been obtained during the course of a Power Curve Run, a Boost Response and an Ignition Advance run, thus covering a wide range of engine conditions. The records were taken from four different points on the engine. - 1. Plug insert. 2. Centre of cylinder head jacket, near the thermocouple tube. 3. Cylinder head flange. 4. Boss on crankcase near base of cylinder. Large amplitudes of vibration were found on the cylinder head jacket, flange and plug inserts. These were all at half order (i.e. firing) frequency. The wave form consisted of sharp peaks lasting 1/2 of a cycle with a flat portion between. It appears that this vibration consists principally of elastic extension of the cylinder under the combustion pressure, rather than any form of resonance. The amplitude is proportional to the maximum pressure not the M.E.P. This accounts for the maximum of 4200 R.P.M. (curve VS.{J. Vickers}1) at which speed the maximum pressure is greatest. The very large amplitudes of the plug inserts and cylinder head jacket may be due to diaphragm vibration of the head itself communicated to the jacket by the water. The existence of such large amplitudes has been confirmed by stroboscopic examination. It has been suggested that accurate amplitude measurements could be performed using a small electric contact attached to a micrometer screw and observing the reading at which current begins to flow. The indicating device could be a neon tube or a milliammeter. The extension of the cylinder barrel has been calculated from the maximum pressure and the structure of the barrel and the result was of the same order as the figure obtained from the vibrograph. The large amplitudes at ignition advances of over 40° are probably due to the occurrence of detonation. The vibrograph is incapable of recording the high frequency vibration present with detonation. The crankcase vibration is small, never exceeding .010". It is mostly of first order engine speed frequency and may be due to out of balance forces. Attach Table. and 3 prints VS.{J. Vickers}1, 2 and 3. Lr{Mr Ellor}/HWS./SGL. | ||