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).
Engine vibration tests, investigating torsional oscillations and the effect of slipper flywheels.
| Identifier | WestWitteringFiles\P\2July1926-September1926\ Scan130 | |
| Date | 4th September 1926 guessed | |
| contd :- -3- normal amount of friction reduced the intensity of the vibrations and the previous 1600 r.p.m. vibration was hardly evident and could only be detected at full load. We were unable to detect the lowest vibration at 1100 r.p.m. We then repeated the test with the slipper flywheels bolted up as tight as possible so that instead of friction dampers they virtually became part of the crankshaft and increased the polar inertia of its front end. The critical speed was now reduced from 3350 r.p.m. to 2500 r.p.m. and as near as could be judged the vibration seemed of greater magnitude. The second and third vibratory periods now became 1240 r.p.m. and 820 r.p.m. respectively. The results of these three tests and particularly the way in which the critical speed was lowered by changing from the standard adjustment of the slipper drive to the solidly bolted wheels gave every indication that the vibration was torsional. Solidly bolting the slipper flywheels would do nothing but increase the polar moment of inertia exactly the same in either longitudinal or transverse directions as with the standard arrangement. Therefore this alteration would be expected to affect only torsional oscillations. The next step was to determine if the explosion pressures were the distrubing forces for these vibrations. The test was made by driving the engine by means of a belt with the cylinder head removed. contd :- | ||