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).
Tests investigating the effect of reducing crankshaft inertia on torsional vibration frequency on a B.60 engine.
| Identifier | ExFiles\Box 124\2\ scan0132 | |
| Date | 17th April 1940 | |
| 1044 To Ev.{Ivan Evernden - coachwork} c. to Jnr.{Charles L. Jenner} Em/JRS.4/JH.17.4.40. The effect of reducing crankshaft inertia on torsional vibration frequency on B.60. These tests were carried out on B.60 No.2. which was fitted with a Wraith Spring Drive. In order to determine the effect of reducing the crankshaft inertia the balance weights were removed. It was found necessary to run without the slipper wheel on the spring drive so as to get a clear diagram of a single critical speed which would give us the natural frequency accurately. The crankshaft was statically balanced for the tests both with and without balance weights. Torsiograms were taken at full throttle at intervals of 100 r.p.m. but the max. speed had to be limited on account of the large amplitudes involved when running without the slipper wheel. Consequently we were unable to get a picture of the 6th. harmonic (1/2 torsional) period but both with and without balance weights the 9th. harmonic showed very definitely. With balance weights this occured at 1700 r.p.m. and without them at 1800 r.p.m. This gives the natural frequency as 15300 per min. and 16200 per min. with and without balance weights respectively and the 6th. harmonic periods at 2550 r.p.m. and 2700 r.p.m. respectively. Torsiograms taken with the slipper wheel in action show the same raising of the critical speed when running without balance weights, by the shifting of the main period upwards by about 150 r.p.m. meaning that P.T.O. | ||