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).
Torsional vibration tests on the B.60 model with and without a rubber coupling.
| Identifier | ExFiles\Box 124\2\ scan0062 | |
| Date | 12th March 1940 | |
| 1044 To Ev.{Ivan Evernden - coachwork} from Rm{William Robotham - Chief Engineer}/JRS. c. Jnr.{Charles L. Jenner} Rm{William Robotham - Chief Engineer}/JRS.10/MH.{M. Huckerby}12.3.40. TORSIONAL VIBRATION ON B.60. In order to distinguish between the two modes of vibration occurring in B.60. Tests were carried out with a rubber coupling between the engine and the brake in order to increase the torsional flexibility of this portion of the system. This would have the effect of reducing the natural frequency of the single node mode of vibration at the same time leaving the two node mode at the same frequency. Figure 1 shows the curves of amplitude with and without this coupling. The curve taken without the coupling shows definitely the 1½ at 1300 r.p.m. and the ½ order at 3900 r.p.m. With the rubber coupling in use the 1st. order occurs at 1150 r.p.m. and the ½ order at 2300 r.p.m. By combining these two curves we get the curve in Fig. 2. This curve is still rising at the higher speeds at a 4000 r.p.m. has attained an amplitude of ± 7°. Fig. 3 shows the curves for the Humber and Studebaker dampers under the same conditions. The Humber has its friction setting at 50 lbs.ins. and the Studebaker is fitted with 45-50 rubbers. Both these give amplitudes slightly less than those obtained with the spring drive and of the two the Studebaker is the best. The half torsional period seems to be the criterion when in a car, and with either of these dampers should not give trouble. The main period is the one which gives camwheel trouble but with a suitable camwheel, i.e. wider tooth surface with a coarser diametral pitch, and or thicker teeth on the wheel compared with the pinion, this should be overcome. | ||