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).
Analysis of propeller shaft vibrations, comparing different bearing support types and investigating frequency matching.
| Identifier | ExFiles\Box 148\4\ scan0156 | |
| Date | 13th September 1940 | |
| -3- Ev.{Ivan Evernden - coachwork}10/JH.13.9.40. prolonged experiments on Wolseley and M.G. cars. On the former, the centre bearing was held synetrically by a circular metallastic rubber, in the middle of a plate crossmember, and this was good. In the latter case the same bearing unit was carried on a plate standing above the cross member and was bad. b. Although theoretically if the fixed prop. shaft and the axle pinion are parallel under torque they have constant angular velocity, whilst the moving prop. shaft has sine curve angular velocity variations. Since the moving shaft has mass the fixed prop. shaft and all in front of it, or the axle pinion and its associates have to produce the forces to provide this motion. Can this be a contributing cause to matched frequencies? c. The moving prop. shaft may be regarded as a gyroscopic wheel attached at one end of its shaft to a vibrating fixing, namely the axle. The other end may be regarded as free or in an elastic support. If we consider the former case first (see Fig.1) the support A moves up and down at road wheel frequency, causing the free end of the axis through precession to describe a quasi circular path. A similar sideways vibration produces a corresponding result. If the end previously considered as free, be placed in a support of uniform radial elasticity the angle of precession will be reduced as measure of the elasticity of the support. Not only should the bearing support be considered in the actual case as half the mass of the fixed prop. shaft forms parts of the oscillating system. We suggest an investigation to discover the likelyhood of a matching between the road wheel frequency, or the rear end shake frequency with the natural frequency of the centre bearing and fixed prop. shaft. FREE END ELASTIC SUPPORT FIG 1 FIG 2 | ||