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 engine vibration, comparing the crankshaft rigidity and damping characteristics of the 20 HP and Phantom engines.
| Identifier | ExFiles\Box 25\3\ Scan164 | |
| Date | 9th November 1926 guessed | |
| contd :- -4- resonance as indicated by the three crests on the diagram. The same diagram reduced to a flat base is given as a comparison with the 20 HP. and we see that the amplitude is less than with the latter engine. All these investigations where we have used the vibration recording apparatus we have been unable to employ our usual slipper damper and therefore, as no external damping has been used, the influence this normally exerts does not enter into the question as to the reason for the vibration on the larger engine being less severe than on the 20 HP. Now the rigidity of the Phantom crankshaft is 2.68 times greater than the 20 HP. but the disturbing force due to the piston inertia torque has increased approx. 2.7 times and while from theoretical considerations we should expect the amplitude of the vibration to increase in proportion to the energy supplied we can only surmise that the reason why the vibration does not build up to the same extent as the 20 HP. is that the internal damping must be greater. Exactly what factors influence the internal damping - which must be present in these shafts in order that they avoid fracture when resonance occurs - we have at present no information. Therefore, working on this supposition, it seems that internal damping exerts a greater influence than can be obtained by the present external damping of reasonable proportions. We think we should direct our further investigation towards elucidating these points. In the case of the Phantom not only do we find contd :- | ||