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).
The possible causes of high-speed roughness and vibration in cars.
| Identifier | WestWitteringFiles\T\November1928\ Scan116 | |
| Date | 13th November 1928 guessed | |
| -1- POSSIBLE CAUSES. The following three are the only possible causes that we know of high speed roughness and vibration in our cars (handwritten above crossed-out 'case') : (1) Out of balance, either 'linear' or 'torsional'. (2) Proximity to principal crankshaft torsional vibration period. (3) Dynamic deflections of the moving parts disturbing the balanced symmetry of the engine. With regard to the valve gear experiments we have done recently show that below the floating speed it is hardly possible to detect whether the valve gear is functioning or not, when the engine is motored by towing the car, so that this may be neglected as a major cause of high speed vibrations. Dealing with the above three possibilities in turn : OUT-OF-BALANCE. In a six-cyl. engine this is purely 'torsional' and is that known as inertia torque. In the following remarks on balance, complete rigidity of the engine is assumed. It can be shewn mathematically that if an engine were running entirely unsupported, any movement of the whole engine produced by out of balance would be constant in magnitude at all speeds, and that there would be no 'period' due to out of balance. This is due to the fact that the movement produced is inversely proportional to (handwritten insertion) the frequency^2, which cancels out with the fact that the disturbing force is directly proportional to the frequency^2 (or r.p.m.^2) Hence out of balance vibration would be no worse at high revs. than at low revs, but would contd :- | ||