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).
Investigating high-speed wheel wobbles and proposals for experiments to understand and eliminate the phenomenon.
| Identifier | WestWitteringFiles\N\2July1925-September1925\ Scan80 | |
| Date | 14th September 1925 | |
| ORIGINAL R.R. 285A (100 T) (S.H. 159. 11-8-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2800 TO HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce} C. to GL.{G. Linnett} WOR.{Arthur Wormald - General Works Manager} " DY.{F R Danby} DA.{Bernard Day - Chassis Design} " EFC.CWB STEERING. X8430 t401 R1/M14.9.25. Naturally you will still be pressing forward the tests to ascertain why the high speed wobbles appear at road wheel speed, and how they are fed so that they build up. It is quite agreed that they only appear at road wheel speeds when this arrives at tramping periodicity, and it also appears that this particular periodicity is fixed by the combined action of the tyres on the road, the car springing, control springs in the longitudinal tube, and the gyrostatic forces set up by the road wheel upon the mass of the road wheels, and axle. We want you to get HS{Lord Ernest Hives - Chair}/RM{William Robotham - Chief Engineer}, and EFC. to continue the work at this problem to find the exact cycle of the phenomenon, especially with regard to whether it is within our power to design the parts so that the vibration does not occur, even when the car is neglected as regards tyre pressure and balance. To the above end we wish you to add stationary masses to the ends of the axle to still further lower the tramping periodicity, using the balloon tyres, and find whether we can by lightening the axle, brakes, and hubs, put the wobbling speed out of reach, or upset its periodicity so that it does not agree with the road wheel speed. Personally I feel that the only way it can be avoided is by making the tramping speed out of reach of the car, if we are to cater for out of balance wheels or tyres. It is just possible that by adding the weight of the brake drums to the masses, we have rendered some natural gyrostatic wobble (conical precession) to a speed of approximately 1 to 1 with the road wheels, and that the phenomenon of feeding the wobble through out of balance, or the action of the road on the tyres, can only take place at road wheel speed. In the first experiment it is assumed that we do not alter the weight of the tyre and rim, and therefore keep our gyrostatic forces constant, but that we lighten the rest of the axle with the object of making the gyrostatic wobble quicker than the road wheel speed. I am nearly convinced that the wobble would occur at all and any speed if it were fed, and that the feeding only takes place at road wheel speed, either by the tyres becoming out of balance, or out of truth. (1) | ||