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).
Investigation into high-speed steering wobbles, asking for specific measurements and proposing a testing method.
| Identifier | ExFiles\Box 28\4\ Scan268 | |
| Date | 14th August 1925 | |
| To Hs.{Lord Ernest Hives - Chair} from DA.{Bernard Day - Chassis Design} X 457 DA{Bernard Day - Chassis Design}2/M14.8.25. X.457 X.8430 HIGH SPEED STEERING WOBBLES. With reference to the conference on Thursday we wish to inform you that we are proceeding to design an hydraulic damper on the front axle, and drawings will be sent along in due course. There were some questions which we meant to ask you: some we succeeded in putting, but others were either not put or left in a rather indefinite state. We should therefore now like to ask you :- (1) Can you measure the frequency of the oscillations during one of these wobbles? This information would be a guide to us as to the source of the energy keeping the oscillation going, as well as an indication of the original cause of the oscillations. Does it correspond with the revs. of the road wheel at that particular road speed? (2) Can you measure - even though it is within a small range - the alteration in the speed at which the wobble comes on made by altering the tyre pressure? (3) Can you try vertical pivots? We understand from you that excessive castoring increases the tendency to wobble. More exact information on this point, including that obtained from the use of vertical pivots, would be very useful. (4) We should like to find out what we could about the gyroscopic properties of the wheels as we suspect that one of the causes of the oscillation is a gyroscopic period which perhaps happens to coincide with some intermittent source of energy at this particular speed. We do not like to suggest any particular method to you of investigating these properties, but it occurred to us that the axle might be jacked up by a jack with a narrow face immediately in the centre of the axle so that the latter was free to oscillate with the jack as a centre. The wheels might then be spun at speeds corresponding to those at which these wobbles occur, and by giving the steering system repeated steady impulses or blows it might be found that at one speed there is a marked tendency to wobble. We may say that our little investigations with a wheel seem to point to there being such a wobble, and it appears to occur if impulses are administered at twice the speed of revolution, such impulses for instances as are administered by unbalanced wheels. DA.{Bernard Day - Chassis Design} | ||