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).
Page analysing the self-exciting nature of high-speed wheel wobble.
| Identifier | WestWitteringFiles\N\July1925-September1925\ Scan284 | |
| Date | 12th August 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-8-25) J.H.D. EXPERIMENTAL REPORT. -4- Expl. No. REF: Ha/Rm{William Robotham - Chief Engineer}2/LG18.8.25. C the wheel manage to give the axle a minute criss cross movement. This little movement is self-exciting, as we shall show later, and builds up into a violent high speed wobble. Considering the sequence of events in a violent wobble for the sake of clearness, though the same thing happens in a less marked manner when the phenomenon starts, we find the following: The axle is vibrating violently in a criss cross manner, and is momentarily parallel with the road, both wheels being in the air. This actually happens from the marks on the road (see Ha/Rm{William Robotham - Chief Engineer}2/LG21.8.25). The descending wheel hits the ground turned inwards looking at it from the front. As soon as it hits the ground it turns rapidly outwards while it is in contact with the ground (see section 6 of report). We do not know why it should be particularly anxious to go beyond the centre position except for the wheel inertia. Having assumed an outward turn, and incidentally turned the wheel in the air inwards, the wheel leaves the ground and the other wheel descends to repeat the cycle. The movement is self-exciting because when the reaction of the ground turns the lower wheel rapidly outwards and the higher wheel inwards, the gyroscopic couple produced tends to lift the lower end of the axle and depress the other end i.e., it tends to increase the tramping. Any increase in the tramping increases the violence of the ground reaction. So from an insignificant beginning a high speed wobble is produced whose period is governed by the criss cross contd :- | ||