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 wheel wobble, axle oscillations, and spring movement based on slow-motion kinematics and tests.
| Identifier | ExFiles\Box 29\1\ Scan102 | |
| Date | 8th October 1925 guessed | |
| contd :- -5- the marks left on the ground of one of the front wheels (see Illustration No.2.) which shows the violence of the tyre when it scrubs on the ground which confirms the indication of our registering instruments. The slow motion kinema has enabled us to establish the attached graphs No.4; which show the oscillations of the axle and the wheel are isochronous. We have observed that the period of the wobble is generally that of the road wheel revolution. We do not know why. We had thought it might be due to peculiar-ity of the tyre or the inner tube, (valves, welding) or to the out of balance of the wheel, but tests with inner tubes with two and three valves and three welding points with wheels statically balanced, have shown us that the shimmy persists and that the period remains for all practical purposes the same. (See further on 'Out of balance'.) One notices also (see pictures 1 and 3.) that the move-ment resulting from the principal movements is a periodic vibra-tion in which the wheel describes a sign curve, half of which lies on each side of a straight line. The maximum extension of the left spring, takes place when the left wheel is turning towards the inside of the chassis, meanwhile the right wheel tends to leave the ground compressing the right springs and describing the portion of the sign curve outside the car. The total movement of the axle varies between 12º and 15º. The maximum compression attained on the right of the axle [handwritten: towards] seat is 40 to 50 m/m and corresponds to a force of 400/600 kilo-grams (880/1320 lbs.) The extension attains contd :- | ||