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).
Continued analysis of wheel shimmy, discussing the effects of pivot axis placement and track width adjustments on steering performance.
| Identifier | ExFiles\Box 29\1\ Scan110 | |
| Date | 8th October 1925 guessed | |
| contd :- -13- ought to be brought back in the plane of the tyre. Firstly because the steering will gain in sweetness, secondly, because the tangential reaction of the ground will have less chance to start and maintain the shimmy. If one has a look, as a matter of fact, at illustration 5, one notices that this reaction is exerted at 'M' and that the retarding couple which tends to make the wheel oscillate round its pivot has for an effective arm lever the distance MM1. This distance is the maximum for one wheel and the minimum for the other each time that owing to external forces (bump, potholes etc.) the car displaces itself laterally to the right or to the left of the tyre. On the contrary with a pivot axis brought into the plane of the tyre, the distance MM1 is normally equal to zero and the lever arm is considerably reduced. Shimmy has then less chance of starting and keeping itself going. Besides this there is the information we have obtained - (see under Wheel Brake Drum.) The track. There are several ways of varying the track - by increasing the distance between the wheel and the axle pivot, or by increasing the distance between the spring pads. The second method has not given results of any significance. The first method was carried out with special hubs and aluminium wedges. It shewed us that shimmy diminishes when the track is increased. The critical speeds falls and the period is also reduced. When the increase in the track attains 3.8", shimmy occurs at 25 to 30 m.p.h., but without violence. We observed at this point that the steering contd : | ||