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 shimmy, covering factors such as toe-in, steering, and spring flexibility.
| Identifier | ExFiles\Box 29\1\ Scan114 | |
| Date | 8th October 1925 guessed | |
| contd :- -17- (2) There is an inevitable tendency with all modern cars with semi-reversible steering to shimmy. (3) There is an increase in steering couple by the employment of low pressure tyres. Toe in. Toe in is so called when the two front wheels look as in the plan, converge towards the front. We measured it by the difference between AB, and CD, in m/m, taken on the wheels the same height from the ground, the extremities of the horizontal diameter of 0 m.{Mr Moon / Mr Moore} 60 long. The toe in is variously fixed by designers as from 1/8 to 1/4", i.e., perhaps 3 to 5/10 of a degree. We have proved that it somewhat opposes shimmy on whose effort it seems to act some-what as a brake. Wheel brake drum. We have actually carried out tests with pivot axis brought into the plane of symmetry of the wheel. We have proved as far as can be proved, that the result is a very sweet steering with considerable reduction in shimmy which starts but does not continue and does not build up. E.{Mr Elliott - Chief Engineer} THE SPRINGS. We have seen during shimmy that the vibration of the springs and the oscillation of the wheels are isochronous. We have proved that when the flexibility of the front springs is increased 10 to 15%, the violence of the shimmy increases. If the deflection is diminished by 5 to 10% the shimmy diminishes. The same thing happens if one employs springs of small deflection instead of springs of big deflection. You are recommended to make sure that the following three points - contd :- | ||