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).
The fundamental conditions of 'wheel fight' on rough roads and methods for tuning the steering mechanism.
| Identifier | ExFiles\Box 170\3\ img067 | |
| Date | 14th March 1936 | |
| March 14th, 1936. Wheel Fight on rough roads. Fundamental Conditions appearing from recent work on road and bump rig. NOTE: The distinction of wheel fight on rough roads is made to indicate that this is not quite the same thing as the pure wobble and shimmy covered in notes of June 5, 1935. (1) There are two typical varieties of wheel fight. The first, occurring about 400 cycles/min. is chiefly wobbling of the wheels; i.e. wheels "flap" around the kingpins, and car oscillates, principally sideways. The second is chiefly hopping of the wheels. It occurs at about 600 cycles/min. Car oscillates torsionally generally twisting the fans. Oscillation of the steering wheel appears to be excited by gyroscopic action of the front wheels. (2) Chief condition for a successful steering which does not fight is to "tune" the steering mechanism by making its flexibility such that the front wheels do not want to flap about the kingpins at either of the above frequencies. Tuning to either frequency will produce violent oscillations of the steering wheel. Most successful tuning so far consists in getting the wheels to flap at about 500 cycles/min. It might be even better to tune the steering to a very high frequency such as 800 cycles/min. The cross steer experimental 1937 Olds has a wheel fight frequency of 700 cycles/min. This is the highest we have ever seen, and seems to be due to extreme stiffness in the steering gear and hook-up. It is evidently not high enough to escape wheel fight which however only occurs as a "nibble" of the wheel at 65 miles per hour. (3) The steering mechanism, as its flexibility affects flap frequency, consists of the steering gear and rods, the side levers on the wheels, the mounting of the steering gear, the frame, and the method of supporting the front wheels. All these parts enter into the natural frequency of wheel flap. | ||