Abstract
Instrumentation techniques are discussed. Particular emphasis is given to those techniques which have been developed to give immediately interpretable results from complex vibration data.
The relative merits of various test methods for the evaluation of tyre vibration performance are indicated. Of particular importance in this respect is the difference between rolling and non-rolling testing. This is illustrated during discussion of cross-ply/radial-ply comparisons using various test methods, and also comparisons between radial tyres of slightly different construction.
A necessary vibration property of a tyre is its ability to absorb single obstacles such as ‘cat's eyes' or road joints. Attempts have been made to simulate such objects on a drum, and various methods of analysing the resulting impulse to the axle are compared. As yet no generally acceptable method of analysis has been found.
The majority of vehicle testing is done using vibrator excitation, as this tends to minimize tyre differences. However, problems involving low frequency excitation due to once per wheel revolution inputs are usually investigated on both drums and vibrators. This type of problem often arises when longitudinal compliance has been introduced in the suspension. Typical curves from suspensions of this type are shown.
An example showing one of the principal modes of oscillation of a tyre is given.
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