Investigation of drum brake noise from a brake mounted on a half vehicle test rig

The paper considers a drum brake mounted on a 1/2 vehicle test rig including suspension, cross beam and transmission differential. It is a continuation of earlier work and so reviews the characteristics of a drum brake when generating noise on a 1/4 vehicle test rig and compares them to those found on the 1/2 vehicle rig. Frequencies of 960, 850, 1400 and 4600 Hz are examined in some detail using the technique of holographic interferometry. It is seen that the modes of vibration of the component parts vary notably over the frequency range considered. This observation allows the significance of each part to be evaluated for each frequency range. With the accumulated information it was possible to predict other possible unstable frequencies and although these were not observed within this series of tests the predicted instability frequencies have been observed on earlier work