Abstract
The noise propensity of a twin calliper brake system is investigated with the brake mounted on a test rig without the suspension system. The mode of vibration of the disc is observed using the whole body visual technique of holographic interferometry. In addition a fundamental thermal analysis is undertaken using a high-resolution thermal camera. The holographic images show that the disc mode of vibration has a preferred position where a disc antinode is situated under one calliper and a disc node under the second calliper. Adjustment of the calliper angular spacing shows that this spacing has an influence on the propensity of the brake to generate noise and also on the frequencies generated. There is evidence that the disc mode position, in relation to the two callipers, may be antinode/node, node/node or antinode/antinode. A revised theoretical study of the disc/pad interface geometry is able to predict these situations and leads to a possible design solution to the alleviation of noise, even on a single calliper system. The theoretical study predicts two stable conditions are possible - if the callipers are positioned either at an angle between 125º to 130º or 165º to 175º. The smaller angle was not tested but the brake became quiet at angles greater than 166º. The thermal study shows that when the calliper is at a reduced angular spacing, and the brake is noisy, there is a higher temperature between the smaller angular setting of the callipers. A brief study of the calliper modes and pad spring retainer is included in the holographic results.