Abstract: Apparatus 10 (FIG. 1), for testing samples of friction material 31, 32 in rubbing contact with a surface 33 of a rubbing element 34, comprises a table 12 for supporting the rubbing element and a load cell 16 for sensing the load imposed by the frictionally coupled rotating samples from which the coefficient of friction can be determined. To make the tests repeatable rapidly and with identical starting conditions cooling means 40 is interposed between the rubbing element and table. Cooling means 40 comprises a fluid cooled heat exchanger 41, conveniently cooled by local main supply water supplied at its natural temperature, and thermoelectric cooling means 75. The thermoelectric cooling means consists of an array of planar peltier cooling elements which develops a temperature gradient there across which, with reference to the heat exchanger temperature, is able to cool and re-cool the rubbing element to temperatures as low as −25° C. within a matter of minutes.

Abstract: A wear determining arrangement (30, FIG. 2(a)) for determining wear of a rubbing member of a friction couple, such as an iron brake disc, which is subject to slow wear by frictional engagement by brake pads, comprises a carrier (31) dimensional to overlie the rubbing surface of the disc and be releasably attached thereto by electromagnet (51). The carrier supports a transducer (33), such as magnetic displacement sensor having probe (43), that is mounted on a carriage (36) for scanning the probe across the surface. After an initial scan to map the surface the carrier is removed and re-attached after a period of brake usage, whereupon the surface is scanned again and wear assessed. The rate of wear is normally small, and to ensure that the amount which occurs in a reasonable period can be measured, the carrier is provided with datum projections (46 and 47) and the electromagnet is mounted by way of resilient coupling means (52) to bias the carrier into a stable “tripod” relationship on the surface.