Wessex Engineering first manufactured an Accelerated Polishing Machine CRT-APM over 30 years ago, and were involved both in the development of the machine and the test procedures. Wessex has sold more than 1000 APMs globally. In 1950 increased traffic flow and higher speeds, together with concerns about road safety led to research into the relationship between road materials and skid-resistance. Research at the UK Transport Road Research Laboratory showed a significant relationship between polishing of aggregates used in road surfaces and skid resistance. Tests were devised using an Accelerated Polishing Machine and a friction measuring device (known as the Pendulum Skid Tester, also supplied by Cooper-Wessex), to determine a Polished Stone Value (PSV).
Fourteen specimen aggregate samples are clamped around a rotating Road Wheel. These samples are subjected to two timed stages of abrasive polishing under a loaded rubber tyre. First by Corn Emery grit, and secondly by Flour Emery powder.
As the best quality market leaders Cooper-Wessex have recently been copied by low quality manufacturers. Imitators’ machines may look similar, but precision, repeatability and reproducibility come only with years of experience.