Fig. 2 shows a typical design and Fig. 3 and Fig. 4 are photographs of the test apparatus which may be constructed from readily available materials. Also, see Ref (2). Several elements are of critical importance to ensure uniformity in test results among laboratories. These are the type of rubber used on the wheel, the type of abrasive and the shape, positioning and the size opening of the sand nozzle, and a suitable lever arm system to apply the required force.