The pins rest onto the surface of the disc. As the disc is rotated the lever arm is forced in the direction of rotation, and against a load cell which then monitors the friction force. A load hanger is suspended from one end of the lever arm such that the contact pressure between the pin and disc can be varied. A set of calibrated weights is supplied. The disc runs inside a surround which enables lubrication to be added without spillage. This varies the experimental parameters and results obtained.