Patent ID: 6928857

Claim:
An apparatus for measuring the co-efficient of friction of a paved road surface comprising: a test wheel for rolling on the paved road surface; a primary frame arranged to be attached to a road transportation vehicle moving along a direction of travel at a location thereon such that the test wheel can roll on the road surface as the vehicle moves in a forward direction over the road surface; an intermediate component pivotally connected to said primary frame by a first swivel connection; a suspension arm pivotally connected to said intermediate component by a second swivel connection and trailing rearwardly and downwardly therefrom relative to the direction of forward movement of the vehicle; said first swivel connection defining a generally upright swivel axis allowing said intermediate component to swivel about said upright axis in response to a torque applied to said suspension arm about the upright axis; said second swivel connection defining a substantially horizontal pivot axis allowing said suspension arm to pivot about the horizontal pivot axis in an ascending or descending direction; the test wheel being rotatably mounted on a trailing end of said suspension arm for rotation of the test wheel about a horizontal rotation axis parallel to said horizontal pivot axis so that the test wheel lies in a wheel plane at right angles to the axis; a first spring applying a spring force between the primary frame and said intermediate component about said generally upright axis of rotation tending to rotate said intermediate component and said test wheel carried thereby around the axis to a position defining for the wheel plane of the test wheel an angle of yaw relative to a direction plane containing the direction of travel of the vehicle, such that, when the vehicle is traveling along the direction plane with adequate co-efficient of friction, the test wheel tends to lie with the wheel plane parallel to the direction plane and, when the co-efficient of friction is reduced, the wheel plane tends to revert to the angle of yaw; a sensor responsive to changes in the angle between the direction plane and the wheel plane; and a display for displaying to an operator of the vehicle data related to the changes in angle detected by the sensor so as to provide to the operator information concerning the co-efficient of friction.