U. S. Golf Association

United States Golf Associatino

Stanley H Johnson

Erik A Ekstrom

The testing apparatus serves to measure the coefficient of friction of a golf ball. The apparatus has a base with a pair of flexure arms which carry inserts between which a golf ball may be pushed under a force in order to flex the flexure arms outwardly. Strain gauges record the flexing of the flexure arms in order to determine the force perpendicular to an insert. A load cell is employed to determine the amount of pushing force on the golf ball in order to determine a force parallel to the surface of the insert. The ratio of the two forces obtained serves as the coefficient of friction of a golf ball.

Apparatus for measuring the coefficient of friction of a golf ball

The experimental determination of the moments of inertia of a rigid body such as a golf-club head about each of three mutually perpendicular axes is described. The club head is suspended so as to swing as a pendulum about an axis that is parallel to each of the axes of interest and the moments of inertia are calculated from the periods of oscillation and physical properties of the body. The products of inertia must be calculated from the moments of inertia in multiple axis systems. Once the inertia matrix is complete, the associated ellipsoid of inertia displays the inertial properties of the rigid body without reference to a specific coordinate system. The inertia ellipsoids of two golf-club heads are determined and compared to demonstrate the procedure.

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Bethlehem, PA, United States of America

Stanley H Johnson