Science and Golf II: Proceedings of the 1994 World Scientific Congress of Golf

By A. J. Cochran; M. R. Farrally | Go to book overview

45

Contact forces, coefficient of restitution, and spin rate of golf ball impact

P.C. Chou, D. Liang, J. Yang

Drexel University, Philadelphia, U.S.A.


and W. Gobush

Titleist and Foot-Joy Worldwide, New Bedford, USA

Abstract

Experimental and finite-element results of golf ball impact are presented. These include the tangential and normal forces acting on golf balls, the normal coefficient of restitution, and the spin rate. Good agreements are obtained between the experimental and finite-element results. Different parameters and mechanisms affecting the impact are discussed.

Keywords: Golf Ball Impact, Coefficient of Restitution, Normal and Tangential Forces, Spin Rate, Viscosity, PGA No..


1 Introduction

Cochran and Stobbs (1989) gave a very thorough and clear discussion of the impact between a golf ball and a clubhead. They pointed out that some of the initial kinetic energy of the clubhead is lost. They did not provide any explanation of the mechanisms of the energy loss process. For a lofted club face, they showed experimental results that the smoothness of the club face does not affect the ball spin rate. They hypothesized that the friction force which causes the spin is resulted from sliding, and when sliding stops, the “rolling” friction retards the spin.

In this paper, we show that our experimental and finite-element results agree with Cochran and Stobbs'. In addition, we provide details on what physical properties contributed to the loss of impact energy. In the lofted club face case, our finite-element results show that for loft angles less than 30°, the friction force is caused mainly by the ball's sticking to the club face, sliding occurs only partially and does not contribute appreciably to the friction and spin.


2 Experimental measurement

In our experiment, a golf ball was launched from an air gun into a plywood box. It struck a steel block of dimension

Science and Golf II: Proceedings of the World Scientific Congress of Golf. Edited by A.J. Cochran and M.R. Farrally. Published in 1994 by E & FN Spon, London. ISBN 0 419 18790 1

-296-

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