Dealing with Stiffness: Shaft Dynamics in the Golf Swing

A study was undertaken to investigate the influence of shaft stiffness on the deflection and the positioning of the club face during a golf swing. To accomplish this task, a theoretical model was developed that calculated deflections of golf shafts during the swing. Applying moment-curvature in relation to a shaft that had the bending stiffness, a differential equation and the boundary conditions that characterized its behaviour over the duration of the swing were generated. Incorporated into the bending moment-distribution are forces and torques acting at each end of the shaft. These loads were calculated using an inverse dynamics problem of the golf club during the swing. A motion capture system was utilized to collect the necessary data. Solutions to the equations of motion for the shaft were calculated numerically. The results have been presented as deflections along the shaft as functions of time. Bending deflections were determined in the plane of the club face and normal to this plane were calculated.