3D-Trajectory Analysis of Side-Spin Knuckle Ball and Quasi-Steady Side-Force in Flight

Flight trajectory path of side-spin type knuckle balls pitched by a newly developed machine are captured using one digital video camera. Various types of 3D-trajectories data are obtained by processing from these video images. Special attention was focused to observe a quasi-steady assumption during ball flight process. Erratic path behaviors of side direction of the ball trajectory with time duration are clarified, and from these results, side force characteristics in flight and ball rotation angle of maximum side force are clearly recognized. As a result, quasi-steady assumption, which was based on knuckleball flutter theory, was verified.