BAT LOADING STRATEGIES

Abstract

The effects of adding mass at different locations along the longitudinal axis of a softball bat on the effective hitting area were compared. Successive loads were added to the exterior of a standard, commercially available aluminum bat (length = 86.7 cm, mass = 741 g) in increments of 93.7 g. The loads were placed at the following sites: (1) at the knob end, (2) at the junction of the bat handle and knob end, (3) at a point 12 cm from the knob end, (4) at a point 16.8 cm from the knob end, (5) at the center of mass, (6) at the center of percussion, and (7) at the barrel end. The second and third points were selected to coincide with the swing axis and impact reaction axis, respectively. The effects of each of these loading conditions on each of the following mechanical parameters were determined theoretically, by physical pendulum testing, and empirically by impact testing: (1) moment of inertia about the swing axis, (I1), (2) distance from the impact reaction axis to the center of percussion, and (3) slope of the impact reaction impulse as a function of impact location. The latter two variables were used to determine the effective hitting area of the bat. Results from impact testing were consistent with theoretical expectations and with results from the physical pendulum tests. Knob end loading had the greatest effect on displacement of the effective hitting area toward the barrel end of the bat and on enlarging the effective hitting area. Loading at the impact reaction axis and center of percussion had no effect on the effective hitting area. Loading at the barrel end of the bat substantially moved the effective hitting area toward the barrel end of the bat, but also caused a large increase in I1.