Effect of ball impact location and temperature on softball bat handle vibration

Abstract

The bat-ball collision is a crucial part of softball, and minimizing excessive vibrations in the bat after impact makes batting more comfortable for the hitter and optimizes the transfer of momentum between the bat and ball. To better understand this collision, the magnitude of bat handle vibrations as a function of ball impact location was measured across three bat brands and at three different temperatures. The bat barrel was struck with an impact hammer and an accelerometer placed near the handle of the bat collected the output data. Following an experiment conducted at room temperature, the bats were placed in extreme heat and cold and the same experiment was performed. The bats resonate in two main frequency ranges associated with the first bending mode and a hoop mode. The bending mode frequency was consistent across all impact locations, but did vary slightly between bat types. The hoop mode frequency varied depending on location. Hitting a ball with the bat's sweet spot, where a node of the bending mode is located, minimizes the magnitude of vibrations at the handle, primarily by eliminating the first bending mode. In general, cold temperatures tend to inhibit the bat's ability to minimize vibrational output, leading to more energy being transferred to the batter's hands.