EXAMINATION OF THE DIVING BOARD VIBRATION MODE OF SOFTBALL BATS

Abstract

The purpose of this study was to investigate the longitudinal oscillations of an aluminum softball bat during the swing and impact and to correlate the vibrations with characteristics of the swing. A highly skilled adult male baseball player hit 20 slow-pitched softballs and 35 balls placed on a tee with a high-performance aluminum softball bat (34 in, 28 oz) that was instrumented with strain gauges to measure strain along the long axis. Analysis of strain gauge records indicate that, in all cases, the bat bent back during the early part of the swing, peaked at approximately 45 ms prior to contact (PC), and was bending toward the ball at impact. The frequency of bat oscillations during the swing was 7.37+.87 Hz and 5.3+1.25 Hz for pitched and teed balls, respectively. For teed balls, strain magnitude was significantly related to swing time, bat velocity PC, and post-impact ball velocity.