Designing a Rod-type Dynamic Damper for Baseball Bats to Simultaneously Reduce Multiple Modes

Abstract

In baseball and softball, sting occurs in the batter’s hand when the batter hits off-center of the bat. In this study, we hypothesized that multiple vibrations have a composite effect on the sting experienced when hitting off-center of the bat, and that the influence of each mode varies depending on the grip position. We conducted a quantitative investigation of the relationship between sting and vibration when a ball was actually collided with a bat. The investigation was divided into two experiments. First, we measured the vibration in the grip when a ball was collided with a bat hung by a string. Second, we conducted a sensory evaluation of the strength of the sting when a subject simulated hitting a ball with a bat, and the ball was collided with the bat. From the results of the vibration measurements and the sensory evaluation, we considered that multiple vibration modes are related to the sting caused when hitting off-center of the bat. Based on this, we designed a lattice-style dynamic vibration absorber for bats that simultaneously reduces multiple vibration modes that cause sting.