Volume 31, Issue 3 (May 2003)
Mechanical Testing of Baseball Bats
Advances in the materials and structure of modern baseball bats have spurred interest in measuring their hitting performance. Many test standards and performance measures have been developed to quantify bat performance. The ability of these tests to simulate a player-swung bat has been largely ignored, however. This study describes the operation of a machine that has been used to measure bat performance and durability. The strain responses of player- and machine-swung bats were compared to determine the ability of laboratory experiments to simulate play conditions. Over much of the range of a full swing, the machine-swung bats experienced considerably higher strain than player-swung bats. During the instant of impact with the ball, however, the response of the player- and machine-swung bats was nearly indistinguishable. The similarity between laboratory tests and a player's swing supports the use of controlled experiments to measure bat performance. The relative response of a bat was shown to depend on the measure used to quantify performance, however. Three measures of bat performance were compared for a series of solid and hollow bats. It was observed that bat-ball efficiency measures may be an unreliable indicator of bat performance in play. Studies have shown that the swing speed depends on the mass properties of the bat and has a large effect on the batted ball speed. Consideration of bat efficiency alone does not fully account for the contribution of a bat-dependent swing speed. It is suggested that bat performance be measured from the batted ball speed in tests using a bat-dependent swing speed.