Mechanical and Aerodynamic Behaviour of Baseballs and Softballs

Authored by: Lloyd Smith , Jeff Kensrud

Routledge Handbook of Sports Technology and Engineering

Print publication date:  November  2013
Online publication date:  November  2013

Print ISBN: 9780415580458
eBook ISBN: 9780203851036
Adobe ISBN: 9781136966606


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The behaviour of the ball is an important part of understanding, playing and watching the games of baseball and softball. The first baseballs were small medicine balls constructed from a rubber pill, wrapped in string and covered by horsehide. The ball has evolved a number of times over the years in size and material, including kapok, rubber and cork. In the 19th century, the game had few restrictions and the baseball itself varied among ball clubs. By the end of the 19th century, the ball was confined to between 5 and 5.5 ounces (142 and 156 g) and 9.25 inches (235 mm) in circumference. This baseball, with its rubber pill, absorbed much of the energy, resulting in dull, short hits. In 1920, a cork pill was implemented to increase the liveliness of the ball, which tripled the number of 0.300 hitters (Johnson 2010). In 1931, a thin layer of rubber was wrapped around the cork pill, to slightly reduce the liveliness of the ball. Except for a change from a horsehide to a cowhide cover in 1974, baseball construction has remained largely unchanged. The softball has evolved in similar fashion to the baseball. Early softballs were made from boxing gloves, which gave way to wound string and cork designs. Today, softballs are nominally 7 ounces (200 g), 12 inches (305 mm) in circumference and made from a polyurethane core with a thin leather or synthetic cover. The formulation of the polyurethane is relatively advanced where ball stiffness and elasticity are controlled independently. In the case of baseballs, the design of the pill and tension of the wool windings effect elasticity and stiffness, respectively.

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