Bat design and ball exit velocity in baseball: Implications for player safety
R.L. Nicholls* , B.C. Elliott & K. Miller
University of Western Australia
the axis of rotation, the sweet spot will potentially develop greater linear velocity during the swing, thereby imparting greater velocity to the ball. The results of this study suggest such design practices increase the risk to infield players of being struck by a linedrive. Hitters in this study achieved significantly greater bat resultant linear velocity when swinging a metal bat (Table 2). The primary manifestation of the difference in bat velocity was in the x-component - that directed toward the pitcher.
The final vertical (y) velocity of the metal bat was opposite in sign to that of the wood bat, indicating the y-component velocity was directed upward (Table 2). An increase in vertical velocity prior to contact has been described as “positioning the bat to meet the ball” (Messier & Owen, 1984), and characteristic of the “optimal power swing” (Williams & Underwood, 1971). In this study, the heavier barrel of the wood bat may have affected the hitter’s ability to position the bat for maximum power, although the effect was not significant. This result is reinforced by the lack of significant difference in TILT (Table 3), which describes the orientation of the bats with respect to the vertical (y) axis.
Great hitters such as Ted Williams have previously indicated the value of contacting the ball with the bat directly over the home plate for maximum ball exit speed (Williams & Underwood, 1971). A less oblique horizontal impact between bat and ball increases linedrive speed through the minimal loss of ball energy as friction, heat and spin (Hay, 1973). This was reflected in the mean position achieved by hitters using metal bats (Table 3). In this study, the orientation of the bat on the transverse plane (TRANS) was described by an angle between the global z-axis, axis of rotation and the bat tip, projected on the XZ plane (Figure 1). The tip of the wood bat was typically located 22 degrees behind the horizontal position achieved by the metal bat 0.005 s prior to impact. The greater angle of incidence and reflection during the bat-ball impact may have resulted in decreased ball exit velocity from wood bats due to greater frictional force.
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