Abstract
The results of a comparative study of five aluminum and one wood baseball bats are presented. The study includes an analysis of field data, high-speed laboratory testing, and modal analysis. It is found that field performance is strongly correlated with the ball–bat coefficient of restitution (BBCOR) and only weakly correlated with other parameters of the bat, suggesting that the BBCOR is the primary feature of a bat that determines its field performance. It is further found that the instantaneous rotation axis of the bat at the moment of impact is very close to the knob of the bat and that the rotational velocity varies inversely with the moment of inertia of the bat about the knob. A swing speed formula is derived from the field data and the limits of its validity are discussed. The field and laboratory measurements of the collision efficiency are generally in good agreement, as expected on theoretical grounds. Finally, the BBCOR is strongly correlated with the frequency of the lowest hoop mode of the hollow bats, as predicted by models of the trampoline effect.
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Notes
In Table 2 of [2] it is observed that the different bat models were sampled roughly uniformly by batters at three different skill levels. Therefore, averaging performances over all batters is expected to preserve the relative performance levels of the different bats.
References
Smith LV (2008) Progress in measuring the performance of baseball and softball bats. Sports Technol 1:291–299
Greenwald RM, Penna LH, Crisco JJ (2001) Differences in batted ball speed with wood and aluminum bats: a batting cage study. J Appl Biomech 17:241–252
Crisco JJ, Greenwald RM, Blume JD, Penna LH (2002) Batting performance of wood and metal baseball bats. Med Sci Sports Exerc 34:1675–1684
Nathan AM (2000) Dynamics of the baseball–bat collision. Am J Phys 68:979–990
Nathan AM, Russell DA, Smith LV (2004) The physics of the trampoline effect in baseball and softball bats. In: Hubbard M, Mehta R, Pallis J (eds) The engineering of sport V. ISEA, Sheffield, pp 38–44
Smith LV (2001) Evaluating baseball bat performance. Sports Eng 4:205–214
Nathan AM (2003) Characterizing the performance of baseball bats. Am J Phys 71.2:134–143
Russell DA (2004) Hoop frequency as a predictor of performance for softball bats. In: Hubbard M, Mehta R, Pallis J (eds) The engineering of sport V. ISEA, Sheffield, pp 641–647
F2219-07 (2007) Standard test methods for measuring high-speed bat performance. West Conshohocken, PA
STAR Modal, Spectral Dynamics Inc., San Jose, CA (http://www.spectraldynamcis.com)
Cross R, Nathan AM (2009) Performance versus moment of inertia of sporting instruments. Sports Technol 2:7–15
NCAA (2007) http://www.ncaa.org/baseballbats. Accessed 9 August 2010
Koenig K, Dillard JS, Nance DK, Shafer DB (2004) The effects of support conditions on baseball bat testing. In: Hubbard M, Mehta R, Pallis J (eds) The engineering of sport V. ISEA, Sheffield, pp 87–93
Smith LV, Broker J, Nathan A (2003) A study of softball player swing speed. In: Subic A, Trivailo P, Alam F (eds) Sports dynamics discovery and application. Melbourne, pp 12–17
Cross R, Bower R (2006) Effect of swing weight on swing speed and racket power. J Sports Sci 24:23–30
Fleisig GS, Zheng N, Stodden DF, Andrews JR (2002) Relationship between bat mass properties and bat velocity. Sports Eng 5:1–14
Koenig K, Mitchell ND, Hannigan TE, Clutter JK (2004) The influence of moment of inertia on baseball/softball bat swing speed. Sports Eng 7:105–117
Adair RK (2002) The physics of baseball. Harper Collins, New York
Cross R (2004) Physics of overarm throwing. Am J Phys 72:305–312
Acknowledgments
The collaboration thanks Bruce Isaacs for help with the laboratory impact experiments and Kyle Kilpatrick for his contributions to the data analysis.