The Physics of Baseball:
Wood vs. Aluminum Bats

With all the recent discussion about about banning aluminum bats in certain venues, I have put together some information that I hope people will find useful as they deliberate this very important issue.

Wood vs. Aluminum Bats and the NCAA Test Protocol , a discussion of the methods used by the NCAA (and most high schools) to regulate baseball bat performance. Included in this report is a quantitative estimate of the difference in performance between NCAA-compliant aluminum bats and wood bats as well as thoughts on how one might reduce that difference. If you only have time to read one article, read this one. Accompanying this article is a powerpoint presentation I gave in May 2007. A more comprehensive presentation can be found here and is based on a talk I gave to the Little League in June 2007.

Wood Versus Aluminum Bats, a nontechnical document I wrote summarizing the reasons why wood and aluminum bats perform differently.

Characterizing the Performance of Baseball Bats, a technical peer-reviewed paper published in the February 2003 issue of American Journal of Physics (Copyright 2003 American Association of Physics Teachers. This article may be downloaded for personal use only. Any other use requires prior permission of the the American Association of Physics Teachers). In this paper I present the issues involved with characterizing the peformance of bats from a physics point of view. I give precise definitions for some commonly used terms, such as COR, BPF, and BESR. I describe laboratory measurements one could to do decide if an aluminum bat outperforms a wood bat. A new method for characterizing bat performance is proposed and compared with existing methods used by the NCAA, ASA, ASTM, etc.

NCAA Test Protocol, the actual document with the current protocol used by the NCAA to regulate the performance of non-wood baseball bats.

BESR White Paper, a tutorial written by the NCAA Baseball Research Panel as a guide to the lay person on the BESR, one of the performance metrics used by the NCAA to regulate the performance of bats.

Batting Performance of Wood and Metal Baseball Bats, a technical peer-reviewed paper by Drs. Trey Crisco, Rick Greenwald, et al. reporting the results of their excellent batting cage study of baseball bat performance (Medicine & Science in Sports & Exercise, 2002). Among other things, these data are the best available in estabishing the relationship between a batter's swing speed and the moment of inertia (MOI) of the bat. The data also conclusively show that the 5 metal bats tested outperform the wood bat tested. Note, however, that many of the aluminum bats tested would be banned under current NCAA rules.

Baseball Research Center , the bat and ball testing facility at University of Massachusetts/Lowell that is used to certify baseball bats for the NCAA. The facility is directed by Professor Jim Sherwood.

Sports Sciences Laboratory, the bat and ball testing facility at Washington State University that is used to certify softball bats for the Amateur Softball Association. The facility is directed by Professor Lloyd Smith.

Professor Dan Russell, my friend and colleague from Kettering Univeristy, who has written extensively on bat performance.