Acoustics of Baseball Bats
Daniel A. Russell
Science & Mathematics Department, Kettering University, Flint, MI 48504-4898
All images and text are ©2002 Daniel A. Russell
This page is still under construction. Check back soon for updates!
The effect of wood grain on vibrational modes of a wood bat
Wood bats manufactured for amateur and youth players are not made from the same quality of wood as those made for professional players. As a result, a wide range of wood properties may be found in a collection of bats which are otherwise the same (same model, length, profile). At a local sporting goods store I found two Little League wood bats which exhibited quite different acoustical behavior. Both bats are Louisville Slugger models 225YB and have identical lengths, barrel diameters and profiles. But, one bat weighs 26-oz and has 8 wood layers (grain density) per inch and the other bat weighs 20-oz and has 20 wood layers per inch. Optimal grain density is around 6-10 layers per inch, though it is possible for two wood samples with 3-5 layers per inch or 12-20 layers per inch to have similar properties.[1]
When players encounter a wood bat for the first time - either as a Little League youngster or as a college player trying to make the transition to the Minor Leagues - they are taught to hold the bat so that they can read the logo. The trademark logo is branded on a wood bat on the side of the bat against the grain. Thus, if held correctly the ball makes contact with the bat along the grain where the bat is strongest and the bat is less likely to break. Apparently the great Yogi Berra didn't like to look at the logo, and had the habit of twisting his bat while at the plate so that he always hit the ball against the grain where the bat is weakest. Hillerich & Bradsby outwitted him by moving the logo on his bats so that when he twisted the bat he would end up hitting the ball along the grain.[2]
[1] S. Ashley, "Getting Good Wood (or Aluminum) on the Ball," Mechanical Engineering, 112(10), 40-47 (1990)
[2] T. Herr, "The Good Wood," Sports Illustrated, 64(15), 66-80 (April 14, 1986)
Back to Acoustics of Baseball Bats