Terry Bahill
Systems and Industrial Engineering
University of Arizona
Tucson, AZ 85721-0020, USA
terry@sie.arizona.edu
http://www.sie.arizona.edu/sysengr/slides/
© 1998-2004 Bahill
Baseball players swung very light and very heavy bats through
our instrument (called the Bat ChooserTM) and we recorded the
speed of the center of mass of the bat. These data were used to
make mathematical models for each individual human. These models
were then coupled to the equations of physics for bat-ball collisions
to compute the Ideal Bat Weight for each individual baseball player.
We measured 28 members of the San Francisco Giants baseball team
and found that 80% of them were using bats in their correct range.
But 10% were using bats that were too light for them, and 10%
were using bats that were too heavy for them. However, only 25%
of the 200 less experienced baseball players that we studied,
e.g. Little Leaguers, were using bats in their correct range.
The force-velocity relationships of some of our subjects were
best modeled with hyperbolic equations. However, for others a
straight line provided the best fit. We divided our subjects into
two groups: "quick" people with large slopes that are
fit best with Hill-type hyperbolas, and others with flatter data
that are fit best with straight lines. He hypothesize that some
people have rigid unchanging control strategies, they swing all
bats the same. Whereas quick people adapt well and change their
control strategies to take advantage of the varying bat weights.
We developed a more complex model for the swing of the baseball
bat that entails one translation and two rotations. We also constructed
a set of bats where each bat had the same mass but a different
inertia. With our new model and bats we can determine the best
shape of the baseball bat for individual players.
But so far all of these recommendations depend on the ball player
using the Bat Chooser in Tucson. At the finale of this talk I
will present rules of thumb that anyone can use to estimate his
or her optimal bat weight.
References [43, 45, 50 and 75]. I can adapt this lecture to make
it suitable for engineers or the general public. This talk requires
an overhead projector, a VHS video tape player and a 35mm Carousel
slide projector. This talk takes one hour.
Ideal Bat WeightTM and Bat ChooserTM are trade marks of Bahill
Intelligent Computer Systems (BICS), 1622 W. Montenegro, Tucson,
AZ, 85704-1822.