The NCAA posted a news article late last month describing new potential upgrades to bat requirements in the upcoming season. There is a new worry that the metal bats are creating an illegal advantage when they are “rolled.” As it stands now, bats are required to have a specific length, weight, center of mass, radius of barrel, and other specifics that you wouldn’t normally consider. One of these is the ball speed exit ratio. Right now, bats are required to not allow a ball be hit more than a certain percentage more than a wood bat. This percentage is fairly small. The NCAA wants to allow wood bats, but let the schools have the option to buy metal bats that will last longer, therefore keeping the cost lower.
The exit speed ratio has been voted as insufficient as of late. With the marked increase in home runs over the last few seasons, the researchers at the NCAA have developed a better model to reduce the ball speed. Their new answer is “ball-bat coefficient of restitution” (BBCOR). It sets limits on how kinetic the partially inelastic collision between bat and ball can create a faster exit speed.
For those non-physics majors out there, I’ll use an example. Consider a ping pong ball bouncing off a tile floor. You hold the ping pong ball and then let it drop. The ball will fall and bounce back up. When the ball hits the floor, its “colliding” with the floor. Now, say you have a equally heavy ping pong ball that is dented. You drop it from the same height, it doesn’t bounce as much. The reason for this is the normal ping ball flexes just a little bit when it collides with the floor. For simplicity’s sake, we’ll just leave it as this little flex pops back to normal and pushes the ball back up off the floor even farther than it would have bounced had it not flexed (like the dented ball).
Baseball bats flex like ping pong balls. When a baseball hits the bat, the bat flexes just a little bit, pushing the ball even faster from its surface. With wood bats, the flexibility is limited, but it does exist. With metal bats, they can be very flexible. What make metal bats even more attractive is that after heavy use, this flexibility becomes even more powerful. A heavily used bat is like a heavily used metal spring. At first you don’t get much spring out of it, but eventually, it becomes very… well, springy.
The NCAA does test for this flexibility. They use vice like readers to place pressure on the barrel. They also check the bats with a ring to make sure no side has become flattened or dented. This flattened side also amplifies the flexibility when hit directly. The NCAA actually threw out 25 of the 500 or so bats tested at Omaha this year for these type of variations.
The rule change to the BBCOR will help eliminate many of these bat problems, but it won’t come into effect until 2011. It’s interesting none the less. With home runs and batting average going up at such quick paces the last 4 years, it’s about time the bar get set a little bit lower.
The NCAA meet July 13-15 to discuss this, as well as the common start date/week they added to the beginning of the season. That will definitely deserve a post or two.