NJIT Professor Tests Bats: Which is Safer -- Aluminum or Wood?

NJIT Professor Tests Bats: Which is Safer -- Aluminum or Wood?

It’s a debate that has roiled amateur baseball leagues: namely, which is more dangerous, aluminum or wooden bats? Some New Jersey towns have banned Little League hitters from using aluminum bats. And a bill in the state legislature would outlaw aluminum bats in children’s leagues.

The bill comes in the wake of an injury suffered by a 12-year-old pitcher who, during a Little-League game, was hit in the chest by a line drive. The pitcher’s heart stopped beating momentarily; he lapsed into a comma and was hospitalized for months. The line drive was hit by a batter using an aluminum bat. Many observers say aluminum bats hit the ball with more force than wooden bats.

Should youth leagues thus be forced to use wooden bats?

To help resolve that question, Ravi Ravindra, a physics professor at NJIT, devised an experiment to test both types of bats. Such an experiment, Ravindra thought, might help the legislature make an informed and scientific decision about the bats.

His idea for the experiment was fairly simple: dip baseballs in liquid nitrogen until they freeze over -- like ice balls. Then have NJIT baseball players hit the balls using both kinds of bats. Afterward, Ravindra would analyze the cracks on the surface of the balls. A wider network of cracks on the ball, with deeper impressions made from the impact of the bat, would obviously mean that that bat was the more potent of the two.

 Ravindra enlisted two NJIT power hitters on the NJIT Division I baseball team, Derrick McCain and Kwesi Mitchell, and hired a student research assistant -- Sushil Sikha -- to help him.

Then, one day last week, the four of them repaired to the NJIT athletic field. Along with them they carried a canister of liquid nitrogen, safety gloves, goggles, a bag of baseballs and a batting tee.

Sikha, the student researcher, set the canister on the sidelines and dipped a batch of balls in a bucket of liquid nitrogen. He submerged the balls for seven minutes. As the temperature dipped to - 320 degrees Fahrenheit and the balls froze solid, Sikha placed a steaming ball on a batting tee.

McCain, one of the hitters, approached the tee, eyed the ball up and swung hard. The ball rose up and over the field, soaring until it eventually hit the wall of Tiernan Hall. “Wow,” said McCain, who held in his hand an aluminum bat.

 Sushil placed another frozen ball on the tee and McCain eyed it up, this time holding a wooden bat. He hit the ball hard but, unlike his previous hit, it failed to take flight, dropping short in the bushes of the athletic field.

Sikha strode into the field and retrieved both balls. He studied them in the bright afternoon sunlight. Both balls bore intricate cracks – telltale signs of the forces imparted by the bats. But the network of cracks on the ball hit by the aluminum bat was far more elaborate than that on the wooden bat.

“The ball hit by the aluminum bat has far more cracks than the ball hit by the wooden bat,” says Sikha. “And the indentation ring on the ball hit by the metal bat was also deeper. I’ve done this test before and found the cracks on the balls hit by the aluminum bat to be, on average, 2.875 millimeters longer than those on the balls hit by the wood bat.”

 Professor Ravindra smiled knowingly.

“This proves,” he says, “what baseball players know by intuition and feel: that the energy transferred by the aluminum bat to the ball is much larger than that transferred by the wooden bat.”

In simple terms, the experiment showed that aluminum bats hit the ball harder and farther than wooden bats.

McCain was not surprised by the result. All baseball players know that aluminum bats are superior to wooden ones, he said. “You can feel it when you hit the ball,” he added. “You can see it when the ball takes flight, and you can hear it – that sweet ping when the ball hits the metal.”

The superior force of the aluminum bat comes from its larger sweet spot.

 Kwesi Mitchell, the other power hitter there, picked up two bats and held them side by side, illustrating the sweet spot. The barrel of the aluminum bat, he explains, is much thicker and wider than the barrel of the wooden bat. It’s that wide barrel, called the sweet spot, which gives batters a better chance of hitting the ball harder. Professor Ravindra agreed, but added another reason.

“Aluminum is also far more elastic than wood,” he says, “and thus imparts an increased momentum back to the baseball. Aluminum gives back the energy to the ball far more efficiently than wood does.”

Professor Ravindra’s experiment was featured in a recent article in the Star-Ledger. The paper also ran a video of his experiment. In the wake of the article, he was contacted by legislators and baseball bat manufacturers. He shared the results of his study with the politicians and the bat makers. But he did not issue an opinion about the bats.

“I’m a physicist, not a baseball expert nor a policy expert,” Professor Ravindra says. “I can say that the energy transferred to the balls by the aluminum bats was significantly higher than that transferred by the wooden bats. But banning aluminum bats is not my decision.”

Part of NJIT’s mission is to do applied research that helps the state, he adds. “But I and my assistants will leave it to the politicians and the people in the state -- the voters -- to decide which bat is best for children.”

(By Robert Florida, University Web Services)