MIT team finds that the ratio of component atoms is vital to performance.
A technical instructor in the Department of Aeronautics and Astronautics hopes to strike paydirt with his patented idea for a better baseball bat.
Jeffrey C. Di Tullio was working with the students in one of his lab courses on the problem of how to reduce drag on cylinders when he realized the applicability of the work to baseball bats. A more aerodynamic bat would result in higher bat speed, more momentum and better results for a hitter, he reasoned.
The aerodynamic principles that make his bat move through the air faster than a conventional bat are not new. However, almost all the published research on this subject involves the use of various types of surface roughness or bumps, he noted. Bumps on the surface of a baseball bat would not be acceptable for obvious reasons. The challenge he faced was to come up with a way to duplicate the effect of the bumps while keeping the surface of the bat as smooth as possible. The answer was to use dimples similar to those found on a golf ball.
After making some calculations and a few guesses about how deep and how far apart the dimples should be, Mr. Di Tullio made a die and pressed dimples into some wooden "blanks" (bats without markings burned into them) obtained from Hillerich and Bradsby Co. of Louisville, KY, maker of the famed "Louisville Slugger." He pressed rather than drilled the dimples so he wouldn't remove any material that would consequently make the bat lighter.
With the first prototypes in hand, he moved into a wind tunnel at MIT to test his hypothesis. They worked, and the development process was underway. More prototypes had to be made and more wind tunnel testing completed in order to optimize the size and spacing of the dimples. Upon the completion of the development process, a US patent was approved.
Contrary to what many may think, a baseball bat (or any cylinder, for that matter) is not a streamlined shape and displays very poor drag characteristics, Mr. Di Tullio explained. As a conventional bat moves through the air, it pushes most of that air out of its way and produces a considerable amount of drag. The qualities of the dimpled bat allow more of the air to flow around the contour of the bat, leaving less air to be pushed and thereby reducing drag, he said.
Drag happens because the air closest to a bat's surface (the boundary layer) moves slowly and contains very little energy-not enough for it to make the turn required to follow the contour of the bat, Mr. Di Tullio said. The dimples cause this low-energy air to mix with the faster-moving, high-energy air slightly above the surface. "The net result is that it adds energy to the air right on the surface and gives it that little extra it needs to follow the contour of the bat," he said. Thus, with a dimpled bat, "you can get around on a fastball a little bit faster-you add more power to the swing."
Mr. Di Tullio tested his invention on a number of semi-pro softball and baseball players, using a timing device while they swung different bats several times each and then compiling a statistical profile of an 18-inch segment of their swings. The hitters' bat speeds using the dimpled bat prototype increased by three to five percent compared to a normal bat of the same dimensions, which would translate to an additional 10 to 15 feet of distance for a fly ball, he said.
Deciding to test his invention with the pros, Mr. Di Tullio took some of his bats to Fenway Park last October for members of the Red Sox to try. "Some of the guys liked it, but more of them couldn't tell the difference," he said. "The difference is subtle." Part of the problem was that some of the other characteristics of the bats, notably the too-thick handles, weren't to the players' liking, he added. Still, visiting Fenway and talking to the players made the experience worthwhile. "That was a lot of fun," said Mr. Di Tullio, a native of Stoneham.
The MIT Technology Licensing Office is trying to get bat manufacturers interested in the idea. The best market will probably be recreational baseball and softball rather than major league baseball, said David McFeeters-Krone, a licensing associate in that office. He has approached several bat makers, "and all of them are mildly interested," he said.
The majority of recreational bats are metal rather than wood because they last longer, but Mr. Di Tullio said it wouldn't be a problem adapting the new design to that material. Hitters in fast-pitch softball would probably benefit most from using a dimpled bat, because in that game, the distance from the pitcher's mound to home plate is considerably shorter than in major-league baseball (46 feet instead of 60.5 feet) and the softball can be pitched at an even greater velocity than a baseball.
Would-be inventors with ideas on ways to improve the company's products approach Hillerich and Bradsby fairly frequently, but many of the ideas are rejected because they would violate the rules of the sport, said Bill Williams, vice president of advertising and public relations. For example, people sometimes suggest strengthening a bat by having the handle and barrel in two separate pieces, but baseball rules state that the bat must be a single piece of wood with no other materials, he said.
Any company would need to do extensive testing of its own on a new product before deciding to manufacture it, said Mr. Williams, whose company turns out about one million wooden bats and 1.5 million metal (aluminum and composite) bats per year. Although he hadn't yet heard of Mr. Di Tullio's invention, he was cautious about its commercial prospects, saying that his company had already tested a dimpled golf club head but found no appreciable difference in performance compared to a regular club. As for baseball bats, "they're only up to a high [swing] velocity for a very short time," he said. "They're basically pretty streamlined already."
But Mr. Di Tullio is optimistic, noting that his modified bat is within the rules and isn't drastically inconsistent with current regulation bats. Balls hit with a dimpled bat aren't scuffed or otherwise changed, and putting in dimples affects the bats aerodynamically even less than the trademark they already carry. At least for softball, "I think there are a lot of possibilities," he said.
A version of this article appeared in the March 2, 1994 issue of MIT Tech Talk (Volume 38, Number 24).