Take MeOut to the Ballgame
Urethane helps machine throw a curve

Pitching machines have been around for decades. These powered hurlers can zing balls at upwards of 90 mph, straight and in pretty much the same location. Even a mediocre player can eventually learn to time the ball and get a good piece of wood on it. But take the same hitter in a batting cage and put him against a real live pitcher, who mixes his fastball with curves, sliders and sinkers, and he hasn't a chance of getting anywhere near the pitch, even if it is considerably slower.

Greg Battersby (no pun intended) can attest to this. Battersby, a patent attorney and one-time member of NASA's lunar module program, is also a former college baseball player and coach. So it's not all that surprising that he happened to have a batting cage and pitching machine in his yard back in 1997. At that time, Battersby realized that while his son was able to smash 95 mph fastballs in the cage, that practice really didn't help him hit any curve balls during a game. Since the old-fashioned batting cage was not helping his son improve his hitting in game situations, he decided to develop a machine that could emulate real live pitching.

Four years later, Battersby's company, ProBatter, Inc., introduced a batting practice system that holds three patents, has more "stuff" than Pedro Martinez and Roger Clemens combined, is always on target, and never gets tired. At one end of the ProBatter batting cage, a life-like video image of a pitcher is projected on a screen. The pitcher winds up and begins his motion. At the exact moment he is about to release, a ball rockets through a hole in the screen. At the moment the video pitcher releases, so does the pitching machine. The system's computer matches the image of the pitcher the batter sees to the pitch type and speed. In an automatic mode, the computer has a semi-random pitch selector that chooses sequences of pitches intended to keep the batter in suspense over what will be coming next. The first pitch might be a 92 mph fastball. Six seconds later the batter might get a slider in another part of the strike zone or a 76 mph curve ball. It could hardly be more lifelike.

"ProBatter can throw hellacious curve balls," Battersby said. "It might start out looking like a fastball coming at your head. After 80 feet it breaks. When it gets to the plate it's 2-ft. wide and down at your ankles. That's a classic, but bigger than a big league curve ball."

A conventional pitching machine works by injecting a ball down onto two wheels spinning together at the same rate. Battersby's machine has three wheels and a system to adjust a wheel's speed independently from 1500 to 2500 rpm, providing an infinite variety of unique spins on a ball to emulate almost anything a major league pitcher can throw.

A problem arose in obtaining the best match between the wheel geometry, wheel material and ball material. The first set of wheels used were hard rubber. The urethane balls tended to skip on the hard wheels, making the pitches difficult to control. Battersby made the next generation of wheels from a much softer nitrile rubber which gave more dwell time for the ball on the wheel, dramatically improving control. However, these wheels began to degrade after 30,000 pitches from the stress of accelerating the ball to 100 mph in the space of 4 in., resulting in replacement after 10,000 pitches.

To get to the bottom of this problem quickly, Battersby enlisted the services of Mearthane Products Corp., Cranston, RI, a company that helped develop cast urethane wheels for use on skateboards and in business machine applications. "Cast urethane is a unique material that can be custom formulated to provide a wide range of properties," said Battersby, adding, "Mearthane showed me that the softness and durability I needed in my wheels did not have to be mutually exclusive. We now use a 40-50 Shore A durometer material that will last five times longer than the rubber wheel without needing to be changed." Based on Mearthane's intimate understanding of the material, Battersby was able to finalize the wheel design for his commercial machine after testing only three sets of prototype wheels.

His next step was to have Mearthane optimize the foam cast urethane balls used in the machine. Standard baseballs are too expensive for amusement parks, so conventional machines generally use a urethane ball dimpled like a golf ball. For the ProBatter system, the dimples are an asset, because they optimize airflow around the ball, making it easier to control the various pitches. A single-color urethane ball was a problem, however, because a batter needs to distinguish the seams of the ball so he can pick up the rotation and adjust his swing accordingly. Mearthane's solution was to develop a white chemically-blown, foam-molded ball, then use a robot to paint red into the ball's seams. This seam is clearly visible and will last for the life of the ball, making it an efficient and cost-effective choice.

How good is the ProBatter system? Good enough that pro clubs are taking notice. The New York Mets are using one at their ballpark for batting practice during the regular season. The Chicago White Sox are ordering three units, and several other clubs are in the process of placing orders. When designing for the pros, Battersby and Mearthane had additional concerns to resolve--the original ProBatter ball was lighter and provided less sting when the batter hit it, and did not give the pros a satisfying feeling of contact. To answer this concern, Mearthane designed a next generation of balls out of a heavier urethane with precise density in the material. Adjusting the material composition to resolve these issues was a straightforward process for Mearthane's lab. "We reviewed the performance data and changed our formulation to meet the new requirements," said Albert Chiang, Mearthane's chief scientist, adding, "The heavier, denser urethane performs well for the hitters now."

"In any unique application, the material is stressed in a variety of very specific ways," said John Roderick, Mearthane's president. "We resolved the wheel and ball interface issues, and can easily make further adjustments if ProBatter users require it." --KC

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