Hal Eustice's latest invention, which looks like a partly dismantled vacuum cleaner, is helping young ballplayers around the country become better hitters. The device, called the Rocket Tee, is a 15-inch-high canister with a rubber nozzle sticking out of the top of it. When the Rocket Tee is turned on, the nozzle emits a stream of air pressurized at 15.1 pounds per square inch; it can suspend a baseball four to six inches above the nozzle's tip, which is bent at a 45-degree angle. Depending upon the direction in which the nozzle is pointed, the ball will spin like a fastball or a curve.

Eustice, the baseball coach and a chemistry teacher at Sahuaro High in Tucson, says the device can help hitters to recognize pitches more quickly. And because the ball jiggles up and down while on the column of air, hitting it requires more concentration than hitting a ball on a stationary tee. "It moves just enough to throw you off, so you have to stay with it," says Eustice. "Kids like it because it's so visual."

Eustice came up with the idea for his tee in the fall of 1986, while at a science convention in Phoenix. He saw a Wiffle Ball suspended on a column of air and wondered if the same could be done with a baseball. He began experimenting in his backyard, using a drum-shaped vacuum cleaner. After two weeks of tinkering, he noticed that by changing the angle of the nozzle, he could make the ball spin in various ways.

As soon as he had his gadget working, Eustice called two of his former players, Sam Khalifa and Lew Kent, who had gone on to be minor leaguers. "I said, 'Come over right away,' " says Eustice. " 'I have something you won't believe.' Their reaction was, 'Oh, no, not again.' "

Khalifa and Kent were skeptical because the Rocket Tee is not the first batting device the 54-year-old Eustice has invented. In 1984 he built what he calls the Quick Strider, a machine triggered to throw a pitch when the batter lifts his front foot. He also invented the Roller Tee, a board-mounted tee that rolls down a track toward the batter. Eustice says both inventions were too impractical to market. But the Rocket Tee is different. "We rigged up a net in my backyard, and Khalifa and Kent tried it out," says Eustice, who pitched minor league ball in the Cleveland Indians' organization in the '50s. "They knew I had something this time."

It took two years, but with the help of his handy son-in-law, Bill Poster, who ironed out the technical problems, Eustice designed a production model, started the Air Tee Company and is now selling his invention for $285.

Thus far, he has sold 200 Rocket Tees. Customers include the Pittsburgh Pirates and the Oklahoma State baseball team, as well as the softball programs at Arizona, Nebraska, Cal State-Fullerton, Trenton State and Northwestern, whose softball coach, Sharon Drysdale, says, "The standard tee can get very monotonous. With the Rocket Tee, the visual impression is more realistic."

Gary Ward, the baseball coach at Oklahoma State, bought a Rocket Tee the first time he saw one—at a baseball clinic in Anaheim, Calif., in the fall of 1987—and likes everything about it. "It offers movement in a tee setting, and the entertainment value is unparalleled," says Ward, who also runs summer baseball camps in Stillwater, Okla. He says the Rocket Tee's biggest plus is that it allows kids to put up nets in their backyards and then practice technical skills by themselves.

Brian Loftus, Sahuaro High's first baseman until his graduation last spring, says that before using the Rocket Tee, he distinguished fastballs from curves by the speed of the ball. "Now I look at the rotation," he says. His classmate, shortstop Doug Palma, likes the tee because it freezes the ball over the plate, giving him time to study its movement. "If you're in a slump, you can spend a half hour on the tee and get out of it," he says.

Helping kids become better hitters is what Eustice has had in mind with all his inventions. "Some people go home at night and read a book," he says. "I invent batting tees."

PHOTODON B. STEVENSONEustice (right) watches Loftus use the Rocket Tee to focus on the ball's rotation.

Leo W. Banks is a journalism teacher at the University of Arizona in Tucson.