Engineers Study Baseball Flight

Graduate students LeRoy Alaways and Sean Mish, with engineering professor Mont Hubbard, used videos of baseball pitches to build computer simulations of the forces on a flying ball.

The studies could aid in design of pitching machines and help pitchers hone their curves, fastballs and sliders, said Alaways, who currently teaches at the California Maritime Academy in Vallejo.

"I'm encouraged that scientists are working to explain the physics of what we do -- I'd like to see it taken further," said UC Davis baseball coach Phil Swimley.

Baseball aerodynamics were first studied experimentally in the 1950s by helicopter pioneer Igor Sikorsky, but the results were lost for over 40 years before Alaways found them in a Cape Cod attic. Working with one of the original scientists involved in the study, Alaways plans to publish Sikorsky's results this year.

Sikorsky's data dealt with baseball pitches over 95 miles per hour, while other experiments looked at pitches up to 40 mph. There was no data covering intermediate spin rates, typical of college and semi-professional baseball.

"Our data fills in the gap beautifully," said Alaways. All the previous experiments were conducted in wind tunnels. The UC Davis researchers studied real balls in flight.

"The great advantage over a wind tunnel is that there's nothing attached to the ball," said Alaways.

Alaways, Mish and Hubbard used two sets of data. At the Atlanta Olympic Games in 1996, they used two high-speed video cameras, one behind home plate and one between second and third base, to film pitches.

In a second set of measurements, they used a pitching machine to throw baseballs marked with four pieces of reflective tape and filmed them with seven cameras simultaneously.

Data from the cameras were digitized, combined and used to build a computer model of baseballs in flight.

"If we measure where the ball goes, we can figure out the aerodynamics," said Hubbard.

Using the simulation, they were able to show the relationship between the spin of the ball and aerodynamic forces. These forces cause curveballs to break, said Alaways. The forces are partly due to spin, partly due to the "roughness" of the ball -- whether it is a two-seam or four-seam pitch, and whether it is scuffed.

"A four-seam pitch curves up to three times as much as a two-seam pitch with the same velocity," said Alaways.

Alaways put his expertise to use last year, working as a consultant for Seattle-based Fastball Inc.

"They'd built a machine to throw random pitches, but they didn't understand it," he said. Using the models developed in his research, Alaways could predict within three inches where the ball would cross the plate.

Alaway's contributions to studying curveball aerodynamics were rewarded recently with a lifetime pass to the Baseball Hall of Fame in Cooperstown, N.Y.

Mish, who now works for Creedence Systems Corporation in Portland, Ore., used the models to build a pitching machine with a radical new design. It allows arbitrary, simultaneous adjustment of the velocity of the ball and the axis of spin.

Other projects in Hubbard's lab include the aerodynamics of frisbees, bungee jump stunts and ice skating. Over the years, Hubbard's students have investigated fly fishing, golf putting and javelin throwing. They also built a bobsled training simulator used by the U.S. Olympic team.

The baseball research is published in the Journal of Applied Biomechanics (February 2001) and a forthcoming issue of the Journal of Sports Science.