Bat man

Speak to a former physics professor about baseball and the conversation is likely to include technical terms like “moment of inertia,” “average exit velocity,” and “vibrational modes.” But speak to the former physics professor who masterminded this season’s popular version of the Torpedo bat, and you’ll also hear the more relatable term “sweet spot.”

Aaron Leanhardt, BSE ’99, field coordinator for the Miami Marlins, is watching the 2025 World Series like any scientist evaluating the progress of an ongoing experiment. His pet project has been about three years in the making: a small, but critical change in bats that could shape the future of the game. And once the Los Angeles Dodgers or Toronto Blue Jays claim the league’s ultimate title, this academic-turned-MLB analyst will be there to assess and utilize a valuable new set of data.

“It’s going to be hard to attribute any credit or penalty to the bat, per se, but I do think over the course of a season, you’re going to see contact rates go up and the quality of play go up a little bit,” he told an audience during a recent presentation of U-M’s Saturday Morning Physics, hosted by Timothy Chupp, professor of physics and biomedical engineering. “I think this will be a big offseason for guys to try to see if they can get a benefit to their liking.”

The appearance of Leanhardt’s version of the Torpedo bat – thinner at the tip than a traditional bat, as its name would suggest – generated headlines, home runs, and debate at the top of the 2025 baseball season. He estimates about 15-20% of the players in the league used the bat regularly.

The torpedo-shaped barrel shifts weight closer to the center for a more balanced swing feel and enhanced barrel control. (Image: amazon.com.)

From the Diag to the dugout

Leanhardt graduated with a degree in electrical engineering from U-M and his PhD in physics from MIT – where he was also a standout shortstop for a local amateur baseball league. He returned to U-M as an assistant professor from 2007-14, but baseball always called.

He exited academics for athletics, first as an assistant coach in New Jersey’s Atlantic Collegiate Baseball League, then as a coach at Montana’s Dawson Community College. From there he joined the New York Yankees where he served as a Major League analyst. That’s where he also came up with the idea for the bats, before joining the Marlins.

The problem he addressed seemed simple: Pitchers had gotten much better, making solid contact at the plate much more complicated.

Leanhardt attacked the challenge with a physicist’s eye and an athlete’s competitive drive. How could contact be increased – how could batters launch more balls from the sweet spot of the bat – while hewing to the constraints of physics and MLB guidelines?

“There were tradeoffs with each step,” he said.

In their first three games of 2025, the New York Yankees scored 36 runs, including nine in one game. Four of five hit off the starting pitcher using Torpedo bats.The challenge of a long rod, with vibrations at the end, comes straight out of physics textbooks. However, weight couldn’t simply be added, nor could the bat tips be significantly shortened without deleterious effects.

Saturday Morning Physics presenter Timothy Chupp, professor of physics and biomedical engineering, swings a Torpedo bat. (Image via Saturday Morning Physics.)

It was a challenge of constrained optimization and stringent creativity, for maximizing the distribution of the wood where the players wanted to hit the ball while providing them with bats and weight distributions with which they were already comfortable.

Like the challenge, the solution Leanhardt discovered was also deceptively simple. Instead of the standard taper of a bat that widens toward the tip, he ideated one with more of the material nearer to the hands. Leanhardt said the idea came from his time as a hitting coach, and ultimately from the players themselves.

In theory, the torpedo shape could increase the size of the bat’s sweet spot – somewhere between four and nine inches from the  tip – as well as possibly the hitter’s swinging speed. But as with other physics challenges, once the idea was discovered, the theoretical had to match up with the reality.

Leanhardt connected with bat makers, plowing through lathe upon lathe, and joining with regulators to ensure the innovations would be legal for gameplay. And while he wasn’t the first to iterate a torpedo design in bats, he certainly created a significant buzz in early 2025.

As the 2025 season comes to a close, the refinement process continues. It remains to be seen which batters will benefit the most from Leanhardt’s adjustment.

“I think over the course of the offseason a lot of players are going to get fitted in a way they can get a bat tailored to their swings, similar to what happens in golf,” he said. “And a lot of guys are probably going into next season with something that’s better designed from a physics standpoint [regarding] the sweet spot, and also from a personal standpoint where the bat has been tailored to their swing a little bit better. And we’ll probably have a little more information to answer the question this time next year.”

(Lead image: At the top of the 2025 season, reporters interview Aaron Leanhardt about his Torpedo bat. Image: Fish on First via YouTube. Saturday Morning Physics is presented by the Department of Physics.)