NEW YORK – The New York Yankees bat was the story of the team's franchise record 9 Homelandy against the Milwaukee Brewers on Saturday. Then came the discussion about the actual bats that some players used in the 20-9 victory.
The uniquely shaped material is the result of two years of research and experiments with a former Massachusetts Institute of Technology physicist coach.
A question at the center of that?
“Where are you trying to hit the ball?” Aaron Leanhardt said in a phone interview Sunday morning. “Where are you trying to contact me?”
Lean Hart, 48, began his job in 2022 when he was a member of the Yankees' minor league hit division, and last season he tried out some players in the game, including shortstop Anthony Volpe. Currently outfielder Cody Bellinger says that as many as five Yankees have used them in at least this season's games.
Torpedo-shaped bats are custom made to suit the player's preferences, and are designed so that the dense part of the bat is where that particular batter most contacts with baseball.
“Really,” he said. “It's about making bats as heavy as possible and fat as possible in areas where you're trying to do damage in baseball.”
Anthony Volpe (who has a “torpedo” bat) congratulates Jazz Chisholm in Saturday's Yankees' 20-9 victory. (Mike Stove/Getty Images)
A major league baseball spokesman said Athletic Bats don't break the rules. MLB Rule 3.02 states that the bat must be “a smooth, round stick with a diameter of less than 2.61 inches and the thickest part is less than 42 inches long. Also, “experimental” bats cannot be used “until the manufacturer ensures approval from Major League Baseball for his design and manufacturing methods.”
When asked if he was the inventor of technology, Leanhardt said it was the group's efforts and a result from conversations with coaches, players, MLB and bat makers.
“The credit goes to the person who takes it,” Leanhardt said. “But if people want to credit different people, I'll cut that down some.”
However, Yankees officials said Lean Hart deserves “a lot” of credit. Kevin Smith, a retired infielder who spent part of his four seasons in the majors, also praised Leanhard as the inventor.
Yes, the Yankees have Renny (the man), a literal genius MIT physicist on their pay. He invented the “torpedo” barrel. It brings more wood and mass to the places you most often come into contact with as a batter. The idea is to increase the number of “barrels” and reduce mistakes. pic.twitter.com/csc1wkam9g
– Kevin Smith (@kjs_4) March 29, 2025
Leanhardt took an unorthodox route to baseball.
He holds a bachelor's and a doctorate in electrical engineering from the University of Michigan. In MIT physics. He was a professor of physics at the University of Michigan from 2007 to 2014.
Leanhardt began coaching in the Atlantic League in 2017 and began coaching at Montana Community College before joining the Yankees in 2018.
Why leave Academia for baseball?
“I think one of the cool things about sports is that it's very competitive,” he said. “Everyone is willing to push the envelopes. It's just an opportunity to bring my background into the area and find ways to innovate.”
Talking with players over the years made it clear that their biggest concerns were two concerns, Leanhardt said. They wanted to make more contact with the pitch, so they wanted to hit the ball more frequently in the “sweet spots” of the bat and in the most dense areas.
“They're going to point to the place on the bat, which is probably six or seven inches below the tip of the bat,” he said. “It's a common place. It's through conversations you think of yourself. How much wood is we put in chips and how much wood is not swapped in sweet spots? That's the original concept.
Leanhardt said there are not many drawbacks to redistribute the weight of the bat.
“The bat should remain the same speed,” he said. “Maybe the bat speed can increase slightly depending on how the bat is redesigned. But in the end, you're getting a thicker barrel, a heavier barrel in the sweet spot. So, in a way, you can eat the cake here too.
Leanhardt said he didn't want to talk about the individual players' experiences with the new bat. Yankees designated batsman Giancarlo Stanton told reporters earlier this month that he stayed on his current list of injured last season, “probably some bat adjustments” but he didn't take any concrete responsibility for anyone, but caused ligament tears in his current elbow. He then added: “I don't know why that happened.” Leanhardt refused to comment on Stanton's situation.
“We'll have to ask Yankees medical professionals about that,” he said. “I'm postponing all these questions to Yankees medical scientists.”
Leanhardt said it was the “matter of our business” that took us years for a fundamentally new bat design to arrive.
“People at the time had this genius idea of ​​rocking a very heavy bat made of hickory, then someone lightly swinging something like Ash. “In the end, it's just people are asking the right questions and being happy to think positively.”
He got a kick from watching the bat social media caused on Saturday. He said that some players started using them last season, but “the whole industry caught the wind of it” and “it exploded in the offseason.”
“That's why you're looking at it in so many people's hands right now,” he said. “Obviously (Saturday) performance gave that a lot of attention.”
Many adjustments were required between the design stage and the production of the bat. Leanhardt said he “guarantees” MLB officials overseeing bat regulations and “everyone who operates the lathes of all bat makers in baseball.”
“You're really communicating with each company and trying to find someone who really knows the wood and knows how to turn the wood on a lathe. You're just building a relationship with them and convinced that this is the best thing to produce for the player. “That's really how it's accumulated.”
(Top photo of Aaron Leanhart with Marlins manager Clayton McCullough: Jacen Vinlow / Miami Marlins / Getty Images)
