Like you, I have read roughly a thousand articles about torpedo bats in the last four days. The bats, which look funny to us right now and will look normal to us in a couple months, taper at the end and bulge slightly at the sweet spot. Like so many good ideas, transferring that mass from the end of the bat, where the batter doesn’t want to make contact, to the sweet spot, where they do, is so simple that it teeters back and forth between elegance and silliness. Reasonable people can smack themselves in the forehead and think, “How is it possible that nobody ever thought to do this before?” Reasonable people can also giggle at pictures of big chonky bowling pin bats.
This innovation was possible because the rules around bats are fairly permissive. The rulebook spends one page on bats and nearly three pages on balks. Given that those three pages do almost nothing to clarify what does or does not constitute a balk, one page for bats seems pretty slight. In fact, we can boil the rules down to one quick sentence. As Patrick Dubuque wrote on Monday for Baseball Prospectus, bats must be solid wood, round, shorter than 42 inches, and no wider than 2.61 inches. That’s pretty much it. Not only does that sentence not contain many rules, but those rules also give batters some serious latitude. No one on earth is using a 42-inch bat. That’s 55% as tall as Jose Altuve. Marucci and Louisville Slugger don’t even offer bats that are longer than 34 inches. Babe Ruth’s famously enormous bats topped out at 36 inches. Fungo bats top out at 37, which means they’d be perfectly legal to use in a game, and they’re not even half an Altuve. The rulebook might as well say that bats may only be as long as the Mississippi River.
Apparently, no one was approaching the diameter limits either. There’s a good reason for that. If you were to increase the width of the barrel to the maximum 2.61 inches, until recently, you’d also be increasing the entire head of the bat too. You’d end up with a bat that was too heavy, and more specifically, too top-heavy. You’d feel like you were swinging a sledgehammer. That’s way too much mass to add to the bat. Eventually, someone was going to realize that you don’t have to increase the entire head of the bat.
Researcher Erica Block found this idea (under the name the “bottle bat”) lurking in the American Journal of Physics all the way back in 1963, but the someone who finally made it happen was physicist Aaron Leanhardt, who taught at the University of Michigan for seven years. He is now the Marlins’ field coordinator and was working in the Yankees’ minor league hitting department when he had the idea. “It wasn’t until now that maybe anyone really thought about this, myself included,” Leanhardt told reporters. “You show up every day, you put the glove on you’re given, swing the bat that you’re given, you put the spikes on that you’re given and you go about your day as best as you can, and every now and then, it takes time to question what you’re doing. Couple of years ago, some of the hitters started questioning what they were doing and I just kind of responded to their questions.”
The answer to those questions is simple enough that the physicist can boil it down to a sentence. “It’s just about making the bat as heavy and as fat as possible in the area where you’re trying to do damage on the baseball,” Leanhardt told The Athletic’s Brendan Kuty. A ballplayer without a physics degree can sum it up too. Wrote Jazz Chisholm Jr. on social media, “you just move the wood from the parts you don’t use to the parts you do!” The parts you don’t use are the reason the torpedo bat works in the first place. As it turns out, you can break a bat down into three distinct parts. The example below uses Cody Bellinger’s traditional CB35 model, made by Louisville Slugger.
No wonder Bellinger ditched this hunk of mostly garbage for a torpedo bat.
The truth is that nothing matters but the barrel. When Statcast first started releasing exit velocity data, we naturally gravitated toward a player’s average exit velocity. However, smart people quickly started focusing on other metrics like maximum EV, 90th or 95th percentile EV, and best speed (which Baseball Savant has since renamed EV50). Those other metrics are useful specifically because they completely ignore weakly hit balls, which were skewing the sample. Here’s Tom Tango’s now classic graph that explains why they set the cutoff for hard-hit balls at 95 mph.
As he put it, that’s where exit velocity starts to matter. If you hit a ball off the end of the bat, you’re going to hit it weakly. If you remove some mass from the end of the bat, you’ll hit it even more weakly, but who cares? There’s hardly any difference between balls hit 80 mph and 60 mph. However, once you get past 90 mph, hitting the ball flush, that graph gets mighty steep. Every extra mile per hour really, really matters.
Leanhardt explained to ESPN’s Jeff Passan that he used the concept of a “wood budget” to think through the idea, getting more wood on the sweet spot without increasing the overall weight of the bat. “Every penny counts. The fact of the matter is you want your barrels to count the most. You want the most bang for your buck there.” Expanding and strengthening the sweet spot by packing it with as much mass and density as possible helps toward that goal. Adjusting the location of the sweet spot so that it’s right where you tend to make the most contact helps toward that goal. Traditional bats have junk in the trunk. Torpedo bats bring the trunk to the junk.
In order to get a better understanding of the forces at play, I reached out to Vivienne Pelletier, a PhD candidate in materials science at Arizona State University and one of the brightest baseball minds in the public sphere. She explained the finer points of collision efficiency and pointed out something really fascinating. Even after super-sizing the sweet spot, its exact center is still not the optimal place to hit the ball. As it rotates, the bat moves faster toward the head, meaning there will always be a spot just past the sweet spot where the fractional increase in velocity will be worth the fractional decrease in mass. “In a real swing the bat is rotating,” Pelletier told me on Bluesky. “Near your hands it moves slowly and at the head it moves fast, there’s this bat speed gradient. The actual max EVs hitters get come above the point of maximum collision efficiency (which we could call the sweet spot) because the bat moves faster up there.” Every bat has a sweet spot, and every batter’s goal should be to just barely miss it.
As it turns out, every batter has their own sweet spot too. I spoke to Andrew Aydt, Driveline Baseball’s assistant director of hitting, to talk about how torpedo bats could be customized. “When I first saw the torpedo bat come out or gain popularity,” he said, “that’s where my mind went with it too, because of Hawk-Eye being in all MLB stadiums now. Teams have very detailed measurements now from bat tracking and tracking the ball. They know exactly where guys are contacting the ball consistently. So I think this is actually a pretty big advantage for teams that have a good R&D department. They can suggest [based on the] overall average [location of contact] where they should beef up the barrel, or adjust the barrel down some or up some.”
Anthony Volpe, who tends to make contact closer to the bat’s label, had his sweet spot moved in that direction, said YES Network broadcaster Michael Kay during the second inning of Saturday’s game. While this should allow Volpe to increase his exit velocity by ensuring that his contact comes closer to the sweet spot, that location also means that his sweet spot will be moving slightly slower because it’s closer to the knob. Then again, the adjustment to the balance of the bat – lowering the moment of inertia, in physics terms – should allow him to swing the bat harder and to have better bat control, offsetting that loss. Pelletier, who has already run some numbers on the potential gains in exit velocity, explained, “The torpedo bat moves the sweet spot down, meaning that it moves somewhere that’s necessarily moving slower. So, even if you make slight gains on max collision efficiency your max EVs decrease as well.” Physics: Sometimes it’s complicated.
For players whose contact tends to come closer to the head of the bat anyway, the news is even more exciting. Adjusting the sweet spot in that direction would allow them both to make more contact at an optimal spot and to increase the bat speed at that spot (though it would also make the bat effectively heavier and worsen bat control some).
On Sunday, Tango posted the scatter plot below. It shows the contact tendencies of every player in baseball, limiting the sample to swings on which the hitter was on time and on target. He split them up into two categories: Those who get tied up (that is, make contact closer to the label) and those who flail (make contact closer to the head). As you might notice, Volpe is not where we’d expect him to be. He’s actually slightly on the flailing side of things. If anything, based on these particular data, his sweet spot should be pushed further toward the head of the bat. However, that doesn’t necessarily mean he’s swinging the wrong torpedo bat. Additional data could’ve been used during Volpe’s bat fitting that supported sliding his barrel toward the label. “I don’t know that necessarily everyone knows about it,” said Yankees manager Aaron Boone in response to a question about whether league-wide offense would increase as more teams adopted torpedo bats. When asked to elaborate, Boone said: “I think there’s just a lot more that goes into it… a lot went into doing that for our individual guys.” Tango highlighted Jhonkensy Noel as a proud member of Team Tied Up who would benefit from moving his sweet spot closer to the handle.
The odd shape is the grabby part of the torpedo bat, but the fanfare of the last week could have a bigger effect, turbocharging the trend toward hyper-customized bats. “The bat is such a unique tool,” Ryan Jeffers told Passan. “You look at the history of the game, and they used to swing telephone poles. Now you try to optimize it, and it feels like some branches are starting to fall for us on the hitting side of things.” Batters have always tinkered, and plenty of trends have swept through the league before. In the early 2000s it was maple bats, and in recent years we’ve seen trends like axe handle bats and hockey puck knobs. Customization has increased steadily. Orioles hitting coach Cody Asche told The Baltimore Banner’s Andy Kostka, “I think if you’re around clubhouses, all 30 teams, you would see a guy or two who’s adopting a bat that is fashioned maybe more specifically for their swing.”
Aydt told me that Driveline started doing bat fittings around four or five years ago. “How much is there to change the bat, or individualize bats to help a player’s performance?” he explained, focusing on the moment of inertia again. “How fast they’re swinging the bat, how hard they’re hitting the ball, consistency. Basically, their collision efficiency (or what we call smash factor), how we can improve that for guys more often, any improvements ball-flight-wise… Since we don’t manufacture bats, it was more finding a good MOI for the guy that we think would help them perform the best. And then recommending bats if they wanted or taking that to their bat manufacturer.” In the last year or two, Driveline has focused less on bat fitting, because bat manufacturers have started doing their own fittings. Aydt mentioned that Marucci has a baseball performance lab for that very purpose. When he saw the torpedo bats take the league by storm, his mind leapt to even more advanced frontiers.
In the coming year or two, we’ll be seeing more torpedo bats specifically, and more bats that are customized to an individual player generally. But they could also be tailored for a specific situation. “I think they could even get more granular than that, having a range of bats made for guys,” Aydt said. “And then depending on that night’s starter or the matchup they’re going to see, they could decide which bat to go with… based off the pitch types they’re seeing, if the hitter misses more at a certain part of the bat based off different pitches or what they’re most likely to see that night. Or if guy has attacked more inside, attacked more outside consistently against that hitter… If they’re going to be facing a ton of velo that night and they’re a guy who doesn’t consistently hit velo well, it could be a good thing to lower that MOI. So that would be moving more of the mass closer to the hands, which is essentially lowering the swing weight. So it’s easier for them to get up to speed quicker, improving the acceleration of the bat to help them catch up to velo.”
Maybe you’re like Rafael Devers and starting the season with a disastrous run of strikeouts because you’re behind on absolutely everything. You’d be a good candidate for a Volpe bat with a lower MOI, helping you get around quicker. Maybe you’re facing a pitcher who loves to attack the outside corner. It might make sense to try a bat with a higher MOI and more mass toward the head. Aydt even raised the possibility of having a two-strike bat. When you fall behind, the bat boy runs out to hand you a bat with a lower MOI so that you can prioritize quickness and barrel control over power.
It’s also possible the torpedo bats will be banned, as one front office source predicted to R.J. Anderson of CBS Sports. If we do see ball boys running out to trade bats every time a hitter falls behind in the count, the league might feel it has to act. It certainly wouldn’t take a particularly dramatic rule change. The rules would just need to specify that no part of the bat may have a diameter bigger than the diameter at a point, say, one inch from the end. It might not even push the bat section of the rulebook past a page.
As with any innovation, buy-in will be a big limiting factor. There will always be old-school baseball men eager to object on principle to any innovation. “When I got jammed, I figured out what I had to do to stop that,” said Angels manager Ron Washington, who ran a lifetime 77 wRC+. “So I didn’t worry about putting more weight in a certain area of the bat.” Current players are much more open to new ideas and technology. Some will be comfortable trying something new, or even following Aydt’s idea and tailoring their bat to the situation at hand. Others will value comfort and consistency. “It is the talk of the game right now,” said Aydt, “but it’s not going to be good for every single hitter.” Said Leanhardt, “Credit to any of the players who were willing to listen to me, because it’s crazy. Listening to me describe it is sometimes even crazier.”
According to The Athletic’s Sam Blum, the Yankees developed torpedo bats in 2022, while the Cubs started working with them last season. Brandon Lockridge was a minor leaguer in the Yankees system at the time and now serves as the small spoon in San Diego’s left field platoon. Lockridge told Blum that when Leanhardt was originally pushing players to try the bats, his pitch wasn’t about exit velocity, but rather about using the bigger barrel to turn some whiffs into foul tips. It’s possible that over the course of 600 plate appearances and 1,000 swings, an extra fraction of an inch could save a player from a third strike or two. However, it’s hard to imagine that this selling point was sexy enough to convince players to try something that looks so different from what they’re used to. Hitters depend on feel. If they’re not comfortable with a bat, no amount of evidence will persuade them to use it.
That’s where the name comes in. You have to imagine it’s more about marketing than anything else. As anyone who’s watched The Hunt For Red October a couple dozen times can tell you, torpedo bats actually look less like torpedoes than traditional bats do, because most torpedoes taper only ever so slightly at the end. What torpedo bats actually resemble is old-timey bombs or pregnant whales.
(Editor’s note: We consulted FanGraphs writer Michael Baumann, who’s seen The Hunt for Red October a couple hundred times, about the torpedo shape issue. His response was very involved and to be honest we started zoning out when he used the word “supercavitating.”)
But as anyone who’s worked for a major league team will tell you, all the evidence in the world won’t help an idea if you can’t sell it to the players and coaches. So while the torpedo bats may have exploded into the public’s consciousness this past weekend, their place in the game owes itself in some degree to Leanhardt’s salesmanship and the open-mindedness of the Yankees, not to mention the bat manufacturers who had to learn how to make them. None of us was there, but I will leave you with a dramatization of Leanhardt’s efforts to get these bats into the hands of the Yankees. I present to you a play in three acts.
ACT ONE
PHYSICIST: Pardon me, young baseball man. Would you be interested in experimenting with our new bowling pin bats? My calculations say that they might help you get more foul tips. [Receives wedgie.]
ACT TWO
PHYSICIST: Hello there, fellow Yankee. Might I be able to persuade you to take a couple whacks with our new juggling club bats? They ever so slightly alter the moment of intertia, and preliminary results indicate that this alteration just might result in an increase in — you know what, I’ll just shove myself into this locker.
ACT THREE
PHYSICIST: Sup, bro. Wanna try this sick-ass torpedo bat? Scientifically proven to make the ball [lowers sunglasses] explode.
Matt Martell contributed reporting to this piece.
