The Act and Art of Bending a Baseball Bat
JUPITER, Fla. — With The Post-Dispatch’s photo maestro Chris Lee and the skilled lens of Scott Rovak around the ballpark constantly, there are plenty of snappy pics of and about the St. Louis Cardinals. No doubt many who are reading this have clipped a few from the paper or taped a Rovak-made poster or two to the wall.
Lee’s snapshots from spring training are still available as slideshows on the Post-Dispatch’s web site (follow this link). And Rovak, the official team photographer, is updating his blog with photos from spring training and discussions about each photo’s composition. You can find his blog, Photography Talk, at this address. If you scroll down about four or five taps of the down arrow, you’ll find the photo that stirred talk in the Roger Dean Stadium media bunker the other day.
Rovak was clicking pics of first-rounder Brett Wallace taking batting practice. Here is the shot:
3B Brett Wallace takes a swing in batting practice earlier this week. (Source: Scott Rovak)
You can also see a full-sized image of the picture by following this link. The picture stirred conversation because of the bend of the bat. Wallace his hand and bat speed is so much that a nanosecond before it strikes the ball, the bat head is bending backward, not unlike the torque you usually see on a golf club. Rovak said as he looked at the picture — and later repeated in his blog entry about the picture — that he’s only snapped two other hitters with “bended” bats: Scott Rolen and Albert Pujols.
There are some pictures of college players and high schoolers — maybe even little leaguers — with bended bats as they prepare to strike the ball, but the bats they are using are aluminum. Have to imagine there’s a point in time during each swing where the bat flexes, bend. Rovak challenged us to go and take a bat and try to bend it by placing against the ground. It gives a good sense of the sort of power needed to bend a bat without breaking a bat. Tremendous hand strength and speed.
“It’s hard enough getting the ball in the frame,” Lee said when asked how often he’s captured the moment the bat bends before greeting the ball. “And then you have to get the exact instance when the ball is at a standstill and changing direction. There is only the briefest of moments when that actually happens, and you can’t possibly count on getting it all time, or even that many times.”
Rovak goes a little deeper into the discussion about timing the best at-bat photo in his blog entry. With the rare photo seen above, Rovak couples it with a true once in a lifetime shot: Allen Craig swinging, his bat splintering, the ball in the frame and … the Cardinals prospect and California native wearing a Team Dominicana jersey.
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Derrick Goold said he was going to Mizzou for capital-J journalism, but after growing up in the Time Zone Baseball Forgot he was really drawn to MU sitting between two major-league cities. Goold joined the Post-Dispatch in 2001 after working for The Times-Picayune and Rocky Mountain News, covering sports from LSU to NHL and every level of baseball in between. 
Derrick, I suspect this is a photographic artifact: the head of the bat is traveling faster than the neck, so it will cover more area while the shutter is open, making the bat appear to bend. If Wallace could somehow flick the bat back and forth it would appear to blur symmetrically, but because it’s traveling back to front it appears to bend backwards.
That’s what I think anyway. I’d love to see evidence otherwise!
All bats, whether aluminum or wood, will bend — or undergo “elastic” deformation — when they encounter a force. They bend — a little — when meeting the ball, for instance. The amount of distortion can easily be calculated knowing the force of bat meeting ball (or ground) and the tensile strength of the bat.
However, the effect seen in the photo is obviously due mainly to distortion from the bat moving at a higher speed than can be “stopped” by the sensor in the camera. The blurring of the bat gives this away, as Matt suggested. With proper equipment a “stop-motion” photo could show if the bending is real or artifact.
To further bore the readers, aluminum bats can undergo “plastic” deformation, i.e., become permanently BENT. Wood bats break, instead.
JDW
While the bats might not actually be bending, the photos still illustrate the incredible bat speed that apparently only very players can generate. Even if the bats aren’t actually bending, I’m still impressed.
Wallace’s arms are not extended, suggesting that this was not an especially powerful swing. The bent bat is not a photo illusion - more BLUR of the bat at the end is a matter of increased bat speed at the bat head (and possibly the focal point of the image) but the curvature of the bat is not illusion. I’m just a history major, so, physics people feel free to correct me… While a golf club bends during the downswing because it has a relatively flexible shaft and considerable mass that resists acceleration at its end, a bat’s bend would imperceptive as it travels through the air. When the bat meets the ball coming the other way, in the sweet spot, the hitter hopes, the head of the bat meets an opposing force (if we knew the weight of the ball and speed of the pitch we would know how much - F = MV squared) and that leads to the bending of the bat. How much the bat bends depends on the speed of the pitch and the speed of the stroke - equally. For REALLY mind bending bat speed/hand strength, remember that Jim Rice broke a but CHECKING HIS SWING!
Back to baseball!
Back to physics. The deflection of the bat is a function of the force imposed upon it and the tensile strength of the bat. (Tensile strength equals the deflection due to a given applied force.)
The force, in the case of a bat not meeting ball, is a function of the deceleration of the bat due to wind resistance. It’s not a big number, which is why the photograph isn’t — or isn’t all — “real” bending.
When bat meets ball, the force is equal to the mass of the ball times the square of the rate at which said ball decelerates because of the bat, less the distortion in the ball itself. In the hitter’s ideal situation, the velocity of the ball becomes zero, for an instant, so if the ball were an incompressible sphere — which it ain’t — then the force would be equal to mass of the ball times the free velocity of the ball divided by the length of time it takes to come to momentary rest. (Not the mass times the square of the velocity.)
Because the ball distorts, the net force is the total, as given above, less that expended to distort the ball. Someone has measured what that is under experimental conditions, but I don’t know it off-hand.
The ball is more nearly perfectly elastic than rigid, and the energy (which is where the square of the velocity comes in) is mostly stored in the ball. When the ball changes direction, this energy is converted to motion again, causing a well-hit ball to jump off the bat. Works every time.
JDW
So if the tremendous bat speed generated actually causes the bat to bend, does that also mean the blazing fastball thrown by the BP pitcher has caused the ball in the picture to take on an egg-like shape?
Cool pic though. Wallace looks as if he’d deliver one heck of a left uppercut.
I have a couple of comments about the picture (which, by the way, is a fantastic shot).
1. I would not rule out a photographic effect. One such effect is the use of a so-called “focal plane shutter”, in which the full detector array is scanned rapidly by the shutter. So, if the scanning is in the up direction, then the bottom of the photo will be slightly earlier in time than the top, so that the tip of the bat will appear to lag behind the handle. This might be what is going on.
2. I have actually modelled wood bats in extensive computer simulations, mainly to see how the ball-bat collision excites vibrations in the bat. I have tried to see what it would take for the batter to make the bat vibrate by swinging it. I find that it would take an enormous amount of torque to make that happen. So, I am very skeptical that any human being can make a normal wood bat bend by as much as the photo indicates merely by swinging the bat. As someone has already pointed out, the shaft of a golf club does bend during the swing and a skilled golfer knows how to utilize that fact to get a bit extra head speed at the moment of contact. But the shaft of a golf club is slender and much more flexible that that of a bat. So, I am skeptical.
3. How do we know the photo was taken *before* contact with the bat. The picture would be much more reasonable from a physics perspective if it was taken just after the contact.
Wow, and I’m caught without my flux capacitor today. Doc’s gonna be so pissed if I can’t get back to the future.
What about when Bo Jackson bent bats?
How do we know that the Wallace photo is before rather than after the ball makes contact? I’m not doubting it, only wondering. Is that like knowing whether it’s a sunrise or a sunset picture?