If you are new to the idea of Seam Shifted Wake pitches, I recommend downloading and viewing this presentation which is about 45 minutes long. I realize that is a lot of time, but this is a complex topic. That said, I think the presentation is easy to understand.
As some of you know, the Seam Shifted Wake (SSW) effect has made me a fan of gyro. Pure gyro refers to a ball spinning like a bullet or a football (thanks, Tom Tango). Most pitches have some amount of gyro and this is quantified by either gyro angle (0 degrees means no gyro, 90 degrees means pure bullet spin) or by the equivalent terms of “active spin” (favored by MLB and seen on baseballsavant.com) or “efficiency” (seen many other places, including Rapsodo outputs). Since gyro spin does not contribute to the Magnus effect (which makes a spinning baseball break), it is commonly thought to be undesirable and of little use. Some have noted that a pure gyro pitch will gain some non-gyro spin as it falls potentially leading to a very small (but perhaps important) amount of “late break.” You can read more about all of that here.
The thing about gyro that I appreciate it that it presents much more opportunity to have a Seam Shifted Wake. With no gyro, you can do a Looper, and probably not much else. Loopers have less SSW effect than other pitches such as the Discoball changeup or Laminar Express. The separation happens over less of the ball.
With gyro, lots of other SSW are possible, and these often have a separation happening over much of the ball and over 3/4 of the rotation. An example is Jared Hughes’s sinker. Here’s one from his backyard in June, 2020.
Using Trip Sommer’s pitch spin simulator, I estimate these top (y) and front (z) orientations.
Here’s that same pitch in a couple of games.
This one is even better.
Hughe’s sinker has a tilt of 2:10 or so (don’t believe what you see on Savant or Brooks on this number–they still use movement and a Magnus model to infer the tilt and efficiency). It should mostly move glove side and have a small amount of ride. But, it actually accelerates downward like a curveball, although not as much. As the season progresses, look him up on Savant and download his sinkers. Check out az, or vertical acceleration. Anything more negative that 32.17 ft/sec^2 is being pushed downward in spite of the spin pushing up. At this writing, that’s 80% of Hughe’s sinkers in 2020, up from 50% last year.
Now, getting to the point. I have commented previously that the orientation of the ball relative to the axis that is required for SSW depends on how much gyro the pitch has. This post will show that the optimum orientation changes with gyro. The change in orientation is not one-to-one with changes in gyro as I previously speculated, however.
I’m going to use the Hughe’s pitch as a guide and UMBA 2.1 to simulate pitches with different orientations and efficiencies to find the optimal downward movement. This version has the option to vary one parameter and in the following results, I will vary either top (y) rotation or front (z) rotation.
First, we need a baseline. For this pitch, with no seam effects, we get this:
The right side is release, the left side is home plate. The pitch arrives 34.5″ off the ground.
Before getting into the results, this animation may help you understand better what 10 degree changes in orientation look like. Note the changing value of top (y) orientation.
I’m going to look at 80%, 75%, and 65% efficiency. Starting with 80%, here is my UMBANQ input:
Result:
Recall this is a sinker and we want it to move down. Let me reiterate that these pitches all have the same axis but different orientations. The changes in trajectory are entirely due to seams.
The best case is clearly y = 0 degrees rotation. A similar run shows that z = β15 degrees rotation is optimal. A couple orientations actually seem to move upward slightly. At lower efficiencies, there is even more potential for upward movement.
I’ve repeated this process for the other two orientations. At 65%, if I keep z = β15 and vary y,
the y = 0 case is now the worst result. If you change your efficiency and do not change your orientation, a SSW pitch can become a non SSW pitch. But SSW is possible over a wide range of efficiencies.
Bellow is the optimal y and z rotation for each efficiency.
80%, y = 0, z = β15
75%, y = 0, z = β10
65%, y = 20, z = β10
As efficiency goes down, the required y rotation increases while the z rotation decreases.
Does this look real?
Well, mostly. If you look above, Hughe’s orientation on a 80% pitch was y = β15, z = β15. According to UMBA 2.1, that should not move very much beyond the baseline. But we know it moves downward based on Savant data.
I believe UMBA is currently able to show us qualitative information. It says that the optimal orientation depends on efficiency and I believe that. It gives an indication of the correct direction of change in orientation that is required as efficiency changes.
We are currently updating UMBA based on more recent results and on fewer simplifying assumptions. Within a few months, we should have improved the model to the point where it can predict pitches.
Dr Smith, could you speculate on the how the physical differences between a baseball and a softball might affect SSW pitches? The softball being much bigger and heavier and thrown with velocities between 60-70mph. And also on how forward spin vs back spin would affect a ball with identical spin axes and seam orientation? Generally speaking back spin is more common in baseball and forward or top spin more common in softball.
Let’s first talk about everything but SSW. Ball aerodynamics depend on a collection of variables that we call Reynolds number.
Re = VD/nu.
V is the ball velocity, D is the diameter, and nu is a property of air. Obviously, nu is the same for baseball and softball.
If Re is the same, then the result is the same for the two different balls.
For baseball, D = 74mm, V = 90 mph
For softball, D = , 96.5 mm, V = 70 mph
Those look like quite similar Reynolds numbers to me, which is pretty interesting. I would expect similar behavior. Now, the seams on the two balls are different. To me, NCAA softballs appear to have very large seams relative to their diameter. For that reason, I think there is a lot of potential for SSW in softball.
Top spin vs backspin means in softball, everything looks like a curve.
Let me see if I understand this; in the case of the pitch that Jared Hughes is throwing the consistent seam presence on the top of the ball causes early wake separation which results in higher pressure compared to the bottom of the ball which forces the ball down?
Yes, that is a very nicely concise description of it.
We are still learning the optimal position of that seam, however.
Alan Nathan just pointed out that softballs are a bit heavier. That will decrease their tendency to break.
Alan Nathan just pointed out that softballs are a bit heavier. That will decrease their tendency to break.
Softballs are heavier, however, but based on my very basic math they are less dense, this seems to me to be a factor. I have heard stories of mysterious breaking pitches based on tipped bullet spin (softball term for gyro) but I can’t reliably reproduce one. Armed with your latest information I will have my pitchers attempt it again. If a ball is thrown with a spin axis like Trevor Bauer’s Laminar Express but it has the opposite spin (forward instead of backwards) how would it break? Last night I saw Jacob Degrom throw a 92mph change up, the bottom dropped out of it. I know he uses a grip similar to Strasburg and is probably utilizing the same SSW effect.
Spin direction will have no effect on SSW.
What makes softballs interesting to me is the big seam. I believe that could lead to the optimal seam position being farther forward resulting in larger effect.
Hello Dr Smith,
I am a softball fastpitch instructor and was looking into the possibility of a SSW screwball. In fastpitch it is virtually impossible to spin a ball in the manner necessary to generate a Magnus force screwball. I made my own ‘ball on a rod’ similar to the one you used in your 2 seam vs 4 seam video. I marked the ‘horseshoe’ part of the seam with a marker. Then I proceeded to spin the ball in a way that would generate the required SSW force for a screwball. While doing this it occurred to me that SSW offers the possibility of a “2 for the price of 1” pitch. A pitcher that can throw an SSW pitch has the choice of two breaks in opposite directions along the plane of the spin axis, depending on where he places the ‘horseshoe’ seam that generates the early wake separation. To understand how this can be done go to your SSW 2-seam vs 4-seam video, at 1:10 you ‘add an element of gyro’ and you point to the seam on the back of the ball. At 2:00 you talk about how that seam causes the ball to move to your right. At this point imagine flipping the ball 180 degrees on the same axis so that the seam that causes the ball to ‘move’ is located in the ‘front right’ instead of the ‘back left’. Now that seam is going to cause separation on the other side of the ball and cause it to move to your left. So a pitcher that has the ability to throw a SSW pitch can chose which direction it will move by placing the ‘steady seam’ either in the front quarter or the back quarter of the ball. It is mechanically the same pitch, thrown the same way with the same spin/axis, the only difference is where he locates the ‘steady seam’ that does the work, in the ‘front quarter’ or the ‘back quarter’ of the ball. I hope I have explained this clearly, simply flip your ball on a rod 180 degrees and you’ll see what I mean.
There are several MLB players doing this currently. The best example that I have pointed to often is Kyle Hendrick’s 2 changeups.