Relationship between Orientation and gyro for Seam-Shifted Wake pitches: Post 52

We have previously stated that the “Looper” works for efficient (no gyro) pitches, and that the “laminar express” and “discoball” changeup require some gyro. I’ve been advocating that folks try the looper since I have been unable to tell them how much gyro they need for the other pitches. But while working on our post on Orientation, it occurred to me that there is a hint in there. It started with this photo that I tweeted some time ago.

The left ball is my looper demo and the right is the discoball. I have the axis straight up on the looper and tilted back a bit on the discoball, and I believe that is how they would look from above while they moved upward on the page toward home plate.

Both of these pitches experience a seam shifted wake. We have laboratory data for the Looper, and we have Stephan Strasburg demonstrating the discoball frequently. I have written about it quite a lot and we also have a video on Youtube.

A Looper Changeup looks like this from above. We call it a looper because the seam on top makes a loop around the pole, and it is that seam that knocks the flow off the ball on top and shifts the wake.

For the Discoball, the seam is better aligned with the axis of rotation and it is clearly visible in video, such as the one below from Rob Friedman.

That pitch has a gyro component (The top of the ball is tilted back toward the pitcher). Unfortunately, we can not throw that in our lab.

Each of these Seam Shifted Wake pitches work when the seam near the top of the ball causes the Boundary Layer to separate there instead of 18 degrees past the top, which is the normal position for turbulent flow.

But, I don’t think the two pitches have the same potential for break. I’ve repeated the first picture below but I have highlighted the area affected by the seams in both cases. The Looper’s seam makes a tight loop around the pole and cannot affect as large of a lateral area as the Discoball can. Basically, the Looper is only affecting the middle (left to right) of the ball. It will help you to understand what I mean if you imagine spinning these two baseballs on that axis. In both cases, there is a seam in the lateral center of the ball on top about 3/4 of the time. But for the Discoball, it’s spread over a wider lateral area.

We know the Looper works with 0 gyro (100% efficiency) because that is what the WSU cannon that launches the ball does. Rapsodo confirms this, but since the cannon cannot throw gyro, we know we have an efficient pitch.

So, how much gyro does the Discoball need to get that seam on the top of the ball? In our recent post on Orientation, we noted that the Discoball has 17º of Z rotation while the Looper has 39º. I believe that difference (22º, give or take) is the amount of gyro required for the Discoball (or the Laminar express, which works the same way). Stras may not have that much on the Discoball initially, but as the ball falls, it gains gyro. Which means that the more that pitch falls, the faster it falls. Pretty neat.

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