Rapsodo 1.0 and Seam Shifted Wake pitches: Post 48

I’ll start right out by saying this post is not a criticism of the Rapsodo technology. I think what these folks have provided for the price is pretty amazing (and I’m really geeked about their new camera, which looks like a game changer) But, like any technology, it has limits, and I am hoping to learn what we can do within those limits to detect Seam Shifted Wake (SSW) pitches.

If you are new to SSW pitches, See Post 34, 36, 37, 41 and others.

In a recent test, we fired two different SSW pitches. In both cases, the tilt was 3:00, the speed 90 mph and the RPM around 1200. So as far as Rapsodo is concerned these pitches are identical. Because of seam effects, they have different break, as shown in the plot below. I will explain this pitch in a future post, but for now, I just want to talk about the Rapsodo results.

Figure 1: Rapsodo pitch location of 2 different SSW pitches with identical spin axis, RPM and speed.

We made this plot by digitizing the pitch locations from the Rapsodo report. Rapsodo 1.0 does a very solid job with the pitch location, which makes it a really good tool for these studies. But, it says the break for all of these was the same which is clearly not true.

My understanding of how this unit works is that speed is determined by radar while the axis, RPM and location are measured by the camera as the ball arrives. Everything else that Rapsodo reports is based on a Magnus model, which cannot account for the seam effects. The plot below shows the derived release parameters for these pitches. The x axis is pitch number. We threw about 12 of each.

Figure 2: Rapsodo 1.0 release metrics. The closed symbols correspond to the red triangles in Figure 1 while the open symbols correspond to the green. Units are inches or degrees.

Here is how Rapsodo describes those metrics.

Since that text is small, let me retype the important one.

Release angle (green diamonds):

Vertical angle of the ball leaving the pitcher’s hand where up is positive (higher pitches or pitches with a large amount of negative vertical movement) and downward angle being negative (pitches lower in the zone or traditionally higher positive vertical break).

It’s easy to see a distinct change in the Release Angle for the two pitches. Since one pitch arrives lower, Rapsodo interprets it as being thrown more downward (not that it was thrown at the same angle as the other pitches).

So the release angle is the telltale for a SSW pitch that breaks or upward due to the seams. Here is the question: Is your release consistent enough that you could detect this change? If you are a pitcher and you have a 1.0, I’d love to see your Release Angle data for the same pitch.

Somewhat ironically, the 2.0 unit may not be as good for this purpose since it measures the spin part way between release and the plate. It must have to use a Magnus model forward and backward. But I’ve never used one and I could be wrong.

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