Is this a bug in Total Spin? 2024 is lowest TS ever shown, and BS + SS != TS

[GungHoGolf]

I usually leave Side Spin display set for Axis, which switches the Back Spin display to Total Spin. I get a Total Spin value of 2024 very frequently - it seems to come up any time the back spin is less than 2024, because I NEVER see a Total Spin less than 2024.

Here is a big hook with driver to show you what I mean. First image is showing Total Spin with Axis. Second image is showing same shot with Back Spin and Side Spin displayed.

Is anyone else seeing 2024 Total Spin (and never lower) with driver? And shouldn't Back Spin + Side Spin = Total Spin? In this case, Total Spin is 2024 and Back Spin plus Side Spin is 2652.

I understand there is only one spin axis, so separating BS from SS is sort of an academic exercise, but at the least, SkyTrak should display the actual Total Spin number even if it's lower than 2024, which should happen frequently with a well-fit driver.

Would love input from SkyTrak_Seth on this...

-Ron

[GungHoGolf]

Here is another shot - first image showing Axis view, second image showing BS and SS view:

[FaultyClubs]

... And shouldn't Back Spin + Side Spin = Total Spin? In this case, Total Spin is 2024 and Back Spin plus Side Spin is 2652.

Conceptually yes, but it is a vector summation not an arithmetic one. Think hypotensue of right triangle.

Your examples all correctly have a TS of 2024.

[GungHoGolf]

Conceptually yes, but it is a vector summation not an arithmetic one. Think hypotensue of right triangle.

Your examples all have a TS of 2024.

Okay, help me understand how BS of 1989, SS of 374 can equal TS 2024, and also BS of 1864, SS of 788 can also equal TS 2024? And why do I get 2024 TS at least 25% of my shots (whenever BS is low) and never see a TS lower than 2024?

Edit: your original message said "your examples all show correctly a TS of 2024", which is why I asked for that explanation.

[JackedUpSwing]

sqrt(1989^2 + 374^2) = sqrt(1864^2 + 788^2) = 2023.719

Think of back spin as the Y component and the Side spin as the X component of a vector.

The length of the vector is the Total Spin RPMs. The spin axis is the degrees from the Y axis that vector points.

It seems the skytrak is getting confused on the total spin, but still able to measure the spin axis. So it takes the spin axis and does some math with the total spin to give different backspin/sidespin numbers derived from different spin axis' and the same 2024 total spin.

Edit: Total spin^2 = Backspin^2 + Sidespin^2

[GungHoGolf]

Thanks JackedUpSwing, that's very helpful. Looking at Seth's response below, it looks likely that 2024 is the lowest possible spin number that the hardware provided by Rapsodo will detect. If that's the case, SkyTrak's software must be, like you say, backing out the backspin and sidespin numbers from that total spin number as proportions of the total.

[GungHoGolf]

This is another user's data from another thread here which I found after posting this topic. I think we can agree it's statistically impossible we're both seeing so many 2024 total spin numbers:

[trumb1mj]

Looks like a bug to me. You can expect a fix in the next 10+ months.

[SkyTrak_Seth]

I'm still investigating this with Rapsodo based on the other thread in here, but it looks like 2024 may be the low threshold of what they are able to capture for total spin. I hope to understand more soon.

[GungHoGolf]

If that ends up being true, it explains everything I'm seeing in the data. It also explains, at least in part, artificially low driver distance for guys like me who are trying to get total spin down to the 1700-1900 range with 15-17 deg launch to maximize total distance.

Doing some back-of-the-envelope math: 2024 RPM is about 34 revs per second. Assuming your two photographs are taken 5ms apart, that would be 0.17 revolutions between photo 1 and photo 2, or 61 degrees of change in the ball logo or whatever else your algo is keying on, so there should be plenty of leeway to pick up slower spin rates. Fingers crossed that this will be a simple fix.

[GungHoGolf]

Here is what the low threshold of 2,024 total spin looks like over 1,637 driver shots taken by a client of mine. Except for one outlier at 1,352 total spin, which is probably a mis-calc of some sort, the distribution has a hard cut-off at 2,024 which is readily visible:

[LEO MODE]

Very interesting thread as I never heard/saw this issue.