Opinion-Launch Monitor Algorithms and How they Dupe People

[whumber]

10 minutes ago, Krt22 said:

This is getting a bit into the weeds, but aren't side spin and spin axis directly linked via mathematical formula? Same goes for backspin and axis tilt, the only way to get more back spin is to delivery more dynamic loft. The more dynamic loft you deliver, the lower the spin axis for the same face/path ratio.  But as total spin goes up, so does side spin for the same given spin axis. I am not certain if there are any inflection points in there.

Unless dynamic lie is way off then the loft of the club shouldn't being adding much sidespin, at least not relative to the contributions of face-to-path and gear effect, and those are mostly independent of the dynamic loft delivered to the ball.

[Krt22]

5 minutes ago, whumber said:

Unless dynamic lie is way off then the loft of the club shouldn't being adding much sidespin, at least not relative to the contributions of face-to-path and gear effect, and those are mostly independent of the dynamic loft delivered to the ball.

Trackman's calculator says otherwise. For the same exact FTP ratio, more dynamic loft delivered results in less spin axis. Logically it makes sense, for the same CHS there is some finite amount of energy delivered to the ball. That energy get's broken into the vector sum of side spin and back spin depending on how much dynamic loft is delivered along with the FTP ratio.

 

https://trackmanuniversity.com/StudyroomLesson?ltid=fc009ebf-b21d-4d31-955c-81eb2dde2ce0&ctid=c6d181b1-640b-49cd-88d3-1c21f2ee9203

Edited November 3, 2021 by Krt22

[HiTrajLoSpin]

@Stuart_G and I have disagreed (at length) about the fact that a golf ball cannot have both backspin and sidespin (hint, it can't), but I think that we've finally just agreed to disagree 😀.

 

In short, a sphere can only have one axis of rotation (tilt axis in our discussion); this results in the overall vector for lift forces (due to spin) to then be tilted with respect to the vertical. In physics, this is treated mathematically by picturing the tilted (overall) force vector as the vectorial sum of its corresponding vertical and horizontal force vectors. To make it easier for golfers to understand, this is instead just explained as total spin (overall vector), backspin (vertical vector) and sidespin (horizontal vector).

 

So let's just stick to using total/backspin/sidespin for simplicity.

 

At launch, a ball has a fixed amount of total spin; if its spin axis is tilted with respect to the horizontal, then that overall spin has both backspin and sidespin components, and the trajectory has curvature. However, due to the spin physics discussed above, increasing the total spin (for example, by increasing the club head loft) has to increase both the backspin and sidespin components; that is, backspin can't be increased independently of sidespin (that is, without changing the initial amount of spin axis tilt). 

 

Therefore, the overall result of increasing total spin is to increase flight time (due to more backspin) and curvature (due to more sidespin). What's even more disconcerting, the sidespin continually increases the spin axis tilt, which means that the curvature continually increases as well. I think that we've all seen this ... no, no, no, stop turning 🙃😜

Edited November 3, 2021 by HiTrajLoSpin

[HiTrajLoSpin]

Sorry, duplicate post

Edited November 3, 2021 by HiTrajLoSpin

[whumber]

51 minutes ago, Krt22 said:

Trackman's calculator says otherwise. For the same exact FTP ratio, more dynamic loft delivered results in less spin axis. Logically it makes sense, for the same CHS there is some finite amount of energy delivered to the ball. That energy get's broken into the vector sum of side spin and back spin depending on how much dynamic loft is delivered along with the FTP ratio.

 

https://trackmanuniversity.com/StudyroomLesson?ltid=fc009ebf-b21d-4d31-955c-81eb2dde2ce0&ctid=c6d181b1-640b-49cd-88d3-1c21f2ee9203

I think maybe you misinterpreted what I wrote. "For the same exact FTP ratio, more dynamic loft delivered results in less spin axis." This is exactly the point, FTP ratio/angle is what is controlling the sidespin (along with CHS and impact location); unless dynamic lie is way off, increasing dynamic loft should not increase the sidespin and thus will drive the spin axis towards neutral.

[whumber]

18 minutes ago, HiTrajLoSpin said:

@Stuart_G and I have disagreed (at length) about the fact that a golf ball cannot have both backspin and sidespin (hint, it can't), but I think that we've finally just agreed to disagree 😀.

 

In short, a sphere can only have one axis of rotation (tilt axis in our discussion); this results in the overall vector for lift forces (due to spin) to then be tilted with respect to the vertical. In physics, this is treated mathematically by picturing the tilted (overall) force vector as the vectorial sum of its corresponding vertical and horizontal force vectors. To make it easier for golfers to understand, this is instead just explained as total spin (overall vector), backspin (vertical vector) and sidespin (horizontal vector).

 

So let's just stick to using total/backspin/sidespin for simplicity.

 

At launch, a ball has a fixed amount of total spin; if its spin axis is tilted with respect to the horizontal, then that overall spin has both backspin and sidespin components, and the trajectory has curvature. However, due to the spin physics discussed above, increasing the total spin (for example, by increasing the club head loft) has to increase both the backspin and sidespin components; that is, backspin can't be increased independently of sidespin (that is, without changing the initial amount of spin axis tilt). 

 

Therefore, the overall result of increasing total spin is to increase flight time (due to more backspin) and curvature (due to more sidespin). What's even more disconcerting, the sidespin continually increases the spin axis tilt, which means that the curvature continually increases as well. I think that we've all seen this ... no, no, no, stop turning 🙃😜

The error in your thinking is you seem to be operating under the assumption that increasing delivered loft affects backspin and sidespin equally, which is incorrect.

[Stuart_G]

20 minutes ago, HiTrajLoSpin said:

@Stuart_G and I have disagreed (at length) about the fact that a golf ball cannot have both backspin and sidespin (hint, it can't), but I think that we've finally just agreed to disagree 😀.

 

That's ok, a lot of people don't properly understand the concept of backspin and side spin. 😉

 

 

20 minutes ago, HiTrajLoSpin said:

@Stuart_G and I have disagreed (at length) about the fact that a golf ball cannot have both backspin and sidespin (hint, it can't), but I think that we've finally just agreed to disagree 😀.

 

In short, a sphere can only have one axis of rotation (tilt axis in our discussion); this results in the overall vector for lift forces (due to spin) to then be tilted with respect to the vertical. In physics, this is treated mathematically by picturing the tilted (overall) force vector as the vectorial sum of its corresponding vertical and horizontal force vectors. To make it easier for golfers to understand, this is instead just explained as total spin (overall vector), backspin (vertical vector) and sidespin (horizontal vector).

 

So let's just stick to using total/backspin/sidespin for simplicity.

 

So, refresh my memory, now that you have shown that you fully understand the concept (and definition) of back spin and side spin, what about that do you actually have a problem with?

 

 

20 minutes ago, HiTrajLoSpin said:

At launch, a ball has a fixed amount of total spin; if its spin axis is tilted with respect to the horizontal, then that overall spin has both backspin and sidespin components, and the trajectory has curvature. However, due to the spin physics discussed above, increasing the total spin (for example, by increasing the club head loft) has to increase both the backspin and sidespin components; that is, backspin can't be increased independently of sidespin (that is, without changing the initial amount of spin axis tilt). 

 

OK onto more important stuff.

 

Actually, yes it can.  Or rather it's not that difficult for different impact conditions to result in different tilt of the spin axis.  So that conditional is a bit pointless to the discussion since we are talking about things that do change the tilt axis.  e.g. Assuming a perfect lie angle.  A change in loft will increase backspin w/o increasing side spin (change both the total spin and the tilt of the spin axis).  The side spin comes from the face-to-path - so same dynamic loft but different face-to-path will keep backspin the same, increase total spin and side spin (which also means a change to the tilt axis).    That's just w/o considering gear effect - which can also change either side or back spin independent of each other.

 

Just as the spin axis and aerodynamic forces can be broken into different components, so can the impact dynamics.   With different components of those dynamics contributing independently to the side and back components of the spin.

 

Main point being that it's actually rare that total spin would increase w/o the axis also changing when making any equipment change.

 

 

 

 

 

Edited November 3, 2021 by Stuart_G

[Krt22]

16 minutes ago, whumber said:

I think maybe you misinterpreted what I wrote. "For the same exact FTP ratio, more dynamic loft delivered results in less spin axis." This is exactly the point, FTP ratio/angle is what is controlling the sidespin (along with CHS and impact location); unless dynamic lie is way off, increasing dynamic loft should not increase the sidespin and thus will drive the spin axis towards neutral.

That isn't quite what I said. You said loft doesn't impart side spin, that is correct, but how much dynamic loft is delivered does directly impact spin axis assuming there is some non-zero FTP relationship. With less loft delivered (all else being the same), you get the same side spin component, but less back spin component, thus the axis tilts more.

 

-4 FTP with driver is going to have much more axis tilt than -4FTP with a wedge.

Edited November 3, 2021 by Krt22

[Stuart_G]

1 hour ago, Krt22 said:

This is getting a bit into the weeds, but aren't side spin and spin axis directly linked via mathematical formula?

 

Yes.   Impact determines total spin and spin axis - that's the really complex math.   But breaking that down to separate side and back spin is pretty simple trig.

 

 

1 hour ago, Krt22 said:

 

Same goes for backspin and axis tilt, the only way to get more back spin is to delivery more dynamic loft. The more dynamic loft you deliver, the lower the spin axis for the same face/path ratio.  But as total spin goes up, so does side spin for the same given spin axis. I am not certain if there are any inflection points in there. Assumptions here are  100mph CHS, 0 AoA, -4 club to path ratio. Shot 1 has 14.5* of dynamic loft, shot 2 has 11.5* of dynamic loft. Playing with trackmans calculators I get the following, with the key caveat being they likely hold total spin constant in their offline calculator where you can play with spin axis.

 

From the spin axis/total spin calculators based off Club, path, dynamic loft, AoA.

Shot 1-14.6 spin axis, 2751 total spin, 693 side spin (based on formula)

 

Shot 2-17.9 spin axis, 2182 total spin, 670 side spin

From the offline calculator for spin axis.

 

Shot 1-14.6 spin axis 238 carry,  ~77 ft offline

 

Shot 2-17.9 spin axis, 236 carry, 95ft offline. 

 

Not familiar w/ Trackman's calculators, only flightscope's.   What formula? 

 

Also, not sure what you did with them, but more loft and more spin also mean a change to the ball speed and launch angle - both of which will effect the distances.  

 

But regardless of what formula's are used,  in that particular type of case, the difference in travel time due to different amounts of backspin and launch angles and ball speed - and the resulting ground path of the ball until it returns to the earch - is a pretty complex.  The more lift, the more upward the velocity vector gets and that actually reduces the ground speed - and therefore distance.  Also more spin will mean more drag and a faster reduction of the ball speed - and the more time in the air, the more the spin decays.

 

So even if you had the ball numbers right for the different cases (I can't say if you do or not), you'd have to plot a LOT of data points over different swing speeds and dynamic lofts to be able to come to any conclusions about what the offline trends might be for any given static loft change.   What might turn out to be significant with one players swing, may result in an insignificant amount for another persons.

 

 

Edited November 3, 2021 by Stuart_G

[whumber]

4 minutes ago, Krt22 said:

That isn't quite what I said. You said loft doesn't impart side spin, that is correct, but how much dynamic loft is delivered does directly impact spin axis assuming there is some non-zero FTP relationship. With less loft delivered (all else being the same), you get the same side spin component, but less back spin component, thus the axis tilts more.

 

-4 FTP with driver is going to have much more axis tilt than -4FTP with a wedge.

Ok, fully agree with everything you wrote here.

[Krt22]

8 minutes ago, Stuart_G said:

 

Yes.   Impact determines total spin and spin axis - that's the really complex math.   But breaking that down to separate side and back spin is pretty simple trig.

 

 

 

Not familiar w/ Trackman's calculators, only flightscope's.   What formula? 

 

Also, not sure what you did with them, but more loft and more spin also mean a change to the ball speed and launch angle - both of which will effect the distances.  

 

But regardless of what formula's are used,  in that particular type of case, the difference in travel time due to different amounts of backspin and launch angles and ball speed - and the resulting ground path of the ball until it returns to the earch - is a pretty complex.  The more lift, the more upward the velocity vector gets and that actually reduces the ground speed - and therefore distance.  Also more spin will mean more drag and a faster reduction of the ball speed - and the more time in the air, the more the spin decays.

 

So even if you had the ball numbers right for the different cases (I can't say if you do or not), you'd have to plot a LOT of data points over different swing speeds and dynamic lofts to be able to come to any conclusions about what the offline trends might be for any given static loft change.   What might turn out to be significant with one players swing, may result in an insignificant amount for another persons.

 

 

Trackman has a lot more stuff to get deep into the weeds lol

 

https://trackmanuniversity.com/Library

[HiTrajLoSpin]

@Stuart_G as I explained above, the concept of total spin, backspin, sidespin is only used to more simply explain curvature of a golf ball's trajectory; just like vertical and horizontal force components are used to mathematically treat a tilted force vector. However, backspin/sidespin don't actually exist in physical reality, i.e., a sphere only has a single spin axis and a single value of (total) spin.

 

Spin axis and total spin, in turn, are determined by the combination impact dynamics, both loft and face-to-path; they don't act independently, one (loft) to produce backspin, and the other (face-to-path) to produce sidespin. However, as you noted, different components of impact dynamics can be used to mathematically treat their corresponding contributions to spin axis tilt.

 

Nevertheless, until you understand that a spinning sphere doesn't physically have both backspin and sidespin, only total spin, it's pointless to argue with you further.

 

 

 

[Stuart_G]

16 minutes ago, Krt22 said:

Trackman has a lot more stuff to get deep into the weeds lol

 

https://trackmanuniversity.com/Library

 

Been there but most of the ones I ran across were either oversimplifactions (for educational purposes) or didn't do very well defining the underlying algorithms or assumptions.

[Stuart_G]

11 minutes ago, HiTrajLoSpin said:

@Stuart_G as I explained above, the concept of total spin, backspin, sidespin is only used to more simply explain curvature of a golf ball's trajectory; just like vertical and horizontal force components are used to mathematically treat a tilted force vector. However, backspin/sidespin don't actually exist in physical reality, i.e., a sphere only has a single spin axis and a single value of (total) spin.

 

Of course it's a mathematical simplification.   Engineers and physicists are lazy when it comes to math.  But that simplification is how those terms are defined.  The use of those terms has never meant or even implied a physical reality of two separate spin axis, only a mathematical reality.  At least not by anyone who actually knows what they are talking about.

 

Edited November 3, 2021 by Stuart_G

[HiTrajLoSpin]

4 minutes ago, Stuart_G said:

 

Of course it's a mathematical simplification.   That's how those terms are defined.  But the use of those terms has never meant or even implied a physical reality of two separate spin axis, only a mathematical reality.  At least not by anyone who actually knows what they are talking about.

 

You seem to agree that a spinning sphere only has a single physical spin axis, but then try to argue that it can have both physical  backspin and sidespin, which in turn, implies that it has two separate spin axes. 

 

Also, please refrain from any more condescending remarks ... I know what I'm talking about.

[Stuart_G]

12 minutes ago, HiTrajLoSpin said:

You seem to agree that a spinning sphere only has a single physical spin axis, but then try to argue that it can have both physical  backspin and sidespin, which in turn, implies that it has two separate spin axes. 

 

I never argued that they were physical.  I argued they were real and exist - in the same way that vector math is real and exists.   The point being that there is not any inherent implication of physical reality in the definition of those terms so therefore there is no such implication in the proper and correct usage of those terms.

 

12 minutes ago, HiTrajLoSpin said:

Also, please refrain from any more condescending remarks ... I know what I'm talking about.

 

Sorry for the misunderstanding, but I wasn't referring to you.   I was talking about the people that actually use that term thinking it does mean there are two separate physical axis.  There are people out there that do believe that - which is what started this whole mess of "there is no side spin and back spin" in the first place.  Started by people who understood the reality of the spin, but did not understand the terminology.

 

Edited November 3, 2021 by Stuart_G

[HiTrajLoSpin]

17 minutes ago, Stuart_G said:

 

I never argued that they were physical.  I argued they were real and exist - in the same way that vector math is real and exists.   The point being that there is not any inherent implication of physical reality in the definition of those terms so therefore there is no such implication in the proper and correct usage of those terms.

 

Now I finally understand the underlying basis for our difference in opinions ... to me real and exist implies physical !

 

Thanks!

Edited November 3, 2021 by HiTrajLoSpin

[Krt22]

2 hours ago, Stuart_G said:

 

Of course it's a mathematical simplification.   Engineers and physicists are lazy when it comes to math.  But that simplification is how those terms are defined.  The use of those terms has never meant or even implied a physical reality of two separate spin axis, only a mathematical reality.  At least not by anyone who actually knows what they are talking about.

 

I resemble that statement!

[ThinkingPlus]

4 hours ago, Stuart_G said:

 

Of course it's a mathematical simplification.   Engineers and physicists are lazy when it comes to math.  But that simplification is how those terms are defined.  The use of those terms has never meant or even implied a physical reality of two separate spin axis, only a mathematical reality.  At least not by anyone who actually knows what they are talking about.

 

Hey, hey, hey watch it with throwing us physics majors under the bus.  STEM folks got feelings too (we really don't, but it’s fashionable these days so...).  LOL!

[hammersia]

17 hours ago, HiTrajLoSpin said:

 

 

Therefore, the overall result of increasing total spin is to increase flight time (due to more backspin) and curvature (due to more sidespin). What's even more disconcerting, the sidespin continually increases the spin axis tilt, which means that the curvature continually increases as well. I think that we've all seen this ... no, no, no, stop turning 🙃😜

 

The term you are looking for is Rifle spin 🙂 

[herdtlocker]

TXG just posted a video reviewing the new Titleist RCT balls, and in the second half of the video, they talk about the exact subject of GCQ and how it overestimates carry on low spin shots. Results clearly show that.

 

[clevited]

On 11/4/2021 at 5:08 PM, herdtlocker said:

TXG just posted a video reviewing the new Titleist RCT balls, and in the second half of the video, they talk about the exact subject of GCQ and how it overestimates carry on low spin shots. Results clearly show that.

 

 

That was a good video for an increasingly popular fitter to post.  Hopefully it will help inform avid golfers of the limitations of LMs and differences in their algorithms for the next time they get fit.  Good to be armed with this knowledge imo and understand that that 1400 spin, 16 degree launching driver they are hitting a massive distance over their old driver isn't real, nor is it playable on the course in reality.

Edited November 9, 2021 by clevited

[clevited]

Just a curiosity.  Do any of you that have Trackman, or GCQuad or what have you, have any ability to test a few shots in the real world?  Ideally you live in a warm climate, have access to a large practice range where you are able to go out and have someone laser you from a ball's landing spot, do it on a very calm day and record temp, humidity and wind direction (if any at all).  It will be some time before I am ever able to do such a thing to the degree I would want to, so it would be cool to see some LM owners able to do some small independent tests.

Edited November 9, 2021 by clevited

[RCGA]

Here's another head scratcher. Ian at TXG plays #12 at Augusta on a GCQuad at varying lengths (135-225y). He hits maybe 12 shots and not only goes 100% GIR but has a few birdie putts inside 10ft. In real life he might hit maybe 6 of 12 greens from those distances? 

 

https://www.youtube.com/watch?v=FgtHUIPxVgA

 

[Caper33]

1 hour ago, RCGA said:

Here's another head scratcher. Ian at TXG plays #12 at Augusta on a GCQuad at varying lengths (135-225y). He hits maybe 12 shots and not only goes 100% GIR but has a few birdie putts inside 10ft. In real life he might hit maybe 6 of 12 greens from those distances? 

 

https://www.youtube.com/watch?v=FgtHUIPxVgA

 

He hit 20 shots in that video so they only showed the shots that hit the green.  Although I tend to agree, it seems pretty forgiving!

[whumber]

1 hour ago, RCGA said:

Here's another head scratcher. Ian at TXG plays #12 at Augusta on a GCQuad at varying lengths (135-225y). He hits maybe 12 shots and not only goes 100% GIR but has a few birdie putts inside 10ft. In real life he might hit maybe 6 of 12 greens from those distances? 

 

https://www.youtube.com/watch?v=FgtHUIPxVgA

 

Don't forget that what makes 12 so difficult is not just the layout of the green but that you cannot tell what the wind is doing...at least in real life. Playing it on a simulator takes away that aspect.

 

EDIT: OK,just watched the video and that's not Augusta it's The Farms.

Edited November 14, 2021 by whumber

[RCGA]

6 minutes ago, Caper33 said:

He hit 20 shots in that video so they only showed the shots that hit the green.  

 

Removing bad shots (40%!) from a club review/overview is like taking mulligans and counting that score towards your handicap. 

[RCGA]

18 minutes ago, whumber said:

Don't forget that what makes 12 so difficult is not just the layout of the green but that you cannot tell what the wind is doing...at least in real life. Playing it on a simulator takes away that aspect.

 

The green is like 12 yards deep. He's hitting within an 15x15 foot circle....from 135y to 225y. Even if you remove these 8 mysterious mulligans, that's some seriously world class ball striking