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**3on3putt** · 01-02-2021, 04:17 AM

I just got done playing tgc and after the round I hit a few 7 irons on the skytrak range to see what kind of spin numbers I would get. Like I said previously, I generally don't pay much attention to spin unless I'm hitting driver. I hit 5 balls and they were all between 6100 and 6400. That was with a taylormade tour response ball and titleist AP2 iron off a rawhide mat.

**Rogala** · 01-02-2021, 06:55 PM

So, I didn't hit off of a short tee (as was suggested) because I could not...for the simple reason that I didn't have one yesterday and couldn;t get one because my club was closed for New year's Day. I was able to go over to my club today and get one, and I will hit some balls later.

I will try it off the tee and then report back on what the "spin loss" is with my exact mat.

Any thoughts about why the 1/2" of extra height casued by the feet on the metal case was causing the spin numbers to be 1,500 to 2,000 RPMs too low versus the RPM numbers with the feet removed ?? Just trying to understand SkyTrak a bit better.

**Rogala** · 01-02-2021, 07:48 PM

Originally posted by 3on3putt View Post

I just got done playing tgc and after the round I hit a few 7 irons on the skytrak range to see what kind of spin numbers I would get. Like I said previously, I generally don't pay much attention to spin unless I'm hitting driver. I hit 5 balls and they were all between 6100 and 6400. That was with a taylormade tour response ball and titleist AP2 iron off a rawhide mat.

Interesting...

Last night, I went back and pulled all the data I had from every club and ball fitting session I have done since 2012. Trackman or other radar-based systems were used for most of these (maybe 3/4 of them?) and the other session were done using either camera-based or combo-based (camera + radar) launch monitor systems. All were done at professional facilities, including two "high-end" facilities known for catering to elite golfers.

All of these sessions I went over were done indoors hitting off of a mat, and my 7-iron back "average backspin rates" for every one of these was reported to be between 5,800 to 6,300 RPMs. With the 5000RPM band being due to some combination of different golf balls, different mats or my swing being different from one session to the next. My point is the range is very consistent for indoor sessions when hitting off of mats. (Note: I also have some trackman data from one other session where I hitting off driving range grass during a PXG fitting...and "yes" my spin rates were higher that day.)

Note: That range of 5,800-6,300 RPMs is, overall, probably a little lower than many other players might have with their 7-irons. It has been my belief that I have always generated a bit less back spin on my shorter irons than what might be expected of a low handicapper. I say this based on my IRL perfomance with my short irons...meaning I was never known for spinning wedge shots backwards, although I can usually stop my wedge shots from good lies after one or two hops....my slightly lower than expected backspin rates are likely due to some idiosyncracy of the way I deliver the clubhead and my clubhead speed itself.

All that being said, the SkyTrak numbers from a mat yesterday are still way below these figures, so it looks like something is still off on my SkyTrak set-up...mat or no mat. As I wrote, I am going to try a short tee today for comparison....but, again, all the above figures from 2012 onward were off mats.

**Rogala** · 01-02-2021, 08:00 PM

Originally posted by Mirek_62 View Post

Backspin has a significant effect on carry distance. You can check how it affects it here

FlightScope Trajectory Optimizer

https://flightscope.com/products/trajectory-optimizer/

FlightScope's Trajectory Optimizer is a golf ball flight trajectory program. The program will plot the flight of the ball in real time after the user's input of the initial launch conditions of the golf ball. Based on scientific algorithms, FlightScope's Trajectory Optimizer will help you find your optimal ball flight trajectory to add distance to your golf shots.

The type of mattress has a great influence on the backspin. It is enough that the contact of the club head is earlier (even minimal) with the mattress than with the ball and the backspin drops dramatically.

OK, that was a FANTASTIC little link.

I plugged in some numbers from various club and ball fitting sessions over the last 8 years (all done indoors using mats) and all the readings from the optimizer page were right on the money with the data I was presented in those sessions.

I then kept all the other variables the same, but lowered the 7-iron backspin RPM rates about 2,000 RPMs (from the 6K range to the 4K range) to match what I am seeing on my latest SkyTrak numbers off of a mat from yesterday, and BINGO...the extra length which SkyTrak is reporting (what I termed the "inflated yardages") are right there.

This strongly suggests to me that we are indeed talking about a backspin reporting issue...either due to my set-up, or some other problem.

I made sure to have the logo on the ball pointing at the camera yesterday...but I will check out some other set-up tips from Gungho and others immediately.

**Rogala** · 01-02-2021, 08:30 PM

Originally posted by Bubba22 View Post

Here is a search on some threads dealing with low spin and Skytrak.

https://www.google.com/search?q=skyt...obile&ie=UTF-8

Thank you !!! The below thread in particular dealt with low 7-iron spin rates in the same exact range as I am seeing...very helpful to know that others have experienced this.

https://golfsimulatorforum.com/forum...low-spin-rates

This comment from a different "low spin" thread on this forum was also what I am seeing:

04-12-2018, 03:52 PM
Originally posted by clark55810 View Post
I am seeing exactly the same thing...

I have had my ST since last June and didn't really follow spin numbers since I was looking mainly at carry distance, which seems to be correct.

With the new optimization measures, it was very obvious that my spin on my 8-iron is about 1/2 of what the standard it. Kind of weird that my other numbers look good (ball speed, carry, etc) which doesn't correlate.

Same here. If the carry and direction is accurate, I'm some what okay with that. But I still would like to know the true (or close) backspin.

If I need to make changes in my SkyTrak set up to get accurate spin numbers, then so be it...just want to figure out how to do it...or have someone else enlighten me.

All these threads make me realize that this has been a question that many other people have been raising (now and again) for years now....

**3on3putt** · 01-02-2021, 09:25 PM

Do you have any other mats lying around that you could experiment by hitting off of? Different mats produce different spins so I wonder if your mat might be the common denominator here.

**RAH5** · 01-02-2021, 09:46 PM

I took the advice above and deep cleaned my clubs/grooves/etc.

Spin went up significantly and carry down accordingly.

Still generally in the low 5’s, probably a bit low, but I’m attributing it to the mat.

Overall I’m very happy with it. I’m loving the feedback and the range session numbers.

Thanks all!

**Rogala** · 01-02-2021, 10:17 PM

Originally posted by 3on3putt View Post

Do you have any other mats lying around that you could experiment by hitting off of? Different mats produce different spins so I wonder if your mat might be the common denominator here.

I do have a different mat I could try...and will probably do so later this evening. In the mean time, please see my next data set which was taken off of a short tee. It does NOT seem to be a mat issue based on that data. Posting it shortly.

**Rogala** · 01-02-2021, 10:53 PM

Please see the attached raw data with a 7-iron off of a short tee for 10 "good shots". I used this to compile a Skytrak comparison for hitting off of my mat vs. hitting off of a short tee.

I have also attached an Excel spreadsheet showing data from both SkyTrak (camera based) and Swing Caddie (doppler radar based) for 10 shots I hit yesterday off of a mat, versus 10 new shots off of a short tee today. The systems were used simultaneously to get this data on the exact same swings (10 yesterday and 10 today).

Findings:

1) There was basically no difference in backspin number off my gel-insert mat vs. a tee. SkyTrak showed an average backspin of about 4,000 RPM for both a mat and a short tee. Swing Caddie showed an average backspin of about 6.300 for both a mat and a short tee. Looks like Gel-insert mat really are a damn good way to go.

2) I did lose ball speed in hitting off the mat vs. the tee. Both the Swing Caddie and SkyTrak showed a 6 mph loss of ball speed...which resulted in a 4 yard loss of carry per both systems.

3) I marked a few excel boxes in RED to show major differences between the SkyTrak numbers and the Swing Caddie numbers. Backspin RPMs stand out, as do (predicatly per the RPM differences) the shot apex numbers....which are 30+ feet lower per SkyTrak. Am I really hitting it 30 feet lower than I think I do based on my IRL experiecne ??

4) One other oddity is that SkyTrak reported a 4.1 mph loss of clubhead speen when going from a tee to a mat. Swing Caddie reports a 2.4 mph loss of clubhead speed for the same transition. Am I hitting it a little fat off the mat ??

So if it is NOT my mat causing the lowered RPM numbers, then what is the issue ?? Something in the device set-up ??

Also attached is a photo of my "short tee" set up.

P.S. As an odd aside, I kind of feel like the SkyTrak yardage numbers (which are a bit lower overall) are actually closer to my IRL despite the backspin numbers appearing to be way too low. How that is possible, I have no idea....but this RPM issue is a fascinating one.

Attached Files

**RAH5** · 01-02-2021, 11:11 PM

I don’t have anything further to add other than we have the Net Return as well and love it.

**3on3putt** · 01-02-2021, 11:59 PM

Does the swing caddie measure side spin? If so, how do those compare to the skytrak side spins?

**Morini** · 01-03-2021, 01:18 AM

Unless there has been an update I am not aware of, I don't think Swing Caddie measures any type of spin. My understanding is that it just estimates it from trajectory and ball speed.

It is possible that I am wrong about the SC spin, but I don't think so. No way skytrak gets spin wrong by that amount consistently. Thus, disregard the SC and ST spin differential.

Second, all the shots used in the Skytrak were calculated on "back spin" not spin, so it understates total spin significantly. With that amount of spin axis, not sure if we should use these shots to draw meaningful conclusions. If these were the "good" shots, what is going on? And why were they chosen to be good? Smash? Smash is meaningless as it is estimated. Ball speed? If the face was shut, club was delofted, so ball speed artificially high. Carry? Same argument as for ball speed. Accuracy? Not with that much spin axis.

Rogala, I think you are working too hard and analyzing too much, when the answer is simply that your spin is low. I don't know what is causing it. It often is caused by mat, but if there is no change with tee, I don't know. Whatever you need to do to address this has nothing to do directly with Skytrak. I suggested you bring the skytrak to your next TM4 session.

**3on3putt** · 01-03-2021, 01:33 AM

Originally posted by Morini View Post

Unless there has been an update I am not aware of, I don't think Swing Caddie measures any type of spin. My understanding is that it just estimates it from trajectory and ball speed.

Rogala, if you are going to do such detailed data analysis, you need to have actual data in the first place. It is possible that I am wrong about the SC spin, but I don't think so. No way skytrak gets spin wrong by that amount consistently. Thus, disregard the SC and ST spin differential.

Second, all the shots used in the Skytrak were calculated on "back spin" not spin, so it understates total spin significantly. With that amount of spin axis, not sure if we should use these shots to draw meaningful conclusions. If these were the "good" shots, what is going on? And why were they chosen to be good? Smash? Smash is meaningless as it is estimated. Ball speed? If the face was shut, club was delofted, so ball speed artificially high. Carry? Same argument as for ball speed. Accuracy? Not with that much spin axis.

Rogala, with all due respect, you are way overthinking this. Your spin is low, fact. I don't know what is causing it. It often is caused by mat, but if there is no change with tee, I don't know. Whatever you need to do to address this has nothing to do directly with Skytrak. I suggested you bring the skytrak to your next TM4 session.

I was curious about this as well, which is why I asked about the swing caddie side spin (never used one so not at all familiar with them). There's a good amount of side spin on these shots. 7 of the 10 were offline by 12 yards or more .... with a 7-iron. The 3 shots that managed to stay somewhat online all happened to be the 3 shots with the most backspin and had far less side spin. Is the excessive side spin taking away from the backspin count? In other words, shot #3 had just under 4,000 backspin and just under 2,000 sidespin. Should we be interpreting that as more like just under 6,000 total spin? I guess what I'm getting at is if you hit two balls and one is dead straight and the other is a big hook, the hook will probably register as having less backspin, because a large amount of that ball's spin is side spin. So is the excessive curvature of these shots affecting the backspin display?

I am more of a TGC player and less of a Skytrak range rat, so perhaps I'm interpreting Skytrak's display of backspin vs. side spin incorrectly. But that was just my thought upon noticing those side spin numbers.

**Rogala** · 01-03-2021, 03:35 AM

Originally posted by Morini View Post

Unless there has been an update I am not aware of, I don't think Swing Caddie measures any type of spin. My understanding is that it just estimates it from trajectory and ball speed.

It is possible that I am wrong about the SC spin, but I don't think so. No way skytrak gets spin wrong by that amount consistently. Thus, disregard the SC and ST spin differential.

Second, all the shots used in the Skytrak were calculated on "back spin" not spin, so it understates total spin significantly. With that amount of spin axis, not sure if we should use these shots to draw meaningful conclusions. If these were the "good" shots, what is going on? And why were they chosen to be good? Smash? Smash is meaningless as it is estimated. Ball speed? If the face was shut, club was delofted, so ball speed artificially high. Carry? Same argument as for ball speed. Accuracy? Not with that much spin axis.

Rogala, I think you are working too hard and analyzing too much, when the answer is simply that your spin is low. I don't know what is causing it. It often is caused by mat, but if there is no change with tee, I don't know. Whatever you need to do to address this has nothing to do directly with Skytrak. I suggested you bring the skytrak to your next TM4 session.

All good points / questions. Here are some responses / answers:

1) On Swing Caddie and other Doppler Radar units (forgive me if this is already clear to everyone here) - You probably already know that if you are standing near the road, and an ambulance zips by you with its siren on, that the tone of the siren changes as it goes by (getting lower in pitch as it gets further away)...same thing with the whistle of a passisg train. That's the Doppler Effect as demonstrated by sound waves created by the siren/whistle, and your ears serving as the "sensors" which detect interference patterns int he waves due to physical position.

That principle is the key to understanding how doppler launch monitoring technology works. As the ball travels away from the launch monitor (which is both sending out microwave signals and receivng signals which bounce back to the unit) it provides measurable clues as to how the golf ball is behaving in flight via the "interference pattern" created by the golf ball travelling through the original waves. All doppler radar units use a series of sensors to analyze the wave interference pattern caused by the moving ball and then make flight predicitons based on the feedback data. The data is recorded by internal sensors in the unit, and fed into an internal algorithm to spit out things like ball speed, launch angles, etc.

The more high end the unit (like Flightscope or Trackman) then the more sensors and higher resolution you get. A second radar unit in the same launch monitor box can be used to collect club head data and determine its speed, face angle, etc. Combining the two data sets open up the full range of club and ball data. That capability (and the ability to take it outside to the range / course) seems to be what made TrackMan the leader in this space for so many years.

Swing Caddie is a very low end doppler radar unit...and unlike Trackman has only a single radar source (which measures the ball only, and not the clubhead). Unlike Tracknan, it only measures a very few parameters. Ball speed and trajectory are two of the ones it can measure but actual backspin in not.

So how do we know if Swing Caddie is any good at REPORTING an item such as "backspin" if it is not actually measuring it...and is instead only predicting it based on the aforementioned algorithms? Becasue in head-to-head tests versus Flightscope and Trackman, Swing Caddie somehow mangaes to consistently come within 1.5-5% of the numbers that these much higher-end machines report. If you trust Trackman and Flightscope, then you can trust Swing Caddie to within a 1.5-5% margin of error...not on every individual shot mind you, but definitely on an averages over a number of shots.

2) My own backspin numbers as cited in this thread were collected over an 8 year period in mutiple fitting sessions (all hitting off mats), and every one of them shows backspin averages for a 34 degree 7-iron (2 degrees strong vs. classical numbers) between 5,800 RPMs and 6,300 RPMs (which, I agree, might be a wee bit low vs. other players of similar handicap).

The fact that my cheap little Swing Caddie unit comes up with numbers in that same range day-in and day-out is very heartening...and inspires confidence in that unit.

Now, maybe those numbers are BS...and maybe the Trackman units and even the other camera-based units which took those measurements over an 8 year period did not really provide accutate backspin data. Maybe the new SkyTrak unit is 100% accurate reporting RPM figures which are about 2,000 revs lower. Well, Inguess that it's theortetically possible that all other systems I tried before sucked, but the "experts" seem to say differently...at least when when it comes to Trackman...and the fact that Swing Caddie gets within 1.5-5% of those numbers is also fairly impressive in the eyes of most reviewers.

Note: In my own experiecne, I would say that Swing Caddie is a few hundred RPMs off, but that it is cCONSISTENTLY off, and mostly in one direction....meaning that it is not 1,000 RPMs off on one solid swing, and then only 200 RPMs off on the next one.

3) You also asked "If these were the "good" shots, what is going on? And why were they chosen to be good?"

I chose them only on feel, sound, and on the resulting shot hitting a 1 foot sqaure target in the dead center of my hitting net (marked by a green square held there by velcro straps)...not on any recorded data from the unit. Any ball which hit the target and felt and sounded solid to me was recorded. It took me 14 shots yesterday to come up with the 10 shots I shared. It took me 16 shots today (when hitting off the low tee) to get 10 "good shots". I was hitting the ball with an easy swing yesterday, but today I really took a rip at these shots as the low tee gave me a bit more confidence. The numbers recorded by SkyTrak happen to validate my own fell, hearing and vision when it came to hitting that target, BTW. Note: You can see that one of the "good shots" from yesterday gave some wonky backspin numbers per SkyTrak, but I left it the mix because it felt and sounded like a pure shot to me, and it also hit the 1 foot square target in the center of my hitting net.

4) Look, SkyTrak should theoretically be far better than a low end doppler radar unit like Swing Caddie at reporting backspin, as it is taking actual measurements based on the spinning ball itself..not making predictions based on secondary measurements. That is one of the reasons I bought one.

I am quickly learning that it is only as good a tool as its set-up (which is fine, and to be expected) and that it is clearly very sensitive to positioning. The experience with the leveling feet as the root cause of a 1,000 to 2,000 RPM difference has taught me that already.

It is currently STILL reading 2,000 RPMs lower than data collected over 8 years worth of previous ball and club fitting sessions however...and also 2,0000 RPMs lower than my cheap (but 1.5-5% accurate vs. Trackman and Flightscope) doppler radar unit on the same exact shots hit off both my mat and off a low tee (as suggested by users on this forum).

That's a fact...and I posted the data to prove it. Furthermore, several other threads mentioning low RPMs also exist in this forum...meaning that other users have experienced the exact same thing I am experiencing.

5) Conclusion: Something really does seem to be amiss here. It does not seem to be my hitting mat as today's test demonstrates. It might be either in my physical set up of the unit, or the lighting, or the position of the golf balls, or (less likely) internal damage or some other variable we have not covered. If it is my set up or the lighting or the ball positioning, or "whatever" then I really do want to correct this so that I can rely on the RPM data being generated and not just "pretend it doesn't exist".

Anyway, I would at least try and get the unit operating as accurately as possible...hope that makes sense.

**Rogala** · 01-03-2021, 03:53 AM

Originally posted by 3on3putt View Post

I was curious about this as well, which is why I asked about the swing caddie side spin (never used one so not at all familiar with them). There's a good amount of side spin on these shots. 7 of the 10 were offline by 12 yards or more .... with a 7-iron. The 3 shots that managed to stay somewhat online all happened to be the 3 shots with the most backspin and had far less side spin. Is the excessive side spin taking away from the backspin count? In other words, shot #3 had just under 4,000 backspin and just under 2,000 sidespin. Should we be interpreting that as more like just under 6,000 total spin? I guess what I'm getting at is if you hit two balls and one is dead straight and the other is a big hook, the hook will probably register as having less backspin, because a large amount of that ball's spin is side spin. So is the excessive curvature of these shots affecting the backspin display?

I am more of a TGC player and less of a Skytrak range rat, so perhaps I'm interpreting Skytrak's display of backspin vs. side spin incorrectly. But that was just my thought upon noticing those side spin numbers.

I found the "offline" numbers today interesting, as each shot I posted hit a 1 foot square target in the dead center of my hitting net (which is about 9 to 10 feet away from the tee off which I was hitting).

The tee itself was offset to the right of the net center, so I angled the SkyTrak unit to the left a bit to compensate. Not sure if that had anything to do with the visual representation showing little draws every time, or if they impact the the side spin calculations.

Yesterday's shots seem to have had very little side spin vs. today's numbers....but, maybe I just learned that I have a tendency to hit little hooky pull-draws off a short tee vs. off a mat ?? I suppose that this knowledge alone, if accurate, would help me on medium length par 3s. A SkyTrak success story on day 3. :-)

That being said, someone else advised me to turn on the "spin axis" feature on the session settings, which I forgot to do before I posted, as this supposedly gives a more accurate representation of total spin (at least per their comments). Attached is the same shot data with that done...and it does bump up the average "total spin" RPMs by about 300 RPMs...meaning that they are still 1,500 to 2,000 RPMs lower than my historical numbers over the past 8 years. See attached file for that raw data.

I am guessing that something is still off in my set-up or the lighting or the ball position, etc. It was NOT just my mat. Something is making the RPMs read low...just want to get to the bottom of it...typical engineer I guess. :-)

Attached Files

Announcement

Clubhead & Ball Speeds Are Correct...but Yardages Are Hugely Inflated...

Clubhead & Ball Speeds Are Correct...but Yardages Are Hugely Inflated...

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