Just a bit dissapointed -- Sim Golf will never be "real"

[GMR]

Hi All,

So after having wanted a golf sim for a very long time now, I finally took the plunge and bought a skytrak a couple weeks back. I used to play regularly in an indoor league on AboutGolf simulators so I was pretty familiar with all the positives and negatives of simulator golf, and was very excited about using the Skytrak to improve my game. I aologise if this comes across as overly negative, as that's not really my intent, but despite being very familiar with indoor golf I've discovered something that I wish I had known before I bought my setup. Not that I wouldn't have done exactly the same, but I just feel like I didn't have the full picture before making the plunge.

So the first thing I will say is I'm actually very impressed by the unit itself. For the cost, I think that the data I'm getting out of it is of extremely high quality. I will happily say that it is absolutely hands-down an improvement on the AboutGolf monitor. First of all the flexibility to use your own balls--and get reasonably accurate spin data doing so--is HUGE, as the AboutGolf makes you use these ridiculous marked balls that don't really spin and, as I found out, are actually lighter than real balls and are therefore subject to crack while using them... Also I think to compensate to the non-real balls, the ball flight model in the AboutGolf is really wonky and would always give me very unrealistic ball trajectories, even if the eventual carry distance was somewhere near correct.

With the Skytrak I really don't doubt the veracity of the data I'm getting at all. Ball speeds, trajectories, mishits--everything seems on point. I'm punished for bad shots and good shots go just about how I'd expect them to. Just about.

So last night I decided to really dig into my numbers and see how I stacked up. Fortunately, my ball speeds are actually pretty much in line with the PGA tour average, so it's a pretty apples-to-apples comparison vs the published Trackman charts showing tour averages by club. Going through my #s club by club, I was pleasantly surprised to see things pretty much in line in terms of ball speeds, but the two numbers that jumped out to me were 1) launch angle and 2) spin rate.

For every club I hit, my launch angle was consistently 2-3* higher than the tour average. Interesting, I thought, but hey I can buy it because we know a number of those guys use a lot of shaft lean to really deloft the clubs and hit them further. But wait...why are my carry distances then actually slightly FURTHER than theirs (e.g. 7i: 180yds vs 172yds, 5i: 204yds vs 194yds, 3h: 231yds vs 225yds)? This is in the standard Skytrak range with altitude set to 0 and no silly boosts on, and ball speeds pretty much in line, so shouldn't be any funky business with the calculations.

Then I noticed the spin. A good 750-1,500 lower than tour average with every club. Before you ask this is using virutually brand new premium balls (Srixon Z Star). OK well I play clubs with shafts that are really stiff--almost on the border of being too stiff for me--so it would make sense that I might have lower spin numbers. But unless I'm just very shallow into the ball (which I never have been) those launch angles and those spin numbers just weren't adding up. If you add to that that I tend to be a low-mid trajectory guy on the course, and these numbers would imply I'm hitting high flat moonballs (110ft peak height roughly according to the flightscope trajectory optimiser), something just wasn't right.

That's when I found this article: https://blog.trackmangolf.com/mats-v...ts-difference/

Turns out the numbers I'm getting from the Skytrak are most likely, as I imagined, on point. Wouldn't have mattered if I had bought a GC2, Trackman, or any other contraption that measures ball data... The numbers were wrong because the ball flight was wrong, because I was hitting off a mat instead of grass. Basically every time I hit the ball off my Fiberbuilt mat, it's as if I'm hitting from a flyer lie in the rough. Which is great if you want to practice hitting from flyer lies, but not so great if you want to get a precise view on your "stock" distances and ballflight from the fairway.

So that's really it. I know it's a bit nitpicky, but I was really excited to really dial in my distances using my real clubs and my real balls all winter in my newly built mancave. And while the Skytrak will still provide me some great feedback and will still be tons of fun to play with, that level of precision that I was hoping for in terms of "real" data just isn't going to happen, which makes me just a little bit sad.

Thanks if you managed to make it this far, and will welcome your feedback.

[BadEddieKit]

Ya id say its a combination here of ball and mat. In my experience the srixon's you are using don't spin as much as other balls like Bridgestone E5's or Pro V1"s. Also it sounds like the Fiberbuilt is allowing you to get under the ball moreso than real turf, or other mats would. Might wanna look at changing one or both for desired results.

[Clevited]

I just thought of another way one can imagine what is happening, its essentially a thought experiment.

Picture a golf ball sitting on a smooth marble floor. You step on it with a grippy rubber shoe and then rock your foot to the side to release all that stored energy and shoot the golf ball out like a bar of soap with as much spin as your weight can create. Now picture doing the same thing but with the ball sitting on sand paper on top of the marble floor. You are not going to be able to create nearly as much spin. Now imagine the same scenario but the ball is sitting on a rubber mat. Even less spin. I would also imagine it would take off at a higher launch angle.

You really have to sit and imagine those things and how the ball would react (one could even test it easily enough), and even though the act of hitting a golf ball is so seemingly different from what I described above, I feel that the underlying physics are basically the same. Its a way to think about the basic problem while eliminating extra variables that might make the problem worse or better. I think it can more simply explain why the launch angle spin can change so much given all thing's are equal except the surface.

Give that thought experimental a go, I feel like it works and would be proven with a test but of course its just my perhaps flawed way of looking at it.

[Clevited]

If you could find one of those articles I would love to give it a read. I am open to finding my thoughts to be completely wrong, these are just my best guesses given what I can find out there for evidence as well as what I can imagine in my head to make sense of it all.

I found a thread about this issue. I feel the Agusta guy gave in too early to the others. I feel he was on to something, and he was a civil engineer, I am a mechancial engineer. While the ball does not get squashed against the ground as many envision pinching or compressing the ball to mean, I do firmly believe the ball interacts with the ground enough to cause some significant change to spin and launch angle. My examples above are very extreme representations of what I feel is happening on a much smaller scale.

https://thesandtrap.com/forums/topic/15607-ball-actually-pinched-against-ground-or-not/

[inorkuo]

the ball's center of mass goes upward at the moment of impact. no doubt about it, but look at this video frame by frame starting at 25s. look at what happens to the tee. the ball starts to rise but because it gets smashed into an oval, the tee gets pushed down into the ground. there's your ball/turf interaction. I would guess this happens with long irons and maybe mid irons.

https://youtu.be/OStvJf9qdUA?t=24s

[Clevited]

Edit again as I misunderstood the above post: (I think in that particular case, the curvature of the tee where it is touching the ball and then the ball moving forward and hitting the "tee lip", along with the deformation of the ball caused most of that downward motion of the tee, and isn't quite what I have been trying to describe as the club was definitely striking the ball on the upswing.)

I think the ball being deformed could be a potential portion of what is happening with downward strikes, but I really think the majority of it is a very very fast, almost instantanious reaction between the ball and ground caused by the small portion of the clubs force that is in the direction of the ground. The only way to see what is happening is to exaggerate the hitting down on the ball strike so one can see what we see in the videos I posted. The tee moving down, from what looked like a punch iron, and the ball skimming the ground more before taking off as shown in that wedge video. Its true isn't it, that the more one hits down on the ball, the more spin you will get and I would hypothesis a large reason is the extremely brief ball and ground interaction.

Edit: I bet this could be easily tested by someone with a really good high speed video camera. All they would have to do is use a tee of some sort that barely holds the weight of the golf ball up, strike it with a definite decending blow, and if the tee drops down right at impact, we know there is for sure some force being transmitted downwards before the ball climbs up the club face and takes off. I would think it would look very similar to the video I posted earlier of the tee sinking down.

[DirtyGarry24]

This poor fella compressed his ball...

[Clevited]

I have done it, I call that one the ground pound. LOL

[Clevited]

Not to start a monologue, but this issue really has me intrigued and I will hopefully find a for sure cause. For anyone who cares, I thought of a clue that I am sure has been mentioned before but its very telling to me.

I have never once felt what I feel off of hard ground, that I do off of fluff. What I mean is, off of hard ground I feel that "compression or pinching feel" when I get ball first, off of fluff I don't get that feeling hardly at all, no matter how hard I try. Maybe its just me? I can however get that pinching feeling off of a tee.

My thoughts are, if there is no pinching or compressing effect, why would there be such a huge difference in feel off of two completely different surfaces? The flights of course are also very different, low and high spin off of the harder lie, and high and low spin off of the fluff lie. Our mats have to be somewhere inbetween.

It could be deformation of the ball, but I get this feeling even if chipping, which I think would cause minimal ball deformation. There has to be some interaction between the ball and the ground. Some mechanism between the two makes the ball slide up higher on the club face even if you hit ball first and at the same face groove, and therefore take off with lower spin and higher launch than off of harder ground. I think maybe we are actually feeling the ball spin increase rather than feeling a pinch, but they could be one and the same.

Edit: I will try and set up an experiment that eliminates variables like blades of turf inbetween the ball and clubface on my fluff lie I have, and get rid of any dirt, or temperature issues. I will also try and make my own iron byron to some extent. Would just be a gravity swing, chipping machine basically, but it would be repeatable.

[inorkuo]

when you get the pinching feeling off of a tee, is the tee very firmly in the ground? I would guess that to be the case since on most teed up iron shots, the tee is almost completely buried, and you wouldn't be able to push it down further without a good amount of force. that would be more like hitting off of hard ground than fluff.

you could try your gravity swing from two tees with one tee loose and the other rigid. you could cut a tee and balance the head on a spring and hold the other tee in place with a pair of vice grips or something like that.

[Clevited]

I guess i never paid attention to the firmess on the ground when I get that feel off of a tee. Tentatively, I hope to do the following experiment.

Hit off of a block of soft foam with packing tape on the surface to make it smooth, and hit off of a block of wood with packing tape on the surface to give it the same surface friction. I then plan to hit off of both again but with grippy tape on them. I would capture the trials with Skytrak, and using my "iron byron". I could then do another experiment with a tee in the wood block, and a tee in the foam. I hope to capture the effects from the extremes, meaning extreamely soft lie and extremely hard lie, and use the tape to eliminate friction differences and then remove the slippery tape from each and put on grippy tape.

I hope to see whether the difference in spin and launch from a ball first, downward strike, is directly influenced by surface firmness or surface friction or both.

Any ideas on other ways I can do this would be appreciated. These are just my tentative ideas. I hope to build my rig and do the experiments by the end of this weekend.

Big Edit: I now hypothesize that the effect is mostly caused by friction. I think that friction on our mats is high, and that, coupled with the fact that they tend to give just a little when the ball is resting on them, increases its hold on the golf ball thus increasing the static friction by quite a lot. It doesn't take much to force a very brief slide and launch rather than an rotate and launch type of reaction. Just try setting a golf ball on a smooth counter and try to induce spin, then try to do the same thing with the ball sitting in the palm of your hand. One is hard and low friction, one is soft and grippy, night and day difference.

I suspect another mechanism might be happening on a fluffy lie.....or sand.....like a tendancy to catch the ball higher up too easily on a fluffy lie and or get blades of grass inbetween clubface and ball (low spin high launch). Perhaps with a sandy lie there is a tendancy for sand to get between the clubface and the ball increasing friction, or maybe that sand "gives" so much that its actually a lower friction surface to hit off of (low launch high spin). I imagine comparing it to snowboarding down a sand dune vs a grass hill. Things behave differently in different circumstances.

[Clevited]

Update:

I haven't forgotten about my plans to do an experiment. I attempted to make a rig out of what I had lying around but it proved to be too unreliable, inconsistent and not very durable. I also found my high speed camera still isn't fast enough to learn anything visually so I will only be using skytrak to get data with. With that, I designed this at work. I will look into getting it made in the near future and see if I can make heads or tails of what is for sure going on.

The green cylinder represents the ball, the green plank represents a mat. I swing the "club" up until it hits the stop, let go and bam, i have a repeatable swing. The trick will be making sure I get the strike the same every time.