Trackman and Gear Effect
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birly-shirly
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Todd's described it the way I understand it. Bulge and roll doesn't cause gear effect - it offsets it. The cause of gear effect is the clubhead's CoG being set back off the fact. So, if an off-centre impact causes the clubhead to twist, the clubhead twists around its CoG - and if the CoG is rearward of the face, the face will move laterally "imparting sidespin" to the ball, or tilting the spin-axis somewhat.
What interests me is whether there is an optimum placement of the CoG relative to the face that's valid across all situations. Or if there are inevitably compromises. I think that a "deeper" CoG will also increase the clubhead's MoI - which some players will like. But if you cannot use bulge and roll to offset the gear effect of the deeper CoG, do you end up with a high-MOI clubhead that "over-corrects"?
What interests me is whether there is an optimum placement of the CoG relative to the face that's valid across all situations. Or if there are inevitably compromises. I think that a "deeper" CoG will also increase the clubhead's MoI - which some players will like. But if you cannot use bulge and roll to offset the gear effect of the deeper CoG, do you end up with a high-MOI clubhead that "over-corrects"?
S
SteveT
Guest
Yes, gear effect,if any, for flat-faced irons is strictly a function of depth of CoG from the face. The center of mass of the ball also plays a role in gear effect, I think.
Pro golfers don't depend on gear effect because most use straight blades with little to no leading edge offset resulting in a CoG close to the face. The closer the CoG is to the face, the more effective is working the ball. Even for their drivers, they prefer the CoG to be as close to the face as possible. Pros are pros because they hit pure regardless of the clubs they play... even for endorsement money.
Driver bulge and roll is getting reduced with the jumbo headed drivers, and there are even flat-faced drivers on the market. Bulge and roll defeats the trampoline effect and I suspect that's why the OEMs are designing driver faces with variable thicknesses. Driver design must involve a lot of conflicting compromises to serve the wild golffing masses need for 'game improvement' equipment... which pros don't need ....
Pro golfers don't depend on gear effect because most use straight blades with little to no leading edge offset resulting in a CoG close to the face. The closer the CoG is to the face, the more effective is working the ball. Even for their drivers, they prefer the CoG to be as close to the face as possible. Pros are pros because they hit pure regardless of the clubs they play... even for endorsement money.
Driver bulge and roll is getting reduced with the jumbo headed drivers, and there are even flat-faced drivers on the market. Bulge and roll defeats the trampoline effect and I suspect that's why the OEMs are designing driver faces with variable thicknesses. Driver design must involve a lot of conflicting compromises to serve the wild golffing masses need for 'game improvement' equipment... which pros don't need ....
Frans@France
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birly-shirly
New
@Steve - why is a "shallow" CoG more effective in working the ball? If you're hitting the ball out of the middle, how does the depth of the CoG affect ballflight? I agree that a deeper CoG might not hold many advantages for a pro, but what are the advantages of a shallow, close to the face, CoG? Or is it just a case of sticking with something familiar. Colin Montgomerie had a torrid time switching from Callys to Hogan blades - although he had some other stuff going on in his life besides a change in equipment.
Are you sure about bulge and roll being reduced in modern drivers (I have to ask, since I don't have one of my own to inspect)? If so, the reason is unlikely to be the spring-like face - since COR has been maxed out (legally) for a while. However, if high MOI drivers are twisting less on off-centre hits, that would in itself be a reason to reduce the bulge and roll. Less twist, less correction needed.
Are you sure about bulge and roll being reduced in modern drivers (I have to ask, since I don't have one of my own to inspect)? If so, the reason is unlikely to be the spring-like face - since COR has been maxed out (legally) for a while. However, if high MOI drivers are twisting less on off-centre hits, that would in itself be a reason to reduce the bulge and roll. Less twist, less correction needed.
Birly, MoI (and the resulting resistance to rotation on off-centre hits) is increased by the distribution off clubhead mass away from the CofG. Moving the CofG back away from the face wouldn't influence MoI much by itself.
Steve is right that the nearer the CofG to the face the more 'workable' the club. This is because you need to rotate the face open/closed which moves the CofG out from behind the impact location. The deeper the CofG, the further it moves away from the impact location. This then gives you more gear effect as impact is essentially off-centre from a clubhead CofG point of view.
Confused? I am. Its a wonder I ever hit it straight (and I play blades!)
Steve is right that the nearer the CofG to the face the more 'workable' the club. This is because you need to rotate the face open/closed which moves the CofG out from behind the impact location. The deeper the CofG, the further it moves away from the impact location. This then gives you more gear effect as impact is essentially off-centre from a clubhead CofG point of view.
Confused? I am. Its a wonder I ever hit it straight (and I play blades!)
birly-shirly
New
leon - I agree re MoI. But in order to move the CoG back off the face, don't you need to have mass distributed on the far side of the CoG from the face. In other words, you're distributing mass fore and aft and not just heel and toe - but I think you're still distributing mass further away from the CoG. Isn't that one major reason why an old, persimmon 4 wood is easier to hit than a 1 iron?
Interesting, what you're saying about workability. I've never really felt that I've understood the advantage of blades here.
If I've understood you correctly, you're assuming that a good golfer will consistently make contact on the same point of the face, but that the CoG will move in relation to the ball as a result of the face being opened or closed. I just wonder whether it's accurate to assume that the delivery of the centre of the clubface relative to the ball is what stays consistent, rather than delivery of the CoG relative to the ball.
Or is it the point of blades that the face and the CoG are so closely related, even where the clubface is not square to the ball, that it doesn't really matter whether its the face or the CoG that gets aligned with the ball because any practical difference is miniscule, rather than magnified by a deep CoG.
In which case, the advantage of blades isn't the capacity to curve the ball a certain amount - but I might see now how they might be more consistent if you're trying to work the ball. And especially if you're trying to hit both draws and fades.
Interesting, what you're saying about workability. I've never really felt that I've understood the advantage of blades here.
If I've understood you correctly, you're assuming that a good golfer will consistently make contact on the same point of the face, but that the CoG will move in relation to the ball as a result of the face being opened or closed. I just wonder whether it's accurate to assume that the delivery of the centre of the clubface relative to the ball is what stays consistent, rather than delivery of the CoG relative to the ball.
Or is it the point of blades that the face and the CoG are so closely related, even where the clubface is not square to the ball, that it doesn't really matter whether its the face or the CoG that gets aligned with the ball because any practical difference is miniscule, rather than magnified by a deep CoG.
In which case, the advantage of blades isn't the capacity to curve the ball a certain amount - but I might see now how they might be more consistent if you're trying to work the ball. And especially if you're trying to hit both draws and fades.
Steve Greffen
New
Todd,
It seems that either I'm misunderstanding your description or there is a conflict as to the information in this Trackman newsletter. It also was explained different to us than your description at the Anti-Summit from Mr. Tuxen. I do agree it is a trickier than on the surface. Please explain if you are describing something different than this.
http://www.trackman.dk/download/newsletter/newsletter5.pdf
birly-shirly
New
Bolt - could you pull out what in the linked newsletter specifically contradicts Todd's version? I'm interested, but not too clear as to where you see the particular conflict.
Steve Greffen
New
The understanding I have is that a toe impact does create the draw with an iron not a push and vice versa with the heel, maybe not as much as with a driver but still a draw and a fade from heel contact.
From the newsletter. "If we take an example of hitting a 6 iron with zero club path and face angle, and impacting the ball 1 dimple towards the toe of the club face, this will cause a spin axis of -2°, resulting in a shot being almost 2½ yards offline at 170 yards carry. A spin-axis of -2° is not a serious problem and often is what we refer to as a ‘baby draw’.
ballaholic
New
Bolt - you are correct in that Todd's post doesn't adequately explain gear effect for irons. I have seen this live on Trackman, where gear effect with an iron created an over-draw even when the face was right of the path. I understand Todd is a tremendous golfer and maybe he's playing tiny blades with very little room to miss of the sweet spot. Or maybe he is a freak who never misses the sweet spot by more than an eyelash. However - from personal experience, in situations where the iron shot should have been a push fade, because of gear effect I got a draw or even downright hook due to gear effect with an iron. I was very surprised by this at first and thought there was an error on the $25,000 device until I understood it. Trackman picked up the leftward trajectory and left of target landing (outdoor session on a range) even though the numbers on screen would have called for a push fade.
So the statement "Rather, with irons, toes tend to just push straight right and heels pull straight left.... a little" is definitely not true. Now of course there are gear effect situations in irons where you could get a push if the gear effect spin imparted isn't enough to draw the ball back to the left (slight toe hit on a big fade path/face) so again it's tough to make generalizations without talking about specific impact conditions with data. But to say you can't draw an iron left of target due to gear effect when the face, path and AoA would otherwise be a push fade is factually not correct in my opinion.
It's easier to understand and see and learn the concept on a big faced driver because you can miss the sweet spot by an inch and still get the ball out there (albeit with massive sidespin). With an iron you would whiff or shank and you don't get those massively off-center hits like you could with the driver, so most of the time the wayward spin is more subtle. With irons the max gear effect issues are diminished because you can only get so far from the sweet spot without whiffing or shanking, plus the swing speeds are lower and effects therefore smaller.
Fascinating area in my opinion - I first understood D plane and new ballflight laws (but really downplayed gear effect) about 18 months ago, but almost completely lost my long game due to hitting a ton of balls without Trackman/Flightscope and trying to interpret ballflight. I screwed myself because I was making assumptions that didn't include gear effect or analysis of whether I was making perfectly centered contact (or close to it). Based on periodic sessions on Trackman/Flightscope I've known my path was consistently good and I consider myself a good athlete with good hands so I couldn't figure out why I was hitting the ball all over the planet. I would hit a big hook and assume that the face somehow shut. So I'd open it more by weakening my grip or holding it off and then a huge push. And then I'd manipulate another variable related to clubface, or find another swing pattern that was supposed to be better at releasing the club squarely... the cycle was never ending. My SS is pretty decent (110-115mph) so the miss pattern was staggering. It's been great for forcing me to learn all the short game shots, but it's pretty sad it took so long to start to figure this out.
What finally turned the tide was deciding that before assuming there was a path/face issue, I needed to see some hooks that were hit on the sweetspot or toward the heel. Anything that was hit on the toe was ignored in terms of prompting me to attempt a path or face angle adjustment. Hello power fade. Maybe I'll even get over my hatred of a ball that falls left and hit draws again (my natural shape before the snap hooks soured me). It's a beautiful time right now. But golf is a dangerous bitch and I'm sure something new is ready to creep in!
I have it on good authority that Fredrik Tuxen (Trackman CTO), continues to try and find an accurate way to give more information about impact location for the exact reason - GEAR EFFECT is a critical piece.
So the statement "Rather, with irons, toes tend to just push straight right and heels pull straight left.... a little" is definitely not true. Now of course there are gear effect situations in irons where you could get a push if the gear effect spin imparted isn't enough to draw the ball back to the left (slight toe hit on a big fade path/face) so again it's tough to make generalizations without talking about specific impact conditions with data. But to say you can't draw an iron left of target due to gear effect when the face, path and AoA would otherwise be a push fade is factually not correct in my opinion.
It's easier to understand and see and learn the concept on a big faced driver because you can miss the sweet spot by an inch and still get the ball out there (albeit with massive sidespin). With an iron you would whiff or shank and you don't get those massively off-center hits like you could with the driver, so most of the time the wayward spin is more subtle. With irons the max gear effect issues are diminished because you can only get so far from the sweet spot without whiffing or shanking, plus the swing speeds are lower and effects therefore smaller.
Fascinating area in my opinion - I first understood D plane and new ballflight laws (but really downplayed gear effect) about 18 months ago, but almost completely lost my long game due to hitting a ton of balls without Trackman/Flightscope and trying to interpret ballflight. I screwed myself because I was making assumptions that didn't include gear effect or analysis of whether I was making perfectly centered contact (or close to it). Based on periodic sessions on Trackman/Flightscope I've known my path was consistently good and I consider myself a good athlete with good hands so I couldn't figure out why I was hitting the ball all over the planet. I would hit a big hook and assume that the face somehow shut. So I'd open it more by weakening my grip or holding it off and then a huge push. And then I'd manipulate another variable related to clubface, or find another swing pattern that was supposed to be better at releasing the club squarely... the cycle was never ending. My SS is pretty decent (110-115mph) so the miss pattern was staggering. It's been great for forcing me to learn all the short game shots, but it's pretty sad it took so long to start to figure this out.
What finally turned the tide was deciding that before assuming there was a path/face issue, I needed to see some hooks that were hit on the sweetspot or toward the heel. Anything that was hit on the toe was ignored in terms of prompting me to attempt a path or face angle adjustment. Hello power fade. Maybe I'll even get over my hatred of a ball that falls left and hit draws again (my natural shape before the snap hooks soured me). It's a beautiful time right now. But golf is a dangerous bitch and I'm sure something new is ready to creep in!
I have it on good authority that Fredrik Tuxen (Trackman CTO), continues to try and find an accurate way to give more information about impact location for the exact reason - GEAR EFFECT is a critical piece.
Steve Greffen
New
The David Howell piece also illustrates the variables that can influence even a tour pro. Tuxen went over this a little further at the Summit too. Makes a short knocker like me feel a little better that I seem to find the middle of the face a bit more consistently.
http://www.trackman.dk/download/newsletter/newsletter8.pdf
Btw I hope you can get things on track because if so you could really take advantage of that swing speed!
birly-shirly
New
The importance of sweet spot contact seems to be golf's dirty little secret. There are plenty of theories on how to cure a slice, or curb a hook, or add more speed - but is there any guidance out there on how to dead solid middle it?
I can guess that it might be quite tedious - but I'm wondering whether practicing with a stack of impact stickers would pay dividends.
I can guess that it might be quite tedious - but I'm wondering whether practicing with a stack of impact stickers would pay dividends.
Steve Greffen
New
The other side of the coin is that the effects can generally help a player to straighten out a poor contact. The avoidance is if you are apt to have a push draw swing, you want to avoid toe contact and vice versa. Reading the news letter also makes a good case for a zeroed out swing (face 0 path 0) so that if you have slight off center hits you won't have much deviation. Just a thought but makes good sense to me.
S
SteveT
Guest
Gear effect is not a panacea for poor contact if you are both off center and with an errant face angle, which usually go together.
Gear effect works if the club face is square to the ball and slightly off-center, but not much. If you're like... 5/8"-3/4" off center, you're dead meat .... believe it.
Birly, you are technically correct, but the point that I was trying to make is that there isn't a direct relationship between MoI and CofG. You could put all the mass directly behind the face centre to move the CofG back, but that wouldn't increase the MoI much. Probably wouldn't feel that great either
birly-shirly
New
Sure leon. I shouldn't have written it as if one directly caused the other. But I was thinking of the sort of iron design that tends to combine a high degree of perimeter weighting and back-weighting.
You have got me thinking though about the effects of depth of CoG. Contrary to SteveT's post above, offset must move the CoG forwards relative to the clubface. So I do wonder whether designers are trying to manage, rather than just maximise, the depth of CoG. And maybe wide soled, back-weighted head designs NEED chunky offset to keep gear effect from getting out of hand when you're constrained to a flat face.
You have got me thinking though about the effects of depth of CoG. Contrary to SteveT's post above, offset must move the CoG forwards relative to the clubface. So I do wonder whether designers are trying to manage, rather than just maximise, the depth of CoG. And maybe wide soled, back-weighted head designs NEED chunky offset to keep gear effect from getting out of hand when you're constrained to a flat face.
Steve Greffen
New
You should definitely get the Anti Summit video when it comes out...so many answers in all of these posts lately! Really.
birly-shirly
New
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