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Post by imperfectgolfer on Aug 4, 2023 21:25:34 GMT -5
I increasingly think that noting the behaviour of the trail wrist through impact can help distinguish between a "handle dragging" release action versus a DH-hand release action. I think that every demonstration made by a golf instructor (eg. Jon Sinclair and Brian Manzella) of a "handle dragging" release action shows that the trail wrist remains significantly extended to well beyond impact, and it is very likely that the trail hand is operating as a negative hand couple through impact, which helps to maintain forward shaft lean to well beyond impact. By contrast, the trail wrist can remain extended between P7 => P7.2 (or even to P7.4) in a DH-hand release action or it may straighten (as seen in those videos posted by DG of Tiger Woods "stinger shots"). I do not know whether the trail hand is really operating as a negative hand couple in DHers who maintain an extended trail wrist to P7.4. For example, consider Jordan Spieth's DH-hand release action. Note that he does not have a large degree of forward shaft lean at impact (as seen in a "handle dragging" demonstration by a golf instructor). Note that the clubshaft does not bypass JS's lead arm between P7 (image 1) and P7.3 (image 2) from an angular rotational perspective, so that makes him a DHer.
However, his lead wrist is becoming less bowed, and his trail wrist is becoming less extended, between P7 => P7.4 and that suggests that he is not using a "handle dragging" technique or manifesting a negative hand couple phenomenon during his early followthrough time period. Jeff.
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Post by dubiousgolfer on Aug 5, 2023 14:02:05 GMT -5
Dr Mann
I don't think the lead wrist becoming less bowed and trail wrist less extending between P7=>P7.4 proves that there is no negative hand couple during JS's early followthrough time period.
The fact that there is still forward shaft bend in image 2 implies a net negative couple exerted by JS's hands. I think there is a momentary period post impact, maybe from P7-P7.1, where the clubface/ball impact slows down the clubhead enough for the hands to have a positive hand couple (ie. some backward shaft bend). The club shaft then rebounds into forward bend too fast for the hands to keep up, so that they end up applying a negative hand couple as in image 2.
DG
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Post by imperfectgolfer on Aug 5, 2023 15:46:43 GMT -5
Dr Mann I don't think the lead wrist becoming less bowed and trail wrist less extending between P7=>P7.4 proves that there is no negative hand couple during JS's early followthrough time period. The fact that there is still forward shaft bend in image 2 implies a net negative couple exerted by JS's hands. I think there is a momentary period post impact, maybe from P7-P7.1, where the clubface/ball impact slows down the clubhead enough for the hands to have a positive hand couple (ie. some backward shaft bend). The club shaft then rebounds into forward bend too fast for the hands to keep up, so that they end up applying a negative hand couple as in image 2. DG I do not understand your opinion that any bending of the peripheral clubshaft after ball impact is reflective of whether a positive or negative hand couple phenomenon exists at the level of the club handle. I think that if the lead wrist is moving in the direction of extension (becoming less bowed) while the trail wrist is becoming less extended, then there is a condition where there is a small degree of counterclockwise rotation of the club handle happening around the coupling point, and I think that is not compatible with a negative hand couple scenario, which would promote a clockwise rotation of the club handle around the coupling point. Jeff.
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Post by dubiousgolfer on Aug 5, 2023 18:00:21 GMT -5
Dr Mann I don't think the lead wrist becoming less bowed and trail wrist less extending between P7=>P7.4 proves that there is no negative hand couple during JS's early followthrough time period. The fact that there is still forward shaft bend in image 2 implies a net negative couple exerted by JS's hands. I think there is a momentary period post impact, maybe from P7-P7.1, where the clubface/ball impact slows down the clubhead enough for the hands to have a positive hand couple (ie. some backward shaft bend). The club shaft then rebounds into forward bend too fast for the hands to keep up, so that they end up applying a negative hand couple as in image 2. DG I do not understand your opinion that any bending of the peripheral clubshaft after ball impact is reflective of whether a positive or negative hand couple phenomenon exists at the level of the club handle. I think that if the lead wrist is moving in the direction of extension (becoming less bowed) while the trail wrist is becoming less extended, then there is a condition where there is a small degree of counterclockwise rotation of the club handle happening around the coupling point, and I think that is not compatible with a negative hand couple scenario, which would promote a clockwise rotation of the club handle around the coupling point. Jeff. Dr Mann If there is forward shaft bend pre-impact or post-impact , there must be a negative couple applied by the hands. If there is backward shaft bend pre-impact or post-impact then there must be a positive hand couple being applied to the grip. If one believes what Dave Tutelman states on his website, the shaft bend and hand couple seem to be inextricably linked. DG PS. If you look at this swing by a phantom camera , one can see the forward shaft bend approaching impact, the backward bend through P7 - P7.4 when the shaft becomes straight. It then seems to have some slight forward bend after P7.4 to P7.5 but I cannot be 100% sure. So in this particular golfers swing , he had negative hand couple pre-impact , positive hand couple P7-P7.4 , negative hand couple from P7.4-P7.5 . In those JS images , was it a high speed camera or one that could be prone to focal plane distortion?
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Post by imperfectgolfer on Aug 5, 2023 19:03:22 GMT -5
DG, You wrote-: " If there is forward shaft bend pre-impact or post-impact , there must be a negative couple applied by the hands. If there is backward shaft bend pre-impact or post-impact then there must be a positive hand couple being applied to the grip." I totally disagree! If the peripheral shaft bends backwards temporarily due to ball contact it does not change what is happening at the level of the hands on the club handle. I don't think that the "wave" created by the peripheral shaft going from forward shaft lean immediately pre-impact to backwards shaft lean immediately after impact even gets to the level of the proximal clubshaft at the level of the club handle. I also fundamentally do not think that the behaviour of the peripheral clubshaft causes the "forces" being exerted by the hands on the club handle, and I think that it is the pattern of motion of the hands through impact that produces the hand couple forces. A "handle-dragger" must be exerting a negative hand couple phenomenon at the level of the hands through impact if he deliberately "holds-off" the release and if he goes through impact with an unchanged degree of forward shaft lean - irrespective of whether ball contact temporarily deflects the peripheral clubshaft backwards immediately after impact. It is biomechanically impossible to go from being in a condition of manifesting a negative hand couple to then be manifesting a positive hand couple in a fraction of a second.
Jeff.
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Post by dubiousgolfer on Aug 6, 2023 18:11:30 GMT -5
Dr Mann Yes, your correct that it is biomechanically impossible to go instantly from negative to positive hand couple and I was in error saying that the phantom camera swing went from negative to positive hand couple at P7. Here is the GIF on Dave Tutelman's website showing the shaft bend through impact and one can see that the proximal end of the shaft is in forward bend just before impact (IMAGE 1) and also for a few inches after impact (IMAGES 2-4). Then a part of the impact wave reaches the proximal end of the shaft so that it becomes straighter (IMAGE 5) before the whole impact wave changes the proximal end into backward bend (IMAGE 6). The GIF swing doesn't look like a DHer and he isn't retaining forward shaft lean through impact, but there is still a negative hand couple applied before and through impact (at least for a few inches even after the ball has flown). Therefore, I doubt whether 'negative hand couple through impact' by itself can define a "handle dragger" from a DHer or non-DHer. However, I think the added criteria you mentioned in your previous post "goes through impact with an unchanged degree of forward shaft lean" seems feasible. DG
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Post by imperfectgolfer on Aug 6, 2023 18:55:28 GMT -5
Dr Mann Yes, your correct that it is biomechanically impossible to go instantly from negative to positive hand couple and I was in error saying that the phantom camera swing went from negative to positive hand couple at P7. Here is the GIF on Dave Tutelman's website showing the shaft bend through impact and one can see that the proximal end of the shaft is in forward bend just before impact (IMAGE 1) and also for a few inches after impact (IMAGES 2-4). Then a part of the impact wave reaches the proximal end of the shaft so that it becomes straighter (IMAGE 5) before the whole impact wave changes the proximal end into backward bend (IMAGE 6). The GIF swing doesn't look like a DHer and he isn't retaining forward shaft lean through impact, but there is still a negative hand couple applied before and through impact (at least for a few inches even after the ball has flown). Therefore, I doubt whether 'negative hand couple through impact' by itself can define a "handle dragger" from a DHer or non-DHer. However, I think the added criteria you mentioned in your previous post "goes through impact with an unchanged degree of forward shaft lean" seems feasible. DG Very nice images! I cannot understand how the hands can go from being in a condition of a negative hand couple at image 4 and then being in a condition of a positive hand couple in image 6. Surely, the backward bend of the clubshaft in image 6 is simply due to ball collision and that one cannot conclude that the hands are working as a positive hand couple at that exact instantaneous moment in time. It could be the type of question to ask David Tutelman. Jeff.
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Post by dubiousgolfer on Aug 6, 2023 20:39:32 GMT -5
Yes, I might ask him for an opinion on each of those images 1-6 I posted.
My own opinion is that the hand torque goes from negative at image 4 to zero in image 5 and then positive in image 6, so it's not instantaneous.
The grip end is angularly rotating so fast pre-impact that it's literally dragging the hands through impact (ie. the hands dragging on the grip end of the shaft equates to negative hand torque).
Then after ball impact with clubhead, the impact wave moves through the shaft decelerating parts of the shaft as it travels upwards towards the grip end. There is a point where the hands end up moving angularly as fast as the grip end (zero hand torque) for a very small moment in time.
Then as the grip end decelerates even more, the hands end up moving angularly faster than the grip end (ie. now the grip is dragging on the hands) which equates to a positive hand torque.
DG
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Post by imperfectgolfer on Aug 6, 2023 21:00:58 GMT -5
Yes, I might ask him for an opinion on each of those images 1-6 I posted. My own opinion is that the hand torque goes from negative at image 4 to zero in image 5 and then positive in image 6, so it's not instantaneous. The grip end is angularly rotating so fast pre-impact that it's literally dragging the hands through impact (ie. the hands dragging on the grip end of the shaft equates to negative hand torque). Then after ball impact with clubhead, the impact wave moves through the shaft decelerating parts of the shaft as it travels upwards towards the grip end. There is a point where the hands end up moving angularly as fast as the grip end (zero hand torque) for a very small moment in time. Then as the grip end decelerates even more, the hands end up moving angularly faster than the grip end (ie. now the grip is dragging on the hands) which equates to a positive hand torque. DG I am sceptical that its possible for the hand couple to change its behaviour as you describe here-: "My own opinion is that the hand torque goes from negative at image 4 to zero in image 5 and then positive in image 6, so it's not instantaneous."
I think that ball collision is producing those changes in the bend of the shaft and that there is no change in the hand couple force/torques between image 4 and image 6. Jeff.
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Post by dubiousgolfer on Aug 7, 2023 20:52:16 GMT -5
Dr Mann
I asked Dave Tutelman and this is his reply:
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I will maintain that the curvature of the shaft just below the hands is a pretty good indicator of the net couple applied by the hands.
I'm reverting to first principles -- in this case, the Bernoulli-Euler equation of bending (https://learnaboutstructures.com/Bernoulli-Euler-Beam-Theory). This should apply whether we are talking about:
*** Static bending - You press your clubhead against the ground and hold it there. *** Pseudo steady state - You are bending the entire shaft against the inertia of the clubhead about a meter away. *** Dynamic (the traveling wave you are asking about) - You are bending the segment of shaft immediately beneath the hands against the inertia of the next segment down the shaft.
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So it seems that the immediate curvature of the shaft segment below the hands is an indicator of hand torque where backward bend will imply positive torque, no bend will mean zero hand torque, forward bend is negative hand torque.
I did ask him about "handle dragging" definition and he replied with the following:
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Here's what "handle dragging" has meant in the discussions I've heard for over a decade. Handle dragging is making your swing by pulling along the hand path; the hand force on the golf club is trying to be tangent to the hand path. That is in distinction to what Brian Manzella coined as "going normal", where the hand force is perpendicular to the hand path -- pulling up and in. When you actually measure the forces (say, in an inverse dynamics analysis), the differences are nowhere near as great as that distinction suggests, because the conscious driving force is heavily dominated by the centripetal force that has to be exerted just to keep the club on a curving path. But the difference is there, and it makes a significant difference in clubhead dynamics.
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If we believe DT's assertions , then it doesn't seem likely that one can distinguish between a handle dragging type swing and a 'DHer/non-Dher' just by hand torque pattern alone. There seems to be negative hand torque 'pre/post-impact' for all of them.
DG
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Post by imperfectgolfer on Aug 7, 2023 21:09:47 GMT -5
DG, Did you ask DT how it is possible for the hands to be in condition of negative hand couple torque in image 4 and then in a condition of positive hand couple torque in image 6 when the time difference is hundreds-of-a-second. Also, that back-bending of the clubshaft due to ball collision is temporary and the clubshaft goes into forward bending again between P7.2 => P7.4. Do you really believe that the hand couple torque goes from negative => positive => negative again in a time period of hundreds-of-a-second? I totally reject DT's definition of "handle-dragging" when he wrote-: "Handle dragging is making your swing by pulling along the hand path". A TGM swinging action involves the hands pulling the club handle along the hand arc path and that does not mean that "handle-dragging" is continuing through impact in the way that BM demonstrates in this video.
Jeff.
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Post by dubiousgolfer on Aug 7, 2023 21:38:34 GMT -5
Dr Mann
The hands are not doing anything actively to change from negative -positive-negative hand torque in that incredibly short time period. They are just responding to the bending of the shaft against the hands. The impact wave moves up (and down) the shaft causing it to bend/torque the shaft segments against the hands, therefore the hands are applying an equal and opposite reaction torque (Newton's 3rd Law). DG
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Post by imperfectgolfer on Aug 7, 2023 22:27:44 GMT -5
Dr Mann The hands are not doing anything actively to change from negative -positive-negative hand torque in that incredibly short time period. They are just responding to the bending of the shaft against the hands. The impact wave moves up ( and down) the shaft causing it to bend/torque the shaft segments against the hands, therefore the hands are applying an equal and opposite reaction torque (Newton's 3rd Law). DG I cannot accept that the hands are responding to the bending of the shaft against the hands in terms of a deliberate action. If the hands are just responding to shaft behaviour according to Newton's 3rd law, then the hands are not under the intentional control of the golfer. My understanding of hand couple torques being applied by the golfer imply a deliberate/intentional action, and thinking of the hands as simply being a body part that is reactive to Newtonian forces is very unhelpful in terms of understanding how best to perform a golf swing action. When BM demonstrates his "handle-dragging" technique he is deliberately causing his hands to produce forces/torques with respect to the club handle that is very different to that happening in a TGM swinging action. The same applies to understanding the difference between a DH-hand release action versus a flipping subtype of non-DH hand release action - one needs to understand what the golfer is deliberately trying to do with his hands with respect to forces/torques being applied to the club handle through impact.
Basically, my primary interest is learning how a golfer should optimally apply forces/torques to the club handle, and I am not interested in the physics regarding how the clubshaft's physical behaviour transmits forces/torques to the hands.
Jeff.
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Post by dubiousgolfer on Aug 8, 2023 7:09:29 GMT -5
Dr Mann
I understand your point of view regarding 'reactive' forces/couples applied by hands on the grip end. Inverse dynamics just calculates the forces and torques and, in my opinion, cannot 100% confirm whether it is caused by a deliberate or reactive action.
For example, as the top of the backswing is reached, is the golfer actively using musculature positive wrist torque to stop the club or just allowing the club to move the wrist joints to the end of their degree of motion? If the golfer allows the latter to happen he has already intuitively predicted that his wrists will create a 'reactive' torque at the end of their degree of motion to stop the club at P4. Inverse dynamics is 'blind' to how that positive hand torque is created and just provides a figure applied via the hands on the club.
If the golfer has already predicted what he dynamically needs to do pre-impact to create the intended post-impact club position in space, he may have worked it out intuitively (probably by feel) how his hands might reactively respond to the actions of the shaft bend.
With regards the hand torque post impact (images 2-6), I think its all reactive to the impact wave considering the below on Dave Tutelman's website. So the ball will also create a 1600 lb force on the clubhead which is very large. The impact wave is going to exert a shaft bend torque on the hands that may dominate anything the hands try to do.
"Impact lasts 0.0004 second (0.4msec). During that time, the force the clubhead exerts on the ball averages about 1600 pounds. (We need that much force in order to accelerate a 46-gram ball to 150mph in 0.4msec.)"
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Post by dubiousgolfer on Aug 8, 2023 19:34:36 GMT -5
Dr Mann
I am now having some doubts about Dave Tutelman's assertions regarding negative/positive hand torque correlation with shaft bend.
I found this video below and one can see the persons hands generating a similar 'impact wave' by moving the steel cable to the right and then sharply to the left. You could actually imagine the persons hands were some virtual clubhead moving to the right which then impacted with the ball.
If you look at the 'Loose End' setup in the video (at 0:14 and slow-motion at 0:50) , the wave moves up the cable and forces that 'Loose End' to the right . Now if that 'Loose End' were analogous to hands on a club , the impact wave might be doing something similar by pushing the hands to the right . Therefore, the hands would exert an equal and opposite reaction force to the left.
I could be mistaken, but I think that could mean negative hand torque while the shaft segments just beneath the hands were in momentary lagging bend (not forward bend).
I've also read the following:
"If you took the shaft in lag deflection and applied a negative couple, the shaft would still be in lag deflection until enough time has passed for the shaft to move into lead. During this period there would be a couple that is negative but a shaft in lag deflection. In general if the shaft is moving fast and forces and torques are changing rapidly (as they are near impact in the golf swing) its hard to read too much into the shaft shape."
DG
PS. When I say I have doubts about DT's assertions about hand torque correlation with shaft bend , I meant during the small time period post-impact.
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