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Post by dubiousgolfer on Feb 22, 2021 22:52:27 GMT -5
I was looking at one of the images in Sasho MacKenzies article below and it seemed to match the image I created in a previous post (when I was trying to decipher Koike's graphs in his 2nd 'Instrumented grip' research article). www.rccssc.ca/pdf/How%20Golfers%20Generate%20Clubhead%20Speed.pdfI think SMK has also used Koike's articles so it looks like I have interpreted the graphs correctly. Here is my image: Here is the image from SMK's article page 15 Note: Koike's graphs for forces and torques in each hand in the early downswing do not seem to match the findings in Choi's research graphs (which was a larger sample of 9 registered professional participants). Choi's graphs show the trail hand torque acting to rotate the grip in the anti-clockwise direction (same as the lead hand), but there seems to be a slightly greater trail hand torque peak being applied just before release. There is a consistency in the Koike vs Choi graphs for the forces being applied across the shaft by the left and right hands in the early downswing and are mainly in opposition to each other. Another thing to note with regards the graphs is one cannot discern between a force/torque (in each hand) that might constrain movement compared to one that might cause movement. DG
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Post by imperfectgolfer on Feb 23, 2021 10:17:55 GMT -5
I cannot understand why the trail hand couple's arrow in the 2nd image is seemingly operating in a clockwise, rather than a counterclockwise, direction.
Jeff.
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Post by dubiousgolfer on Feb 23, 2021 10:50:09 GMT -5
I cannot understand why the trail hand couple's arrow in the 2nd image is seemingly operating in a clockwise, rather than a counterclockwise, direction. Jeff. Doesn't seem feasible but I think I can replicate that clockwise torque . If I tried to uncock the left wrist anti-clockwise while allowing my right hand to just be dragged around, the right hand/wrist would passively apply an impeding torque in the clockwise direction. One could highly exaggerate that impedance by just holding your bent right arm (and dorsiflexed right wrist) solid (as in the 2nd image) while trying to actively uncock your lead wrist . When you do this you can feel your right wrist applying a 'constraining' torque in the clockwise direction. I am assuming that the pro golfer in Koike's research did not use his right arm as actively as the 9 pros in Choi's research. DG
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Post by imperfectgolfer on Feb 23, 2021 14:32:29 GMT -5
I cannot understand why the trail hand couple's arrow in the 2nd image is seemingly operating in a clockwise, rather than a counterclockwise, direction. Jeff. Doesn't seem feasible but I think I can replicate that clockwise torque . If I tried to uncock the left wrist anti-clockwise while allowing my right hand to just be dragged around, the right hand/wrist would passively apply an impeding torque in the clockwise direction. One could highly exaggerate that impedance by just holding your bent right arm (and dorsiflexed right wrist) solid (as in the 2nd image) while trying to actively uncock your lead wrist . When you do this you can feel your right wrist applying a 'constraining' torque in the clockwise direction. I am assuming that the pro golfer in Koike's research did not use his right arm as actively as the 9 pros in Choi's research. DG Your answer makes no sense to me! When a golfer has a positive hand couple torque in the early-mid downswing, the trail hand must be producing a counterclockwise torque on the clubshaft to offset the negative MoF torque that produces a clockwise rotary torque on the clubshaft - as shown in Dr.Kwon's images below.
Here is Dr. Kwon's image of the hand couple torque.
Note that the right hand is applying a counterclockwise torque around the mid-hand point (see red arrow).
Jeff.
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Post by dubiousgolfer on Feb 23, 2021 19:48:52 GMT -5
I was just theorising what a golfer might be doing to explain Koike's graphs , not Dr Kwon. Here is something that I find confusing: Below is a frame image of SMK's 'In-Plane Couple and Moment of Force During the Golf Swing' video . It shows the graphs of a 'Multiple Major Winner' and the vertical black line is at approximately the P4 position where the clubhead speed was as close to zero that I could manage (when clicking through the frames). Look at the blue line representing the 'In Plane Hand Couple' which is generally decreasing from P4 - P6. P6 would be approximately where the black and blue lines cross Now look at the Choi graphs 'N' and 'R' below for 9 pro golfers where I have drawn vertical coloured lined to represent P4 (Green) , P6 (red) , P7 (black). Both Choi graphs show the 'real' measured hand torques between the Green (p4) and Red (p6) vertical lines which show a gradual increase in torque from P4-P6. These graphs show the reality of what the golfer is doing via his hands (not split into hand couple and MOF graphs using inverse dynamics). So doesn't this mean that a golfer must apply a steadily increasing anti-clockwise torque with both hands from P4-P6 to recreate which would be the equivalent of the 'hand couple and MOF' shown in SMK/Dr Kwon graphs? If you added those 2 Choi graphs together (from P4-P6) to get the 'net torque' they would be similar in shape to the 'Net Torque' red graph in SMK video image. DG
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Post by imperfectgolfer on Feb 23, 2021 20:06:45 GMT -5
Does Dr. Kwon's diagram below not show a positive torque promoting a counterclockwise rotation of the club being produced by both hands? Note the green arrows showing the forces being produced by the left hand are directed outwards (and not inwards) so they are both producing a positive torque.
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Post by dubiousgolfer on Feb 23, 2021 20:16:41 GMT -5
No , those green and blue arrows do not show that both hands are producing positive torque because the axis of rotation is the MH point . The blue arrow forces would rotate the club counterclockwise about MH . The green force arrows would promote a clockwise rotation around MH.
DG
PS. But I do now agree that both hands need to apply a positive torque because of Choi's graphs.
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Post by imperfectgolfer on Feb 23, 2021 23:12:14 GMT -5
No , those green and blue arrows do not show that both hands are producing positive torque because the axis of rotation is the MH point . The blue arrow forces would rotate the club counterclockwise about MH . The green force arrows would promote a clockwise rotation around MH. DG PS. But I do now agree that both hands need to apply a positive torque because of Choi's graphs. We harbor contrary opinions about the green arrows. I think that the green force arrows would promote a counterclockwise rotation around the MH point because they are pointing downwards in a lead wrist uncocking direction. I think that they would produce a clockwise rotation if they were pointing more upwards in a lead wrist upcocking direction. Jeff.
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Post by dubiousgolfer on Feb 24, 2021 8:03:52 GMT -5
Those Dr Kwon images are just an example showing how he might simplify multiple forces applied by each hand into a net force and couple. How would he know what forces/torques are being applied by various areas of each hand ? He doesn't possess an instrumented grip handle or hand sensor technology.
DG
PS.
This is what Dr Kwon says about those images in his article.
Net Mid‐Hand Force and Moment
Figure 1 shows the forces acting on the grip by golfer’s hands. The small arrows in Figure 1A are the grip forces acting on the club by the hands. Let's assume here that we have a grip force measurement system consisting of an array of force sensors covering the entire grip. Then each sensor will pick up the force acting on it and we end up with a large number of small grip forces with varying magnitudes and directions. In reality there is no reliable and validated grip force measurement system available at the moment and it is almost impossible to accurately measure these forces directly. Since it is impossible to measure these forces directly and accurately, this individual force perspective is not that useful. Conceptually, the hand‐club interaction can be simplified substantially by reducing individual grip forces to a net force and a net moment (Figure 1B). Computation of the net force should be straightforward as it is the vector sum of all the forces.
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Post by imperfectgolfer on Feb 24, 2021 10:13:12 GMT -5
Those Dr Kwon images are just an example showing how he might simplify multiple forces applied by each hand into a net force and couple. How would he know what forces/torques are being applied by various areas of each hand ? He doesn't possess an instrumented grip handle or hand sensor technology. DG PS. This is what Dr Kwon says about those images in his article. Net Mid‐Hand Force and Moment
Figure 1 shows the forces acting on the grip by golfer’s hands. The small arrows in Figure 1A are the grip forces acting on the club by the hands. Let's assume here that we have a grip force measurement system consisting of an array of force sensors covering the entire grip. Then each sensor will pick up the force acting on it and we end up with a large number of small grip forces with varying magnitudes and directions. In reality there is no reliable and validated grip force measurement system available at the moment and it is almost impossible to accurately measure these forces directly. Since it is impossible to measure these forces directly and accurately, this individual force perspective is not that useful. Conceptually, the hand‐club interaction can be simplified substantially by reducing individual grip forces to a net force and a net moment (Figure 1B). Computation of the net force should be straightforward as it is the vector sum of all the forces. I agree that Dr. Kwon's and Sasho's hand couple concept is purely theoretical and not based on direct grip handle measurements. However, I find the ideas useful, and I have not found a better alternative explanation. I personally think that we have far too few instrumented grip handle measurements that have been published to learn "something" truly useful. Jeff.
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Post by dubiousgolfer on Feb 24, 2021 13:15:43 GMT -5
Dr Mann Have you ever seen these graphs relating to shaft bend and clubhead droop on DT's website? If we are able to assume that the 'barometer' of shaft bend in the downswing is directly related to torques applied via the hands, wouldn't this provide a general idea of the types of swings being performed? The link below relates to some research done by 'ShaftLab Tool' which is basically a way to measure shaft bend and clubhead droop during the golf swing. www.tutelman.com/golf/shafts/ShaftLab.phpThe individual golfer 'ShaftLab ' graphs that DT possessed are in the table in the link below called 'Scans of the actual ShaftLab traces'. There are separate graphs for Driver and 5 irons if you click on the hyperlinks. www.tutelman.com/golf/shafts/ShaftLab/rawData.html#tracesAccording to DT there are 3 types of swing profiles that all golfers fit into (see link below) . If that is the case then that means golfers are applying different hand torques at different times in the downswing that generally fit into one of those 3 profiles. www.tutelman.com/golf/shafts/ShaftLab2.phpDG
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Post by imperfectgolfer on Feb 24, 2021 15:21:50 GMT -5
Dr Mann Have you ever seen these graphs relating to shaft bend and clubhead droop on DT's website? If we are able to assume that the 'barometer' of shaft bend in the downswing is directly related to torques applied via the hands, wouldn't this provide a general idea of the types of swings being performed? The link below relates to some research done by 'ShaftLab Tool' which is basically a way to measure shaft bend and clubhead droop during the golf swing. www.tutelman.com/golf/shafts/ShaftLab.phpThe individual golfer 'ShaftLab ' graphs that DT possessed are in the table in the link below called 'Scans of the actual ShaftLab traces'. There are separate graphs for Driver and 5 irons if you click on the hyperlinks. www.tutelman.com/golf/shafts/ShaftLab/rawData.html#tracesAccording to DT there are 3 types of swing profiles that all golfers fit into (see link below) . If that is the case then that means golfers are applying different hand torques at different times in the downswing that generally fit into one of those 3 profiles. www.tutelman.com/golf/shafts/ShaftLab2.phpDG I think that a TGM swinging action should result in the 3rd (Ramp) profile. The other profiles would presumably be secondary to a TGM hitting action or swing-hitting action. Jeff.
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Post by dubiousgolfer on Feb 24, 2021 22:13:13 GMT -5
Actually , those graphs do not just represent the downswing but also some of the backswing . DT found this discrepancy in a later chapter and reviewed/corrected what he thought was happening. "But once we correctly identify the transition point, there are only two shapes of downswing: Early Peak and Late Peak. The other differences in the profile are due to differences in the backswing, not the downswing at all." www.tutelman.com/golf/shafts/ShaftLab4.phpDG
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Post by imperfectgolfer on Feb 24, 2021 23:21:08 GMT -5
Actually , those graphs do not just represent the downswing but also some of the backswing . DT found this discrepancy in a later chapter and reviewed/corrected what he thought was happening. "But once we correctly identify the transition point, there are only two shapes of downswing: Early Peak and Late Peak. The other differences in the profile are due to differences in the backswing, not the downswing at all." www.tutelman.com/golf/shafts/ShaftLab4.phpDG OK - then I am misinterpreting the graphs. I am too disinterested to continue to read all of DT's writing on this topic. Jeff.
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Post by dubiousgolfer on Feb 25, 2021 23:33:07 GMT -5
Here is the reply I received from Dr Kwon concerning those images for Fig 1A and 1B
"On Thu, Feb 25, 2021 at 5:55 PM <kwon3d@kwon3d.com> wrote:
The images do not show the actual forces. They just show the concept of net force/moment: reduction of multiple eccentric forces to a net force and a net moment. ^_^
Cheers, Young-Hoo Kwon, Ph.D. Biomechanics & Motor Behavior Laboratory Texas Woman’s University P. O. Box 425647 Denton, TX 76204-5647, USA ykwon@twu.edu | kwon3d@kwon3d.com
DG
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