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Post by dubiousgolfer on Feb 24, 2020 11:19:08 GMT -5
Here is JS at the top of the backswing . If he is using an active pivot and his left shoulder socket is pulling on his left arm (in the direction of the red arrow) , why isn't PA#2 releasing early from P4? According to physics that red arrow is an eccentric force and will cause the COM of the club to rotate in a counter-clockwise direction as shown by the blue arrow. But it obviously isn't and I cannot imagine that JS is using muscular wrist torque to retain lag when it is a requirement to have passive wrists so that PA#2 can be released using a 'natural release' using D'Alemberts principle (or the pseudo 'Centrifugal Force' from a pragmatic explanation standpoint). Can we therefore assume that a right arm 'adduction/pitch elbow' intent from P4 is causing a negative torque (in the clockwise direction ) as per Dave Tutelmans suggestion below which is more than enough to prevent a substantial PA#2 release (via any pull forces through the left arm caused by an active pivot)? Won't doing the above also create hand speed while also retaining lag with passive wrists? --------------------------------------------------------------------------------------------------- Tutelman says below: Tucking the right elbow prevents it from extending, "shortening" the right arm. Do this assertively and not just passively, and the right hand is pulling the grip.
The net result is a negative torque, one that prevents the release of the lag until inertial forces are irresistible in releasing the clubhead. ----------------------------------------------------------------------------------------------------------------- DG
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Post by syllogist on Feb 24, 2020 13:19:27 GMT -5
www.youtube.com/watch?v=V1kUkgOSuyMHi DG, The link shows his swing in slow motion (288 yd. 2-iron) Looks like as he starts down, the club is rotating around its center of gravity, a hand's width from the clubhead. There isn't much clubhead momentum at the start down. His hand acceleration during the start down results in a negative torque on the wrists, where the club can't overcome that force. Given his normal pro-like hand path, release won't happen until clubhead momentum overcomes the negative torque on the wrists. Bear in mind that the greater the hand acceleration, the greater the negative torque on the wrists. I believe that the "right elbow tuck" will naturally occur as the left arm slightly increases its distance from the chest and, therefore, I don't think that its a matter of an requiring an"assertive" move. The move may look assertive during rapidly accelerating rotation. I think that his release point is quite normal for the elite tour golfers. A strong grip with a cupped wrist position might obscure this. S
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Post by dubiousgolfer on Feb 24, 2020 13:46:15 GMT -5
www.youtube.com/watch?v=V1kUkgOSuyMHi DG, The link shows his swing in slow motion (288 yd. 2-iron) Looks like as he starts down, the club is rotating around its center of gravity, a hand's width from the clubhead. There isn't much clubhead momentum at the start down. His hand acceleration during the start down results in a negative torque on the wrists, where the club can't overcome that force. Given his normal pro-like hand path, release won't happen until clubhead momentum overcomes the negative torque on the wrists. Bear in mind that the greater the hand acceleration, the greater the negative torque on the wrists. I believe that the "right elbow tuck" will naturally occur as the left arm slightly increases its distance from the chest and, therefore, I don't think that its a matter of an requiring an"assertive" move. The move may look assertive during rapidly accelerating rotation. I think that his release point is quite normal for the elite tour golfers. A strong grip with a cupped wrist position might obscure this. S Hi S Not sure what you mean by the club is rotating around its COG. As far as I am aware you can't have negative torque in the wrists when the clubshaft is in lagging bend from P4 to just before release P5.5. There must be a positive torque happening between hands and grip between P4-P5.5 while the clubshaft is in lagging bend but PA#2 is not being released by any significant amount. Quite confusing ! DG
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Post by syllogist on Feb 24, 2020 16:39:15 GMT -5
Hi DG,
Positive applied torque on the arm (and thus hand), negative torque affecting the wrist joints, at the start down. If there was a net positive torque affecting the wrists joints, the wrists would release. For all intents, the cocked, flexible wrists make the hands part of the length of the club. (If there is negative shaft bend, then the wrists are forced into a cocked position.)
As far as the club rotating around is COG, that is, its balance point, its rotating around a fulcrum placed, say, five increase from the clubhead. Absent hand motion downward, if the club rotated around the clubhead, then only the grip end would describe circular motion, and v.v. for rotating around the butt of the grip. The club will begin to rotate around points more toward the grip and beyond when its momentum increases.
S
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Post by dubiousgolfer on Feb 24, 2020 20:02:00 GMT -5
Hi DG, Positive applied torque on the arm (and thus hand), negative torque affecting the wrist joints, at the start down. If there was a net positive torque affecting the wrists joints, the wrists would release. For all intents, the cocked, flexible wrists make the hands part of the length of the club. (If there is negative shaft bend, then the wrists are forced into a cocked position.) As far as the club rotating around is COG, that is, its balance point, its rotating around a fulcrum placed, say, five increase from the clubhead. Absent hand motion downward, if the club rotated around the clubhead, then only the grip end would describe circular motion, and v.v. for rotating around the butt of the grip. The club will begin to rotate around points more toward the grip and beyond when its momentum increases. S Hi S Sorry but I don't understand what you are trying to describe. As far as I am aware the physics shows that a clubshaft with lagging bend will mean positive torque via the hands. What do you mean by negative shaft bend (is that lagging bend or forward bend)?. If you mean lagging bend than , then as far as I am aware, that doesn't force the wrists into a cocked position. I also don't understand what the below sentences mean and how it would relate to PA#2 release. Maybe you could illustrate and provide an example of what you mean. "Absent hand motion downward, if the club rotated around the clubhead, then only the grip end would describe circular motion, and v.v. for rotating around the butt of the grip.
The club will begin to rotate around points more toward the grip and beyond when its momentum increases"So do you disagree with Tutlemans diagrams below? DG
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Post by dubiousgolfer on Feb 25, 2020 7:18:24 GMT -5
Even more confusing is this vimeo by Sasho Mackenzie where he isolates the forces of the lead and trail hand for Adam Scott from 6:00 -10:24 onwards I have no problem with the influence of the lead hand in that video , but the direction of that trail hand force (towards the target in transition) is difficult to comprehend without actually seeing the test golfers swing used in Koike's research (with his instrumented grip for measuring net forces/torques in each hand). I think some golf instructors (maybe Brian Manzella) may have used that 'trail hand' force to surmise that the bent right arm is extending at transition to help 'lag' but that contradicts Tutelmans diagram below (which shows a positive torque that will tend to release PA#2). I'm more inclined to believe that the trail arm is adducting while also using a pitch-elbow action (flexing the elbow not extending it) so how can that trail hand force be pointing more up in SMK's vimeo video? Could it be that that 'upwards' trail hand force is being transmitted through the 'folded right arm unit' by the reduction in lever arch extension from P4 - P5 ? DG
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Post by syllogist on Feb 25, 2020 7:37:29 GMT -5
Hi DG,I agree with DT's illustration except that the positive couple could only be achieved with a club whose mass is much smaller or perhaps in the case of a very short swing condition where the wrists cannot release.
First, to clarify and just considering the downswing, shaft bend is evidence of both (left) arm acceleration and deceleration. The hands are essentially "flaps" connected to the arms via a "universal ball joint" (wrists). The hands can be considered a part of the shaft in terms of their alignment to the shaft, and also considering that any movement of the hands equates to a equal movement of the shaft.
In the beginning of the downswing, when the arm accelerates, the hands fold backwards or "lag" the accelerating arm in circular motion. The lag is aided by the mass of the club. When clubhead momentum becomes great enough in relation to arm velocity and given the mass of the club, the condition reverses, though it may not be visually evident until later in terms of the hands unfolding.
Although Sadlowski has a clubshaft pointed well beyond common top-of-the-swing positions, he does not release early because the club does not have enough momentum in relation to the speed at which the arm accelerates. Hand path of course also plays a part to keep the radius of circular motion small.
S
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Post by dubiousgolfer on Feb 25, 2020 9:58:13 GMT -5
Hi S
I think you are saying that its the dynamic weight of the clubshaft that is bending the clubshaft as the left arm 'angularly accelerates' in the downswing. That even as the left arm accelerates and increases the clubhead speed , the 'inertia' of the club is still causing the clubshaft to bend during this downswing phase (ie. from P4-P5.5) and this is why you think PA#2 does not release.
That might be a valid pragmatic explanation but I am looking at the general forces in play and what biomechanics are involved that would facilitate that 'pragmatic explanation' (if it was correct).
When JS has reached the top of backswing the clubhead will be stationary at this point because of a positive stopping/bracing force via the wrists. It looks like there will be a generally downward force at the start of the downswing via his lead arm caused by an active pivot . That, according to physics, will create an 'eccentric force' (ie. a force non-aligned through the COM of the club) which will cause a torque that will rotate the COM to become aligned with the force tail end. As far as I am concerned that will cause an uncocking of the left wrist (even when the clubshaft is in lagging bend).
So the only way to stop that uncocking is by muscular wrist torque (in which case the hands are no longer passive or can be deemed 'part of the club' - you call them 'flaps' ) or by introducing a negative torque (to negate that left wrist uncocking) by using 'right arm adduction/pitch elbow' but still allowing the hands/wrists to remain passive and act as 'flaps'.
DG
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Post by imperfectgolfer on Feb 25, 2020 11:11:22 GMT -5
DG, You posted this image of Jamie Sadlowski. You then wrote-: "If he is using an active pivot and his left shoulder socket is pulling on his left arm (in the direction of the red arrow) , why isn't PA#2 releasing early from P4? According to physics that red arrow is an eccentric force and will cause the COM of the club to rotate in a counter-clockwise direction as shown by the blue arrow." I don't know why you drew the red arrow in a direction that is vertically downwards. That is not the direction of pull of the left hand on the club handle between P4 and P4.5 and it is in the direction of his hand arc path. Here is Jamie Sadlowski's hand arc path.
Note that it is directed away from the target and it is roughly 45 degrees from being vertical between point 1 and point 2. That hand arc path is still eccentric relative to the his club's COM and it theoretically should produce a "torque" that will rotate the club counterclockwise. However, if the right arm adducts while maintaining the right elbow's bend angle then it is biomechanically easy to use the extended right wrist/hand unit to "hold" the lag angle because the speed of hand/club motion between P4 and P4.5 is still slow. Between point 2 and 3 of his hand arc path, his hand speed is greater and the degree of circularity of the hand arc path is greater, so the club-releasing "torque" is much greater. Jeff.
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Post by syllogist on Feb 25, 2020 11:35:07 GMT -5
Hi DG,
When the force of left arm motion is roughly perpendicular to the top position of the club, yes, an eccentric force is at play which would cause the club to rotate. However, when the arm starts down, bringing the club along, the club is actually rotating even though the wrists have not yet released. The change in the club's position in space as it is brought down is rotation of the club. It is just that the arm is keeping up with the rotation, for the arm is rotating. The club will rotate faster than the arm when its momentum is sufficiently developed, which will cause arm slowing and resultant release.
S
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Post by syllogist on Feb 25, 2020 12:07:28 GMT -5
Hi DG,
I think that what may confusing the issue of wrist release is the origin of rotation. I don't believe that one can consider the wrists as that point of origin. Consider the standard double pendulum model. The origin of rotation of the proximal segment is the fixed point to which it is attached and not the point at which the proximal and distal segments are attached. The difference in the golf swing is that the fixed point (torso) rotates. Therefore, one can consider the center of rotation of the system as the rotating torso. The club rotates around the torso. The arm is merely the connection of the club to the torso.
S
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Post by dubiousgolfer on Feb 25, 2020 21:56:16 GMT -5
Dr Mann
Yes I should have drawn that red arrow more at a 45 degree angle.
Many thanks
DG
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Post by dubiousgolfer on Feb 25, 2020 22:17:17 GMT -5
Hi DG, When the force of left arm motion is roughly perpendicular to the top position of the club, yes, an eccentric force is at play which would cause the club to rotate. However, when the arm starts down, bringing the club along, the club is actually rotating even though the wrists have not yet released. The change in the club's position in space as it is brought down is rotation of the club. It is just that the arm is keeping up with the rotation, for the arm is rotating. The club will rotate faster than the arm when its momentum is sufficiently developed, which will cause arm slowing and resultant release. S Hi S The physics can get quite complicated when you start looking at 'relative motion' between the left arm and clubshaft. I understand what you mean as its akin to pushing a car with the 'same angle bend' in the arms as long as one can perfectly keep up with the increasing speed of the car. I suppose its another way of trying to explain in some pragmatic fashion why PA#2 is not increasing but I'm more interested in the anatomical movements that can create the general forces being transmitted through the arms and via the passive wrists onto the club grip. DG
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Post by syllogist on Feb 26, 2020 7:23:19 GMT -5
Hi DG,
OK, I hope we've established that the club immediately begins to rotate when it is pulled from the top and that doesn't mean rotation around the wrists.
The reason why the wrists can maintain wrist cock is because there should be 1) rotational acceleration of the torso and 2) ideal shortened radius of rotation of left arm which implies what you call a pitch elbow. Pitch elbow is a function of 1) slight release of PA 4 through first half of downswing and 2) right arm rotated in a position opposite that of a "flying right elbow."
People may have a different opinion on this but mine is that there need not be an intent as you say to make a right arm adduction maneuver, especially provided that the right arm is rotated in a fashion at the top such that a rotational compensation of that arm need not be made. In other words, one need not try to "jam" the elbow toward the side or in front of the hip. The early momentum of the club provides the force for the slight release of PA 4.
S
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Post by dubiousgolfer on Feb 26, 2020 7:50:34 GMT -5
Dr Mann You said: "However, if the right arm adducts while maintaining the right elbow's bend angle then it is biomechanically easy to use the extended right wrist/hand unit to "hold" the lag angle because the speed of hand/club motion between P4 and P4.5 is still slow. "I understand the speed of the hand/club could be slow , but that does not necessarily mean the acceleration (and therefore force across the shaft) is low. I don't know what the approximate size of that eccentric force would be in JS's swing, but if it was large wouldn't holding the lag angle with musculature wrist muscles risk the efficient timing of the release of PA#2 (which requires passive wrists)? To remove that risk mentioned above could the retention of the lag angle be dictated by an active 'adduction of right arm/lateral flexion/pitch elbow' which will reduce the instantaneous position distance between the right hand (in its downswing path) and shoulder socket allowing a degree of 'right elbow flexion' to create a negative torque (as per that Tutelman image in my opening post)? The wrists could stay passive and allow a more natural release of PA#2 . DG PS. Maybe this rough image below can explain what I mean by allowing a degree of 'right elbow flexion'. I've drawn some curved red lines (sorry they are so faint) to just show that the left side is more stretched than the 'crunched' right side
CE would be extended length of left side due to right lateral flexion (left shoulder joint to pelvic crest) AD would be the shortened length of right side due to lateral flexion (right shoulder joint to pelvic crest) CB would be the extended length of the left arm from shoulder joint to left hand. The shortened distance between right shoulder joint and left hand AB means that one can flex the right elbow to a certain degree. I'm assuming that a golfer can start 'tucking' the right elbow a small degree as and when lateral flexion starts to happen in the downswing.
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