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Post by imperfectgolfer on Aug 27, 2020 12:22:57 GMT -5
I started a thread called "A Major transformation of my thinking" to describe why I no longer believe that the release of PA#2 happens passively according to the D'Alembert principle, and I now believe that it requires a "manual force" to optimally induce the left wrist uncocking action that happens during the release of PA#2. The more I think about the nature of that "manual force", the less I believe in the validity of the SMK-Kwon model which works on the principle of there being a hand couple where the hands apply a force on the club handle around the fulcrum point of the mid-hands point. I now believe that the fulcrum point must be be within the lead wrist joint (lead radio-carpal joint) in the plane of radial => ulnar deviation. Consider this image - using Adam Scott's hands as an example. The red circle with the red dot in the center represents the fulcrum point of the left wrist uncocking action. The fulcrum point is not in the club handle, but it is located in the lead hand's wrist joint.
The forces inducing a PA#2 release action between P5 and P6 are depicted by the red and blue arrows. The lead hand's 4th and 5th fingers are pulling upwards (red arrows) against the club handle while the lead hand's 2nd MC area and lead thumb are pushing against the club handle in the opposite direction (two right-most blue arrows). The trailing hand's proximal palm is applying push-pressure against PP#1 thereby producing a push-force across-the-shaft in the direction of the blue arrows. The trailing hand's peripheral palm and 2nd/3rd fingers are also pushing against the aft side of the club handle in an across-the-shaft direction in the direction of the two left-most blue arrows. There is no hand couple involved, and there is no need to postulate that the club is rotating around its COM. I found DG's physics-based reasoning in the "A major transformation of my thinking" thread both irrelevant and irrational. I think that the "force" required to induce a PA#2 release action is primarily a biomechanical force, and I don't understand why one needs to provide other physics-based explanations. Jeff.
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Post by dubiousgolfer on Aug 27, 2020 20:21:53 GMT -5
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Post by imperfectgolfer on Aug 27, 2020 20:40:02 GMT -5
I don't see any connection between Lee Comeaux's slap hinge motion using the right hand and my opinions. I am only implying that there is enough outward force in a counterclockwise direction (left wrist uncocking direction) being applied by the right hand at the level of the lead wrist joint to counteract the tendency of the club to rotate clockwise at the level of the lead wrist joint due to the negative MoF being generated by the lead hand pulling the club handle down the inclined plane between P4 => P6. I also am not advocating a positive torque being applied by the right hand after P6 because the MoF is increasingly positive after P6 and it can cause the clubhead to accelerate all the way into impact and no additional positive torque is needed. The positive torque being applied by the right hand (and the radial side of the left hand and left thumb) between P4 => P6 is only enough to induce the start of the release of PA#2 when the MoF value is negative and small. Jeff.
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Post by imperfectgolfer on Aug 28, 2020 18:33:08 GMT -5
I am increasingly enamored of my present "idea" that the club is released manually by forces produced by the two hands at the level of the lead wrist joint, and that it does not involve a hand couple phenomenon. If you look at page 16 of the thread on "A major change in my thinking", SMK and Kwon give different explanations about whether the forces acting around the mid-hand points (via a hand couple phenomenon) affects the COM and induces it to gain angular momentum (relative to the hand arc path). I also find the hand couple idea problematic because I don't know of any biomechanical reason why the left hand and right hand should be producing equal forces across-the-shaft, but in exactly opposite directions, so that they cancel each other out. I have no "feel" in my golf swing of equal forces being produced around the mid-hands point by my two hands. I actually "feel" the forces depicted in the following image. I feel" these forces peaking at P5 => P5.2 when the hand arc path changes direction, and the release of PA#2 usually starts between P5 => P5.2 (according to Kwon) and not at P5.5 (which was my previous "belief"). I used to argue that the PA#2 release phenomenon started at P5.5 because I used to wrongly believe in the D'Alembert principle and I also wrongly thought that the hand arc path changed direction at ~P5.5 and that would induce a passive PA#2 release phenomenon according to the physics underlying the D'Alembert principle.
Here are three pro golfers and you can see that the first sign of a PA#2 release phenomenon happens between P5 => P5.2, which happens to be the exact time period when the hand arc path changes from being "out-and away from the target" to becoming "in-and towards the target". Colin Morikawa Image 1 is at P5 and CM's hands are at their furthest point from the target. Between P4 => P5, I can imagine that CM is applying a finite amount of force-across-the shaft with the radial half of his left hand and left thumb + right palm/right hand applying a push-force against the aft side of the club handle in an across-the-shaft manner that counteracts the tendency of the club to rotate clockwise due to the negative MoF torque phenomenon. I can imagine those forces peaking at ~P5.
At P5 => P5.2, when the left hand moves "inwards-and-towards the target" it can induce the ulnar half of the left hand (4th and 5th fingers pulling the club handle) to pull inwards thereby inducing a counterclockwise motion of the club handle around the fulcrum point of the lead wrist and that represents the start of the induction of the release of PA#2. Note that CM's right elbow starts straightening at that exact time period. Bryson DeChambeau Image 1 is at P5 and BD's hands are at their furthest point from the target. Between P4 => P5, I can imagine that BD is applying a finite amount of force-across-the shaft with the radial half of his left hand and left thumb + right palm/right hand applying a push-force against the aft side of the club handle in an across-the-shaft manner that counteracts the tendency of the club to rotate clockwise due to the negative MoF torque phenomenon. I can imagine those forces peaking at ~P5.
At P5 => P5.2, when the left hand moves "inwards-and-towards the target" it can induce the ulnar half of the left hand (4th and 5th fingers pulling the club handle) to pull inwards thereby inducing a counterclockwise motion of the club handle around the fulcrum point of the lead wrist and that represents the start of the induction of the release of PA#2. BD's right elbow starts straightening at that exact time period. Adam Scott
Image 1 is at P5 and AS's hands are at their furthest point from the target. Between P4 => P5, I can imagine that AS is applying a finite amount of force-across-the shaft with the radial half of his left hand and left thumb + right palm/right hand applying a push-force against the aft side of the club handle in an across-the-shaft manner that counteracts the tendency of the club to rotate clockwise due to the negative MoF torque phenomenon. I can imagine those forces peaking at ~P5.
At P5 => P5.2, when the left hand moves "inwards-and-towards the target" it can induce the ulnar half of the left hand (4th and 5th fingers pulling the club handle) to pull inwards thereby inducing a counterclockwise motion of the club handle around the fulcrum point of the lead wrist and that represents the start of the induction of the release of PA#2. Note that AS's right elbow starts straightening at that exact time period. Jeff.
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Post by dubiousgolfer on Aug 28, 2020 20:15:11 GMT -5
Dr Mann
So is this a qualitative opinion considering that MOF is a qualitative (but pragmatic) notion put forward by Sasho MacKenzie?
After taking into consideration all the reply emails from the golf scientists I'm inclined to believe there aren't any 'hand couples' or 'MOF' in a real golfers swing.
DG
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Post by imperfectgolfer on Aug 28, 2020 22:33:39 GMT -5
Dr Mann So is this a qualitative opinion considering that MOF is a qualitative (but pragmatic) notion put forward by Sasho MacKenzie? After taking into consideration all the reply emails from the golf scientists I'm inclined to believe there aren't any 'hand couples' or 'MOF' in a real golfers swing. DG I don't understand your question. What are you asking? Jeff.
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Post by imperfectgolfer on Aug 28, 2020 23:27:54 GMT -5
Another interesting fact about the release of the peripheral lever in a double pendulum swing model.
Here is my video on the double pendulum swing model using two paint sticks joined with a bolt-and-nut.
Note how I performed the passive release action. First of all, i) I started with the two levers at a right angle and ii) I moved the hinge joint downwards-and-forwards in a circular manner thereby mimicking the hand arc path between P5 => P6 in a pro golfer's swing. Under those conditions, the peripheral lever passively released (according to the principle of the double pendulum swing model).
I recently repeated that experiment, but I moved the hinge joint outwards and away from the target - thereby mimicking the hand arc path seen in a pro golfer between P4 => P5. Then, I could not get the peripheral lever to release.
Then, I tried the same release experiment by angling the club back so that there was an acute angle of <90 degrees between the two levers - thereby mimicking a golfer who has a lot of lag between P4 => P5 like Jamie Sadlowski - and I moved the hinge joint downwards-and-forwards. The peripheral lever would not release.
What this experiment suggests is that the double pendulum's passive release model only applies to a pro golfer's golf swing after P5 - when the hand arc path changes direction to downwards-and-forwards and when the lag angle is ~90 degrees. That is roughly equivalent to SMK/Kwon's "belief" that the club releases after P5.5 due solely to the large MoF, which increases steadily between P5.5 and impact, as long as the lead hand continues to pull the club handle along the hand arc path. During that late downswing time period, there is no need for a positive torque force.
So, a positive torque "force" is only needed to start the PA#2 release action at about P5, and my present "idea" of a manual force being applied by the two hands (as previously described) could causally produce that temporary positive torque "force".
Jeff.
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Post by imperfectgolfer on Aug 29, 2020 10:37:50 GMT -5
I was looking over the thread on "A major transformation in my thinking" to see what problems I could not solve in that thread, and I now think that I have potential solutions to some of those problems. Problem 1: Why does the force-across-the shaft produced by the right hand (in an outwards-counterclockwise direction) peak at ~P5 and then diminish between P5 => P5.5? Look at the these capture images of Dustin Johnson's downswing. Image 1 is at P4, image 2 is at P5 and image 3 is at P5.5. Theoretically, the clubshaft should rotate clockwise between P4 => P5 due to a negative MoF produced by the left hand pulling the club handle down the hand arc path in a direction that is downwards-and-outwards (away from the target). However, the right hand can produce a force-across-the-shaft to induce a counterclockwise rotation of the shaft that will balance the effect of the MoF due to the fact that the right arm is adducting while keeping the right elbow bend unchanged while the right shoulder socket is moving away from the target as the upper torso rotates counterclockwise between P4 => P5. What will cause the right hand induced "force-across-the-shaft" to automatically decrease between P5 and P5.5? Note that DJ's right shoulder socket is not moving away from the target between P5 => P5.5, but it is moving groundwards, so it will no longer be producing an outward force that is directed away from the target. At the same time, DJ's right elbow is moving closer to the right side of his mid-torso as the hands move downwards-and-forwards down the hand arc path, and that should automatically diminish the force-across-the-shaft being produced in an outwards (counterclockwise) direction by the right hand.
Problem number 2: Why does the MoF increase between P6 => P7 even though left hand speed is decreasing by 20% during that time period? Look at this Kwon graph. The black arrow represents the line of action produced by the left hand pulling the club handle down the hand arc path. Note that the pull is at an angle to the hand arc path between P4 => P5.5, but it is parallel (tangential component) to the hand arc path at P6 before becoming increasingly normal (where the pull is directed inwards-and-upwards) to the hand arc path as the hands get closer to P7. So, even if left hand speed decreases between P6 and P7, the tangential component (that is parallel to the hand arc path) and the normal component (which is now directed upwards-and-inwards) of the left hand's net pull force can steadily increase the MoF value working to move the clubshaft in a counterclockwise club-releasing direction. Jeff.
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Post by dubiousgolfer on Aug 29, 2020 22:03:39 GMT -5
Dr Mann
The black arrows are not just the left hand pulling force .
Dr Kwon's article says the following: Figure 5 shows the swing‐axis component of the moment produced by the net MH force about club’s COM (let’s call this as the ‘MH force moment’) in the moving MH reference frame. Black broken lines included in the stick figure visualize the lines of action of the net MH forces at various swing events.
Further, if you are now using the '"fulcrum point within the lead wrist joint (lead radio-carpal joint)" rather than the mid-hand-point in your theories, then there is no point looking at Dr Kwon or SMK graphs regarding MOF or hand couples , etc . The graphs will change as soon as you alter the 'virtual joint' reference point (ie.the Mid-hand-point). The only parameter that won't change is the 'Net Force' vector magnitude and direction.
DG
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Post by dubiousgolfer on Aug 30, 2020 9:50:46 GMT -5
Dr Mann
I disagree that an MOF is causing your two lever contraption to release. You are starting the motion of the whole contraption down and out (away from target) which sets the COM of the peripheral lever (call it number 2 lever) in that same direction , then you suddenly change direction of the proximal arm (number 1 lever) which creates increased tension in the 2nd lever which will pull/accelerate the COM causing another change in its instantaneous direction. At the same time , that increased tension in the 2nd lever will pull on the 1st lever slowing it down and its a continuous process causing a curvilinear path of number 2 lever.
This also explains how energy is passed from the 1st lever to the 2nd via the virtually 'frictionless hinge joint'.
It is the divergence of the different directions of the levers which cause increased tension pulling forces on their COM , not some qualitative MOF concept that Sasho Mackenzie created for pragmatic instructional reasons.
DG
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Post by imperfectgolfer on Aug 30, 2020 14:34:49 GMT -5
Dr Mann I disagree that an MOF is causing your two lever contraption to release. You are starting the motion of the whole contraption down and out (away from target) which sets the COM of the peripheral lever (call it number 2 lever) in that same direction , then you suddenly change direction of the proximal arm (number 1 lever) which creates increased tension in the 2nd lever which will pull/accelerate the COM causing another change in its instantaneous direction. At the same time , that increased tension in the 2nd lever will pull on the 1st lever slowing it down and its a continuous process causing a curvilinear path of number 2 lever. This also explains how energy is passed from the 1st lever to the 2nd via the virtually 'frictionless hinge joint'. It is the divergence of the different directions of the levers which cause increased tension pulling forces on their COM , not some qualitative MOF concept that Sasho Mackenzie created for pragmatic instructional reasons. DG I disagree! I deliberately move the proximal lever in such a away that the hinge joint (equivalent to the left wrist joint) moves along a circular path (equivalent to the hand arc path). The hinge joint bolt pulls the peripheral lever along a circular path at the point of attachment of the peripheral lever to the bolt, which is equivalent to the left hand pulling the club handle down the hand arc path, thereby creating a MoF effect. Jeff.
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Post by dubiousgolfer on Aug 31, 2020 19:07:51 GMT -5
Dr Mann
You mentioned in the previous post
"I don't know of any biomechanical reason why the left hand and right hand should be producing equal forces across-the-shaft, but in exactly opposite directions"
Isn't it simply the case that the PA#2 angle is actually being held in place isometrically by the dorsiflexed right wrist?
The left hand is pulling down across the handle from P4 causing (what you may regard) as a positive MOF but the right hand will be applying a negative wrist torque as mentioned above while applying PP#1 . You therefore get antagonistic components of the left and right hand (ie. PP1) forces across the shaft while still registering a stabilising negative torque in the right hand (and a stabilising reactive positive torque in the left hand).
As the swing progresses the right hand relaxes its isometric holding lag (while PP1 still in place) and this allows the release of PA#2 between P5 and P5.5. In my opinion the PP#1 is required (even through impact) and is used as a 'regulator' to stabilise the grip handle and help prevent early uncocking of the lead wrist (ie. early release of PA#2) and any extension before impact.
If you check out DT website it says the following:
"Interestingly, Jorgensen found that the same critical time works the other way as well. If you use negative torque (that is, use strength in the wrist to prevent uncocking) early in the swing and then release it 100 milliseconds before impact, you will increase the clubhead speed. In fact, you'll get as much increase in clubhead speed as that well-coordinated athlete would have gotten by a late application of positive torque. And it's much easier to hold off release than to apply a release-aiding torque at exactly the right time."
DG
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Post by dubiousgolfer on Aug 31, 2020 20:49:39 GMT -5
Dr Mann I disagree that an MOF is causing your two lever contraption to release. You are starting the motion of the whole contraption down and out (away from target) which sets the COM of the peripheral lever (call it number 2 lever) in that same direction , then you suddenly change direction of the proximal arm (number 1 lever) which creates increased tension in the 2nd lever which will pull/accelerate the COM causing another change in its instantaneous direction. At the same time , that increased tension in the 2nd lever will pull on the 1st lever slowing it down and its a continuous process causing a curvilinear path of number 2 lever. This also explains how energy is passed from the 1st lever to the 2nd via the virtually 'frictionless hinge joint'. It is the divergence of the different directions of the levers which cause increased tension pulling forces on their COM , not some qualitative MOF concept that Sasho Mackenzie created for pragmatic instructional reasons. DG I disagree! I deliberately move the proximal lever in such a away that the hinge joint (equivalent to the left wrist joint) moves along a circular path (equivalent to the hand arc path). The hinge joint bolt pulls the peripheral lever along a circular path at the point of attachment of the peripheral lever to the bolt, which is equivalent to the left hand pulling the club handle down the hand arc path, thereby creating a MoF effect. Jeff. Dr Mann I plotted the path of the COM of the peripheral lever below . Although your hand path was circular and you moved it to enact release of the 2nd lever so that is ended up with both arms vertical , the COM path was virtually a straight line. This shows that the COM is being pulled in a more linear direction than being rotated in space. In a real golfers swing , another force is required (ie. PP1 ) to stabilise the handle and that will cause the COM to actually move in a more curved path. The PP1 is what I regard as the 'crosswise force' that DT mentioned in his email to me . It is required to help move the COM to become in line with the 'Net Force'. "Yup, you got it! The 'A' force isn't the only force at the handle, if the handle is constrained to move in the A direction. You need a little crosswise force to keep the handle on the line, which also brings the CoM into line." DG
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Post by imperfectgolfer on Sept 1, 2020 6:40:41 GMT -5
DG,
Look at any golf robot machine and note that the clubhead arc is circular and not a straight-line. A golf robot machine works the same as my simplified double pendulum model - the club is simply puled along by its hinge joint attachment to the central arm.
In my video demonstration, I was probably moving the fulcrum point (my right hand) too much in a linear manner.
Jeff.
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