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Post by dubiousgolfer on Sept 6, 2020 13:03:26 GMT -5
I was looking again at SMK's club squaring MOF and added in a 'crosswise force' ( see green arrow) that is required to allow the COM of the club to move (as he has perceives it doing) due to his 'Linear Force' produced MOF concept (ie. the yellow arrow). Again , without doing the physics to determine the 'real' forces required to move the COM so that it can align with the linear force , the crosswise force would have remained 'hidden'. I understand it could be deemed obvious to some of the golf biomechanics scientists but in my opinion it is an important subtlety. Now is a 'crosswise force' in the direction of the green arrow a feasible action for a golfer to do in a real swing? I think that green arrow force is possible with a right arm adduction pitch elbow move . So it seems the club shallowing effect caused by the latter and the crosswise force can be coupled together. But this movement of the COM is not a 'Torque' and his inference that the COM will not rotate rapidly (in that yellow direction) about the longitudinal axis of the left arm (because of the large MOI) may no longer apply. He claims that as the club becomes more in line with the left arm , the MOI gets smaller and the previously static 'Torque' will now act 'dynamically' to rapidly increase the ROC angular velocity approaching impact (ie. a passive club squaring process without the need for muscular forearm rotation) . But as I've previously commented , there is no MOF (torque) moving the COM for his passive club squaring concept, just the 'Linear' and 'Crosswise' forces, therefore Torque equations (ie. Torque= MOI * angular acceleration) may no longer be applicable. DG PS. Question: As the lead forearm rotates (if adopting a neutral grip) , the crosswise force has to also rotate more in the targetwards direction to keep the club orbiting around the hands and control the lowpoint and prevent a flip of the clubface (by ensuring that the handle doesn't spin around the clubs COM). But how can that happen? One cannot be regripping the club with the right hand to apply this newly directed crosswise force from P6-P7. As the lead forearm rotates to square the clubface , the crosswise force will be pointing more towards the golfers body and not targetwards, so what are the possible biomechanics to prevent too much lead forearm rotation? It could mean that more pivot needs to be used to square the clubface and ensure a component of the crosswise force is directed targetwards enough to stop the handle spinning (ie. in the targetwards direction). This means that the golfer may need to have more open hips and shoulders by impact if he wants the crosswise force facing more targetwards (than towards the golfer's body). From the golfers perspective (with a weak -neutral grip) , could it be possible that an applied crosswise force will need to 'feel' as if he's slicing across the ball but with an 'in-out' clubface path? Don't know the answer and probably cannot prove any of the above without more detailed hand/grip force data (including the directions in which the forces are instantaneously being applied).
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Post by dubiousgolfer on Sept 23, 2020 7:52:58 GMT -5
Now that I have been convinced about the SMK MOF concept via DT's recent email , the above post is no longer applicable.
DG
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Post by dubiousgolfer on Nov 28, 2020 10:43:11 GMT -5
After seeing Choi's graphs 'O' and 'S' below I now think that SMK's MOF impulse is actually mainly responsible for the squaring of the clubface . Note that there is no significant torque being applied by each hand on the grip to twist the shaft. However, their segment model show significant positive torques in both wrists approaching impact (graphs C and G)Addendum 29/11/20 : I inserted the wrong graphs before so have added the correct one below . Graph C shows that the left wrist goes into negative torque approaching impact while the right wrist (graph G) is significantly and increasingly becoming more positive approaching impact. So it looks like the right forearm is the main contributor being used to keep both forearms rotating to keep up with the SMK passive club squaring passive torque effect . So how can that be? I can only assume that the torque required to rotate the wrists is just enough to keep up with the SMK MOF impulse (created earlier in the downswing) whose club rotating effect progressively 'kicks in' during the downswing. DG
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Post by imperfectgolfer on Nov 28, 2020 11:52:06 GMT -5
DG, You wrote-: "After seeing Choi's graphs 'O' and 'S' below I now think that SMK's MOF impulse is actually mainly responsible for the squaring of the clubface." SMK's MoF impulse idea is based on the fact that the clubshaft is on a shallower plane than the left arm/hand. However, Phil Mickelson does not shallow his clubshaft between P4 => P6 and both his left hand/clubshaft comes down the TSP so there cannot be a SMK type of MoF impulse present - and yet he successfully squares his clubface via a lead forearm supinatory action. How do you explain that fact? Secondly, in Henrik Stenson's golf swing his lead hand and clubshaft are coming down paths with different slope steepness angles between P4 => P6, which can create a SMK type of MoF impulse. However, no counterclockwise rotation of the clubshaft happens between P4 => P6 and it only happens after P6. After P6 the lead hand and clubshaft are both on the same functional swingplane, so a SMK type of MoF impulse cannot exist during the P6 => P7 time period when a PA#3 release action is actually happening.
How do you explain these facts? Jeff.
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Post by dubiousgolfer on Nov 28, 2020 17:54:22 GMT -5
Dr Mann
I agree that players like PM and Adam Scott do not seem to shallow the clubshaft plane more than the lead arm plane and SMK has mentioned this in his video with Chris Como (but I could not fully understand his explanation -please see the video below up to 3:34 ).
SMK says in his article that the reason why the clubshaft doesn't rotate between P4-P6 is the large MOI (Moment of Inertia ) of the club around the longitudinal axis of the lead arm but this will reduce as the lead wrist ulnar deviates and the net result will be a rapid increase in the clubshaft rotational angular acceleration later in the downswing.
DG
PS. You can feel the difference in the MOI yourself by holding your lead arm straight and then radial deviating your wrist until the club is vertical . Then try rotating your lead arm/forearm and feel how difficult it is to rotate compared to holding the club in full ulnar deviation. So the SMK MOF torque is not enough to rotate the forearm when in radial deviation but it's impulse is still acting when ulnar deviation happens and the MOI reduces, then the rotational angular acceleration increases rapidly.
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Post by imperfectgolfer on Nov 28, 2020 19:33:10 GMT -5
Dr Mann I agree that players like PM and Adam Scott do not seem to shallow the clubshaft plane more than the lead arm plane and SMK has mentioned this in his video with Chris Como (but I could not fully understand his explanation -please see the video below up to 3:34 ). SMK says in his article that the reason why the clubshaft doesn't rotate between P4-P6 is the large MOI (Moment of Inertia ) of the club around the longitudinal axis of the lead arm but this will reduce as the lead wrist ulnar deviates and the net result will be a rapid increase in the clubshaft rotational angular acceleration later in the downswing. DG PS. You can feel the difference in the MOI yourself by holding your lead arm straight and then radial deviating your wrist until the club is vertical . Then try rotating your lead arm/forearm and feel how difficult it is to rotate compared to holding the club in full ulnar deviation. So the SMK MOF torque is not enough to rotate the forearm when in radial deviation but it's impulse is still acting when ulnar deviation happens and the MOI reduces, then the rotational angular acceleration increases rapidly. What SMK states about Adam Scott's swing makes no sense! He implies that although Adam Scott does not seemingly shallow his clubshaft between P4 => P6, he surmises that the force being applied to the club handle by the lead hand is actually steeper than his lead hand's arc path because Adam Scott's hands move inside-left post-impact. On what basis can he establish that causal connection between those pre-impact and post-impact events? Also, how can he rationally surmise that the force being applied by the left hand is actually steeper than his hand arc path. Chris Como at 2:23 minutes states that golfers (like Zach Johnson) squares the clubface by steepening the clubshaft plane around P6. That claim makes no sense to me. Zach Johnson uses a very strong left hand grip and he therefore does not have to use much PA#3 release action. Also, where is the "evidence" that he is actually steepening his clubshaft around P6? Another problem I have with SMK's model is that it presumes that the left arm is an unitary structure and that rotation of the clubshaft happens when the entire lead arm rotates around the fulcrum point of the shoulder joint. The reality is that a PA#3 release action happens at the level of the lower lead forearm where the lower 3" of the lead forearm and lead hand rotate counterclockwise relative to the lead upper forerarm, and it happens after P6.
You also wrote-: "So the SMK MOF torque is not enough to rotate the forearm when in radial deviation but it's impulse is still acting when ulnar deviation happens and the MOI reduces, then the rotational angular acceleration increases rapidly." Ulnar deviation of the lead hand happens after P6, at which time there is seemingly no SMK torque present because the left hand's path of motion is on the same functional plane as the clubshaft.
Jeff.
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Post by dubiousgolfer on Nov 28, 2020 21:51:26 GMT -5
I agree that what SMK says about Adam Scott's swing makes no sense, in which case what is the explanation of virtually zero wrist torques being applied on the grip in Choi graphs? I suspect it could be the Ryke effect and I've actually queried SMK about that phenomenon (no reply yet). Yes , there is an issue about SMK's model having a unitary left arm structure because that would make the net MOI (ie. arm and club together) much greater than if it was just forearm alone. Therefore the 'passive' torque could be great enough to rotate the lead forearm and start toppling the club over by P6. I don't think SMK took that factor into account in his research article. "Ulnar deviation of the lead hand happens after P6, at which time there is seemingly no SMK torque present because the left hand's path of motion is on the same functional plane as the clubshaft."That is also a good point which creates more doubt about the reality of a SMK passive torque in a real golfers downswing. DG Addendum: I am just reading the SMK research article again and the model does have an 'upper arm' and 'forearm' segment and is not a unitary left arm. He also states the following: "It should be noted that the increase in angular momentum was not clearly evidenced in the longitudinal rotation of the forearm until the moment of inertia began to decrease rapidly near the end of the downswing (Figure 3d). As demonstrated in Figure 3, if the moment of inertia is small, then a small amount of angular momentum can be associated with a high rate of change in angular displacement."
So he is saying that there is a small amount of angular momentum created by the passive torque from P4 to just before P6 that will start rotating the clubshaft and lead forearm to align with the lead arm plane . By the time it reaches P6 (with the shaft and lead arm plane almost identical with zero passive torque effect) it is this angular momentum that is conserved even as the MOI reduces due to lead wrist ulnar deviation. Because of conservation of angular momentum ,while the MOI decreases there must also be a rapid increase in the rotational angular velocity of the clubshaft which will square the clubface by impact. I actually did a thread about this before but I'd forgotten about it. newtongolfinstitute.proboards.com/thread/601/sasho-mackenzie-shaft-underplane-downswingIt might actually explain why PM is erratic with his driver because his clubshaft is slightly above his lead arm plane which is more reflective of the SIM2 experiment in SMK's article where the clubshaft was angled 10 degrees above the lead arm plane during the downswing (while forearm torque generator switched off - he's made a type error in his article page 7 saying it was -10 degrees). "In Sim2, the forearm angle showed a gradual decrease throughout the first half of the downswing, crossing 0 degrees at 0.17 s, and remaining negative until 0.28 s. The forearm then rapidly supinated to 36 degrees, which resulted in the clubface being open by more than 50 degrees to the target line at impact"Maybe this necessitates that PM has to actively supinate his lead arm to try and square the clubface by impact ? Note that I mentioned 'conservation of angular momentum' above which is not strictly accurate (because angular momentum decreases see diagram 3c) but one can get a good idea of the physics involved . It's a playoff between the instantaneous angular momentum while MOI suddenly reduces which results in an increased angular rotational velocity of the clubface as it approaches impact. This is similar to an ice-skater whose speed of rotation quickens as she pulls her extended arms to her side .
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Post by imperfectgolfer on Nov 29, 2020 10:28:39 GMT -5
DG, You stated-: " So he is saying that there is a small amount of angular momentum created by the passive torque from P4 to just before P6 that will start rotating the clubshaft and lead forearm to align with the lead arm plane . By the time it reaches P6 (with the shaft and lead arm plane almost identical with zero passive torque effect) it is this angular momentum that is conserved even as the MOI reduces due to lead wrist ulnar deviation. Because of conservation of angular momentum ,while the MOI decreases there must also be a rapid increase in the rotational angular velocity of the clubshaft which will square the clubface by impact." That's a reasonable idea. Here is Henrik Stenson's clubshaft shallowing action between P4 => P5.5. Image 1 is at P5.5. The red splined path represents his hand arc path. Note that HS has shallowed his clubshaft by P5.5 relative to the hand arc path. The blue line is the elbow plane and also the functional swingplane between P6 => P7.
According to the SMK model, the clubshaft shallowing phenomenon will allow HS to start the release of PA#3 between P5.5 (image 1) => P6.2 (image 2). Then the lead wrist is becoming increasingly ulnar deviated and that will decrease the MOI allowing HS to complete the release of PA#3 between P6.2 => P7 with very little force/effort. Also, the RYKE effect may be playing a role in the continued release of PA#3 between P6.2 => P7.
There is no clubshaft steepening phenomenon as suggested by Chris Como. I have no idea what he is talking about in that video.
Jeff.
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Post by dubiousgolfer on Nov 29, 2020 10:55:31 GMT -5
Dr Mann
Yes , I think its also a reasonable idea and seems to marry together the kinetics and kinematics until some new research provides more accurate data.
DG
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Post by dubiousgolfer on Nov 29, 2020 12:50:48 GMT -5
Dr Mann
There is however one issue that is still a puzzle. If the club squaring is a passive affect and creates a large increase in shaft rotational angular velocity , how can we explain a DH hand release action from a rotational perspective?
The only means to reduce the ROC would be to increase the MOI through impact. I can only assume that the forearm/club is the major contributor to the MOI from P4-close to P7 but that somehow the upper arm then get fully engaged and adds to the MOI through impact. But how does the upper arm get engaged ? Does it need to be internally rotated approaching impact to prevent excessive rotation of the forearm/club just before impact, then both 'upper arm/forearm/club' rotate together at the same rate through impact to limit ROC through to P7.2?
If you look at SMK's graph 3d , the MOI rate of decrease is starting to level off as impact approaches and maybe starting to change direction and increase post impact. It's a pity that SMK didn't plot some more data points post-impact to P7.4
DG
ps. Note that I posted the wrong 'body segment' graphs for Choi in the previous post (they were the force graphs rather than the torque ones), so now corrected - see Addendum above the image.
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Post by dubiousgolfer on Nov 30, 2020 16:55:06 GMT -5
I asked Kevin Ryan about the SMK's passive torque and he said he was not prepared to answer until his own investigations are completed.
But he did say this:
" I would be asking the question how does a passive torque rotate and square the clubface with the precision required to hit a target 200 metres away with a very narrow dispersion accuracy that pro golfers can achieve? If it was "passive", you would expect small changes in technique could cause changes in face angle and therefore reduced accuracy."
DG
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Post by imperfectgolfer on Dec 1, 2020 10:02:18 GMT -5
Dr Mann There is however one issue that is still a puzzle. If the club squaring is a passive affect and creates a large increase in shaft rotational angular velocity , how can we explain a DH hand release action from a rotational perspective? The only means to reduce the ROC would be to increase the MOI through impact. I can only assume that the forearm/club is the major contributor to the MOI from P4-close to P7 but that somehow the upper arm then get fully engaged and adds to the MOI through impact. But how does the upper arm get engaged ? Does it need to be internally rotated approaching impact to prevent excessive rotation of the forearm/club just before impact, then both 'upper arm/forearm/club' rotate together at the same rate through impact to limit ROC through to P7.2? If you look at SMK's graph 3d , the MOI rate of decrease is starting to level off as impact approaches and maybe starting to change direction and increase post impact. It's a pity that SMK didn't plot some more data points post-impact to P7.4 DG ps. Note that I posted the wrong 'body segment' graphs for Choi in the previous post (they were the force graphs rather than the torque ones), so now corrected - see Addendum above the image. I don't believe that the decreasing MOI near impact will mean that the lead forearm will likely want to continue to supinate counterclockwise in a scenario where the golfer uses a passive release of PA#3 and a DH-hand release action. In that scenario, the lead forearm pronated in the backswing and early downswing from being neutral at address, and the lead forearm rotates in the opposite direction to get back to neutral by impact. Why should it want to continue to supinate counterclockwise at a fast rate between P7 => P7.4? I believe that it only happens in a roller subtype of non-DH hand release action because the golfer programs that type of lead forearm behaviour into his golf swing action.
Also, in a DH-hand release action, the golfer rotates the lead humerus counterclockwise between P7 => P7.4 after the intact LFFW becomes an intact LAFW by P7.1 and that means that any counterclockwise rotation of the GFLW is mainly due to rotation of the entire intact LAFW between P7 => P7.4 - as seen In Tommy Fleetwood's DH-hand release action below.
Note that there is little lead forearm supination happening between image 1 => image 3 and a lot of lead forearm supination only happens between image 3 and image 4 when he transitions into his finish swivel action.
Jeff.
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Post by dubiousgolfer on Dec 1, 2020 17:14:49 GMT -5
Yes, that also makes sense from both a kinematic and kinetic perspective too because an entire LAFW also maximises the MOI and will tend to slow the ROC.
This is great and hopefully we are getting closer to the truth of the golf swing biomechanics.
DG
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