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Post by dubiousgolfer on Dec 20, 2019 10:57:29 GMT -5
If future research does indeed prove categorically that there is negative torque in the hands at impact, then Dr Manns explanation makes logical sense.
There are some issues that I'd like to add below for future debate:
When forward shaft bend happens, is the angular velocity of the club faster than the physical 'uncocking' ability of the hands? If yes, then the hands must be further enough in the downswing hub path so that the clubhead doesn't overtake the hands by impact (ie. flipping). Doesn't this mean the golfer has got to do either of the following:
1. Create enough angular velocity in his arms early enough in the downswing so that the hands have a head start (before they slow down) such that the hands still lead the clubhead by impact.
2. If not capable to generate enough angular velocity as in point 1 , continue to add torque to the arms later in the downswing to ensure the hands lead the clubhead by impact.
Lets assume that points 1 or 2 were met in a golfers downswing
Look at page 145 'Search For the Perfect Swing' (Cochran & Stobbs). Also look at their experiment with a hinged clubhead on P146-147.
"Impact with the ball pushes the clubhead back on the shaft by only a few tenths of an inch. To bend the shaft by this amount requires a force of only a few pounds;and conversely in this bent-back condition the shaft applies only a few pounds' force to the clubhead. So this is all that the shaft (and with it the player's hands) can apply to the clubhead during impact- quite negligible compared with the force approaching one ton which the clubhead applies to the ball-and the ball to the clubhead. It means that virtually all the resistance to impact, during actual contact, is borne by the inertia of the clubhead. That is to say, at that moment it might just as well not be connected to the player"
If Cochran and Stobbs are correct then Berties vimeo video regarding a 'stable hinge' (see his vimeo video from 29:34 - 31:00) is questionable.
I also have questions about when the shaft can be considered similar to a 'piece of string'. Cochran & Stobbs claim that the shaft may as well be a 'piece of string' through impact but when exactly does that 'string' effect happen in the downswing? Wouldn't it depend on how quickly an 'action' on the grip takes to perpetuate itself via the shaft to the clubhead?
For example, if the angular velocity of the clubhead is much faster than that 'action' time during the late downswing, then would it matter what was happening at grip level (in terms of negative/positive torque or maybe even twist 'torsional' forces)? I would like to know, when forward shaft bend occurs, when does an action on the grip become irrelevant in a PGA Tour players downswing.
DG
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Post by imperfectgolfer on Dec 20, 2019 12:24:07 GMT -5
DG, You wrote-: " When forward shaft bend happens, is the angular velocity of the club faster than the physical 'uncocking' ability of the hands? If yes, then the hands must be further enough in the downswing hub path so that the clubhead doesn't overtake the hands by impact (ie. flipping). Doesn't this mean the golfer has got to do either of the following:
1. Create enough angular velocity in his arms early enough in the downswing so that the hands have a head start (before they slow down) such that the hands still lead the clubhead by impact.
2. If not capable to generate enough angular velocity as in point 1 , continue to add torque to the arms later in the downswing to ensure the hands lead the clubhead by impact." I think that the hands obviously have a head start relative to the club's COM between P4 and P5.5 because the golfer starts at P4 with ~90 degree of clubshaft lag. Then, during the PA#2 release phenomenon that mainly happens between P5.5 and P6.5 (presuming a good quality hand arc path shape) the club's COM acquires a lot of increased angular momentum. If the left arm stalls pre-impact between P6.5 and P7, then pre-impact flipping would likely happen. The fact that the hands still reach impact ahead of the club's COM in skilled golfers means that the left arm must still be traveling fast enough in the later downswing to prevent pre-impact flipping - even if additional torque is not applied to the left arm in order to prevent stalling. In other words, an efficient release of PA#4 should allow the left arm to still have enough targetwards momentum in the later downswing to prevent pre-impact flipping - without any need to add additional PA#4 releasing torque in the later downswing.
You also wrote-: "I also have questions about when the shaft can be considered similar to a 'piece of string'. Cochran & Stobbs claim that the shaft may as well be a 'piece of string' through impact but when exactly does that 'string' effect happen in the downswing? Wouldn't it depend on how quickly an 'action' on the grip takes to perpetuate itself via the shaft to the clubhead?
For example, if the angular velocity of the clubhead is much faster than that 'action' time during the late downswing, then would it matter what was happening at grip level (in terms of negative/positive torque or maybe even twist 'torsional' forces)? I would like to know, when forward shaft bend occurs, when does an action on the grip become irrelevant in a PGA Tour players downswing."
The way I envisage the scenario of what is happening when the clubhead reaches impact under conditions when the peripheral clubshaft is bent forward is that a condition of negative torque exists at the level of the left wrist and that the clubhead at impact is equivalent to a free-floating object in terms of its behaviour relative to the ball. However, torque being applied at left wrist level still controls the motion of the proximal clubshaft so that a golfer can still maintain an intact LAFW through impact. Ball collision causes the peripheral clubshaft to temporarily bend backwards, but it doesn't significantly affect the targetwards motion of the proximal clubshaft, which can still be straight-line-aligned with the left arm throughout the immediate impact zone if the left arm maintains its forward angular momentum to perfectly match the forward angular momentum of the proximal clubshaft. The additional presence of a negative hand couple force phenomenon happening at the level of the left wrist may provide a small additional element of club handle stability (relative to the left arm) during this time period, but it likely plays a minor role in a golfer's ability to maintain an intact LAFW between P7 and P7.2 in a driver swing. However, I can easily imagine that a negative hand couple force phenomenon can play a much larger role when putting or chipping - when using an intact LAFW (non-flipping) technique. Jeff.
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Post by dubiousgolfer on Dec 20, 2019 18:19:12 GMT -5
Many thanks Dr Mann
DG
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Post by syllogist on Dec 21, 2019 9:15:03 GMT -5
Dr. Mann,
We can agree to disagree. However, as neither of us has the tools to measure what is happening immediately preceding impact, it becomes an exercise in logic. In order to have negative wrist torque immediately preceding impact, there are only two possibilities. One, the golfer must directly apply a negative torque to the wrists, retaining the cocked wrist position with muscular contraction in the lower arms, or two, the golfer's hands must travel faster than the clubhead measured in radians per second. To explain the later, let's define a line segment which includes the hands and clubhead. Both have their own "circular" orbit during release. The distance of the orbit of the hands is obviously must shorter than the distance of the orbit of the clubhead. To have negative wrist torque, the hands must travel a greater number of degrees per second of their "circle" than the clubhead travels in its "circle." To accomplish this means that angular velocity of the clubhead is sacrificed as compared to having no negative torque at the wrists. Furthermore, Champ swings his driver at approx. 130 mph. Do you believe that at such speed his hands can "keep up"? I assure you that if his hands could more than keep up, he would feel like the weight of the clubhead prevented him from swinging even faster!
DG,
At impact, the only thing that the ball recognizes at impact is the orientation and velocity of the club face. In his own way, Bertie was trying to describe a means of delivering the proper club face orientation.
S
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Post by imperfectgolfer on Dec 21, 2019 10:20:33 GMT -5
S, You wrote-: " In order to have negative wrist torque immediately preceding impact, there are only two possibilities. One, the golfer must directly apply a negative torque to the wrists, retaining the cocked wrist position with muscular contraction in the lower arms, or two, the golfer's hands must travel faster than the clubhead measured in radians per second. To explain the later, let's define a line segment which includes the hands and clubhead. Both have their own "circular" orbit during release. The distance of the orbit of the hands is obviously must shorter than the distance of the orbit of the clubhead. To have negative wrist torque, the hands must travel a greater number of degrees per second of their "circle" than the clubhead travels in its "circle." To accomplish this means that angular velocity of the clubhead is sacrificed as compared to having no negative torque at the wrists. Furthermore, Champ swings his driver at approx. 130 mph. Do you believe that at such speed his hands can "keep up"? I assure you that if his hands could more than keep up, he would feel like the weight of the clubhead prevented him from swinging even faster!" I disagree with your argument. First of all, if a golfer maintains an intact LAFW throughout the downswing and through impact then I do not perceive that the hands are traveling faster (in its circle) than the clubhead (is traveling in its circle) - except that during the release of PA#2 the clubhead must be traveling faster (in its circle) due its gained momentum derived from the release of PA#2. If the peripheral clubshaft bends forward after P6 (as routinely seen in pro golfers' driver swings) then there must be a negative torque at left wrist level according to David Tuteleman. Are you disputing his reasoning?
I have also argued that a golfer can theoretically apply a negative hand couple torque between P7 and P7.2 when the clubshaft has caught up to the left arm and when both the left arm and clubshaft are traveling at the same angular velocity in a DH-hand release action. What is the mechanism? If a golfer applies a positive push-force against the aft side of the club handle at PP#2 in a targetwards direction with the ventral aspect of his left 3rd, 4th and 5th fingers and simultaneously contracts his right wrist's extensor muscles to prevent any right wrist straightening action while the left hand travels at the same angular velocity as the clubshaft, then he is applying a negative hand couple force with respect to the coupling point without it affecting the speed of left hand motion during that P7 => P7.2+ time period. You stated-: "To have negative wrist torque, the hands must travel a greater number of degrees per second of their "circle" than the clubhead travels in its "circle." I disagree. I think that if the hands start moving faster in its orbit than the clubhead is traveling in its orbit between P7 and P7.2+, that it will create a positive wrist torque phenomenon at left wrist level and not a negative wrist torque phenomenon. Jeff.
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Post by syllogist on Dec 21, 2019 11:38:30 GMT -5
Dr. Mann,
I agree with Dave Tutelman that for forward shaft bend, there is a negative torque on the wrists. However such phenomenon happens before the onset of release when the wrists are fully cocked and the clubhead's angular acceleration is increasing. Keep in mind that there is a difference between a torque exerted on an object and a direct torque applied to an object. For example, the slowing of the arms as the downswing progresses (negative torque) is a torque exerted from the outward movement of the club. Intentionally delaying wrist release is an applied torque by the forearms.
When one describes a maintained flat left wrist after impact, one must consider that club/ball collision results in an approx. 20% decrease in clubhead velocity. One can also consider the extent to which the hands/arms rotate post impact. However, nothing really matters post impact.
We may be thinking about different things as I am focusing on the period from release to impact.
S
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Post by imperfectgolfer on Dec 21, 2019 12:15:21 GMT -5
S, You wrote-: "I agree with Dave Tutelman that for forward shaft bend, there is a negative torque on the wrists. However such phenomenon happens before the onset of release when the wrists are fully cocked and the clubhead's angular acceleration is increasing." I think that you are 100% wrong regarding your claim that forward shaft bend of the peripheral shaft happens before the onset of the release of PA#2. Also, when the left wrist is fully upcocked between P4 and P5.5 and no PA#2 release is happening, then the clubhead's angular velocity cannot be accelerating (relative to the left hand). The clubhead's angular momentum is undergoing a condition of acceleration after the start of the release of PA#2. Here is Rory McIlroy's downswing action. His left wrist is fully upcocked in images 1, 2 and 3 - and the peripheral clubshaft is bent backwards, and not forwards. That represents a condition of positive wrist torque, and not negative wrist torque. You also wrote-: "Keep in mind that there is a difference between a torque exerted on an object and a direct torque applied to an object. For example, the slowing of the arms as the downswing progresses (negative torque) is a torque exerted from the outward movement of the club." I regard your bold-highlighted sentence as being incomprehensible. Regarding your 2nd sentence, the left arm slows down as result of the release of PA#2 (due to the COAM principle), but that is a different issue than the issue of whether there is a positive or negative torque existing at the level of the left wrist. Going back to a previous claim of yours that "to have negative wrist torque, the hands must travel a greater number of degrees per second of their "circle" than the clubhead travels in its "circle" - consider the example of a person spinning a rock attached to the end of a string around his head. If the hand is moving along its inner circle at a certain finite speed then the rock will be spinning along its outer circle at a certain finite speed. To get the rock to spin around its outer orbit at a faster speed, the hand must first increase its speed of motion along its inner orbit and that creates a positive torque situation, and not a negative torque situation, at the level where the string abuts against his hand. Jeff.
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Post by dubiousgolfer on Dec 21, 2019 18:29:30 GMT -5
Hi S
You can test out the negative torque pressure feel in your hands just using a flexible stick or long ruler. Hold one end with a neutral grip and try and press the proximal end against a door frame to create forward shaft bend so that its ahead of your hands (I know this a static experiment but the physics still applies). You will feel pressure forces in the hands/fingers as per Dr Manns previous posts above.
DG
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Post by syllogist on Dec 22, 2019 7:01:32 GMT -5
Dr. Mann,
Before we can delve into what's actually happening in terms of torques, let's define them:
Applied positive wrist torque - forearm muscular action that rotates wrists to increases wrist cock angle Applied negative wrist torque - forearm muscular action that prevents rotation of wrists to increase of wrist cock angle Zero applied wrist torque - completely passive wrists that allows for wrist rotation to increase wrist cock angle
If an object is accelerating, then there must be a positive torque acting on it. Conversely, if an object is decelerating, then there must be a negative torque acting on it.
From this, I would think that when the wrists begin to release, that motion of the wrists begins to accelerate. The momentum of the clubhead along its rotational path causes the onset and acceleration of wrist release. At the onset of release, the clubhead is traveling not in the direction of the "target" while the hands are traveling in the direction of the "target." Such exerts a negative torque on the arms which slows the hands since the hands are connected to the arms. But wrist motion is accelerating since wrist release motion begins in the direction of the travel of the clubhead upon release and the clubhead is accelerating. Therefore, during release, there is not a negative torque exerted on the wrists, but rather, it is the arms and thus the hands.
When the arms accelerate prior to the release stage and the club and wrists are "folded," arm acceleration exerts a negative torque on the wrists which keeps the wrists "folded."
The shaft will bend backward or "lag" from its neutral position when there is an abrupt deceleration at the end of the backswing and, especially, in the beginning of the downswing upon torso/arm acceleration. The shaft begins its forward bend from its LAG position and not its neutral position. Therefore, its begins its forward bend BEFORE release as a result of angular velocity.
From this, you can hypothesize about the physical necessities and resultant effects of any of your release classifications that take 0.05 sec. to reach impact.
S
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Post by syllogist on Dec 22, 2019 9:54:42 GMT -5
Hi DG,
Shaft bend is indeed interesting. At the start of the downswing and for a short while, the shaft is bent backward and a negative torque is exerted on the wrists by way of arm acceleration.
I can feel this negative torque (retaining my wrists in the cocked position) deep into the downswing until the force of the clubhead releases my wrists.
I think that Dave Tutelman may have substituted the word wrists for hands (arms) when describing positive and negative torques associated with direction of shaft bend. In any case, I don't think that the understanding of shaft bend is important.
S
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Post by imperfectgolfer on Dec 22, 2019 10:00:03 GMT -5
S,
I personally regard your definitions and your reasoning as being nonsensical!
We mentally operate in very different mental universes!
Jeff.
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Post by dubiousgolfer on Dec 22, 2019 10:11:25 GMT -5
Hi S There is positive wrist torque from P5- Release , but its a passive 'stopping' positive torque that prevents the clubs clockwise rotation from a face-on view. For me personally , its the limitation in my left wrist radial deviation and that stopping torque is 'positive'. The physics does get a bit more complicated but it is explained by Sasho MacKenzies vimeo video below. vimeo.com/1588569981. See 5:50 - 8:00 -describes the action of a 'couple' (ie. a Torque) via the hands 2 See 8:00 - 12:14 - describes how the Net Force (ie. an 'eccentric' force- that does not go through the clubs COM) across the club which creates a 'Moment Of Force' (ie. a 'Torque') on the clubs COM. 3. See 12:15 - end of video - describes the 'Total Torque' the sum of 1 and 2 above. It also shows that the torque element caused by the 'couple' (in the hands) becomes negative at around P6. One can readily imagine that this is the point where the shaft is starting to forward bend and where the hands cannot keep up with the angular velocity of the club . Note that the 'Net Torque' which is increasing the clubs angular velocity from P6-P7 is the 'Moment of Force' caused by the 'Net Force' (ie. eccentric force) across the clubs COM. DG
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Post by syllogist on Dec 22, 2019 12:06:56 GMT -5
Hi DG,
I got the impression that Sasho was merely describing in that video the physics of terms of net force as the reason why the club rotates during the backswing and downswing. (As a side, I have no idea why these vimeos freeze while running in my state of the art laptop!), I write this while chuckling a bit as I have no idea how my opinion and Dr. Mann's opinion about how Champ exits through release morphs into a heated debate about torques in the midst of my nonsensical reasoning. :-)
As a gentleman, I will concede that Champ, knowingly or not, pulls his geometrically flat left wrist through release, to impact, so as not to destabilize his left hand, by way of extension of that hand, before impact. As you might suspect, there can be nothing that would explain it.
S
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Post by imperfectgolfer on Dec 23, 2019 11:58:44 GMT -5
More comments on Bertie Cordle's golf instructional teaching. Look at the following video. Bertie emphasizes the point that getting forward shaft lean at impact is not enough, but he also believes that there must still be a positive wrist torque phenomenon existing at impact. So, he was not satisfied with that amateur golfer's impact alignment on his first golf swing - see the 1:27 minute time point of the video. Note that the amateur golfer has forward shaft lean, and that the hands are appropriately ahead of the ball - but Bertie prefers to see the hands even further forward so that the clubshaft is not straight-line-aligned with the left arm (despite the same degree of forward shaft lean). Bertie claims that the difference is substantial because he believes that even if two golf strikes with the same club have the i) same degree of forward shaft lean and ii) the same degree of dynamic loft (due to the forward shaft lean) that the ball strike is better if lag tension (positive wrist torque) is present. However, I know of no scientific evidence to support his opinion. Note that the amateur golfer has a very strong left hand grip so if his hands are further forward at impact, that means that the left wrist is not more bowed (because the back of his left hand is roughly facing the ball-target line at impact and it is slightly cupped at impact), but it is very slightly more radially deviated at impact - as seen at the 10:36 minute time point of the video where he compares the two swings. The difference in the degree of forward shaft lean is insignificantly small, but Bertie believes that the 2nd swing is better because he believes (without providing any scientific evidence) that an increased degree of positive wrist torque must be present in his 2nd swing, while none is present is his first swing. I suspect that the degree of positive wrist torque at impact between the two swings is insignificant and inconsequential, and that although it is a very good golf instructional idea to come into impact with the hands ahead of the ball and to avoid pre-impact flipping, the benefit has nothing to do with the presence of a positive wrist torque being present at impact. The other major disagreement that I have with respect to Bertie's golf instructional approach can be seen at the 9:35 minute time point of the video where he demonstrates his desired impact alignment by pressing the clubhead into the ground to create backward bend of the peripheral clubshaft. He states that he can create pressure down into the shaft by performing this action, but he does not explain why creating pressure down into the shaft in order to make it bend is beneficial. How is that demonstration biomechanically possible? I believe that he is pushing against the aft side of the club handle below the coupling point with his right hand while he maintains a bent right wrist. That biomechanical action is only compatible with a TGM hitting action and it not compatible with a TGM swinging action where the right hand should not be applying a positive push-pressure against the aft side of the club handle below the coupling point at impact. Also, if he is experiencing any positive pressure of the club handle against his left hypothenar eminence (left hand's heel pad) during his demonstration, then it cannot be due to Bertie pushing his left hand away from the target because he has a bowed left wrist at impact (which moves the butt end of the club handle targetwards and not away from the target). There are only two potential causes of him experiencing an increased degree of positive pressure of the club handle against his left heel pad in his simulated impact position - i) push pressure of the right hand against the aft side of the club handle (while maintaining a bent right wrist) is pushing the club handle against his left heel pad and /or he is unconsciously pulling the club handle forward with the ventral aspects of his left hand's 3rd, 4th and 5th fingers in order to create a bowed left wrist scenario, and that action is only compatible with a negative hand couple phenomenon and not a positive hand couple phenomenon (which Bertie recommends). His simulated impact demonstration is very compatible with a TGM hitting action (eg. hitting a punch shot to get the ball out of woods and back to the fairway), but I do not believe that it is happening in a pro golfer's driver swing action (which is due to a TGM swinging technique). Jeff.
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Post by syllogist on Dec 24, 2019 7:35:32 GMT -5
Dr. Mann,
There are studies that show that the right hand pressure of the elite golfer decreases to about zero by impact.
As for the aspiring tour golfer, it looks like there's little difference impact alignments between the before and after swings. To me, it looks like his arms outrace his body rotation early and, consequently, his upper body is nowhere near as open at impact as the tour pros that Bertie mentioned and mimicked by demonstration. In my opinion, one cannot just try to get the hands more forward using the same swing that naturally fails to get the hands forward enough. On second thought, I suppose one can if one tries to hold off release and "drag" the club.
I don't see where Bertie's demonstration of downward pressure on the shaft from the right hand equates to hands more forward upon release.
S
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