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Post by syllogist on Nov 4, 2019 13:04:28 GMT -5
DB,
His tweak for lack of right arm was to increase left shoulder torque. Tutelman stated that the 85 Nm torque used was greater than that previously reported. What previously reported means I don't know. I couldn't find MacKenzie's paper on the topic on the net. I relied on Tutelman's article. I assume that the golfer as well as the club had sensors but can't be sure. I don't know what the usefulness is of developing a model that seeks to optimize torques to match the data output generated from the low handicap golfer. A mathematical exercise to pass the time?
S
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Post by dubiousgolfer on Nov 4, 2019 19:38:43 GMT -5
DB, His tweak for lack of right arm was to increase left shoulder torque. Tutelman stated that the 85 Nm torque used was greater than that previously reported. What previously reported means I don't know. I couldn't find MacKenzie's paper on the topic on the net. I relied on Tutelman's article. I assume that the golfer as well as the club had sensors but can't be sure. I don't know what the usefulness is of developing a model that seeks to optimize torques to match the data output generated from the low handicap golfer. A mathematical exercise to pass the time? S Hi S I've got a copy of the SMK's article (link below). It says the following : "M_Shoulder peaked at 85 Nm which is slightly greater than maximum shoulder abduction torques (*80 N m) previously reported .However, this was as expected since Tm for M_Shoulder was doubled to compensate for the lack of a trailing arm" www.researchgate.net/publication/225442233_A_three-dimensional_forward_dynamics_model_of_the_golf_swingI suppose the model could provide some useful data if SMK was 100% certain that all the biomechanical actions of a trailing right arm to optimise a golf swing could be complemented by just increasing left M_Shoulder torque. DG
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Post by imperfectgolfer on Nov 4, 2019 20:10:12 GMT -5
DB, His tweak for lack of right arm was to increase left shoulder torque. Tutelman stated that the 85 Nm torque used was greater than that previously reported. What previously reported means I don't know. I couldn't find MacKenzie's paper on the topic on the net. I relied on Tutelman's article. I assume that the golfer as well as the club had sensors but can't be sure. I don't know what the usefulness is of developing a model that seeks to optimize torques to match the data output generated from the low handicap golfer. A mathematical exercise to pass the time? S Hi S I've got a copy of the SMK's article (link below). It says the following : "M_Shoulder peaked at 85 Nm which is slightly greater than maximum shoulder abduction torques (*80 N m) previously reported .However, this was as expected since Tm for M_Shoulder was doubled to compensate for the lack of a trailing arm" www.researchgate.net/publication/225442233_A_three-dimensional_forward_dynamics_model_of_the_golf_swingI suppose the model could provide some useful data if SMK was 100% certain that all the biomechanical actions of a trailing right arm to optimise a golf swing could be complemented by just increasing left M_Shoulder torque. DG This does not really answer my question as to why M shoulder torque has a second peak in the late downswing after P5.5 - when the left arm's angular velocity is actually slowing in most pro golfers. If SMK claims that the 2nd peak is due to a right arm straightening action happening during the later downswing, then he is presumably implying that it will cause the left arm to move faster if the right palm pushes against PP#1 and the club handle - but the left arm speed actually decreases in the later downswing in a TGM swinger's action and the right arm straightening action should not be used to try to make the left hand move faster. Jeff.
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Post by dubiousgolfer on Nov 5, 2019 6:32:14 GMT -5
Hi S I've got a copy of the SMK's article (link below). It says the following : "M_Shoulder peaked at 85 Nm which is slightly greater than maximum shoulder abduction torques (*80 N m) previously reported .However, this was as expected since Tm for M_Shoulder was doubled to compensate for the lack of a trailing arm" www.researchgate.net/publication/225442233_A_three-dimensional_forward_dynamics_model_of_the_golf_swingI suppose the model could provide some useful data if SMK was 100% certain that all the biomechanical actions of a trailing right arm to optimise a golf swing could be complemented by just increasing left M_Shoulder torque. DG This does not really answer my question as to why M shoulder torque has a second peak in the late downswing after P5.5 - when the left arm's angular velocity is actually slowing in most pro golfers. If SMK claims that the 2nd peak is due to a right arm straightening action happening during the later downswing, then he is presumably implying that it will cause the left arm to move faster if the right palm pushes against PP#1 and the club handle - but the left arm speed actually decreases in the later downswing in a TGM swinger's action and the right arm straightening action should not be used to try to make the left hand move faster. Jeff. Dr Mann I am unsure whether that graph relates to the instantaneous 'net' torques on the Torso, Shoulder, Arm, Wrist. Say for example the original torque applied to rotate the 'Torso' was 'X' but an amount 'Y' was used to rotate the 'Shoulder', then , according to physics, there will be an equal and opposite Torque Y applied against the Torso which will decelerate it . So does the graph below for Torso relate to the instantaneous X-Y values over time? And does the same principle apply between Shoulder and Wrist? If yes, then couldn't that double-peak relate to the sum of the below: 1. The amount of instantaneous (unknown) 'Y' that was transferred from Torso to Shoulder in the late downswing? plus 2. The amount of instantaneous (unknown) independent original shoulder torque applied. DB PS. The physics could become even more complicated , because any independent positive torque made by the 'Shoulder' might also transfer a negative torque to the 'Torso' too .
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Post by syllogist on Nov 5, 2019 6:47:47 GMT -5
Dr. Mann, Sorry about that - got off track.
There is a difference between torque and velocity. Torque on a segment can be increasing while the velocity of that segment decreases, meaning that if one uses muscular force to speed the arm during release, for example, one's arm will still decelerate (in a swing of sufficient speed).
I wouldn't draw conclusions from the torque profiles such as the one I posed above since is it impossible to know the actual torque profiles of the tested golfer.
S
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Post by imperfectgolfer on Nov 5, 2019 9:56:21 GMT -5
S,
You wrote-: "There is a difference between torque and velocity. Torque on a segment can be increasing while the velocity of that segment decreases, meaning that if one uses muscular force to speed the arm during release, for example, one's arm will still decelerate (in a swing of sufficient speed)."
We definitely have a very different perspective on golf swing mechanics!!!
Jeff.
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Post by syllogist on Nov 5, 2019 11:26:53 GMT -5
Dr. Mann,
Perhaps in some aspects we differ on golf mechanics but overall, probably not.
If I decided to hang in door in my home, I would need to install a hinge that is attached to both the door jam and door. As I begin to drive a screw into the door jam, I begin to encounter the resistance of the hard wood. The torque I am applying is increasing but the rate at which I turn the screwdriver begins to decrease. This isn't exactly analogous to a golf swing but it shows that an increase in torque does not always equate to an increase in velocity.
Have you ever encountered those stubborn projects? Next time I'll use a drill and not a hand screwdriver.
S
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Post by syllogist on Nov 5, 2019 12:22:30 GMT -5
Dr. Mann - to make it more analogous to the golf swing:
Torque on club which slows the hands and thus the left arm is greater than the Shoulder M torque in the model which moves the left arm. The torque on the club creates resistance with respect to the hands.
S
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Post by dubiousgolfer on Nov 5, 2019 18:26:07 GMT -5
Here is the complete set of graphs in SMK's article. If you look at the top graph , it seems like Q_Shoulder 'angular velocity' (ie. the left arm angular velocity=> the gradient of the Q_Shoulder graph) is almost constant from P5.5-P7 and is at odds with the 3D Kinematics of the real life swing of Jamie Sadlowski. DB
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Post by imperfectgolfer on Nov 6, 2019 1:28:47 GMT -5
Dr. Mann, Perhaps in some aspects we differ on golf mechanics but overall, probably not. If I decided to hang in door in my home, I would need to install a hinge that is attached to both the door jam and door. As I begin to drive a screw into the door jam, I begin to encounter the resistance of the hard wood. The torque I am applying is increasing but the rate at which I turn the screwdriver begins to decrease. This isn't exactly analogous to a golf swing but it shows that an increase in torque does not always equate to an increase in velocity. Have you ever encountered those stubborn projects? Next time I'll use a drill and not a hand screwdriver. S I can understand your bold-highlighted analogy when you state that the resistance of the hard wood can slow the rotation of the screw - thereby requiring an increased degree of torque. However, I know of no increased resistance to the targetwards motion of the left arm happening in the late downswing that would require an increased M arm torque. Your secondary post claiming that "The torque on the club creates resistance with respect to the hands" does not make sense to me. Interestingly, DG has pointed out the fact that the Q arm displacement graph increases all the way into impact in SMK's graphs (which I didn't notice before) and under those conditions I can imagine a need for an increased M arm torque in the later downswing. However, the left arm slows down quite dramatically in the late downswing in most pro golfers - as previously shown in the 3-D graph of Jamie Sadlowksi's driver swing. Here are more 3-D graphs showing the same phenomenon in other pro golfers. Jon Rahm Rory McIlroy
Cheetham's kinematic sequence graphs comparing a pro golfer to two amateur golfers Jeff.
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Post by dubiousgolfer on Nov 6, 2019 6:13:43 GMT -5
Dr Mann - Is this a typo error above? Don't you mean 'Q or M_Shoulder' rather than 'Q or M_Arm' in your above post (see image below)? . Q_Torso is the angle of body turn. Q_Shoulder is the angle between the torso and the left arm. Q_Arm is the angle of rotation of the left arm about its own axis. Q_Wrist is the angle between the left forearm and the club shaft at the grip. To denote the muscular torque at the joint, the Q_ is changed to M_ (e.g., M_Shoulder). DG PS. Does my diagram below show some rationale as to why the left arm slows down? I've added another diagram that might tentatively explain why an increased shoulder torque might be required even if left arm slows down (as shown above by that 'black arrow' force component due to the increase tensile strain force in the clubshaft).
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Post by syllogist on Nov 6, 2019 10:03:58 GMT -5
Dr. Mann,
Instead of focusing on graphs, let's address your question in another way.
First, a few observations about a double pendulum set at let's say a 90 degree angle and only under the influence of gravity - When the distal segment begins to release from its starting angle, such release action places a torque on the proximal segment. The proximal segment decelerates as the distal segment accelerates. The center of mass of the distal segment travels in a direction different from the direction of the proximal segment. So, the acceleration of the proximal segment impedes, or creates "resistance" to, the velocity of travel of the proximal segment.
In a real golf swing, the impediment, or "resistance," slows the proximal segment, or arm. However, unlike the double pendulum solely under the influence of gravity, the golfer employs applied force to swing the club. The applied force is what you see as estimated torque profiles in studies. However, in a real swing, it is likely that the elite golfer stops applying torque to swing the club just before release. Continuation of applied torque that moves the arms would inhibit clubhead velocity during release. The cessation of applied torque is also what shows up as deceleration of velocity of body segments in swing analyses. So, two phenomena are at work in determining deceleration.
S
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Post by imperfectgolfer on Nov 6, 2019 10:11:29 GMT -5
Dr Mann - Is this a typo error above? Don't you mean 'Q or M_Shoulder' rather than 'Q or M_Arm' in your above post (see image below)? . Q_Torso is the angle of body turn. Q_Shoulder is the angle between the torso and the left arm. Q_Arm is the angle of rotation of the left arm about its own axis. Q_Wrist is the angle between the left forearm and the club shaft at the grip. To denote the muscular torque at the joint, the Q_ is changed to M_ (e.g., M_Shoulder). DG PS. Does my diagram below show some rationale as to why the left arm slows down? I've added another diagram that might tentatively explain why an increased shoulder torque might be required even if left arm slows down (as shown above by that 'black arrow' force component due to the increase tensile strain force in the clubshaft). DG, Yes - it was a typo error. I obviously am referring to M shoulder and Q shoulder. I think that the force (due to the peripheral shaft being bent forward in the late downswing) that theoretically may cause cause the left hand to slow down is probably very small and insignificant. I suspect that the left arm slows down due to the COAM principle that applies to the PA#2 release phenomenon (where the central arm slows down when the peripheral arm speeds up), and due to the fact that the left shoulder socket moves upwards after P5.5 thereby not exerting a targetwards pull on the left arm in the late downswing. I have no sympathy for your 2nd diagram. If the outward fleeing club is exerting a center-fleeing force that can potentially unbalance a golfer, then the corrective remedy is a centripetal force directed in the opposite direction, which is not in the direction of the M shoulder torque force, which is perpendicular to the Sz axis (and not parallel to that Sz axis).
Jeff.
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Post by imperfectgolfer on Nov 6, 2019 10:26:12 GMT -5
Dr. Mann, Instead of focusing on graphs, let's address your question in another way. First, a few observations about a double pendulum set at let's say a 90 degree angle and only under the influence of gravity - When the distal segment begins to release from its starting angle, such release action places a torque on the proximal segment. The proximal segment decelerates as the distal segment accelerates. The center of mass of the distal segment travels in a direction different from the direction of the proximal segment. So, the acceleration of the proximal segment impedes, or creates "resistance" to, the velocity of travel of the proximal segment. In a real golf swing, the impediment, or "resistance," slows the proximal segment, or arm. However, unlike the double pendulum solely under the influence of gravity, the golfer employs applied force to swing the club. The applied force is what you see as estimated torque profiles in studies. However, in a real swing, it is likely that the elite golfer stops applying torque to swing the club just before release. Continuation of applied torque that moves the arms would inhibit clubhead velocity during release. The cessation of applied torque is also what shows up as deceleration of velocity of body segments in swing analyses. So, two phenomena are at work in determining deceleration. S What you are describing is the COAM principle as it applies to the release of PA#2 - where the central arm of a double pendulum will slow down as the peripheral arm speeds up (as shown in the animated gif below). The slowing of the left arm in the late downswing of a golf swing is an analagous event that must happen if the club has to successfully catch-up to the left arm by impact. Applying an extra M shoulder torque in the later downswing will be disadvantageous because it will cause the left arm to slow down less so that the hands get to impact with too much forward shaft lean and an open clubface (due to an incompleted PA#2 release action). Jeff.
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Post by dubiousgolfer on Nov 6, 2019 11:13:31 GMT -5
Dr Mann There was an old thread about COAM on this link below: richie3jack.proboards.com/thread/2908/conservation-angular-momentum-golf-swingNmgolfer (whose article was used to describe D'Alemberts principle to explain release) seems to discount the use of COAM and the double-pendulum analogy. He said the following: ---------------------------------- COAM applies to a system that is in stasis. i.e. No forces are doing work. No energy is being added or subtracted. During the golf stroke muscles apply forces across joints causing movement and are therefore doing work (in the physics definition of the word) therefore COAM does not apply. Momentum can be conserved. Think of a flywheel battery where its mass gets spun up to high rpm then sits there in stasis. Since the mass on its shaft is supported by low friction bearings, no energy is lost. Then when that energy is needed, the momentum can be tapped and trained off. That is a case in which momentum is conserved. Does this in any way apply to the golf stroke? NO..." With regards to parameteric acceleration... I'm not certain as to Prof. Muria's area of expertise but I believe his concept as expressed in that paper is derived from vibration control research. Vibration control researchers most definitely do describe parametric damping. (To damp a vibration is to reduce the magnitude of oscillation). Suppose you have a mass hanging from a flexible support like a wirerope. Its swinging like a pendulum, the wind or whatever is driving it and you don't want the oscillation to get out of control where it might break something. The way to control it is by using parametric damping. Judiciously applied force at the opportune time (i.e. parametric damping) can extract or add energy to that oscillating system. Prof. Muria took this concept and applied it to analysis of the golf swing to explain what better golfers do in that late stages prior to impact. That's all well and good. But I would argue better golfer are in effect applying parametric acceleration through out the latter two stages of the downswing (Nesbit's research shows all full swing golf strokes are characterized by three distinct phases as defined by changes in instantaneous swing center) It is the off-axis component owing to the changing radii which accelerates the clubhead in a tangential direction. That off-axis component is maximized by continually shorten the swing center radius during the last two phases of the downswing not just the last few microseconds. Ideally there is not "something different" that happens just before impact.A hitter's torque (push-pull exertion at the hands) complicates the equations but considering just the swinger's effort I believe it can be shown mathematically (as an analytical solution) that the optimal hand path is synonymous with optimal "parametric acceleration" and traces a contracting spiral not unlike the one shown: It does not even help to think of momentum being conserved with respect to the golf swing. That was one of those blind alley of misconceptions book authors have led people down. Science is a process which begins with at testable hypothesis and perhaps a "mathematical" basis i.e. "the math says do this..." Suppose a golfer writes a book and says hit down with your driver. Scientist says that's crazy... the math says hit up (maximize launch angle for maximum carry). Test the hypothesis... result: all long drivers are hitting up some more than others... the science rules. Consider COAM... never-mind that it cannot apply to the golf swing because the very definition of the term is violated, just consider the mental image it conveys. It says spin like an ice-skater and you'll win the tournament... it says bring your hips then shoulders then arms to a stop then you'll maximize your CHS... The science says baloney. The science says "cracking the whip" analogies are bogus. Test the hypothesis. What do long drivers do? They certainly don't spin like an ice dancer and their swing is one continuous motion, with no discernible slowing of body parts into and through the ball. Science (the testable hypothesis) rules. Theorizing scientists need to exercise caution. If they're basing their theory on a faulty deficient math model then the results of the test are inconclusive. A faulty math model like say the double pendulum may predict one outcome that happens to coincide with the test result outcome but that does not mean the theory is validated. It simply means a bad model matched the test results. -------------------------------------------------------------------- DG PS. The bold highlighted section seems to be interesting. NMgolfers statement which I bolded seems to match Mandrins article below. ------------------------------ When a mass circles with constant angular velocity around a fixed center at any time the centripetal force is perpendicular to the path of the mass. There is hence no tangential force acting on the mass, Fig 6a. When there is a shortening of the swing radius there is a transition from the old to the new shorter swing radius. During this transition the physical center of rotation and the actual instantaneous center of rotation don't coincide. The angle between the centripetal force and the trajectory is not anymore a perfect 90 degrees and a lateral component is created tangentially to the trajectory as illustrated in Fig6b/c. A faster transition results in greater tangential force. At first it might appear a bit strange to obtain greater velocity for an object by having a perpendicular force exerted on it. But once we realize that there is also a tangential force component created it might be more easier accepted. The tangential force, acting on the mass, results from there being an angle between trajectory and centripetal force, deviating from 90 degrees, during the shortening process of the swing radius. Hence without resorting to any mathematics it can also be understood that if this transition in swing radius occurs faster than we have also a greater resulting tangential force as there is a larger angle, deviating from 90 degrees, between trajectory and centripetal force vector. The analysis of the parametric acceleration in a golf swing is more complicated as it involves not simply a point mass but several linked segments. However the underlying physics remains the same. For instance it might be understood from above why parametric acceleration is only significant when the centripetal force is large, hence only close to impact, and also why the upward motion of the center of mass of the golfer has to be very brisk to have some effect, see Fig6b/c. However there is no magical untapped force being discovered. Golfers have been using it without any idea of parametric acceleration. Its use in a golf swing is a minor clubhead speed contributor when executed properly. --------------------------------- So I am assuming the changing centre of curvature of the clubhead path , secondary to the changing centre of curvature of the hand path causes the increase in clubhead tangential speed.
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