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Post by imperfectgolfer on Dec 7, 2012 22:04:12 GMT -5
See this jeffy-forum thread - jeffygolf.com/showthread.php?529-More-stumbling-in-the-dark-at-The-Land-of-the-Blind&p=5221#post5221KM states that to get a straight left arm a golfer has to contract his left triceps muscle and his left forearm wrist extensor muscles. That's factually incorrect. Left elbow extension is required to straighten the left arm at the left elbow joint and the relevant muscle is an upper arm extensor muscle - the left triceps muscles. Forearm muscles are not involved. The extensor carpi radialis/ulnaris muscles are used to extend (dorsiflex) the left wrist joint. KM is totally wrong to claim that the triceps muscle is connected to the forearm's wrist extensor muscles. They operate totally independently as they have different bony origins and insertions. Many golfers can acquire a straight left arm with ease in their golf swing action, and it doesn't necessarily require a lot of left triceps muscle activity for those golfers. I think that it is a great advantage to have a straight left arm if it is acquired without a great deal of muscle tension activity. Note how easily Rory and Lexi Thompson acquire a straight left arm in their swing action. Here is Lexi Thompson. Here is a swing video Jeffy posted this photo of Jamie Sadlowski. The fact that JS has a bent left elbow is atypical and it is most likely due to the fact that he has lot of secondary axis tilt at impact, which means that his left shoulder socket is positioned behind the standard low point position. By having a bent left elbow, JS can get his left forearm and clubshaft in a straight line/vertical alignment at ball impact when the ball is positioned at low point. That's a great advantage if one wants to have a square clubface at impact while having an intact LAFW (where the clubshaft is straight-in-line with the left forearm and where there is no flipping action through impact). Jeff.
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Post by imperfectgolfer on Dec 10, 2012 10:35:49 GMT -5
See this BM-forum thread - www.brianmanzella.com/golfing-discussions/17889-derisable-bend-left-elbow-thro-impact-2.htmlBM wrote the following-: " If you are performing "Going Normal" to the max, your club HAS NO IDEA what is pulling it inward, your elbow is a good enough source for many swings." The club obviously has no idea what is producing the normal force during the club-release phase of the downswing. However, the left elbow cannot possibly be the source of that normal force. How could it provide any pulling-up-force? The centripetal/normal force is produced by the elevation of the left shoulder socket and the left arm is merely a lever of a certain length that transmits that force to the grip via the left hand. The length of the left arm is maximal if the left arm is very straight, and less if the left elbow is bent - but that only changes the radius of the swing and not the magnitude of the normal force. Jeff.
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Post by tapiosantala on Dec 11, 2012 3:47:14 GMT -5
BMans idea about normal is bit funny over all and these kind of "scientific" results makes me smile very often.
It's really far away from real understanding that if you measure biggest force at impact you would know that player is producing force to that direction. In reality that force is big because there is huge tangential force in the club which is produced bit after transition and the thing I call "main corner" in hands around the right hip. So to reach the balance and circular move player has to produce same amount of force inwards than the tangential force is pulling it outwards. In other words centripetal force have to be equal (about) with tangential force to produce steady arc. That got nothing to do with the force applied to the club head toward the target.
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Post by imperfectgolfer on Dec 11, 2012 10:10:18 GMT -5
Tapio,
You wrote-: "In other words centripetal force have to be equal (about) with tangential force to produce steady arc. That got nothing to do with the force applied to the club head toward the target."
I agree with you. The force that is applied to the clubhead comes from two factors - i) the linear motion of the left hand that moves along the circumference of the hand arc path and the left hand pulls the grip end of the club, and ii) the club-releasing action which happens because the left hand changes direction in a circular manner during its linear motion along the hand arc path (primarily during phase 2 of the downswing).
Jeff.
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Post by tapiosantala on Dec 11, 2012 11:14:39 GMT -5
Tapio, You wrote-: " In other words centripetal force have to be equal (about) with tangential force to produce steady arc. That got nothing to do with the force applied to the club head toward the target." I agree with you. The force that is applied to the clubhead comes from two factors - i) the linear motion of the left hand that moves along the circumference of the hand arc path and the left hand pulls the grip end of the club, and ii) the club-releasing action which happens because the left hand changes direction in a circular manner during its linear motion along the hand arc path (primarily during phase 2 of the downswing). Jeff. Do you know the corner? It's not circular from every projection.
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Post by imperfectgolfer on Dec 11, 2012 11:22:46 GMT -5
Tapio, The corner is between point 2 and point 3 in this hand arc path of Sadlowski. It doesn't have to be perfectly circular as long as the hands are changing direction so that the club will be induced to release - according to the mathematical factors used in the D-Alembert calculation. See - perfectgolfswingreview.net/New%20Millennium%20Golf%20Science.htmJeff.
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Post by tapiosantala on Dec 11, 2012 11:25:43 GMT -5
Tapio, The corner is between point 2 and point 3 in this hand arc path of Sadlowski. It doesn't have to be perfectly circular as long as the hands are changing direction so that the club will be induced to release - according to the mathematical factors used in the D-Alembert calculation. See - perfectgolfswingreview.net/New%20Millennium%20Golf%20Science.htmJeff. Not the same. Wrong projection and it's after 3 usually.
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Post by imperfectgolfer on Dec 11, 2012 11:41:20 GMT -5
I believe that it is impossible for the "corner" to be after point 3 if a golfer uses a random club release action (like Sadlowski and the majority of professional golfers) rather than a late club release action. By definition, a random club release action happens between P5.5 and P6.5. The projection doesn't matter - because the camera does not have to be perpendicular to the hand arc path between P5.5 and P6.5 to know that the hands are not moving in a straight line manner. Addendum added later: A golfer may think that Sadlowski is not releasing his club much between P5.5 and P6.5 (compared to between P6.5 and P7) but that refers to the degree of angular rotation of the club relative to the left arm. It doesn't refer to the amount of work (energy) needed to release the club - and the maximum amount of work needed happens in the early phase of the club release phenomenon. I described this club-release phenomenon in detail in this review paper - perfectgolfswingreview.net/endlessbelt.htmHere is the "waterskier analogy" diagram from that review paper. Imagine two waterskier's being pulled by a speedboat that is traveling at a constant speed in a straight line direction. Image 1 shows that the two waterskiers will travel at the same speed as the speedboat if they angle their skis so that they travel in a straight line - directly in-line with the speedboat's linear travel in a straight line direction. Image 2 shows what will happen if one of the waterskiers (skier 2) angles his skis so that he travels in a circular arc. As skier 2 angles his skis sideways at an angle to the direction of travel, he will acquire angular momentum so that he travels faster than skier 1. By point A, he will be traveling faster than skier 1, and it takes a lot of "energy" to cut across at that angle to get to point A. Eventually, skier 2 can build up enough angular momentum to catch up to the speedboat - point C. The amount of energy required to go from point B to point C will be far less than the amount of energy required to first get to point A and secondly to go from point A to point B - because the skier is constantly acquiring angular momentum due to his circular direction of travel. According to the D'Alembert calculation, angular momentum is being created when the hands move in a non-straight line direction, and angular momentum builds-up on the angular momentum already acquired, and therefore more angular momentum gets acquired for a given degree of circular hand arc travel the faster the club movies in an angular manner during its progressive acquisition of angular momentum. Jeff.
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Post by tapiosantala on Dec 11, 2012 13:35:28 GMT -5
Why camera? Why not 3D measurement to see all projections? Look at the red line. There is the missing corner that is not visible from videos. It's pretty sharp even if we calculate that angle. Or maybe even better with this where the blue line tells hands lateral orientation and the red one their path (distance from target line) It's easy to see that hands are moving first only down and toward the target line, but not at all toward the target, and not even at circle.
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Post by imperfectgolfer on Dec 11, 2012 16:50:38 GMT -5
Nonsense! Your 3-D graphs that measure the distance of the left hand from the ball-target line are irrelevant. I can easily see that Lexi Thompson's hand arc path is *relatively circular between P5 and P6 in this 2-D image. (* my definition of "relatively circular" is a hand arc path that constantly changes direction to a variable degree and not necessarily to a consistent degree along every inch of travel along the circumference of the hand arc path) Ben Hogan's and Tiger Woods' hand arc path is also relatively circular between P5.5 and P6.3 (yellow zone). Jeff.
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Post by imperfectgolfer on Dec 11, 2012 17:16:44 GMT -5
Consider this graph presented by Tapio. The red line apparently represents the distance of the hands - relative to the ball-target line. Tapio then stated-: " here is the missing corner that is not visible from videos. It's pretty sharp even if we calculate that angle." I presume that he is talking about the dip in the red graph that reaches its nadir at the 205-210 time point. What does that dip really represent? It may only reflect the fact that the left hand is closest to the ball-target line at that time point because there is certain amount of outward movement of the left arm away from the torso due to left arm elevation. However, the hand arc path is really happening in a more ferris-wheel manner, and not a merry-go-round manner, so any "evidence" of the hands moving in a circular manner along the hand arc path must be looked for in the more vertical plane (and not a horizontal plane - outwards in the direction of the ball-target line). Here is Badds' hand arc path - as seen from a DTL view (see image 2). A face-on view camera lens is nearly perpendicular to the hand arc path, and it can it therefore accurately discern the circularity of the hand arc path (see image 1). What has the "missing corner" got to do with the physics (as described by nmgolfer) underlying the club release phenomenon? The circularity of the hand arc path is not only dependent on the position of the left shoulder at different time-points during the downswing. It is also dependent on the amount of left arm motion that occurs in the left shoulder socket per unit time, and to make things even more complicated, the hand arc path is affected by the amount the left arm moves outwards (away from the torso due to elevation of the left humerus within the left shoulder socket) while the left arm abducts during the release of PA#4. Jeff.
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Post by tapiosantala on Dec 12, 2012 0:20:28 GMT -5
Nonsense! Your 3-D graphs that measure the distance of the left hand from the ball-target line are irrelevant. I can easily see that Lexi Thompson's hand arc path is *relatively circular between P5 and P6 in this 2-D image. Jeff. LOL.. this is enough for me Jeff. You are funny old man, but I can't stand this any more. Are you really telling me you can see that projection from face on 2D?? You cant be serious... Do you want to get one hour demonstration of 2D distortions? Or 2 hrs. I'm cheap, just 200/h and I do it for you.
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Post by imperfectgolfer on Dec 12, 2012 0:29:27 GMT -5
Tapio,
You wrote-: "LOL.. this is enough for me Jeff. You are funny old man, but I can't stand this any more."
You are free to stop posting in this forum. If you decide to continue posting here and you then post another post like this one (that is merely an ad hominem insult), then you will definitely be banned from this forum. I am giving you a lot of leeway to freely criticise my opinions re: golf swing biomechanics/mechanics/geometry, and you are also free to express contrary opinions, but I will not tolerate flagrant ad hominem insults.
Jeff.
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Post by imperfectgolfer on Dec 12, 2012 0:39:18 GMT -5
Tapio wrote-: " Are you really telling me you can see that projection from face on 2D?? You cant be serious..." I am serious. When I go to the movies and watch a person holding a hula hoop, I have no difficulty realizing that the hula hoop has a round shape. When I look at this hand arc path of Robert Rock's swing, I have no difficulty realizing that it has a rounded, and not a straight line, shape. I obviously cannot determine whether it is perfectly circular, or whether it is more likely elliptical in shape, but I certainly know that it is not a straight-line path. Jeff.
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Post by tapiosantala on Dec 12, 2012 1:06:21 GMT -5
Tapio wrote-: " Are you really telling me you can see that projection from face on 2D?? You cant be serious..." I am serious. When I go to the movies and watch a person holding a hula hoop, I have no difficulty realizing that the hula hoop has a round shape. When I look at this hand arc path of Robert Rock's swing, I have no difficulty realizing that it has a rounded, and not a straight line, shape. I obviously cannot determine whether it is perfectly circular, or whether it is more likely elliptical in shape, but I certainly know that it is not a straight-line path. Jeff. Jeff, in reality you are now telling people you understand nothing about that move and it's because you are so used to that 2D distortion you cant even see it. I posted you real 3D measurement results to make you see what really happens and you said they are worth for nothing? What the heck? You get that level information and you are ready to say it's worth for nothing because it puts you at the situation where you should think everything new way and change your opinion? I know how it feels. Been there, done that! But really this is enough for me now and I hope all good for you Jeff anyway. For the moment you make all classical mistakes that can be done with those analyzes, but at least you believe yourself. I have done the same mistakes and before I had measurements and videos side by side I couldn't even imagine it was like that. After understanding it, it made me laugh because it was so clear and there is no other way. But it took time to find it. I offered that knowledge for you for free, but you didn't accept it. I will continue in Acegolf forum at january.
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