daryl
New Member
Posts: 18
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Post by daryl on Dec 7, 2010 3:52:48 GMT -5
Longitudinal Center of Gravity
A question that pops up from time to time is whether the Clubhead rotates around the shaft or does the shaft rotate around the Longitudinal center of gravity of the Golf Club.
Maybe one or the other or maybe both. Maybe it depends on the stroke? Does it matter? Could it matter? Would our swing strategy change if we knew the answer?
Does anyone know of specific research about this matter?
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Post by machinestacker on Dec 7, 2010 7:57:08 GMT -5
Regardless of where the Clubshaft and Clubhead are joined together, it always feels as if they are joined at the Sweet Spot – the longitudinal center of gravity, the line of the pull of Centrifugal Force. So there is a “Clubshaft” Plane and a “Sweet Spot,” or “Swing”, Plane. But herein, unless otherwise noted, “Plane Angle” and “Plane Line” always refer to the Center of Gravity application. Study 2-N. Except during Impact, the Clubshaft can travel on, or to- and – from, either Plane because the Clubshaft rotation must be around the Sweet Spot – not vice versa. So Clubhead “Feel” is Clubhead Lag Pressure (6-C) and is a Golfing Imperative. (2-0). If Lag Pressure is lost the Hands tend to start the hosel (instead of the Sweet Spot) toward Impact – that mysterious “Shank.” When in doubt, “Turn” the Clubface so both the Clubshaft and Sweet Spot will be on the same plane at Start Down. Both Planes always pass through the Lag Pressure Point. Study 6-C-2-A.” Homer Kelley
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Post by imperfectgolfer on Dec 7, 2010 10:20:45 GMT -5
Daryl,
You asked-: "A question that pops up from time to time is whether the Clubhead rotates around the shaft or does the shaft rotate around the Longitudinal center of gravity of the Golf Club."
I don't think that it does either in a full golf swing. I think that if the LAFW is intact throughout the downswing, then the clubface is always parallel to the back of the GFLW. That means that the clubface will always rotate exactly as the back of the GFLW rotates. In the release swivel action (release of PA#3), the entire LAFW rotates off the inclined plane to face the target at impact - therefore, the same phenomenon applies to the clubface, and it rotates off the inclined plane to become square to the target at impact.
Jeff.
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Post by machinestacker on Dec 7, 2010 11:09:10 GMT -5
GFLW? Geometrically flat left wrist? If so, do you differentiate between a GFLW and an AFLW?
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Post by imperfectgolfer on Dec 7, 2010 12:02:38 GMT -5
MS, I definitely differentiate between an AFLW and a GFLW. A GFLW is a neutral LW that occurs when the LAFW is intact. An AFLW is a palmar flexed LW that occurs at impact if there is forward shaft lean at impact. See - my grip chapter. perfectgolfswingreview.net/grip.htmJeff.
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Post by ringer on Dec 7, 2010 18:37:11 GMT -5
Jeff, you said that the clubface will always rotate relative to the FLW. I think there is something missing here though that you're stopping short of. What is the connection between the FLW and the clubface? What axis does the wrist and the clubface rotate around? Is it around a sweetspot axis or a shaft axis?
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Post by imperfectgolfer on Dec 7, 2010 20:01:40 GMT -5
If one has an intact LAFW - then the toe of the clubface, the sweetspot, and the heel of the clubface and GFLW are always in a straight line relationship. That's why they cannot rotate around relative to each other. It requires a disrupted LAFW to cause the angular velocity of one of those points to change relative to another eg. toe to travel faster than the heel in terms of angular velocity.
Jeff.
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Post by ringer on Dec 7, 2010 20:13:14 GMT -5
Sorry Jeff but that's avoiding the question. If they are rotating TOGETHER, then they have a fixed axis point that they are rotating around. What is that axis?
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Post by imperfectgolfer on Dec 7, 2010 21:00:50 GMT -5
Ringer,
Think of a tennis player performing a back-handed tennis stroke (using an intact LAFW) - where is the axis of rotation of the stroke?
I don't believe that there is a specific axis of rotation for the intact LAFW in a golf downswing because it is not always rotating, and when it rotates in the late downswing it has a variable "imaginary" radius of rotation because the degree of rotation changes constantly.
Jeff.
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Post by ringer on Dec 8, 2010 12:37:57 GMT -5
Correct ans: doesn't matter. Golf club is not like a hockey stick and no golfer uses a hockey slap shot. Think of rotating machinery like say a turbine. An unbalanced shaft/turbine assembly will put tremendous forces on the bearings because the unbalanced assembly wants to rotate about an axis that is not aligned with the bearing axis. Causes vibration problems leading to failure. Same thing with a golf club except a golf club is not constrained to rotate about any axis. It matters to the equipment and the distance of the CG from the shaft. If the shaft rotates around the CG, then it doesn't matter where the CG of the clubhead is. But if the CG rotates around the shaft then it matters a LOT to how much torque you need to apply to rotate the clubface. The further out on the toe that the clubhead's CG is, the more torque it takes to rotate. This actually has a DIRECT implication to how you swing a golf club and your ability to time the clubface closure.
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Post by ringer on Dec 8, 2010 12:51:12 GMT -5
Ringer, Think of a tennis player performing a back-handed tennis stroke (using an intact LAFW) - where is the axis of rotation of the stroke? I don't believe that there is a specific axis of rotation for the intact LAFW in a golf downswing because it is not always rotating, and when it rotates in the late downswing it has a variable "imaginary" radius of rotation because the degree of rotation changes constantly. Jeff. We are talking about the relationship between the left hand and the clubface (or racketface). In a tennis racket the sweet-spot is balanced in line with the shaft of the racket making it an unusable comparison to a golf club. In a golf club the sweet-spot is out AWAY from the shaft. I think you are trying to say there is no torque applied to the clubhead through the shaft at all. I would be hard pressed to understand how you could believe this. You don't have to be an engineer to know that if the left arm rotates at all, the clubface will rotate with it. That rotation MUST have an axis.
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Post by ringer on Dec 8, 2010 12:59:08 GMT -5
There are numerous papers on the dynamics of the shaft during the downswing you should read. The club twists and bends a myriad of different ways and looks NOTHING like it does in and unloaded condition. And these variables change with every club shaft/head and golfer combination! The head of the golf club is not constrained to any axis of rotation and is free to move ANYWHERE it wants to move. The amount of torque required to rotate the loaded (ie bend and twisted) assembly is completely inconsequential in comparison to all other factors. I maintain it does not matter... just another of the endless sources of instructor induced golfer confusion. The underlined part doesn't make any sense. The amount of torque required to close the face is inconsequential? You're kidding right? Just because a shaft is loaded doesn't mean no torque is there. Nor does it mean we should ignore it. Whether you're swinging a steel rod or a fiberglass shaft you MUST apply torque to the shaft to cause the clubhead's CG to rotate around it. The clubheads CG would stay in a trailing position of the shaft if you did not and we would only produce the shank to the ball. Why else would you need to rotate the left arm???
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Post by ringer on Dec 8, 2010 16:09:24 GMT -5
Ok...Ringer...Time to put up... Consider the driver swing. HOW MUCH IS THAT TORQUE AND WHAT MUSCLES DELIVER IT? You think you're so smart on this lets find out what you know. The underlined part doesn't make any sense. The amount of torque required to close the face is inconsequential? You're kidding right? Just because a shaft is loaded doesn't mean no torque is there. Nor does it mean we should ignore it. Whether you're swinging a steel rod or a fiberglass shaft you MUST apply torque to the shaft to cause the clubhead's CG to rotate around it. The clubheads CG would stay in a trailing position of the shaft if you did not and we would only produce the shank to the ball. Why else would you need to rotate the left arm??? Depends on the weight of the clubhead and where the CG is relative to the shaft. Pecks, Lats, Deltoids, and Teres major rotate the upper arm. Biceps, Brachoradialis, Pronator teres, Pronator quadratus, and Supinator rotate the forearms. I am smart and you need to come to grips with it.
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Post by ringer on Dec 8, 2010 16:10:05 GMT -5
OK ... Time's up ... here's the answer ... axial torque is minimal in even the best golfer's swings (about 2 nm maximum in a scratch golfer) practically nothing in others'. AND it becomes negative before impact at that! *the wrists actually resist closing of the clubface*... they can't keep up! Thats what the data says anyway and until someone produces something that contradicts it... thats what we know. www.jssm.org/vol4/n4/18/v4n4-18pdf.pdfGoto Page 530 scroll down to gamma torque.... look at the value 2 n-m for a scratch golfer.. THATS FRICKIN NOTHING compared to the alpha and beta torques! I'm not kidding! The torque required to close the face is INCONSEQUENTIAL. times up? What, I can't work for a living? Gees. look at the value 2 n-m for a scratch golfer.. THATS FRICKIN NOTHING compared to the alpha and beta torques!Who care's how little it is in comparison to the others, it's the torque that makes the ball go one way or the other. Seems to me that no matter what the other torques are involved, that "little one" is possibly the most important to the whole golf swing. Or do you just not care at all which direction the ball goes?
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Post by imperfectgolfer on Dec 8, 2010 18:31:35 GMT -5
Ringer,
You wrote-: "I think you are trying to say there is no torque applied to the clubhead through the shaft at all. I would be hard pressed to understand how you could believe this. You don't have to be an engineer to know that if the left arm rotates at all, the clubface will rotate with it. That rotation MUST have an axis."
I never stated that there no torque applied to the shaft/clubhead.
The axis of rotation of the LAFW, and therefore the clubface, in the late downswing is primarily the left forearm, although it is complicated by the fact that the left forearm itself is being rotated in space due to external rotation of the left humerus in the left shoulder socket while the left shoulder socket is itself in constant motion. With three connected body parts in constant circular motion during the late downswing, I cannot plot the "true" axis of rotation of the LAFW, and therefore clubface.
Jeff,
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