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Post by imperfectgolfer on Jul 15, 2012 0:03:33 GMT -5
Dexterous,
You asked-: "Do you believe a stable left wrist (whatever that is) can somehow minimize whatever effect to the face angle is caused by a strike where the ball is not in alignment with the CG? What evidence do you have that proves that may be true? I think what BM is saying is NO it doesn't matter if the left wrist is bowed or cupped or flat, the effects of an off center strike will not be affected by any kind of hand/wrist manipulation."
Here is some evidence.
In John Erickson's hitting action, he stabilises the FLW through impact by simultaneously applying push-pressure with the bent right wrist through impact in order to stabilize the FLW - equivalent to a two-handed backhanded tennis stroke versus an one-handed backhanded tennis stroke.
Jeff.
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Post by imperfectgolfer on Jul 15, 2012 8:53:36 GMT -5
Jeffy wrote-: "Don't misquote me. I never said a player "must" hit it low on the racquet for a topspin shot. But often they do, just as they often hit it high on the racquet for slice spin."
Where is the "evidence" that a professional tennis player deliberately hits the ball off-center when hitting top-spin and slice-spin shots. I think that they try to always hit it at, or near, the center of the racquet face. If the ball is hit off-center, then it is due to the effect of the angle of the racquet face orientation and also the racquet face path as it comes into impact - and that will cause top-spin shots to more likely be hit slightly below the equator of the racquet face and slice-spin shots to be hit slightly above the equator of the racquet face.
Jeff.
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Post by virtuoso on Jul 16, 2012 10:23:56 GMT -5
On the Erickson vid it looks to me like the "swinging" strike was bit more toward the toe. Am I on the crack again?
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Post by imperfectgolfer on Jul 16, 2012 13:11:52 GMT -5
It could be that the toe impact points are not exactly the same in his swinger's versus hitter's swings. John Erickson would have produced a much more scientifically-conclusive video if he used impact tape and conclusively demonstrated that the impact points were identical. Nonetheless, his results are very intriguing and I think that this issue needs much more scientific study. I would not be surprised to discover that a "stable left wrist" could result in less clubface distortion/displacement with off-center hits, and I therefore remain open-minded about this possibility.
Jeff.
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Post by virtuoso on Jul 16, 2012 20:17:00 GMT -5
Jeff, isn't the exact hit location the whole enchilada? How can we be missing the most critical piece of data and still be very intrigued?
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Post by imperfectgolfer on Jul 16, 2012 21:56:09 GMT -5
I have no idea what you are talking about!
I am intrigued by the possibility that the same degree of off-center strike can produce different degrees of clubface displacement and different ball flight patterns when comparing a stable clubface to a non-stable clubface.
Jeff.
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Post by gmbtempe on Jul 16, 2012 21:57:49 GMT -5
Jeff, isn't the exact hit location the whole enchilada? How can we be missing the most critical piece of data and still be very intrigued? I agree, seeing impact numbers from TM and video's like this take a bit of a hit without knowing exactly where it was struck on the clubface.
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Post by imperfectgolfer on Jul 16, 2012 22:15:16 GMT -5
Greg,
I think that "knowing exactly where it has been struck on the clubface" has been the Achilles heel of all attempts to scientifically study the impact collision phenomenon. Trackman cannot see the clubface and it only infers its orientation at impact. High speed videos at 10,000 frames per second can see the clubface and its degree of displacement secondary to impact with the ball, but I have never seen any studies combining high speed videos and ball flight patterns - specifically related to off-center strikes. We then also need to study whether a "stable clubface" affects the degree of clubface displacement and the ball flight secondary to off-center strikes - if we can agree on a definition of a "stable clubface". I think that we would need to have pressure sensors embedded in the clubshaft at PP#2, PP#1 and PP#3 to more clearly define what best represents "stable clubface" parameters.
Jeff.
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Post by virtuoso on Jul 17, 2012 12:42:15 GMT -5
Jeff, in the hammer throw, does the thrower do the "lean back" just to counterbalance cf-loading or is it because the hammer is not rotating around the thrower as much as they are both rotating around a point somewhere between the two?
In other words, both objects are traveling in an orbit around a common point but the thrower has a smaller orbit because the mass is greater than the hammer?
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Post by imperfectgolfer on Jul 17, 2012 13:47:47 GMT -5
I think that the hammer thrower "leans back" isometrically so that he can maintain a "fixed" spinal bend inclination of his mid-upper torso and he is basically rotating around an imaginary fulcrum point that is located near his upper swing center (midway point between the two shoulder sockets). The amount of isometric force used to maintain his spinal bend inclination angle constant is directly proportional to the CF-loading force and it also reflects the magnitude of the normal force that is needed to keep the hand arc path constant. The hammer thrower's torso/arms and the hammer-ball are all rotating around the same imaginary fulcrum point, but the radius of the hammer-ball arc is greater than the radius of the hand arc path, which (in turn) is greater than the radius of the shoulder socket path.
Jeff.
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Post by virtuoso on Jul 17, 2012 15:06:02 GMT -5
Wait a second! Jeff, you think the fulcrum point (center of rotation) of the entire thrower/hammer ball system is between the shoulder sockets of the thrower?
I thought the fulcrum point was way out in front of his chest somewhere. Think of a barbell with 20 lb weight on one end and a 50 pound weight on the other. Then to balance and spin the barbell you would have to choose a fulcrum point much closer to the 50 lb weight, but not the center of the 50 lb weight.
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Post by imperfectgolfer on Jul 17, 2012 18:41:39 GMT -5
I didn't say that the fulcrum point is at the upper swing center - it is only near the USC. It is the imaginary central point of the circle of rotation of the entire system - if he wasn't moving his feet around and thereby constantly moving the fulcrum point in space. The fulcrum point would be at the USC if he had a vertical posture and his arms were horizontal to the ground and he simply spun his torso around his vertical axis, but it must be more forward (towards his toes) if he adopts a bent-over spinal inclination angle.
Jeff.
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Post by imperfectgolfer on Jul 17, 2012 21:28:07 GMT -5
What is worthless about that video?
Why do you believe that a clockwise rotation of the straight left arm/FLW through the immediate impact zone (between P6.9-P7.2) cannot open the clubface relative to the target and clubhead arc?
Jeff.
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Post by imperfectgolfer on Jul 17, 2012 22:35:39 GMT -5
Dexterous, In this forum, you are free to express any opinion, but your criticisms are worthless from my perspective (especially considering the fact that they contain no explanatory detail). Here are capture images from John Erickson's video. Swinger - 1a (impact) 1b (soon after ball-clubface separation) Hitter - 2a (impact) 2b (soon after ball-clubface separation). What's invalid about those images? Do you have ENSO images/measurements of a golfer who is deliberately rolling his FLW clockwise through impact? Jeff.
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Post by tomdavis76 on Jul 18, 2012 9:46:33 GMT -5
Erickson's "hitter" looks similar to this clubface behavior:
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