namj
Junior Member
Posts: 88
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Post by namj on May 8, 2011 1:22:22 GMT -5
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namj
Junior Member
Posts: 88
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Post by namj on May 8, 2011 1:23:42 GMT -5
Seems to be a slight glitch in the concept.
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namj
Junior Member
Posts: 88
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Post by namj on May 8, 2011 1:25:43 GMT -5
namj, I answered your question about a random release when I answered Greg's question about a late/snap release. Jeff. Thanks. I read it.
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Post by natep on May 8, 2011 1:28:49 GMT -5
Every measurement of kinematic sequencing i have seen so far shows the lead arm slowing down before impact, such as this from Phil Cheetham:
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Post by gmbtempe on May 8, 2011 1:28:40 GMT -5
But even if the hands are slowing down for everyone the the idea of a smaller pulley, which is the part of interest to me, would still be correct would it not?
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Post by natep on May 8, 2011 1:31:56 GMT -5
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namj
Junior Member
Posts: 88
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Post by namj on May 8, 2011 1:36:39 GMT -5
What was interesting was at the end of the Zuback video there was a softball pitcher and her motion of the release of the ball was quite interesting I don't know about the pulley size but it sure looked like her hand slowed down at release point.
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Post by imperfectgolfer on May 8, 2011 1:40:03 GMT -5
Natep,
They are measuring the lead arm's rotational speed based on a certain axis.
I have already referred you to a Rob Neal article that showed that there is no concordance between linear hand speed and rotational lead arm speed - because of how they measure them. The endless belt concept is based on the effect of hand arc path changes for a given level of linear hand speed.
Jeff.
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namj
Junior Member
Posts: 88
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Post by namj on May 8, 2011 1:40:22 GMT -5
But even if the hands are slowing down for everyone the the idea of a smaller pulley, which is the part of interest to me, would still be correct would it not? I wish I knew. It seems logical but every time I think something is logical I find out there's some kind of issue with it...lol.
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Post by imperfectgolfer on May 8, 2011 1:44:03 GMT -5
namj, You are free to believe that the hands slow down prior to impact - based on 3jacks' blog comments. Here is a graph of hand speed from a Rob Neal research article. Jeff.
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namj
Junior Member
Posts: 88
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Post by namj on May 8, 2011 1:51:41 GMT -5
namj, You are free to believe that the hands slow down prior to impact - based on 3jacks' blog comments. Here is a graph of hand speed from a Rob Neal research article. Jeff. Ok let's not start off on this path, I never said I believed anything and it didn't relate to Richie's blog comments. It was just another piece of info to look at and that's it. Also I don't need you to tell me what I can choose to believe in like if I do I'm wrong in believing it. Keep it civil.
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namj
Junior Member
Posts: 88
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Post by namj on May 8, 2011 1:54:48 GMT -5
If the endless belt concept is correct I don't see how you could keep a constant hand speed.
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Post by gmbtempe on May 8, 2011 1:56:10 GMT -5
yea, this is a good discussion, he never said he believed.
Wonder what BM's take on this is because Neal is one of his main guys for his research project.
Does the graph change for say a 5 iron?
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namj
Junior Member
Posts: 88
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Post by namj on May 8, 2011 2:03:41 GMT -5
yea, this is a good discussion, he never said he believed. Wonder what BM's take on this is because Neal is one of his main guys for his research project. Does the graph change for say a 5 iron? I would like to look at Grober's take on it and some others. I'm wondering if the hands do slow down it must be something that's unavoidable and we can't do anything about it? I have no clue.
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Post by natep on May 8, 2011 2:05:41 GMT -5
Here is the article about Neal's modified measurement of hand speed. golfbiodynamics.com/downloads/newsletters/GBD_Newsletter_4.pdfHe changed his measurement of hand speed to essentially measure "release speed". If the new hand speed measurement were to peak before impact, it would mean that the subject had "casted" the club, not that his arm speed had slowed down into impact. Clearly this is not the same as measuring the arm/hand "swing" speed. Neal's old method, which measured the linear hand speed toward the target, did in fact detect the linear hand speed decreasing before impact. Jeff has stated that the arm speed measurement in the kinematic sequencing chart I posted are measurements of arm rotation around a particular axis and not arm "swing" speed. His statements are incorrect. At Phil Cheetham's site: amm3d.com/ one can see on the homepage a kinematic sequence chart. The corresponding text states that the measurements of the hips and ribcage are rotational, but the arm and club speeds are angular swing speeds. There is also a FAQ section of the website here: www.amm3d.com/Support/FAQs.aspxQuestion #4 in the FAQ asks "What do each of the curves in the kinematic sequence measure?" The paragraph that answers this question explains that while the pelvis and thorax measurements are rotational measurements around a particular axis, the arm and club measurements are not, and are measurements of angular speed, i.e. pendular swinging speed from the shoulder socket. Here is a copy of the text: "There are currently four curves in our Kinematics Sequence; pelvis, thorax (upper torso), lead upper arm, and club shaft. Each curve is a measure of the angular speed (aka rotational speed) of that segment at each instant throughout the swing; angular speed is measured in degrees per second (not miles per hour, that would be linear speed). More specifically the pelvis speed (red curve) is the angular speed around an up/down axis through the middle of the pelvis; similarly with the thorax (green curve). This up/down axis is embedded in the segment and moves with it, so if you are bent forward then this "up/down" axis is also bent forward. So for both the pelvis and the thorax you can think of it as how fast they are turning (turning speed around the up/down axis); first backwards in the backswing then forward in the downswing and follow through. Note that if the curve value is negative then it is in the backswing phase, if it is positive then it is in the downswing or follow through phase. Now for the arm (blue curve) and shaft (brown curve) it is slightly different. Since both of these swing around an end point (shoulder joint or mid-grip), it is of more interest to measure their angular speed around that point; just like the swinging of a pendulum. To calculate angular swing speed of the club shaft just before impact, for example, we would take the shaft position before impact and the shaft position at impact and create a plane from these two lines, we then calculate the angluar speed from position one to position two and divide by the time it took took. This gives us degrees per second. This is good especially for the club shaft because is tells us how fast the club shaft is swinging in an "instantaneous swing plane" or simply in the current swing plane direction. The curve for the club is often confused with club head speed. They are not the same. The one in the Kinematic Sequence is the angular speed of the entire club shaft in degrees per second but the club head speed is specifically the linear speed of a point in the middle of the club head measured in miles per hour (or meters per second etc.). They are related to each other but they are not exactly the same." So, the following chart from Cheetham is measuring the angular swing speed of the arm and club (in degrees per second), and not the rotational speed of the arm and club around a particular axis, as Jeff stated. This chart shows that the lead arm/hand does in fact slow down prior to impact.
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