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Post by dubiousgolfer on Nov 10, 2019 8:15:35 GMT -5
Hi DG, Yes, White's paper which I've read, is applicable. Instead of describing it as an energy transfer, I simply chose to call it a short, or efficient, release radius over which the hands travel during release. Same thing. It's also essentially what Dr. Allen would argue - if a clubhead has a given velocity at the release point , clubhead acceleration during release is less over a longer release distance than a shorter distance. So, if one tries to "motor" the hands through the release interval, one creates a greater radius of release over which the clubhead travels.
Dr. Allen's evidence of degrees of efficiency of release are based on photographic observations, with respect to both face-on views that show whether the club has quickly passed the hands or not, or based on the relative strength of the left hand grip and associated forearm rotation. However I'm not so sure that such "evidence" is actual evidence of the distance of the release radius and whether the selected tour pros continued to "motor" the hands through release. S Hi S Can you please try and explain in more specific terms what you mean by the bolded sections above, especially the underlined phrases? Also how would you perceive the golfer to 'motor the hands' through the release interval when there is forward bend in the shaft? Check this out on Tutelmans site www.tutelman.com/golf/swing/handhit.phpExcerpts From that article is below: In fact, a leading bend at impact says that the head is pulling the hands through, so the hands must be exerting torque that resists the release of the clubWhy? Ben Hogan is convinced that hitting the ball with his hands is a big source of his power. Rock and, to a lesser extent, Lee Comeaux lean toward that opinion as well. They have worked and practiced to make it happen. They can feel it happening. But the physics and the videos say that the clubhead is pulling the hands into the ball; their hand-hit is not accelerating the clubhead. What is going on here? My take on Tom Wishon's statement is the key. If you try to add wrist torque late enough in the swing to help (the last 70msec before impact), the hands just can't keep up. Centrifugal acceleration is turning the hands so fast that the wrist muscles and right-arm piston can't turn the hands as fast as the club is already turning them. And if the muscles can't make the hands exceed what the club is doing, then they can't add any acceleration to the clubhead.
In order to test this theory, we need to measure the speed the hands can rotate a club without the load of a club's moment of inertia. Today's digital cameras make video the most convenient way to measure such speeds. So I made a quick video. Click on the photo at the right below to view it ( note : If you click on the image on the website it will download a video file on your computer that you can play using windows player).
I took a short length of PVC plastic pipe, about the diameter of a golf grip. I did a 90º back-and-forth whipping of this baton as fast as I could, simulating the attempt of the hands to uncock and recock the wrists. Because the baton is short and light, it offers little resistance to the turning, so I could measure what the hands would do moving unconstrained at full speed. (An engineer would say that the baton's moment of inertia is negligible compared to that of a golf club.) I examined the video in a movie editor that could identify frame times to within 10msec. (Actually that is more precise than the video itself; the inter-frame period of my camera is 33msec, so I would not trust an answer to be more precise than that.) What I discovered was that it took at least 150msec to make the move of a nearly 90º release. With a ten-finger grip, it was more like 200msec. True, others may be able to make a quicker move than I, and perhaps the back-and-forth is not as fast as a single forward slap (though I suspect it is). So we may do better, but we are not likely to see an improvement to twice that speed. Why do I mention twice the speed? Let's remember that, when we looked at the "standard swing" the same change of wrist angle occurred in just 70msec. That's just inertial acceleration, no wrist torque (no hand hit) at all. So the hands would have to move more than twice the speed they do, just to keep up with what the clubhead is doing to pull the hands around. In order to actually push the clubhead (rather than be pulled by it) the hands would have to go even faster than that. In fact, this test was tried by Rick Malm using better cameras and swing analysis software. (One of the lovely things about science is that it invites others to validate or disprove results by doing their own testing.) In addition to being a scientist and researcher, Rick teaches speed training for golf, so if anybody can demonstrate "fast hands" it should be Rick. Rick was able to create a 90º release using wrist torque much faster than I could. Depending on the details of the experiment, it took between 60 and 83msec. That is roughly the same as the 70msec it takes for inertial release. So Rick can possibly keep the shaft from bending forward, but even he would not be able to apply much "slap" to the head to increase clubhead speed. Conclusion: the clubhead is pulling the hands around as fast or faster than the hands can move under their own muscle power. So the hands just can't keep up well enough to apply a hit that could increase clubhead speed.
------------------------- DG
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Post by dubiousgolfer on Nov 10, 2019 8:36:09 GMT -5
Dr Mann
I've just noticed that DT mentioned the underlined section below:
"Centrifugal acceleration is turning the hands so fast that the wrist muscles and right-arm piston can't turn the hands as fast as the club is already turning them. And if the muscles can't make the hands exceed what the club is doing, then they can't add any acceleration to the clubhead."
Doesn't this mean that if there is forward shaft bend any PP1 and PP3 pressure can only be used to help PA#3 release? That there is no physical way to apply any pressure below the 'coupling point' that could cause a flipping action when forward shaft bend is happening. Doesn't the same limitation apply for adding any push pressure above the coupling point too?
DG
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Post by syllogist on Nov 10, 2019 9:03:05 GMT -5
Hi DG,""
So, if the club shaft were made of a material that were infinitely stiff, such would completely alter the mechanics of release? The flexible shaft whose bend recovers, and thus kicks in the opposite direction of its initial lag, pulls the hands through impact?
Tutelman later states, "Centrifugal acceleration is turning the hands so fast that the wrist muscles and right-arm piston can't turn the hands as fast as the club is already turning them. And if the muscles can't make the hands exceed what the club is doing, then they can't add any acceleration to the clubhead. "
This later statement is true beyond the attainment of a certain clubhead speed, when the onset of release has already occurred.
Also, note how the wording has changed from hands to wrists. The angular velocity of the clubhead works to slow the hands. The hands are being pulled through in the form of uncocking of the wrists.
One can resist the slowing of the hands by trying to speed them, especially prior to the onset of release. The average person does not know how to properly develop angular acceleration of the clubhead from the top of the swing and, as a result, further tries to develop it at the bottom of the swing .... thus the difference between the release velocity of the average person vs. the skilled person.
S
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Post by dubiousgolfer on Nov 10, 2019 9:31:40 GMT -5
Hi S
The recovering kick in the opposite direction of 'lag shaft bend' is small and doesn't fully explain the measurements and degree of forward bend that were found by 'TruTemper ShaftLab'.
Quote by DT
"There is certainly bending early in the downswing, where the "stop" of the standard swing is applying torque. Some "rebound" from this initial bend may occur. But, if the wrists were truly hinging, then this effect would be small and short-lived; it would be long gone well before impact."
I agree that one can help retain hand speed later in the downswing by building up enough hand speed just before release.
DG
PS. Actually, I'm not 100% certain about my last sentence above and need to check it out . It could actually be the point of release (and amount of wrist cock) that dictates hand speed later in the downswing (if one is assuming a 'natural release' and COAM).
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Post by imperfectgolfer on Nov 10, 2019 10:16:09 GMT -5
Dr Mann I've just noticed that DT mentioned the underlined section below: "Centrifugal acceleration is turning the hands so fast that the wrist muscles and right-arm piston can't turn the hands as fast as the club is already turning them. And if the muscles can't make the hands exceed what the club is doing, then they can't add any acceleration to the clubhead." Doesn't this mean that if there is forward shaft bend any PP1 and PP3 pressure can only be used to help PA#3 release? That there is no physical way to apply any pressure below the 'coupling point' that could cause a flipping action when forward shaft bend is happening. Doesn't the same limitation apply for adding any push pressure above the coupling point too? DG Let's presume that a golfer has an efficient release of PA#2 that causes the peripheral clubshaft to become bent forward after P6. What would happen if he stalled his left arm's targetwards motion between P6.5 and impact? Would left wrist flipping not occur due to the proximal shaft traveling faster than the left arm (from an angular velocity perspective) even if the peripheral clubshaft was still traveling marginally faster than the proximal clubshaft? I think that it would be interesting to examine pre-impact flipping videos to see whether the peripheral clubshaft is bent forwards during the pre-impact time period. Regarding the application of push-pressure at PP#1 (which is above the coupling point) in the late downswing - it only involves the speed of motion of the right hand relative to the speed of motion of the left hand and I cannot understand why it should be affected by the presence (or absence) of forward bend of the peripheral clubshaft. Jeff.
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Post by syllogist on Nov 10, 2019 10:22:09 GMT -5
Hi DG,
I can see intuitively how forward shaft kick is not due entirely to the rebound from the lag position. I could be wrong but it seems obvious that the only other thing that could cause greater kick than is explained by recovery is the slowing of the hands. Ball on a string when hand decelerates, for example, from one velocity to a new lower constant velocity the string bends in the forward direction.
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Post by dubiousgolfer on Nov 10, 2019 12:59:35 GMT -5
Dr Mann I've just noticed that DT mentioned the underlined section below: "Centrifugal acceleration is turning the hands so fast that the wrist muscles and right-arm piston can't turn the hands as fast as the club is already turning them. And if the muscles can't make the hands exceed what the club is doing, then they can't add any acceleration to the clubhead." Doesn't this mean that if there is forward shaft bend any PP1 and PP3 pressure can only be used to help PA#3 release? That there is no physical way to apply any pressure below the 'coupling point' that could cause a flipping action when forward shaft bend is happening. Doesn't the same limitation apply for adding any push pressure above the coupling point too? DG Let's presume that a golfer has an efficient release of PA#2 that causes the peripheral clubshaft to become bent forward after P6. What would happen if he stalled his left arm's targetwards motion between P6.5 and impact? Would left wrist flipping not occur due to the proximal shaft traveling faster than the left arm (from an angular velocity perspective) even if the peripheral clubshaft was still traveling marginally faster than the proximal clubshaft? I think that it would be interesting to examine pre-impact flipping videos to see whether the peripheral clubshaft is bent forwards during the pre-impact time period. Regarding the application of push-pressure at PP#1 (which is above the coupling point) in the late downswing - it only involves the speed of motion of the right hand relative to the speed of motion of the left hand and I cannot understand why it should be affected by the presence (or absence) of forward bend of the peripheral clubshaft. Jeff. Many thanks Dr Mann DG
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Post by dubiousgolfer on Nov 10, 2019 13:14:40 GMT -5
Hi DG, I can see intuitively how forward shaft kick is not due entirely to the rebound from the lag position. I could be wrong but it seems obvious that the only other thing that could cause greater kick than is explained by recovery is the slowing of the hands. Ball on a string when hand decelerates, for example, from one velocity to a new lower constant velocity the string bends in the forward direction. Hi S Yes, that's what DT has surmised. The forward bend is greater than expected by something called 'eccentric loading' and he thinks its because the hands are actually resisting because they cannot keep up with the clubshaft angular velocity at the proximal end. I need to find out if I can contact Rod White about his article as there are several questions I'd like to ask him about the Simple DP model. a. For a natural release , if the DP folded system is made to initially move at a greater speed before release (with same PA2 angle), will the stopping/bracing 'positive' torque also have to increase. b. For a natural release, if the DP folded system is made to initially move at a greater speed before release (with same PA2 angle), will it affect the point of release in the downswing path. c. For scenarios 'a' and 'b', how will this affect the speed of the proximal arm as clubhead release progresses into impact. DG
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Post by syllogist on Nov 11, 2019 8:03:36 GMT -5
Hi DG,
White's simple DP model is solely under the force of gravity. His complex DP model assumes that the proximal segment rotates at a constant velocity, which is why his model shows a natural release point where positive wrist torque 20% above that point and negative wrist torque until 20% below that point yield the same results. The assumption of a constant velocity is problematic and can't answer the that you posed.
Intuitively I believe that the proximal segment should accelerate until the release point and that there's no way, at least in a meaningful sense, to slow that segment at the release point except to cease acceleration. In order to accelerate efficiently, the left arm and club should remain as "folded" as hand path permits and the club should remain folded. To extend the model to a triple pendulum as did MacKenzie and Sharp, and as White acknowledged, the torso rotation is what accelerates and, itself, is a "short lever" in relation to the left arm with the shortest radius of curvature in the swing's rotational system.
S
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Post by dubiousgolfer on Nov 11, 2019 8:39:23 GMT -5
Hi DG, White's simple DP model is solely under the force of gravity. His complex DP model assumes that the proximal segment rotates at a constant velocity, which is why his model shows a natural release point where positive wrist torque 20% above that point and negative wrist torque until 20% below that point yield the same results. The assumption of a constant velocity is problematic and can't answer the that you posed. Intuitively I believe that the proximal segment should accelerate until the release point and that there's no way, at least in a meaningful sense, to slow that segment at the release point except to cease acceleration. In order to accelerate efficiently, the left arm and club should remain as "folded" as hand path permits and the club should remain folded. To extend the model to a triple pendulum as did MacKenzie and Sharp, and as White acknowledged, the torso rotation is what accelerates and, itself, is a "short lever" in relation to the left arm with the shortest radius of curvature in the swing's rotational system. S Hi S Here is Rod White's reply to my email: Responses interleaved below... For that Simple DP system where you created the condition that the blue ball stop when the system is fully extended (ie. 100% efficient transfer of Kinetic Energy) what would happen if that same system was given a greater speed before removing the string? > Yes, though the scaling is not always directly proportional. if you double the angular velocity, the torques go up 4 times (scale factor squared) I have raised specific questions below: a. For a natural release , if the 'Simple DP folded system' is made to initially move at a greater angular velocity just before release (with same wrist cock angle), will the stopping/bracing 'positive' torque also increase? > Yes, as above. b. For a natural release, if the DP folded system is made to initially move at a greater angular velocity before release (with same wrist cock angle), will it affect the point of release in the downswing path? > If I recall correctly, the point of release and impact point remain the same. c. For scenarios 'a' and 'b', how will this affect the angular velocity of the proximal arm as clubhead release progresses into impact and will there still be a 100% efficient transfer of Kinetic Energy (with blue ball still stopping when system fully extended)? > Yes all the velocities scale in proportion, forces scale as the square. How would greater wrist cock effect that simple DP with regards: d. The bracing torque > greater wrist cock => lower torque required e. The point of release in downswing > greater wrist cock => later release f. The angular velocity of the proximal arm > greater wrist cock => greater velocity g. Will there still be a 100% efficient transfer of Kinetic Energy - blue ball stopping when system extended)? => no. Hope this helps. Unfortunately, I up graded the software I used for these simulations a couple of years ago, and all the old scripts I used for the golf analysis no longer run. and I can no longer read them to fix them. Ain't software wonderful!! I think the software Dave recommends will do these simulations a bit easier nowadays anyway. best wishes Rod ---------------------------------- DG
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Post by imperfectgolfer on Nov 11, 2019 10:15:45 GMT -5
S,
You wrote-: "To extend the model to a triple pendulum as did MacKenzie and Sharp, and as White acknowledged, the torso rotation is what accelerates and, itself, is a "short lever" in relation to the left arm with the shortest radius of curvature in the swing's rotational system."
In a triple pendulum system all the pendular arms have to move in the same plane and that certainly does not happen in a full golf swing action. The clubshaft moves in the same plane as the left arm during the release of PA#2 if a golfer maintains an intact LAFW, but the left arm does not move in the same plane as the rotating torso (as seen in SMK's computer model) during the release of PA#4, and I therefore think that it is wronghheaded to believe that a simplistic triple pendulum model helps us to better understand the release of PA#4 in a full golf swing action.
Jeff.
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Post by dubiousgolfer on Nov 11, 2019 10:26:51 GMT -5
If I understand this correctly , a 'Driven DP' takes out the 'release' point timing aspect of the swing compared to the 'Simple DP ' swing (if you are a golfer that might use varying wrist cock). Rod White has inferred in his reply to my questions that increased wrist cock (for that 'Simple DP ' pendulum where one has given the 'folded system' some angular velocity just before release) will require later release (ie. smaller downswing angle). . But varying the wrist cock angle in a 'Driven DP' , passive wrists seems to facilitate release points (downswing angle) that are virtually the same to get peak clubhead speed (see graph below). I suspect it might depend on the golfer whether they prefer a similar release point with varying wrist cock for a 'Driven DP' type swing or Different release points with varying wrist cock for a 'Simple DP' type swing. Whatever their preference it is important in both types of swing to have passive wrists to allow a natural release. -------------- FOR DRIVEN DP . The figure to the left above shows the clubhead speed versus downswing angle (the angle between the arms and where they were at the beginning of the downswing), for three different wrist cock angles (the angle between the arms and the club shaft). Note again that the wrist-cock angle is measured between the arms and the club, so a smaller angle corresponds to greater wrist cock, or greater "lag" as it is often called. If there were no wrist cock at all, the angle would be 180 degrees. As expected, increasing the amount of wrist-cock (reducing the angle between the arms and shaft) increases the efficiency of the swing. The key point is that the peak speeds all occur at a very similar downswing angle, showing that the swing timing is almost unchanged. The golfer expends the same effort for all three swings, yet we see a 10% increase in head speed resulting in a 10% increase in distance – say 20 m for a 200 m drive -- with no extra effort.
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Post by syllogist on Nov 11, 2019 11:24:34 GMT -5
Hi DG,
As I mentioned, from having read White's study, in the driven DP model, there is an acceleration from the top of the swing that becomes to a constant velocity at a chosen point. I believe that such is why the model shows a "natural release point" which White stated is the most inefficient release point to have greatest clubhead speed at impact. He stated that the most efficient points are 20% before and 20% after. This implies that either one has to apply positive wrist torque prior to natural release or delay the release through negative wrist torque.
I didn't see in the study that he used a parameter to purely accelerate to a point. With pure acceleration and without a parameter for constant velocity, I believe that a "natural release point" is dependent on a given acceleration profile and that the greater the acceleration, the later the release point.
S
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Post by dubiousgolfer on Nov 11, 2019 18:31:01 GMT -5
Hi DG, As I mentioned, from having read White's study, in the driven DP model, there is an acceleration from the top of the swing that becomes to a constant velocity at a chosen point. I believe that such is why the model shows a "natural release point" which White stated is the most inefficient release point to have greatest clubhead speed at impact. He stated that the most efficient points are 20% before and 20% after. This implies that either one has to apply positive wrist torque prior to natural release or delay the release through negative wrist torque. I didn't see in the study that he used a parameter to purely accelerate to a point. With pure acceleration and without a parameter for constant velocity, I believe that a "natural release point" is dependent on a given acceleration profile and that the greater the acceleration, the later the release point. S Hi S Unsure about the swing becoming a constant velocity at a chosen point. In the driven (and also simple) DP models, the natural release is when the 'braking/positive' force (ie. to stop the peripheral arm collapsing on the central hub) is allowed to 'naturally' reduce to zero which then also allows the unfolding of the 2nd arm. He mentions something called advance release (which I have problems understanding- maybe he means 'float loading') and delayed release that could improve the 'efficiency' of the swing ' stroke' (ie . see graph 10 and extract below) but its only about 5 m extra distance (for a difference of 20 degrees either side of the natural release 'downswing angle). The downswing angle which he mentions in his published article is that angle formed between the upper arm and the vertical (ie. like β in diagram 'a' below) Release delay: Figure 10 plots the stroke efficiency versus the release delay. The delay is expressed as the difference in downswing angle between the angle of release and the natural-release angle. Surprisingly, the swing with the natural release is the least efficient: either delaying or advancing the release results in a more efficient swing. An advanced release results in the club swinging closer to the hub, so that the wrist-cock angle decreases, and the swing becomes more efficient. When the release is delayed, the wrist-cock is maintained in the more efficient position for longer so increasing the efficiency. As a consequence of these two effects, the overall effect of release timing is second order and has little effect on the swing efficiency. To obtain a gain of 5 m in distance, the release angle must be advanced or delayed by about 20°. ---------------- What I find amazing about all this research is that they must be spending enormous sums of money and time investigating impacts on clubhead speed but there is very little research about how to square the clubface (which I think is just as important). DG
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Post by syllogist on Nov 12, 2019 6:23:17 GMT -5
Hi DG, I looked back at the study. I was wrong - he did state that he used a constant torque and not a constant velocity. His term advanced release is "downcocking." So, it's not surprising that downcocking 20% before the natural release (assumed by the acceleration) used results in slightly greater efficiency. I don't know how much money is spent researching by modeling the swing but I can imagine how much money is made by the devices that measure force and motion and club movement. MacKenzie is the only one to my knowledge who has considered clubface squaring (axial rotation of the shaft) vis a vis technique. It was a parameter that was measured in Cheetham's dissertation. My guess is that, given a swing that near optimal, squaring without having to try to square is a function of grip, the degree to which the forearms are rotated at transition, and the amount of upper body rotation in the downswing. Probably best not having to try to square. S
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