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Post by syllogist on Nov 6, 2019 13:17:13 GMT -5
Hi DG - your summary is very good.
Your points raised are good summaries and are why I had given an example of parametric acceleration using Dr. Mann's double pendulum on the floor and pulling one segment of the 90 degree angle pendulum. It's also why I stated in another thread that COAM doesn't apply to the golf swing. Changing radii of curvature where the radii shorten are more effective at increasing angular velocity of the club than is purely circular path. The final means of ensuring that angular velocity is maximized given force and changes in radii is to stop applying force so as not to inhibit maximum velocity of the club (the means of "transferring" force from arms to club).
The two plastic threads of a weedwacker lag in a bent state the turning rotor from which they protrude when the rotor accelerates or moves at a constant speed. The threads will only be induced to return to a straight state toward perpendicular to the rotor when the rotor decelerates.
S
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Post by dubiousgolfer on Nov 6, 2019 17:38:04 GMT -5
Hi S
I've been looking on the internet on physics forums to try and get a better intuitive idea on how clubhead speed can be increased. Here is a question and answer that might also apply to a real life golf swing and finally makes some sense to me.
---------------------------------- Question: I completely understand the concepts behind uniform circular motion. But let's say you are spinning a ball connected by a string to a motor in a horizontal circle. When increasing the angular velocity of the spinning motor, I can't see how the ball connected to the string will have any force that allows it to increase its tangential velocity. How would the string be able to pull it so it accelerates tangentially all while undergoing circular motion? An example would be if you are swinging a ball in a circle above your head and you begin to spin it faster. How is the string causing the object to increase its linear speed? I believe tension can't cause it unless it's working at an angle less than 90 to the tangent because work must be done to increase the kinetic energy.
Answer (and it seems similar to Nmgolfer and Mandrins opinions) In the case that you describe, an individual swinging a mass horizontally on the end of a string, the string does not run directly to the centre of rotation. Instead, it runs to your hand, which in turn is moving in a circle about its centre of rotation . Sometimes the arm is involved, sometimes only a rotation at the wrist. ( Mime winding up a sling to throwing speed to see what I mean)
If everything is constant (and there's no drag on the mass), the line from mass to hand to centre of rotation is straight; the string tension exerts only the centripetal force needed to maintain the circle, as well as an upward component to keep the mass from dropping downward.
If you then speed up the circular motion of your hand to a new constant angular velocity, your hand's angular motion gets ahead of the mass's angular motion, and gets continuously farther ahead. So now the tension in the string is not in the line from the mass to the centre of rotation. There is a tangential component to the tension, constantly increasing, which serves to speed up the rotation of the mass.
This tangential force speeds up the mass's rotation, until the mass is rotating faster than your hand. Then the mass gets ahead, and your hand slows it down, and so on. ------------------------------------------
DG
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Post by imperfectgolfer on Nov 6, 2019 17:45:07 GMT -5
DG, I have addressed these issues repeatedly in the past, so I don't know why you are bringing these issues up again. I have previously stated that the COAM principle applies to a simple double pendulum swing model, where there is a "fixed" amount of energy inputted at the onset and where the central arm slows down as the peripheral arm releases. The full golf swing is more like a driven double pendulum swing model where "extra" energy can be inputted during the downswing to prevent the left arm from slowing down too much when PA#2 releases. However, the "extra" energy (M shoulder torque) added is just enough to keep the left arm moving at a sufficient speed through impact so that a golfer can match the angular velocity of the left arm to the angular velocity of the clubshaft between P7 and P7.2 so that the intact LAFW can be maintained intact (thereby representing a DH-hand release action). You also wrote-: " It is the off-axis component owing to the changing radii which accelerates the clubhead in a tangential direction. That off-axis component is maximized by continually shorten the swing center radius during the last two phases of the downswing not just the last few microseconds. Ideally there is not "something different" that happens just before impact." I don't know why you think that it is an off-axis phenomenon. To release PA#2 the one must continually shorten the swing center radius (shorten the radius of the hand arc path) between ~P5.5 and P6.2, but the hand arc path can be on-plane with respect to the ball-target line - as seen in these DTL capture images of Jamie Sadlowski's driver swing.
Jeff.
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Post by imperfectgolfer on Nov 6, 2019 17:51:28 GMT -5
DG,
You wrote-: "Answer (and it seems similar to Nmgolfer and Mandrins opinions) In the case that you describe, an individual swinging a mass horizontally on the end of a string, the string does not run directly to the centre of rotation. Instead, it runs to your hand, which in turn is moving in a circle about its centre of rotation . Sometimes the arm is involved, sometimes only a rotation at the wrist. ( Mime winding up a sling to throwing speed to see what I mean).
From my perspective, that's the D'Alembert principle in play. The hand is constantly changing its direction of travel in a circular manner.
Jeff.
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Post by dubiousgolfer on Nov 6, 2019 18:04:27 GMT -5
Dr Mann
What confused me was your previous comment
"I suspect that the left arm slows down due to the COAM principle that applies to the PA#2 release phenomenon (where the central arm slows down when the peripheral arm speeds up), and due to the fact that the left shoulder socket moves upwards after P5.5 thereby not exerting a targetwards pull on the left arm in the late downswing."
As far as I am aware you can either have COAM in the full swing like a simple DP (as you've mentioned above) or not have COAM as in a driven DP. Therefore your explanation for the slowing down of the arm using the COAM analogy of a simple DP cannot be applicable in a driven DP type golf swing.
DG
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Post by dubiousgolfer on Nov 6, 2019 18:25:10 GMT -5
DG, You wrote-: " Answer (and it seems similar to Nmgolfer and Mandrins opinions) In the case that you describe, an individual swinging a mass horizontally on the end of a string, the string does not run directly to the centre of rotation. Instead, it runs to your hand, which in turn is moving in a circle about its centre of rotation . Sometimes the arm is involved, sometimes only a rotation at the wrist. ( Mime winding up a sling to throwing speed to see what I mean). From my perspective, that's the D'Alembert principle in play. The hand is constantly changing its direction of travel in a circular manner. Jeff. Dr Mann From my perspective , that example is the same as an off-axis component owing to the changing radii. If you plotted the loci of that mass on the string and calculated the instantaneous radius of curvature as its being swung faster, the increase in tangential velocity would correspond to a sudden decrease in its radius. I am not talking about the hub path curvature but the clubhead path radius. My issue has always been what actual real forces increases tangential clubhead speed and now I finally understand that it is ultimately the tension in the shaft. This has just been a bit of a confusing issue for me from a physics perspective but now its resolved (I hope!). DG
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Post by imperfectgolfer on Nov 6, 2019 23:00:14 GMT -5
DG, You wrote-: " Answer (and it seems similar to Nmgolfer and Mandrins opinions) In the case that you describe, an individual swinging a mass horizontally on the end of a string, the string does not run directly to the centre of rotation. Instead, it runs to your hand, which in turn is moving in a circle about its centre of rotation . Sometimes the arm is involved, sometimes only a rotation at the wrist. ( Mime winding up a sling to throwing speed to see what I mean). From my perspective, that's the D'Alembert principle in play. The hand is constantly changing its direction of travel in a circular manner. Jeff. Dr Mann From my perspective , that example is the same as an off-axis component owing to the changing radii. If you plotted the loci of that mass on the string and calculated the instantaneous radius of curvature as its being swung faster, the increase in tangential velocity would correspond to a sudden decrease in its radius. I am not talking about the hub path curvature but the clubhead path radius. My issue has always been what actual real forces increases tangential clubhead speed and now I finally understand that it is ultimately the tension in the shaft. This has just been a bit of a confusing issue for me from a physics perspective but now its resolved (I hope!). DG I disagree 100% with your perspective. If a person swings a mass attached to the end of a string of "X" length, then the radius (length of the string) will stay the same even if the hand swings it faster-and-faster. I think that clubshaft tension plays no role in increasing clubhead speed in a TGM swinging action. Jeff.
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Post by syllogist on Nov 7, 2019 7:46:37 GMT -5
Hi DG,
You were looking for an intuitive idea as to how clubhead speed can be increased assuming proper rotational sequencing.
If you set aside radii of hand path, there are only two factors that can increase speed.
1) Rotational velocity of the torso; and 2) Late release
With respect to 2 above, if it is a natural consequence of the swing and it is not "manufactured" in a way that velocity is inhibited, the radius of release will be the shortest possible. In other words, speed is maximized when the distance over which release occurs is minimized. The "late release" minimizes the radius of release.
Remember A=V^2/R, acceleration = velocity squared divided by radius.
S
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Post by imperfectgolfer on Nov 7, 2019 9:54:14 GMT -5
Hi DG, You were looking for an intuitive idea as to how clubhead speed can be increased assuming proper rotational sequencing. If you set aside radii of hand path, there are only two factors that can increase speed. 1) Rotational velocity of the torso; and 2) Late release With respect to 2 above, if it is a natural consequence of the swing and it is not "manufactured" in a way that velocity is inhibited, the radius of release will be the shortest possible. In other words, speed is maximized when the distance over which release occurs is minimized. The "late release" minimizes the radius of release. Remember A=V^2/R, acceleration = velocity squared divided by radius. S How does increased rotational velocity of the torso increase clubhead speed at impact? Jeff.
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Post by syllogist on Nov 7, 2019 21:04:06 GMT -5
Dr. Mann,
Just consider above the waist for these purposes. If you believe that the sequence of the downswing is 1) torso with arms beginning at the same rotary speed, then 2) arms, and then 3) wrists, to increase "hand speed," the speed of the first stage of the sequence must increase. This sequence has a timing. If one does anything else to try to increase hand speed, then one will alter the relative timing of the sequence.
S
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Post by imperfectgolfer on Nov 7, 2019 23:17:34 GMT -5
Dr. Mann, Just consider above the waist for these purposes. If you believe that the sequence of the downswing is 1) torso with arms beginning at the same rotary speed, then 2) arms, and then 3) wrists, to increase "hand speed," the speed of the first stage of the sequence must increase. This sequence has a timing. If one does anything else to try to increase hand speed, then one will alter the relative timing of the sequence. S I would agree if the kinematic timing sequence remains perfectly synchronised and functionally intact, so that any increased speed of torso rotation causes a proportionately increased speed of release of PA#4. Jeff.
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Post by dubiousgolfer on Nov 8, 2019 8:06:22 GMT -5
Dr Mann From my perspective , that example is the same as an off-axis component owing to the changing radii. If you plotted the loci of that mass on the string and calculated the instantaneous radius of curvature as its being swung faster, the increase in tangential velocity would correspond to a sudden decrease in its radius. I am not talking about the hub path curvature but the clubhead path radius. My issue has always been what actual real forces increases tangential clubhead speed and now I finally understand that it is ultimately the tension in the shaft. This has just been a bit of a confusing issue for me from a physics perspective but now its resolved (I hope!). DG I disagree 100% with your perspective. If a person swings a mass attached to the end of a string of "X" length, then the radius (length of the string) will stay the same even if the hand swings it faster-and-faster. I think that clubshaft tension plays no role in increasing clubhead speed in a TGM swinging action. Jeff. Dr Mann I think we will have to agree to disagree on the mechanism of tension in increasing clubhead speed. D'Alembert principle and 'Sasho MacKenzie's' 'Net force causing a moment of force at a distance' (ie. shown by the white and blue arrows in diagram below) are (imho) identical but just being explained in different ways. I found both concepts 'intuitively' difficult to understand because I think one needs a force applied physically to the COM of the club to accelerate it tangentially. I cannot envisage any means of 'pushing/pulling' against the COM of the club other than whatever is touching the COM and that is via medium of the shaft (or some other external force that I cannot comprehend). Further , my diagram below of Bobby Jones swing is also (again in my humble opinion) another identical way of explaining how clubhead speed increases and probably the maths will end up exactly the same as D'Alembert and SMK' MOF concepts. The increasing of tangential speed of that mass on a string obviously doesn't change the length of the string although the maths implies a 'shortening' of the 'swing radius' (too complicated for me to understand). The 'swing radius' would have to match the clubheads instantaneous 'circular path' and 'speed' to comply with the 'a=v 2/r' equation and does not relate to the length of the string (from mass to fingers of hand). One can easily see that the tangential velocity of the clubhead can be increased by the misalignment (and tension) of the club shaft vs the instantaneous centripetal force that's keeping it moving on its instantaneous curved path. That misalignment gets smaller as forward shaft bend happens in the late downswing as shown in modern Tour pro swings (and I cannot imagine that the tension in the shaft will increase dramatically from say P6-P7). Therefore the rate of increase in 'Tangential Velocity' will decrease in the late downswing as the shaft and instantaneous 'centripetal force' vector become more aligned'. DG
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Post by syllogist on Nov 8, 2019 9:17:05 GMT -5
Hi DG,
I looked at the answer you showed for the ball on the string question:
"In the case that you describe, an individual swinging a mass horizontally on the end of a string, the string does not run directly to the centre of rotation. Instead, it runs to your hand, which in turn is moving in a circle about its centre of rotation . Sometimes the arm is involved, sometimes only a rotation at the wrist. ( Mime winding up a sling to throwing speed to see what I mean)
If everything is constant (and there's no drag on the mass), the line from mass to hand to centre of rotation is straight; the string tension exerts only the centripetal force needed to maintain the circle, as well as an upward component to keep the mass from dropping downward.
If you then speed up the circular motion of your hand to a new constant angular velocity, your hand's angular motion gets ahead of the mass's angular motion, and gets continuously farther ahead. So now the tension in the string is not in the line from the mass to the centre of rotation. There is a tangential component to the tension, constantly increasing, which serves to speed up the rotation of the mass.
This tangential force speeds up the mass's rotation, until the mass is rotating faster than your hand. Then the mass gets ahead, and your hand slows it down, and so on. "
This answer involves a rotational acceleration of hand where the hand then rotates at a constant velocity (ceases to accelerate), which is why the ball's rotational speed catches up to the rotational speed of the hand. When the ball is in the process of catching up with the hand's now constant rotational velocity, the tension on the string diminishes. The same phenomenon happens to the golf club because the hands cease to accelerate.
It is the cessation of acceleration of the hands that increases the speed of the clubhead. So, to answer your original question about how one goes about increasing clubhead speed, the practical answer is to stop applying rotational force before the release point.
S
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Post by imperfectgolfer on Nov 8, 2019 10:27:14 GMT -5
DG, Your explanations do not resonate with me. It is obvious to me that there must be a tangential force component to clubshaft tension in order for the club to acquire increased angular momentum during the release of PA#2. However, the cause of that clubshaft tension force does not come from the clubshaft itself, but it is due to the constantly changing hand direction secondary to the hand arc path being circular. When the hand's move to the next instantaneous point of the hand arc's circular path, where the hand direction is not aligned with the COM of the club, then a "force" will be created that will induce the tangential component of clubshaft tension that is needed to cause the continued release of PA#2. I still find nmgolfer's explanation below the best conceptual explanation to explain the release of PA#2, and I will only replace it if I find a better explanation. nmgolfscience.tripod.com/release.htm
S,
You wrote-: "his answer involves a rotational acceleration of hand where the hand then rotates at a constant velocity (ceases to accelerate), which is why the ball's rotational speed catches up to the rotational speed of the hand. When the ball is in the process of catching up with the hand's now constant rotational velocity, the tension on the string diminishes. The same phenomenon happens to the golf club because the hands cease to accelerate.
It is the cessation of acceleration of the hands that increases the speed of the clubhead. So, to answer your original question about how one goes about increasing clubhead speed, the practical answer is to stop applying rotational force before the release point."
You seem to be implying that the club releases during a PA#2 release action because the hands cease accelerating. I don't believe that this true because the release of PA#2 in a 'real life" golf swing happens well before the left hand slows down in the later downswing. When I perform my double pendulum swing action using the two paint-mixing sticks in the video below, the PA#2 release phenomenon happens even if I move the hands (= hinge joint of the central arm) at a constant velocity - as long as the hand arc path is circular.
DG - what is causing the release of PA#2 in that video demonstration? Do you think that it due to a tangential force component of "force tension"in the peripheral arm? How does that "force tension" in the peripheral arm originate - other than being due to the fact that the hinge point moves in a circular manner where the motion of the hinge point is not aligned with the COM of the peripheral arm?
Jeff.
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Post by syllogist on Nov 8, 2019 11:04:27 GMT -5
Dr. Mann,
If the left wrist uncocks prior to maximum velocity of the hands, then there is something the golfer physically does to cause that, which may be undesirable or simply unavoidable based on human physiology.
However, I can assure you that cessation of hand acceleration speeds clubhead release, which causes the hands to decelerate further, which causes the clubhead to speed further, etc. It's an infinitely iterative process during the release phase.
S
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