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Post by imperfectgolfer on Oct 21, 2019 17:39:13 GMT -5
DG, You wrote-: " That Miura diagram above doesn't make any sense to me . It looks like the tangential force he is showing is in line with the clubshaft but I cannot see how that force will increase the 'angular velocity' of the club.
Does it make any sense to you how a force applied by the hands (on the club handle) along the hand path will increase the angular velocity of the club?" It does make sense to me how a force applied to the club handle in a direction that is along the hand arc path will increase the angular velocity of the clubshaft (via the D'Alembert principle). If you look at every point along the hand arc path between P4 and P6 (for example) where the hand arc path's "directional force" is momentarily at a tangent to the hand arc path - as shown in the Miura diagram - the next point along the hand arc path is more inside the previous point because the path is circular, and that means that the hands are constantly changing direction relative to the previous point thereby fulfilling the criteria needed to invoke the D'Alembert phenomenon.
Look at figure 1 and note that hand vector 2 is slightly more inside relative to hand vector 1 because the hand arc path is circular. Each vector is at a tangent to the circumference of the circular path described by the hand arc path.
Jeff.
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Post by dubiousgolfer on Oct 21, 2019 20:53:26 GMT -5
DG, You wrote-: " That Miura diagram above doesn't make any sense to me . It looks like the tangential force he is showing is in line with the clubshaft but I cannot see how that force will increase the 'angular velocity' of the club.
Does it make any sense to you how a force applied by the hands (on the club handle) along the hand path will increase the angular velocity of the club?" It does make sense to me how a force applied to the club handle in a direction that is along the hand arc path will increase the angular velocity of the clubshaft (via the D'Alembert principle). If you look at every point along the hand arc path between P4 and P6 (for example) where the hand arc path's "directional force" is momentarily at a tangent to the hand arc path - as shown in the Miura diagram - the next point along the hand arc path is more inside the previous point because the path is circular, and that means that the hands are constantly changing direction relative to the previous point thereby fulfilling the criteria needed to invoke the D'Alembert phenomenon.
Look at figure 1 and note that hand vector 2 is slightly more inside relative to hand vector 1 because the hand arc path is circular. Each vector is at a tangent to the circumference of the circular path described by the hand arc path.
Jeff.
Dr Mann What would be the biomechanics involved in creating that tangential force component (via the hands) on the handle of the club between P6-P7? Is it the left shoulder girdle muscles still pulling the left arm down and also the synergistic passive release of PA#1 ? Creating more hand speed along their curvilinear path would also require a greater 'centripetal' force via the lead arm (maybe a reactive centripetal force to facilitate increased hand speed along its curved/circular path). But you still need a torque to increase the angular velocity of the clubhead , and that requires an actual physical force to act on the COM of the club. D'Alembert principle doesn't explain the physics involved , just the maths so its difficult to comprehend how a force is acting on the COM of the club when its being applied at the grip end. This is physics at its worst because it doesn't seem to provide any logical reasoning to explain this phenomenon and just says 'it happens' and is described by the formula 'Torque= Force (acting in the direction of motion) x Distance (distance between the pivot and acting point of force). I must admit that I also find it very difficult to understand the physics involved in 'levers' too . How can a small force acting at a long distance from a fulcrum create a large force at a point closer (and on the other side) of the fulcrum? How can all this be explained at a molecular level (I've asked the question and no-one can provide an answer) , it just doesn't make sense and all we have is a formula that works to explain a 'pattern of behaviour'. Sometimes physics can be very frustrating and irrational!!! DG
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Post by imperfectgolfer on Oct 21, 2019 23:38:51 GMT -5
DG, You wrote-: " That Miura diagram above doesn't make any sense to me . It looks like the tangential force he is showing is in line with the clubshaft but I cannot see how that force will increase the 'angular velocity' of the club.
Does it make any sense to you how a force applied by the hands (on the club handle) along the hand path will increase the angular velocity of the club?" It does make sense to me how a force applied to the club handle in a direction that is along the hand arc path will increase the angular velocity of the clubshaft (via the D'Alembert principle). If you look at every point along the hand arc path between P4 and P6 (for example) where the hand arc path's "directional force" is momentarily at a tangent to the hand arc path - as shown in the Miura diagram - the next point along the hand arc path is more inside the previous point because the path is circular, and that means that the hands are constantly changing direction relative to the previous point thereby fulfilling the criteria needed to invoke the D'Alembert phenomenon.
Look at figure 1 and note that hand vector 2 is slightly more inside relative to hand vector 1 because the hand arc path is circular. Each vector is at a tangent to the circumference of the circular path described by the hand arc path.
Jeff.
Dr Mann What would be the biomechanics involved in creating that tangential force component (via the hands) on the handle of the club between P6-P7? Is it the left shoulder girdle muscles still pulling the left arm down and also the synergistic passive release of PA#1 ? Creating more hand speed along their curvilinear path would also require a greater 'centripetal' force via the lead arm (maybe a reactive centripetal force to facilitate increased hand speed along its curved/circular path). But you still need a torque to increase the angular velocity of the clubhead , and that requires an actual physical force to act on the COM of the club. D'Alembert principle doesn't explain the physics involved , just the maths so its difficult to comprehend how a force is acting on the COM of the club when its being applied at the grip end. This is physics at its worst because it doesn't seem to provide any logical reasoning to explain this phenomenon and just says 'it happens' and is described by the formula 'Torque= Force (acting in the direction of motion) x Distance (distance between the pivot and acting point of force). I must admit that I also find it very difficult to understand the physics involved in 'levers' too . How can a small force acting at a long distance from a fulcrum create a large force at a point closer (and on the other side) of the fulcrum? How can all this be explained at a molecular level (I've asked the question and no-one can provide an answer) , it just doesn't make sense and all we have is a formula that works to explain a 'pattern of behaviour'. Sometimes physics can be very frustrating and irrational!!! DG As you know, I am not good at physics, so take my explanations with a pinch-of-salt. You asked-: "What would be the biomechanics involved in creating that tangential force component (via the hands) on the handle of the club between P6-P7? Is it the left shoulder girdle muscles still pulling the left arm down and also the synergistic passive release of PA#1 ?"
Yes - but the tangential force decreases between P6 and P7 because the left hand is not pulling the club handle forward along the hand arc path as much with a lot of positive alpha torque (compared to the P4 => P6 time period). In fact, there may be a negative alpha torque secondary to the release of PA#2, which causes the peripheral clubshaft to travel faster than the central clubshaft.
You wrote-: "Creating more hand speed along their curvilinear path would also require a greater 'centripetal' force via the lead arm (maybe a reactive centripetal force to facilitate increased hand speed along its curved/circular path). But you still need a torque to increase the angular velocity of the clubhead , and that requires an actual physical force to act on the COM of the club."
A centripetal force must exist if the hand arc path is curved, and not straight, but a golfer is not consciously doing anything deliberately to create that centripetal force.That centripetal force (radial force) naturally increases after P5.5 when the left shoulder socket moves more upwards, and less targetwards.
Regarding your bold-highlighted statements, I think that a torque is automatically/naturally created when the hand arc path becomes more "tightly" curvilinear between P5.5 and P6.2 because the hands are changing their direction of travel more per unit amount of hand distance covered when the hand arc path becomes more "tightly" curvilinear. I do not need to posit the presence of another physical torquing force. You wrote-: "D'Alembert principle doesn't explain the physics involved , just the maths so its difficult to comprehend how a force is acting on the COM of the club when its being applied at the grip end."
I disagree! I think that the D'Alembert phenomenon explains the physics. Think of pulling the club along a straightish path towards the ground between P4 and P5.5 so that the left hand pulls approximately down the longitudinal axis of the clubshaft. Under those conditions, the hand pulling force is aligned with the COM of the club as they are both traveling approximately in the same "straightish" direction and there is no rotary torque created. Then, if the hand arc path turns "tightly curvilinear" towards the target after P5.5, then the hand pulling force is angled relative to the COM of the club and it automatically/naturally creates a torque that will torque the COM of the club to release (representing the release of PA#2) in the direction of the hand arc path.
Here is my video showing that phenomenon.
Jeff.
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Post by dubiousgolfer on Oct 22, 2019 5:48:41 GMT -5
Many thanks Dr Mann
DG
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Post by imperfectgolfer on Oct 22, 2019 9:49:55 GMT -5
Syllogist, I am going to expand on my personal perspective regarding the phenomenon of parametric acceleration - as described my Miura. Here is quote from his paper-: "The inward pull motion at the impact stage of the golf swing commonly observed with expert players was investigated in this paper. First, a model of non-concentrated rotation was studied. It was found that, for a mass rotating around a pivot, if the pivot is moved in the direction opposite to the direction of centrifugal force of the mass, the kinetic energy of the mass could be increased. The increase is a result of the mutual action of the two governing factors of the system, which are the centripetal force and the pull velocity. A special type of equation of motion governs this phenomenon h n_ sin h 0,and the parameter in the second term of the left-hand side of the equation n_ characterizes its behaviour. The phenomenon is called the parametric acceleration, following the parametric excitation of vibration problems also governed by a similar equation. ----- it is interesting to note that if a golfer can supply an extra amount of centripetal force, the club will be pulled inward and the work is done by the centripetal force. With this logic, the pull motion will eventually increase the kinetic energy and velocity of the club."
Note that Miura states that if the pivot is moved in the opposite direction of the centrifugal force of the mass, that the kinetic energy and velocity of the club could be increased. At impact, the CF of the club is outwards away from the left shoulder socket and the pull action must be opposite that direction. From my perspective, that means that the pull force (responsible for generating parametric acceleration) is working in the same direction as the centripetal force, which is directly opposite in direction to the centrifugal force (even if the CF-force is considered to be an imaginary force), and that pull force is supplying an extra amount of centripetal force (as Miura states). A sign that a parametric-inducing pull force is present at impact is an abrupt shortening of the hub path radius near impact. Here is an example - featuring Lexi Thompson.
This image was created by Brian Manzella and it shows that Lexi's hand arc path shortens near impact - due to the fact that her left shoulder socket gets a lot higher near impact (due the combination of i) straightening her left leg and lifting the left side of her pelvis + ii) getting up on her toes + iii) extending the left side of her mid-upper torso + iv) elevating the peripheral end of her left clavicle).
The green arrows show the magnitude of radial force nearing impact and it increases due to elevation of the left shoulder socket, which lifts the hands upwards, thereby generating an increased inward pull force that is responsible for parametric acceleration of the club. Note that the green arrow at impact is directed upwards away from the clubhead and its magnitude is equal to the combination of the CP-force + extra pulling force due to shortening of the hub path radius near impact.
Jeff.
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Post by syllogist on Oct 22, 2019 10:01:45 GMT -5
Dr. Mann,
A double pendulum as you created in the video you just posted does not require circular motion for the upper segment to seek to align 180 degrees with the lower segment. If, from a face-on view, you held the double pendulum in the shape of an L and then tugged the lower segment purely horizontally rightward, then the upper segment would move downward and leftward, seeking alignment with the lower segment.
In fact, a purely horizontal tug of the lower segment of your double pendulum (in a direction perpendicular to the upper segment of the pendulum) is a demonstration of parametric acceleration. Miura simply applied the concept to a real golf swing where there is a curvilinear hand path and resultant centripetal force.
S
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Post by dubiousgolfer on Oct 22, 2019 17:19:05 GMT -5
Hi S Is this what you mean (see below from Adam Young's web article)? ----------------- If you look at the below picture, it shows a pendulum swinging back and forth. Just like any circle with a fixed hub, it will have a very small ‘low point’, marked out in green (the reality is the lowest point of the swing is infinitely small). Hopefully, this is simple to understand. If a pendulum (or club) is swinging from left to right across the screen, we could speed up the pendulum by pulling the end of the string (or club) in the direction of the green Arrow. Forces want to line up in the direction of the pull, so the bottom end of the pendulum will try and line up with the dotted line by speeding up towards it. This has been coined ‘parametric acceleration’. If we are pulling the top of the pendulum in the direction of the green arrow, not only does it speed the bottom of the pendulum up, but it will raise the overall height of the pendulum (as it is being pulled upwards). But the act of pulling upwards whilst the pendulum head is still moving downwards neutralizes each other. The result is a longer ‘low point’ in the arc of the pendulum swing. This is highlighted in red. handle moving up, clubhead moving down = long ‘low point’ If we are to apply this to the golf swing, look at the below picture. The pendulum is being swung along the hand path, which is moving down and forwards, before moving forwards and upwards. This dramatically increases the speed of the clubhead, and also creates a much longer and shallower low point. Actually , this is what I was inferring to in that image of Jamie Sadlowski (if you look at the red force arrow I drew going up his arm). Although I cannot be 100% certain of the real net force direction as there could be other component forces acting via the hands on the club grip . See example image below where I've added a tangential hand force and a radial hand force to get a 'Net Force ' (red arrow). In that scenario , the 'Net Force' direction wouldn't be aligned with the left arm. DG
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Post by imperfectgolfer on Oct 22, 2019 18:31:46 GMT -5
Dr. Mann, A double pendulum as you created in the video you just posted does not require circular motion for the upper segment to seek to align 180 degrees with the lower segment. If, from a face-on view, you held the double pendulum in the shape of an L and then tugged the lower segment purely horizontally rightward, then the upper segment would move downward and leftward, seeking alignment with the lower segment. In fact, a purely horizontal tug of the lower segment of your double pendulum (in a direction perpendicular to the upper segment of the pendulum) is a demonstration of parametric acceleration. Miura simply applied the concept to a real golf swing where there is a curvilinear hand path and resultant centripetal force. S I haven't the foggiest idea of what you are describing. Can you please demonstrate with images or a video demonstration or a much more detailed prose explanation? Jeff.
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Post by imperfectgolfer on Oct 22, 2019 18:37:31 GMT -5
DG, You wrote-: "If we are to apply this to the golf swing, look at the below picture. The pendulum is being swung along the hand path, which is moving down and forwards, before moving forwards and upwards. This dramatically increases the speed of the clubhead, and also creates a much longer and shallower low point."
Where is your scientifically-based "evidence" that demonstrates that it will dramatically increase clubhead speed? You also wrote-: "If a pendulum (or club) is swinging from left to right across the screen, we could speed up the pendulum by pulling the end of the string (or club) in the direction of the green Arrow. Forces want to line up in the direction of the pull, so the bottom end of the pendulum will try and line up with the dotted line by speeding up towards it. This has been coined ‘parametric acceleration’." Where is your "evidence" that pulling up on the end of the string will increase the speed of angular motion of the pendulum? Also, in Miura's model, he only applied an upward force on the club handle in the last 0.04 seconds of the downswing, and that represents Miura's phenomenon of parametric acceleration. You seem to be pulling up on the string when the pendulum first starts to release and that's not same model.
Jeff.
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Post by dubiousgolfer on Oct 22, 2019 20:46:03 GMT -5
DG, You wrote-: "If we are to apply this to the golf swing, look at the below picture. The pendulum is being swung along the hand path, which is moving down and forwards, before moving forwards and upwards. This dramatically increases the speed of the clubhead, and also creates a much longer and shallower low point."
Where is your scientifically-based "evidence" that demonstrates that it will dramatically increase clubhead speed? You also wrote-: "If a pendulum (or club) is swinging from left to right across the screen, we could speed up the pendulum by pulling the end of the string (or club) in the direction of the green Arrow. Forces want to line up in the direction of the pull, so the bottom end of the pendulum will try and line up with the dotted line by speeding up towards it. This has been coined ‘parametric acceleration’." Where is your "evidence" that pulling up on the end of the string will increase the speed of angular motion of the pendulum? Also, in Miura's model, he only applied an upward force on the club handle in the last 0.04 seconds of the downswing, and that represents Miura's phenomenon of parametric acceleration. You seem to be pulling up on the string when the pendulum first starts to release and that's not same model.
Jeff.
Dr Mann Those claims were made by Adam Young not me (I just copied and pasted it from his web article). www.adamyounggolf.com/low-point-and-parametric-acceleration/Personally , I do not agree there is a dramatic increase in clubhead speed from P6.5 -P7 when the 'Net Force' direction is aligned more with the clubshaft. I actually agree with that 2nd paragraph about pulling up on the end of the string club . It was demonstrated in Sasho MacKenzie's video below 'Intro to Club Kinetics' (see 02:50 - 03:57) and I am assuming that it based on proven Physics laws. I think Adam Young's diagram showing a pulling up on the string club (it has to be a rigid body not a string) when the pendulum starts to release is just an exaggeration to demonstrate how a force (not passing through the COM of the club) can cause angular rotation (similar to Sasho MacKenzie's video). I don't think he meant it as a reflection of a real golfers swing or the double-pendulum model. DG PS. Here is a real life example how a force (not directed through the COM of an object causes rotation). See how the chair rotated so that its COM aligned with that 40N force.
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Post by syllogist on Oct 23, 2019 6:59:00 GMT -5
Hi DG,
You showed and explained precisely Miura's work on parametric force. And you're correct in that in a real golf swing, there would be no "dramatic" increase in clubhead speed. The other thing is that Miura found the phenomenon in each swing tested in varying degrees. Thus, one can conclude that gains, from both a slightly upward movement of the hands (with little upward velocity) plus the reduction in radius of the path of the clubhead, is already built into a sound golf swing.
Dr. Mann,
It would be easier if I could find some simple drawing software with premade shapes. If you have Jorgensen's book (I can't find mine) , there is a section on "three experiments" that describe what I posted. There are diagrams. Otherwise, you can place your double pendulum device on the ground and tug one of the segments horizontally in the direction that the segment lies. The untouched segment will rotate to align with the segment you tugged. A circular path for tugging is not required for the distal segment to rotate.
S
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Post by imperfectgolfer on Oct 23, 2019 9:35:32 GMT -5
DG, You wrote-: " Personally , I do not agree there is a dramatic increase in clubhead speed from P6.5 -P7 when the 'Net Force' direction is aligned more with the clubshaft." Why did you not say this in your original post when you provided text from Adam Young's website? I gathered the impression that you supported Adam Young's opinion by posting text from his website.
The apparent reason why there cannot be a significant increase in clubhead speed as a result of pulling up on the club's handle is the fact that it only happens very late in the later downswing in a skilled golfer's golf swing action. At that time point, PA#2 has already completed most of its release and Miura showed that it could only increase clubhead speed by an additional amount of ~5%. I know of no other golf research study that provides any evidence that pulling up on the club handle can dramatically increase clubhead speed.
Jeff.
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Post by imperfectgolfer on Oct 23, 2019 9:52:25 GMT -5
S,
You wrote-: "Otherwise, you can place your double pendulum device on the ground and tug one of the segments horizontally in the direction that the segment lies. The untouched segment will rotate to align with the segment you tugged. A circular path for tugging is not required for the distal segment to rotate."
I tried your experiment by first adopting a 90 degree angle between the two segments (L-shape arrangement between the two segments) with the proximal segment aligned perpendicular to my body and the peripheral segment aligned to the right at a 90 degree angle relative to the proximal segment - and I noted that the peripheral segment did not rotate if I tugged on the proximal segment in a leftwards direction in such a manner that the central and distal ends of the proximal segment moved at the same speed, which caused the hinge joint to move in a straight line manner in a leftwards direction. I could only get the the peripheral segment to rotate if I pulled the distal end of the proximal segment leftwards while keeping the central end of the proximal segment fixed in position. Under those conditions, the hinge joint moved leftwards, but in an arced (circular) manner. That experiment supports my opinion that the hinge joint must transcribe a circular path to induce the release in a double pendulum swing model.
Watch the following video between the 1:17 -1:30 minute time points, and note that the peripheral segment does not rotate when the hinge joint moves in a straight line manner.
Jeff.
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Post by dubiousgolfer on Oct 23, 2019 10:49:27 GMT -5
DG, You wrote-: " Personally , I do not agree there is a dramatic increase in clubhead speed from P6.5 -P7 when the 'Net Force' direction is aligned more with the clubshaft." Why did you not say this in your original post when you provided text from Adam Young's website? I gathered the impression that you supported Adam Young's opinion by posting text from his website.
The apparent reason why there cannot be a significant increase in clubhead speed as a result of pulling up on the club's handle is the fact that it only happens very late in the later downswing in a skilled golfer's golf swing action. At that time point, PA#2 has already completed most of its release and Miura showed that it could only increase clubhead speed by an additional amount of ~5%. I know of no other golf research study that provides any evidence that pulling up on the club handle can dramatically increase clubhead speed.
Jeff.
Dr Mann I believe that Adam Young has weaknesses in his knowledge of physics pertaining to the golf swing (like we all seem to struggle with sometimes) but his diagrams on his website were useful to clarify the comments made by Syllogist in one of his previous posts. We are already aware, from a previous video I posted (where he was analysing Matthew Wolff's swing), that some of his opinions regarding the biomechanics of the golf swing can be questionable. DG
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Post by imperfectgolfer on Oct 23, 2019 11:00:27 GMT -5
S,
You wrote-: "Otherwise, you can place your double pendulum device on the ground and tug one of the segments horizontally in the direction that the segment lies. The untouched segment will rotate to align with the segment you tugged. A circular path for tugging is not required for the distal segment to rotate."
After re-reading your your experimental advice, I repeated the experiment in a different manner - by rigidly following your advice.
I placed my double pendulum device on the floor in a L-shaped relationship with the peripheral segment at right angles to my body and the proximal segment at right angles to the peripheral segment and parallel to my body with the distal end of the proximal segment pointing to the right, and I then pulled on the proximal segment in a horizontal direction to the right so that the hinge joint moved in a straight line direction (parallel to my body). What happened is that the central part of the peripheral segment (nearest the hinge joint) moved to the right because it was pulled by the hinge joint while the distal end of the periperal segment temporarily remained stationary (due to inertia). Then, after I pulled the hinge joint a few inches to the right, the peripheral segment was angled relative to the horizontal direction of travel of the hinge joint. As I continued to pull the proximal segment to the right while keeping the hinge joint traveling in a straight line direction to the right (parallel to my body), the peripheral segment rotated so that it became aligned with the proximal segment. However, I think that the reason why it happened is that the hinge joint is moving out-of-aligment with the COM of the distal end of peripheral segment because the peripheral segment is angled relative to the direction of the pull exerted by the hinge joint. In other words, the hinge joint can be conceived to be moving circularly (angularly) with respect to the COM of the distal end of the peripheral segment.
Jeff.
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