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Post by imperfectgolfer on Jul 22, 2012 20:27:10 GMT -5
Todd posted these capture images of a baseball strike. How do you interpret the "evidence" for a normal force being present through impact - considering the fact that his hand arc radius is increasing (arms are getting straighter) while his degree of lean-back posture (tilt of the upper torso away from the pitcher) is remaining relatively constant? Jeff. p.s. Bluebird incorrectly wrote in the BM-forum thread-: "Does anybody notice how much the batter's shoulder and head are moving in the "normal" direction?" I think that his head/shoulders are not moving significantly in a normal direction (further away from his hands/pitcher) in those two images - look at the position of the head relative to background figures in the stands.
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Post by natep on Jul 22, 2012 20:55:38 GMT -5
The top of his spine is definitely moving away from the pitcher.
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Post by imperfectgolfer on Jul 22, 2012 21:12:26 GMT -5
Where is the "evidence" that the top of his spine is moving significantly away from the pitcher?
Secondly, do you believe that movement of the top-of-the-spine away from the pitcher is necessary to produce a normal force? If yes - why?
By the way, I presume that you agree that his hands are moving closer to the pitcher, and is that phenomenon compatible with the presence of a normal force?
Jeff.
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Post by imperfectgolfer on Jul 23, 2012 18:49:17 GMT -5
BM has expressed his opinion and he agrees that the head is moving away from the pitcher while the arms are extending. See reply #86 here www.brianmanzella.com/golfing-discussions/17458-release-description-9.htmlSo what if the head is moving slightly away due to straightening of his right leg +/- minimal extension at the level of the hip joints? That doesn't produce a normal force, because a normal force doesn't require movement of the fulcrum point up-and-away from the handle of the club, and any movement of the fulcrum point up-and-away only produces parametric acceleration of the club, which is a different issue. A normal force is needed to respond to the CF-loading force (equally counterbalance the CF-loading force) - even if the hands are moving away from the torso due to increased arm extension (which is biomechanically incompatible with BM's idea of "pulling up on the grip with all one's might" in order to shorten the hub radius). I have yet to see any forum member prove that a golfer needs to pull the grip handle inwards thereby shortening the hub radius path in order to create a normal force (that counterbalances the CF-loading force). I think that the baseball player is producing a normal force - even though his hand arc radius is increasing (and not decreasing). Jeff.
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Post by imperfectgolfer on Jul 23, 2012 20:10:48 GMT -5
Consider Drew's suggested answer.
He wrote in the BM-forum thread.
"Thanks for the Pic Todd. No question that the arms are extending past impact as you suggest. And it appears that they were pulled in before and at impact. As bluebird suggests I think a going normal move is evident. Maybe the extension is a reaction to going normal. What do you think?"
What represents the visual evidence for the "going normal move"?
He actually suggests that the arm extension is a reaction to "going normal". Amazing! That would be like suggesting that a golfer releases his power accumulators as a reaction to "going normal" - rather than as a means of powering the golf swing.
Jeff.
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Post by imperfectgolfer on Jul 24, 2012 20:02:58 GMT -5
Todd wrote the following in the BM-forum thread-: "The distance from the hands to a point between the shoulders INCREASES past impact for great ball-strikers. Its a fact. Check with your scientists. That is all."
BM responded with the following comment-: "Trying to MAKE someTHING happen, that should HAPPEN because SOMETHING ELSE was done besides the THING, probably is not a good idea, no?"
That cryptic comment from BM has even confused a BM-groupie, who wrote-: "I cant wrap my little brain around this one Bmanz. Ive read it over and over."
I would like to see BM, or another BM-groupie, clearly explain this BM-comment as it pertains to the specific issue that Todd has introduced.
Jeff.
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Post by imperfectgolfer on Jul 25, 2012 22:42:16 GMT -5
spktho wrote in the BM-forum thread today-: "Since you have all the answers, why is it that when scientists measure the forces on the club, that the force being exerted on the club is inward toward the body around and past impact of great swingers?" Which scientist has ever measured the forces on the club at impact? Which scientist has ever measured an inward force at impact? It is my impression that any calculation of the normal force at impact is a calculated theoretical value using the following formula-: perfectgolfswingreview.net/NormalForce.jpg [/img] It is my understanding that the normal force calculation is used to work out the CP-force needed to keep the hands/club traveling along a circular path in the presence of a CF-loading force. In other words, it is a theoretical calculation and it is not derived from any scientific measurement. Virtuoso also wrote in that thread-: "At the start of the downswing, the force on the club is tangential. As it moves down, the force becomes progessively exchanged for a more radial force (more normal to the instantaneous center of rotation)." I think that's BS! The force doesn't get exchanged. I think that Virtuouso has derived that wrong belief from this Miura diagram. Note that the tangential force decreases in phase 3 of the downswing and becomes zero at impact. However, that is based on a double-link model where the torque motor stops producing a force that moves the central arm in phase 3 of the downswing. That situation is equivalent to the following simple double pendulum model. In a simple double pendulum model, the central arm slows down when the club releases - due to a COAM phenomenon. Note that the clubhead flips after low point. However, a golfer can produce a swing that is based on a driven double pendulum model. Note that the central arm doesn't slow down when the club releases. In other words, a golfer can choose to maintain the speed of forward motion of the left arm (maintain the speed of release of PA#4) throughout the late downswing and into impact. That will allow him to maintain an intact LAFW beyond impact, and prevent the clubhead from flipping. Jeff.
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Post by imperfectgolfer on Jul 26, 2012 21:51:15 GMT -5
Here is Art's post in the BM-forum thread.
"As this thread continued from this Post #60, to its present length of at least #113, I realized I did not go far enough in describing the forces being applied to the entire body due to the many rotating parts.
Above, I got into the club's effect on the hands, and introduced the torso's effect on the hips, but I did not describe the rotating arm(s) centripetal forces pulling on the shoulders. To envision the magnitude, and much more importantly the instantaneous 3D DIRECTION of these 4 forces (club to hands, arms to shoulders, torso to pelvis, and pelvis to feet/ground), is , as you have guessed, a monumental job that I have only done once, by hand. (I have tried to encourage scientists with refined computer models to do this 'automatically' with a software module, and am presently awaiting an opportunity to present my work to Taylor, using their MATT;s system as the basis for the raw data).
At any rate, as mandrin would say, "as a first order approximation", from basic data using the AMM/TPI 12 sensor system, and for one swing of one golfer, I found centripetal forces during the downswing over 100 pounds, but at different times, and in different directions, for ALL four of the rotating elements noted above, with the 3D values of rotational velocity and acceleration/deceleration from the 'kinematic sequence' graphs provided by the software, and data noted every 0.004 seconds.
So, what does all this mean to the ORIGINAL question of a release that 'throws the club head off the shaft', or a release that as 'Virtuoso' so aptly put it, "At the start of the downswing, the force on the club is tangential. As it moves down, the force becomes progressively exchanged for a more radial force (more normal to the instantaneous center of rotation)"?
It simply means that there are 4 MAJOR forces ON THE BODY during the downswing ALL over 100 pounds at one time or another, ALL pulling radially, from their 'instantaneous centers of rotation', and in my hopefully 'applied scientific opinion', displacing the relative locations of the moving body on video in ways that change AND ARE DIFFERENT for every golfer, and maybe for every swing.
What IMO remains the same however, are the relative movement similarities shortly before and after impact where the angular velocities, and therefore the centripetal forces are reasonably proportional to the quality of the golfer, ie., high quality, high forces, and therefore larger displacements, or significantly more strength required to control the movement from the high forces.
Finally, I see the 'throwing the club head off the shaft' as a more violent approach to rotating around the coupling point, and believe that both result in higher club head velocities at impact. Therefore, both provide the environment BY THE BODIES NATURAL REACTIONS and desire to hit the ball squarely, in a 'radial', or normal restraining and 'pulling' force creating the environment for additional 'parametric acceleration' benefits, but only if IF TIMED CORRECTLY. And that is where I switch to OPINION, for IMO, any 'throwing' actively during the downswing has a high potential for developing undesirable timing, path, and club head position errors that I BET YOU will easily show up in inaccuracy and more dispersion, consistently.
Hope this helps shed a little light as to why , when keeping the center of the ball CONSTANT, the body has such a hard job to do dynamically balancing these disturbing centripetal forces, while accommodating very accurately, the total length of the golf club and the arms/body in the midst of this 'storm' of changing forces. So I see the relative positions of a golfer on video, as a 'fingerprint', as to how they are accomodating these changing forces, and by NO means a source to estimate these forces."
He then expanded on the four forces as follows-:
"The easiest to discuss is the force developed by the club on the hands as the downswing progresses, so lets start with the golf club forces.
If you were lucky enough to have access to MATT's, or the TPI/AMM systems (and to a degree K-Vest), you would be able to 'see' the angular velocity of the club, lead arm and upper body angular velocities as the swing progressed. These graphs are called the 'kinematic sequences', and for the club, usually goes from 0 to over 2000 degrees per second in about 0.25 to 0.30 seconds. As previously noted produces 'centripetal and tangential forces' that vary with position and time. But, at or near impact, the forces are predominantly centripetal, so this approximate 100 pounds is PULLING on the hands, and therefore on the body too by this amount. Earlier in the downswing, the size AND 3D DIRECTION of this club-created force is very different.
Next, the centripetal forces produced by the rotating arms around the spine for the lead arm alone are moving at 600 degrees a second, and at this peak, about 2/3 of the downswing time also develop over 100 pounds of force, which PULLS on the top of the torso, through the shoulders. Again, later in the swing, the 3D direction and value of the forces are reduced due to the deceleration as noted by the kinematic sequence characteristics, which PROBABLY differ by individual, club and maybe every swing.
Finally, for the FORWARD FORCE DISTURBANCES, the torso rotating around the spine at over 400 degrees per second, and weighing the most of the 4 rotating parts, because of its large moment of inertia, also develops over 100 pounds of centripetal force at its peak, also about 2/3 of the downswing tim. Like the arms, however, it also decelerates from this peak angular velocity, and at impact is less than half the velocity, and therefore less than 1/4 the force. But the 3D direction of these forces are very different than the club and arms vectors, necessitating an instant by instant 'vector addition' of these forces.
The 4 th force is created by the rotating pelvis and legs, and because of a greatly dispersed location of the 'instantaneous axis of rotation', can produce BOTH additional disturbances OR, if BBKIB is utilized, a stabilizing vector against the other 3, resulting in a more balanced swing.
I realize that as the angular velocities for the 4 elements develop, there are INTERNAL reactions to the torques that produce these body rotations, but as previously noted above, this is just a 'FIRST ORDER' analysis of what happens kinetically during the explosive downswing.
This has led to a new hypothesis, as yet unproven, that the foot reaction forces, in 6D, and obtained from high quality, high response force plates are the LEFT OVER FORCES not accommodated by the bodies compensations. If true, these ground reaction force vectors may be able to 'immediately' detect the degree of dynamic IMBALANCE that must be generated for a well balanced golf swing."
If you think he expresses himself in a precisely coherent manner (as nmgolfer claimed, and Virtuoso seconded, in another thread) then we definitely have different perspectives regarding "sense versus nonsense" in the intellectual world of golf swing mechanics/biomechanics. I particularly think that his last sentence epitomizes his capacity (or lack of capacity) for logical thinking when he stated-: "This has led to a new hypothesis, as yet unproven, that the foot reaction forces, in 6D, and obtained from high quality, high response force plates are the LEFT OVER FORCES not accommodated by the bodies compensations. If true, these ground reaction force vectors may be able to 'immediately' detect the degree of dynamic IMBALANCE that must be generated for a well balanced golf swing."
Jeff.
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