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Post by dubiousgolfer on Jul 25, 2020 8:00:39 GMT -5
Just thought I'd inform everyone there is a new Dave Tutelman article tutelman.com/golf/swing/gripPressure.phpIt estimates how much grip pressure is needed to make the swing without losing control of the golf club. DG
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Post by imperfectgolfer on Jul 25, 2020 10:06:42 GMT -5
Here is Greg McHatton performing a golf swing while holding the club handle with only the tips of two fingers (thumb and index finger) of the lead hand.
How does he manage to hold onto the club handle through impact?
Jeff.
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Post by dubiousgolfer on Jul 25, 2020 10:20:23 GMT -5
Dr Mann
Imho , he is not swinging the club very fast and therefore one doesn't need much friction between the fingers and grip material to 'hold onto' the club.
DG
I suspect it also depends on how strong the golfer is (see Gary Player).
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Post by imperfectgolfer on Jul 25, 2020 10:24:14 GMT -5
Here is a quote from DT's article.
"This rather neatly brackets the sort of numbers we got for centripetal force. For professional golfers, we can expect the driver clubhead speed to be 110-125mph, giving a centripetal force of 85-110 pounds.
What should that tell us? My conclusion is not tightly reasoned, but seems (intuitively, to me, at least) to be a good working hypothesis. Top-notch golfers apply all the centripetal force they can, and get their clubhead speed from keeping the line of that force as far ahead of the club as they can. The way a Dustin Johnson generates big clubhead speed is to keep his pulling force further ahead of the club than other golfers can."
I think that this represents bizarre reasoning to believe that Dustin Johnson gets his high clubhead speed at impact by "keeping his pulling force further ahead of the club than other golfers can". What could DJ be doing biomechanically different (compared to other pro golfers) to get his pulling force further ahead of the club?
Jeff.
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Post by imperfectgolfer on Jul 25, 2020 10:31:06 GMT -5
Dr Mann Imho , he is not swinging the club very fast and therefore one doesn't need much friction between the fingers and grip material to 'hold onto' the club. DG I suspect it also depends on how strong the golfer is (see Gary Player). Even if Greg McHatton is swinging his club at only 50mph clubhead speed at impact, it would require 17 lbs of centriptetal force (according to DT'c chart) and the appropriate amount of calculated friction between the hand and the club. Can one really achieve that goal when holding the grip between the tip of your thumb and index finger of the lead hand? Jeff.
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Post by imperfectgolfer on Jul 25, 2020 10:36:54 GMT -5
DG,
What do you think regarding the scientific validity/utility of DT's conclusion when he writes-: "The second discrepancy, the near absence of any significant right-hand influence, is much harder to explain. Perhaps Schmidt got it right and Koike did not. Perhaps they both got it right for the population of golfers they tested. I don't know."
Jeff.
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Post by dubiousgolfer on Jul 25, 2020 10:39:06 GMT -5
Here is a quote from DT's article. " This rather neatly brackets the sort of numbers we got for centripetal force. For professional golfers, we can expect the driver clubhead speed to be 110-125mph, giving a centripetal force of 85-110 pounds.
What should that tell us? My conclusion is not tightly reasoned, but seems (intuitively, to me, at least) to be a good working hypothesis. Top-notch golfers apply all the centripetal force they can, and get their clubhead speed from keeping the line of that force as far ahead of the club as they can. The way a Dustin Johnson generates big clubhead speed is to keep his pulling force further ahead of the club than other golfers can." I think that this represents bizarre reasoning to believe that Dustin Johnson gets his high clubhead speed at impact by " keeping his pulling force further ahead of the club than other golfers can". What could DJ be doing biomechanically different (compared to other pro golfers) to get his pulling force further ahead of the club? Jeff. It makes sense to me because I cannot see any other way ' from a purely physics perspective' that a golfer can generate the necessary forces that create angular acceleration of the club into impact. I cannot conceptualise how else a golfer could generate that MOF in the later downswing than via a pull force via his lead arm? DG
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Post by dubiousgolfer on Jul 25, 2020 10:42:28 GMT -5
DG, What do you think regarding the scientific validity/utility of DT's conclusion when he writes-: " The second discrepancy, the near absence of any significant right-hand influence, is much harder to explain. Perhaps Schmidt got it right and Koike did not. Perhaps they both got it right for the population of golfers they tested. I don't know." Jeff. Yes, I sent DT an email asking whether he read the most recent article by Choi before he wrote his new chapter. especially this section : "To our knowledge, this is the first study that quantitatively demonstrates the dominant role of right-hand grip torque in club rotation, which was consistently observed among all nine professional licensed golfers. Despite the negligible net hand-grip force in the x- and y-direction during the first half of the downswing, non-negligible hand-grip forces of similar magnitude and opposite directions were applied by each hand (Figure 5A–J)." DG
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Post by imperfectgolfer on Jul 25, 2020 10:50:56 GMT -5
Here is a quote from DT's article. " This rather neatly brackets the sort of numbers we got for centripetal force. For professional golfers, we can expect the driver clubhead speed to be 110-125mph, giving a centripetal force of 85-110 pounds.
What should that tell us? My conclusion is not tightly reasoned, but seems (intuitively, to me, at least) to be a good working hypothesis. Top-notch golfers apply all the centripetal force they can, and get their clubhead speed from keeping the line of that force as far ahead of the club as they can. The way a Dustin Johnson generates big clubhead speed is to keep his pulling force further ahead of the club than other golfers can." I think that this represents bizarre reasoning to believe that Dustin Johnson gets his high clubhead speed at impact by " keeping his pulling force further ahead of the club than other golfers can". What could DJ be doing biomechanically different (compared to other pro golfers) to get his pulling force further ahead of the club? Jeff. It makes sense to me because I cannot see any other way ' from a purely physics perspective' that a golfer can generate the necessary forces that create angular acceleration of the club into impact. I cannot conceptualise how else a golfer could generate that MOF in the later downswing than via a pull force via his lead arm? DG I am not stating that a golfer must not be generating a MoF between P6.5 and P7 in order to continue to accelerate the clubhead all the way to impact. I am implying that DJ does not get his large clubhead speed at impact by " keeping his pulling force further ahead of the club"! What does that claim actually mean? Do you not think that golfers (like DJ and Cameron Champ and Bryson DeChambeau) get a lot of their very high clubhead speed at impact because they already achieve a very high clubhead speed by P5.5 (before the release of PA#2 starts in earnest)? Do you have any "evidence" that they are releasing PA#2 more efficiently than other pro golfers by " keeping the pulling force further ahead of the club" (whatever that statement actually implies)? Jeff.
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Post by dubiousgolfer on Jul 25, 2020 10:52:40 GMT -5
Dr Mann Imho , he is not swinging the club very fast and therefore one doesn't need much friction between the fingers and grip material to 'hold onto' the club. DG I suspect it also depends on how strong the golfer is (see Gary Player). Even if Greg McHatton is swinging his club at only 50mph clubhead speed at impact, it would require 17 lbs of centriptetal force (according to DT'c chart) and the appropriate amount of calculated friction between the hand and the club. Can one really achieve that goal when holding the grip between the tip of your thumb and index finger of the lead hand? Jeff. I've also had problems understanding how high those lbs force values are in his table . But when you looked at that dynamometer device, four fingers were applying 100 lbs force which I found 'intuitively' difficult to believe. DG
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Post by dubiousgolfer on Jul 25, 2020 10:58:01 GMT -5
It makes sense to me because I cannot see any other way ' from a purely physics perspective' that a golfer can generate the necessary forces that create angular acceleration of the club into impact. I cannot conceptualise how else a golfer could generate that MOF in the later downswing than via a pull force via his lead arm? DG I am not stating that a golfer must not be generating a MoF between P6.5 and P7 in order to continue to accelerate the clubhead all the way to impact. I am implying that DJ does not get his large clubhead speed at impact by " keeping his pulling force further ahead of the club"! What does that claim actually mean? Do you not think that golfers (like DJ and Cameron Champ and Bryson DeChambeau) get a lot of their very high clubhead speed at impact because they already achieve a very high clubhead speed by P5.5 (before the release of PA#2 starts in earnest)? Do you have any "evidence" that they are releasing PA#2 more efficiently than other pro golfers by " keeping the pulling force further ahead of the club" (whatever that statement actually implies)? Jeff. Now I understand what you mean and yes, I agree with you. DG
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Post by dubiousgolfer on Jul 25, 2020 12:06:18 GMT -5
Checking DT's statement again: "I chose a picture of Dustin Johnson (as opposed to some other golfer) because it gave me the most easily understood diagram; few other golfers, if any, have the line of force leading the CoM by as much as he does". What if a golfer has a very strong left hand grip like Jamie Sadlowski, wouldn't he be creating a lot of forward shaft lean and therefore have a greater angle between the left arm and clubshaft approaching impact? Also if the golfer was using a strong grip with a 'finger or low palmar' grip pattern, wouldn't this also tend to create a greater angle (and therefore moment arm distance) between the left arm and clubshaft? Also , even if the golfer created that bigger 'moment arm' approaching impact by adopting a strong grip and 'finger/low palmar' grip pattern , that doesn't necessarily mean that the club will release quicker because won't it also depend on the golfers ability to ulnar deviate his lead wrist (or try and prevent his lead wrist from stalling in its hand path especially if he's reached the limit of his ulnar deviation)? DG
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Post by imperfectgolfer on Jul 25, 2020 14:36:07 GMT -5
Checking DT's statement again: "I chose a picture of Dustin Johnson (as opposed to some other golfer) because it gave me the most easily understood diagram; few other golfers, if any, have the line of force leading the CoM by as much as he does". What if a golfer has a very strong left hand grip like Jamie Sadlowski, wouldn't he be creating a lot of forward shaft lean and therefore have a greater angle between the left arm and clubshaft approaching impact? Also if the golfer was using a strong grip with a 'finger or low palmar' grip pattern, wouldn't this also tend to create a greater angle (and therefore moment arm distance) between the left arm and clubshaft? Also , even if the golfer created that bigger 'moment arm' approaching impact by adopting a strong grip and 'finger/low palmar' grip pattern , that doesn't necessarily mean that the club will release quicker because won't it also depend on the golfers ability to ulnar deviate his lead wrist (or try and prevent his lead wrist from stalling in its hand path especially if he's reached the limit of his ulnar deviation)? DG In that diagram of DJ at impact, DT has drawn the line of force as acting upwards (radially/centripetally). However, am I not correct to state the line of force causing the MoF that provides the clubhead with its angular acceleration in the late downswing between P6 => P7 is also due to the tangential force component, and not only the radial force component? Here is Dr. Kwon's graph showing the forces/torques present during the downswing. The main force causing clubhead angular speed in the late downswing is the MoF, because the hand couple torque is negative. What is causing that MoF? Here is Dr. Kwon's diagram of the tangential and radial forces. The tangential force peaks soon after P5.5., but it is still present all the way to impact. Surely, it is the summation of the tangential force and radial force produced by the left hand moving along the hand arc path between P6 => P7 that is causally responsible for producing the MoF. The radial force is most prominent force at impact, but PA#2 release has already happened between P5.5 => P7.
Also, why is he looking at the degree of forward shaft lean at impact when determining the MoF. Here are capture images of Bradley Keegan and Dustin Johnson at impact. They both have the same amount of forward shaft lean at impact. However, doesn't that just reflect their ball position relative to their hand position at impact? The only difference is that although both golfers use a moderately strong left hand grip, DH has to supinate his lead forearm more to get the same degree of forward shaft lean at impact as BK, seeing that he has a bowed lead wrist at impact that angles the clubshaft backwards away from the target. Surely, one cannot claim that the degree of forward shaft lean at impact is a direct reflection of the MoF being generated during the later downswing! I think that it depends on grip strength and ball position and hand position at impact, and I don't think that it has anything to do with the speed of release of PA#2 or the forces causing the release of PA#2. Jeff.
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Post by dubiousgolfer on Jul 25, 2020 18:14:06 GMT -5
Dr Mann Yes , the tangential force does need to be included. DT mentions this in his article but was more concerned about the 'centripetal force' aspect and how one can estimate the grip forces required to prevent the grip slipping out of the hands. From his article: -------------------------------------------------- "But we have to remember that the clubhead's velocity is due to two effects: the angular velocity of the club (hence the emphasis on centripetal force) and the linear velocity of the hands' motion. On the diagram (built on top of a photo from the Howard's Golf web site), we show these two velocities, which add together to create the clubhead speed. ----------------------------------------------------- With regards using the forward shaft lean at impact and whether it has a direct relation to the MOF being generated , I don't really know for certain. Theoretically, if the golfer can keep the 'moment arm' large while exerting that 'Net' force (ie. the sum of the tangential and normal components of the Net Force via the hands), then he can preserve the angular acceleration. DG PS. In DT's article he says "how much additional force does the golfer exert to keep the clubhead accelerating through impact?" So it looks like he is not looking at overall clubhead speed production but just concentrating on how the MOF can influence angular acceleration through impact phase only. Note that the objective of his whole article was to work out what grip pressure forces are required to 'make the swing' and assumed that the 'centripetal force' maxed at impact.
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Post by dubiousgolfer on Jul 25, 2020 19:26:20 GMT -5
Goodness , I am having problems understanding DT's article when he uses different units like slugs , etc . Not something I am familiar with.
These are examples of the difficulties I am having understanding some of DT's explanations.
"So I will provisionally state that the force exerted by these guys is nearly the centripetal force, but deflected backwards to move the extended line of the force forward of the club's CoM. When you deflect a force, you turn it into two component forces: a slightly smaller force in the original direction, plus a component perpendicular to the original direction. We can do a similar graph to the one above, to see how much of a difference this makes in the force."
"The graph at the right shows how much we have to multiply our original force by to get back to the same centripetal component we had before we deflected the force."
DG
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