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Post by dubiousgolfer on Jul 25, 2020 20:29:57 GMT -5
Dr Mann
DT says the below :
If you watch the tour pros play on TV, you will have noticed some big hitters that actually let go with their right hand at or just after impact. For instance, Vijay Singh, Fred Couples, and Phil Mickelson. (I don't know if any golfers from the most recent generation do, but these guys did even at their prime.) That is zero percent right hand at impact, even more extreme than the 5% we used in our calculations earlier. There is even a video by Clay Ballard explaining how and why this works.
But on your website you mention the following:
"Some professional golfers are so conscious of their propensity to hook the ball left (due to flipping through impact) that they deliberately allow their right palm to lose contact with the left hand (at PP#1) through impact. The three PGA tour golfers who particularly manifest this biomechanical idiosyncracy are Phil Mickelson, VJ Singh and Freddie Couples."
Isn't the loss of right hand contact due to the fact that they are 'running of right arm' because their right shoulder has not moved downplane enough (ie. a stalled pivot)?
DG
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Post by imperfectgolfer on Jul 25, 2020 20:49:23 GMT -5
DG,
You wrote-: "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."
I cannot fathom why anyone would believe that the degree of forward shaft lean at impact has any connection with the MoF being generated during the late downswing between P6 and P7. For example, if I perform a golf swing using the same forces/torques, but simply place my ball ahead of low point so that my clubhead will be traveling slightly upwards at impact, I can produce a scenario where the shaft has backwards shaft lean with the clubhead ahead of my lead hand at impact.
By the way, I performed a "real life" experiment of holding my driver's club handle with the tips of my thumb, index and middle fingers of each hand and then swung the driver at my usual driver speed of 85-92 mph and the club handle did not slip out of my hands. I could even do it by just using the lead hand and letting go with the trail hand in the later downswing, so that only my lead hand's 3 fingertips (thumb DP, 2nd and 3rd fingertips) are holding onto the club handle through the impact zone. I believe that any CP-force present at impact - even if large - is so momentary that it is biomechanically possible to prevent the club handle from slipping out of the lead hand when performing a full golf swing action as described. Try this simple "real life" experiment yourself.
Jeff.
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Post by imperfectgolfer on Jul 25, 2020 20:53:16 GMT -5
Dr Mann DT says the below : If you watch the tour pros play on TV, you will have noticed some big hitters that actually let go with their right hand at or just after impact. For instance, Vijay Singh, Fred Couples, and Phil Mickelson. (I don't know if any golfers from the most recent generation do, but these guys did even at their prime.) That is zero percent right hand at impact, even more extreme than the 5% we used in our calculations earlier. There is even a video by Clay Ballard explaining how and why this works.But on your website you mention the following: "Some professional golfers are so conscious of their propensity to hook the ball left (due to flipping through impact) that they deliberately allow their right palm to lose contact with the left hand (at PP#1) through impact. The three PGA tour golfers who particularly manifest this biomechanical idiosyncracy are Phil Mickelson, VJ Singh and Freddie Couples."Isn't the loss of right hand contact due to the fact that they are 'running of right arm' because their right shoulder has not moved downplane enough (ie. a stalled pivot)? DG I think that the loss of contact of the right palm with the aft side of the grip can be due a "running-out-of-right arm" scenario - although it can also be a deliberate act. I can generate a faster clubhead speed at impact if I deliberately let my right hand lose contact with the club handle in the later downswing. Jeff.
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Post by dubiousgolfer on Jul 26, 2020 7:37:45 GMT -5
DG, You wrote-: " 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." I cannot fathom why anyone would believe that the degree of forward shaft lean at impact has any connection with the MoF being generated during the late downswing between P6 and P7. For example, if I perform a golf swing using the same forces/torques, but simply place my ball ahead of low point so that my clubhead will be traveling slightly upwards at impact, I can produce a scenario where the shaft has backwards shaft lean with the clubhead ahead of my lead hand at impact. By the way, I performed a "real life" experiment of holding my driver's club handle with the tips of my thumb, index and middle fingers of each hand and then swung the driver at my usual driver speed of 85-92 mph and the club handle did not slip out of my hands. I could even do it by just using the lead hand and letting go with the trail hand in the later downswing, so that only my lead hand's 3 fingertips (thumb DP, 2nd and 3rd fingertips) are holding onto the club handle through the impact zone. I believe that any CP-force present at impact - even if large - is so momentary that it is biomechanically possible to prevent the club handle from slipping out of the lead hand when performing a full golf swing action as described. Try this simple "real life" experiment yourself. Jeff. Dr Mann Say a golfer wants to ensure he doesn't prematurely peak his clubhead speed before impact, wouldn't it be of benefit for him to try and accelerate the ball through impact? And to efficiently do that at high clubhead speeds requires a situation where he can still apply an MOF using an increased pull via his lead arm with some 'moment arm' created (due to 'some' forward lean lead angle between the lead arm and clubshaft at impact). From a physics standpoint , increasing that 'moment arm' at impact (with an increased clubshaft forward lean) would create a very small increase in clubhead speed because impact is only 1/4000 sec. Therefore from a purely clubhead speed perspective, I cannot see any advantage in DJ having more forward lean at impact than other golfers. In fact , DT has mentioned this in previous articles himself: www.tutelman.com/golf/swing/accelerateThru.phpIn DT's new article he says the following: "For good quality swings, somewhere between 12% and 20% of the clubhead speed depends on the linear hand speed VL. Actually, that variation is mostly from study to study, not from golfer to golfer; the results of any one study seem to come out within a range of a couple of percentage points across the golfers. So let's arbitrarily use 15%, an 85-15 split between speed due to rotation of the club and speed of the hands. That means 85% of clubhead speed can be attributed to rotation of the club, and contributes to the centripetal force"
"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."DJ might be doing the underlined during release (with his hand path shape) but I think any forward clubshaft lean at impact is totally within the golfer's control dependent on his own biomechanics and judgement and not just an uncontrolled 'cause and effect' due to the degree of MOF being applied between P6-P7 (ie. by trying to retain a large 'moment arm'). DG PS. With regards your experiment and the biomechanically possibility to perform the swing with very little grip pressure (without any slippage) over such a short period of time. That seems highly plausible during impact which is 1/4000 sec and where the clubhead loses about 20% speed just after impact. The amount of pressure applied by the fingers will also depend on the static coefficient of friction between the contact surfaces. Maybe DT hasn't taken into account the short time involved and whether there is enough time for slippage to occur from P6 onwards.
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Post by dubiousgolfer on Jul 26, 2020 8:56:34 GMT -5
Interestingly enough , I've found another research article www.tandfonline.com/doi/pdf/10.1080/14763141.2013.878377?casa_token=6kHd4RVd3uAAAAAA:x40kyKNsKNKG-mdv8P-1v5v708JhBJIy07SmFdOY9O1lMk9Ugrf2oY8okRPa9zGIlaNloz5GA_ChEgI noted this section: Consistent with the results reported by Budney (1979), Komi et al. (2007), and Broker and Ramey (2007), the proficient golfers in this study demonstrated low total grip forces at takeaway, high forces during the acceleration phase, and markedly reduced total grip forces at impact. The elevated grip forces during the acceleration phase might support the golfer’s actions in generating torques and linear forces present in this phase as reported by Nesbit (2005). The findings of the current study also indicate that the lead hand is dominant during this acceleration phase. Finally, reduced grip forces at impact are consistent with some popular golf instruction theory, which links relaxed hands through impact with full release of the club (McLean & Golf Digest, 2003); yet, they appear counterintuitive given the high associated centripetal forces and need for high ‘net’ forces on the club handle as quantified in an inverse dynamics analysis (Nesbit, 2005). What is clear is that the forces on the grip, during this swing phase associated with high rotational velocity situation, are mostly supplied by the lead hand. Whether or not these high lead hand forces are necessary to generate sufficient frictional forces tangential to the club surface to prevent club slippage is beyond the capability of this instrumentation system and associated analysis. Nevertheless, reduction of grip forces at impact is certainly an interesting finding, uniquely interweaving golf biomechanics with golf observations and modern coaching advice.DG PS. The above seems to contradict DT's assumption regarding point 2 below. It seems that golfers are not applying an increasing greater grip pressure before impact which I assume means they are not generating some additional MOF induced increase in clubhead angular acceleration through impact. The first question we must answer is: at what point in the swing does the maximum force requirement occur? The intuitive and obvious answer is: just before impact, where the maximum angular velocity of the club requires hands to exert the maximum centripetal force to hang onto the club. We will proceed in this vein, and I believe it gives the most useful answer. But at the end of this article, we will discover a point in the swing that may call for an even larger hand force -- though not one that involves keeping the club in the hands.
Given that assumption, there are three things we have to concern ourselves with:
1.The centripetal pull we have to exert just to keep the club on its rotational path, and not let it fly out of our hands. This depends on clubhead speed and some of the club's dimensions. This peaks out at or near impact, which is why the pictures is shown just before impact.
2. Any additional force we need to continue to accelerate the clubhead near impact.
3. The hand forces on the handle of the club to resist the forces from #1 and #2.
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Post by syllogist on Jul 27, 2020 6:05:55 GMT -5
Hi DG,
A photo of DJ at impact with some forward lean at impact is hardly proof that DJ is one of the best at "maintaining a pulling force ahead of the clubhead." Wasn't DJ obviously chosen because of his 120+ mph clubhead speed, which involves factors other than the phrase above, which itself means that DJ is not an early releaser of the clubhead? Furthermore, if in fact he does, for how long does he do so prior to impact and why does doing so not negatively affect release velocity?
Another thing about DT's conclusion regarding grip force required to hold onto the club during peak clubhead velocity - doesn't the centripetal force vector continuously change direction, in that what is the direction of the clubhead when peak velocity occurs (which may be halfway through the uncocking of the wrists)? Does such direction of clubhead force lend itself to want to cause the club to be "pulled out" of our hands, also considering that our hands are traveling somewhat horizontally from the left thigh to impact?
S
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Post by dubiousgolfer on Jul 27, 2020 8:52:46 GMT -5
Hi DG, A photo of DJ at impact with some forward lean at impact is hardly proof that DJ is one of the best at "maintaining a pulling force ahead of the clubhead." Wasn't DJ obviously chosen because of his 120+ mph clubhead speed, which involves factors other than the phrase above, which itself means that DJ is not an early releaser of the clubhead? Furthermore, if in fact he does, for how long does he do so prior to impact and why does doing so not negatively affect release velocity? Another thing about DT's conclusion regarding grip force required to hold onto the club during peak clubhead velocity - doesn't the centripetal force vector continuously change direction, in that what is the direction of the clubhead when peak velocity occurs (which may be halfway through the uncocking of the wrists)? Does such direction of clubhead force lend itself to want to cause the club to be "pulled out" of our hands, also considering that our hands are traveling somewhat horizontally from the left thigh to impact? S Hi S The centripetal force vector does change direction . The club doesn't 'pull' out of the hands , the hands will just slip off the grip if the friction (between the 2 surfaces) is not enough to sustain the curved motion of the clubs COM. If there isn't enough friction, the COM of the club will tend to continue to remain in its original motion (in the direction of its instantaneous linear velocity vector). If for example the friction was not enough from P6 onwards - I would normally expect the club to slip out of the fingers and the clubhead to hit the ground before the ball (ie. the radius of the clubhead path would get larger). As Dr Mann mentioned in his previous post , there is the possibility that even if the friction is insufficient , there might still not be enough time in the downswing for any significant amount of slippage to occur before club/ball impact. I imagine it could be quite difficult to assess what effect any 'slippage' would have on a golfers downswing and club/ball impact considering all the other biomechanical dynamic events that could be happening at the same time (ie. left arm bending , left leg straightening , lateral flexion, etc etc). I seem to remember there was a time where golf instruction advocated some ' slipping and regripping' movement called the 'piccolo' and I actually found a video below. Funny how golf instruction has evolved over the decades. DG
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Post by dubiousgolfer on Jul 28, 2020 6:56:41 GMT -5
I found another article (great what one can find on the internet) which did a study on 'pinch grip ' forces in adults www.researchgate.net/publication/50224866_Grip_force_and_pinch_grip_in_an_adult_population_Reference_values_and_factors_associated_with_grip_forceFor a 60-69 yr old man the average pinch grip is about 60-63 Newtons (13.4- 14.1 lbs force) for each hand, so lets just assume 14lb force for each hand totalling 28lb force just using a pinch grip. According to DT's required grip strength table an 80mph swing speed will require 59 lbs force for a typical Driver with a graphite shaft. Dr Mann used 1 thumb + 2 fingers in each hand so not exactly a pinch grip, so lets add another 7lb force for each added finger which would equate to 21lb force for each hand and 42 lbs force in total. The standard deviation in the above article is around 22 Newtons (approx 5lb force) so lets assume Dr Mann has pretty strong fingers and can apply an extra 5lb force per hand (top end of the standard deviation) Instead of 42lbs force we would get 52lbs force which is still 7lbs force under the 'required' 59lb shown in DT's table but not too bad considering all the assumptions being made by DT in his physics/maths. However if DT's table is presumed accurate , we might have to also assume that Dr Mann has extra strong fingers for his age group. DG PS. I think we also have to be aware that when DT created that 'required table' he was making an assumption that the golfer is applying some extra pull force via his lead arm to continue applying an MOF through impact (which another article seems to contradict because the grip pressure dips into impact) . Therefore DT's table may be overstating the required grip forces at impact.
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Post by imperfectgolfer on Jul 28, 2020 18:46:08 GMT -5
I found another article (great what one can find on the internet) which did a study on 'pinch grip ' forces in adults www.researchgate.net/publication/50224866_Grip_force_and_pinch_grip_in_an_adult_population_Reference_values_and_factors_associated_with_grip_forceFor a 60-69 yr old man the average pinch grip is about 60-63 Newtons (13.4- 14.1 lbs force) for each hand, so lets just assume 14lb force for each hand totalling 28lb force just using a pinch grip. According to DT's required grip strength table an 80mph swing speed will require 59 lbs force for a typical Driver with a graphite shaft. Dr Mann used 1 thumb + 2 fingers in each hand so not exactly a pinch grip, so lets add another 7lb force for each added finger which would equate to 21lb force for each hand and 42 lbs force in total. The standard deviation in the above article is around 22 Newtons (approx 5lb force) so lets assume Dr Mann has pretty strong fingers and can apply an extra 5lb force per hand (top end of the standard deviation) Instead of 42lbs force we would get 52lbs force which is still 7lbs force under the 'required' 59lb shown in DT's table but not too bad considering all the assumptions being made by DT in his physics/maths. However if DT's table is presumed accurate , we might have to also assume that Dr Mann has extra strong fingers for his age group. DG PS. I think we also have to be aware that when DT created that 'required table' he was making an assumption that the golfer is applying some extra pull force via his lead arm to continue applying an MOF through impact (which another article seems to contradict because the grip pressure dips into impact) . Therefore DT's table may be overstating the required grip forces at impact. I prefer "real life" empirical testing. I can swing a driver at 90mph clubhead speed using a pinch grip of only one hand (lead hand) without the club handle pulling out of my grip, and I don't believe that I have a particularly strong pinch grip. Jeff.
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Post by dubiousgolfer on Jul 28, 2020 20:40:53 GMT -5
Dr Mann This would imply that DT's formula is flawed . I suspect it could be the use of 'R' R is the distance from the mid-hands point to the center of mass of the clubhead, in inches. As per image below (from Dr Kwons website), the clubs 'COR' (centre of rotation) is not the mid-hand point approaching impact but higher up which would make R larger and the centripetal force smaller. F = 0.00129 V 2 *(M + m/2)/ R (this is the formula DT has used in his article). DG
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Post by dubiousgolfer on Jul 29, 2020 9:44:06 GMT -5
I think DT's article contains too many assumptions, especially points 1,4 and 5 below which can cause his formula to produce results that do not match empirical testing.
1. 85% of clubhead speed is due to angular rotation + 15% linear 2. Driver mass 3. Shaft mass 4. R as the radius of curvature of the club approaching impact (where he uses the length between the mid-point of the hands and the clubs COM). 5. He is assuming an extra additional grip pressure being applied to increase the MOF induced angular acceleration through impact.
Dr Mann's empirical test proves there is a flaw in DT's assumptions and that a 90mph swing can be completed with a pinch grip averaging 14 lbs force (as per article)
DG
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Post by dubiousgolfer on Jul 29, 2020 12:52:37 GMT -5
Dr Mann
Did you measure your clubhead speed using some device like 'Trackman'? Would be nice to see a video of your pinch grip swing and then use it to raise a question to DT about his logic used in his article.
DG
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Post by imperfectgolfer on Jul 29, 2020 16:19:01 GMT -5
Dr Mann Did you measure your clubhead speed using some device like 'Trackman'? Would be nice to see a video of your pinch grip swing and then use it to raise a question to DT about his logic used in his article. DG I don't have a Trackman, or other device, to measure clubhead speed. I don't need to perform a swing video because the "best proof" would be for every sceptical golfer to personally perform his own test in order to see whether it works. Jeff.
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Post by dubiousgolfer on Aug 24, 2020 12:00:09 GMT -5
I've found an article with grip pressure graphs and thought I'd just post it for future reference (it might be useful). therecreationalgolfer.com/blog/2016/12/more-on-grip-pressure/If one looks at the PGA pro graph , the Right hand grip pressure at impact is approx '2.5 lbs per square inch' pressure while the left thumb and last 3 fingers are exerting about '10 lbs per square inch' each. One thing I noted was the much larger grip pressure in the left hand in the early downswing compared to the right hand. If we assume that there isn't any change in the 'hand/club' contact areas during the downswing and Pressure = Force/Area , then there are much greater forces being applied by the left hand than the right hand. The other thing I noticed is that the pressure in the last 3 fingers of the left hand is virtually constant for the early downswing , while the pressure in the left thumb is increasing. Doesn't that suggest that there is some positive torque happening in the left hand in the early downswing ? Or The extra pressure being exerted on the left thumb could really be due to increased pressure acting on it by the base of the right thumb (applying extensor action). DG On reflection the above graphs from Budney have limited use. "Grip force has been previously measured in golf, but only to a very limited extent. The bulk of this research has been done by Budney ( 1979) and Budney and Bellow ( 1990), with additional observations provided by Cochran and Stobbs (1968). and Nikonovas ct al (2004). In all cases, data from very few golfers were obtained and few conclusions about total grip force during play could be drawn"
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Post by dubiousgolfer on Aug 14, 2023 7:43:07 GMT -5
Looks like in the future we may have lots more grip pressure data being used by golfers.
DG
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