|
Post by dubiousgolfer on Jul 3, 2020 19:33:37 GMT -5
Dr Mann Have you ever read this article by Dave Tutelman? 'What Powers The Golf Swing' www.tutelman.com/golf/design/swing1.php?ref=He mentions Jorgenson creating that double pendulum model where he had to tweak it to exactly match a real golfers swing by : 1. Adding a 90 degree stopper at the peripheral 'wrist' joint (ie. the positive torque element to prevent the club rotating clockwise during the early-mid downswing). 2. A little sway of the central hub targetwards. He realised that his use of 'Centrifugal Force' can be a valid criticism but also says it can still produce the correct mathematical results as D'Alembert principle. What still interests me is the bolded sections below which suggests to me that the application of positive torque via the hands to 'kick start' release of PA#2 would require incredible timing at 70 milliseconds before impact. He also says its easier to hold the lag and allow it to release 100 msecs before impact to get an equivalent increase in clubhead speed as the 'kick start' positive torque release of PA#2 Because PGA pros have been swinging from a very young age I don't find it surprising that they are able to fine-tune this 'kick start' PA#2 release. But I still do not think it can be assumed as an optimal technique , just something they have 'fine-tuned' by intuitive 'feel' after so many hours practice for many years. --------------------------------------- "But the important change he did not have to make was to add any wrist torque to release the club at the bottom of the swing. That is accomplished completely by centrifugal force. In fact, once he had a mathematical model that behaved like the golf swing, he ran some "what if" analyses to see whether application of wrist torque could add to power. He found that there is a critical time about 70-100 milliseconds before impact (where the arms are 60 degrees before the impact position) where torque changes from hurting clubhead speed to helping it. That is, any uncocking wrist torque before the critical time will reduce clubhead speed at impact. You can indeed increase clubhead speed a bit by applying wrist torque, but only if you can do it for just the last 70 milliseconds before impact, and not before. It takes a very well-coordinated athlete to get away with this. (If you are interested in more detail about this, I have worked it to death in another article. In particular, the difficulty of applying torque during those last 70 milliseconds is discussed here.) Interestingly, Jorgensen found that that the same critical time works the other way as well. If you use negative torque (that is, use strength in the wrist to prevent uncocking) early in the swing and then release it 100 milliseconds before impact, you will increase the clubhead speed. In fact, you'll get as much increase in clubhead speed as that well-coordinated athlete would have gotten by a late application of positive torque. And it's much easier to hold off release than to apply a release-aiding torque at exactly the right time.
So Jorgensen's study confirms the notion that power in a golf swing -- clubhead speed -- is a product of centrifugal force and not wrist torque. He adds a lot of detail, but nothing that denies that basic truth." ------------------------------------ DG
|
|
|
Post by imperfectgolfer on Jul 3, 2020 20:53:16 GMT -5
DG,
That's a very old DT-article written many years ago.
It is my impression that DT now believes in the legitimacy of the hand couple phenomenon - based on his verbal response at the Michael Finney zoom 2 conference a few months ago.
Jeff.
|
|
|
Post by dubiousgolfer on Jul 3, 2020 21:02:47 GMT -5
I wondered if he actually said anything at that conference.
So the whole double-pendulum model, including DT's & Rod White articles are now obsolete.
DG
|
|
|
Post by imperfectgolfer on Jul 4, 2020 0:02:53 GMT -5
I wondered if he actually said anything at that conference. So the whole double-pendulum model, including DT's & Rod White articles are now obsolete. DG From the perspective of the PA#2 release action in "real life" pro golfers, those articles could be considered to be obsolete. I personally don't think they are of value. Jeff.
|
|
|
Post by syllogist on Jul 4, 2020 6:56:42 GMT -5
Hi DG,
I don't think for a moment that DT's articles or White's model is obsolete. The value of White's model is that he realized that the model should be a triple pendulum (added rotation of the pivot) in order to search for optimal swing sequence. Professor Robin Sharp concluded the same at about the same time and shortly thereafter, MacKenzie used the same concept. I haven't seen that the assumption of a calculation of a net hand force couple or, for that matter, gross individual hand forces (whether at the wrist joints or as measured by the accel/decel of the hands) adds any practical value to the understanding of how the swing is accomplished.
S
|
|
|
Post by dubiousgolfer on Jul 4, 2020 7:42:42 GMT -5
Dr Mann Dave Tutelman has replied back to me and he says: * I am not planning to rewrite "What Powers the Golf Swing". * I am planning to write a separate very long tutorial on the forces and torques in the swing. But, rather than contradicting the original article, it provides great detail and more precision about what is going on. So it seems he regards his article as still very relevant. I have referred him to Dr Kwon's graphs showing positive hand couple (even when the red and green lines cross) and also the frame image below from SMK's video that show a positive hand couple of 5.2N (at P6) which would probably have been even larger at P5.5 (the probable point of PA#2 release). Maybe DT has missed what you have noticed on those graphs but I will await his reply. DG
|
|
|
Post by dubiousgolfer on Jul 4, 2020 8:39:50 GMT -5
Hi DG, I don't think for a moment that DT's articles or White's model is obsolete. The value of White's model is that he realized that the model should be a triple pendulum (added rotation of the pivot) in order to search for optimal swing sequence. Professor Robin Sharp concluded the same at about the same time and shortly thereafter, MacKenzie used the same concept. I haven't seen that the assumption of a calculation of a net hand force couple or, for that matter, gross individual hand forces (whether at the wrist joints or as measured by the accel/decel of the hands) adds any practical value to the understanding of how the swing is accomplished. S Hi S As per previous post it seems that DT still thinks his article is relevant but it doesn't provide enough detail about what is happening in the early stage of 'Release' (ie. uncocking of the left wrist which in TGM terms is the release of PA#2). DT says the following in his email sent today but I don't know why he started mentioning the 'late downswing' as I was questioning him about assisting 'Release' with the hand couple. "On the contrary! You want the wrists as passive as possible. The hands and wrists cannot move fast enough to keep up with the angular velocity created by the inertial forces. The more you try to exert a positive couple late in the downswing, the more negative the couple is in fact. You definitely want passive wrists."Not sure what he meant about that underlined section above but I suspect the act of trying to exert a positive couple in the late downswing will probably cause a 'Net Force' across the COM of the club which will tend to create an MOF that would assist rotation clockwise (from a face-on view). He also says the following in reply to my statement below: "the 'positive hand couple' is not just muscular wrist torque but probably some other biomechanics involved that will create forces via the hands to the club."DT's response: Agreed. But there is nothing mysterious here. We are talking (a) early in the downswing, where (b) the wrists are cocked as much as the joints (bones, ligaments, tendons) will allow. Early in the downswing, the positive couple is exerted in large part by the limit to the wrists' range of motion.The physics of the double-pendulum is still applicable in some shape or form to create clubhead speed but cannot , by itself, explain the triggering of PA#2 release. DG
|
|
|
Post by imperfectgolfer on Jul 4, 2020 9:15:25 GMT -5
DG,
You wrote-: "The physics of the double-pendulum is still applicable in some shape or form to create clubhead speed but cannot , by itself, explain the triggering of PA#2 release."
If it cannot explain the triggering of the release of PA#2 then how does it explain the physics of the release of PA#2?
Jeff.
|
|
|
Post by dubiousgolfer on Jul 4, 2020 9:44:36 GMT -5
DG, You wrote-: " The physics of the double-pendulum is still applicable in some shape or form to create clubhead speed but cannot , by itself, explain the triggering of PA#2 release." If it cannot explain the triggering of the release of PA#2 then how does it explain the physics of the release of PA#2? Jeff. Dr Mann The physics of the 'release' in the double pendulum model is the MOF that you see in Dr Kwon's graphs and SMK videos. So although you have observed that the hand couple is assisting release, the MOF (ie. the physics that explains the release of the double pendulum) is still mainly responsible for increasing clubhead speed in the late downswing when the hand couple become zero/negative (the rest of the release of PA#2). DG
|
|
|
Post by syllogist on Jul 4, 2020 10:26:32 GMT -5
Hi DG,
You wrote that the physics of the double pendulum cannot explain the triggering of the release of PA#2 then how does it explain the physics of the release of PA#2.
Obviously, where the force acting on the double pendulum is gravity alone, the physics explains the swinging out of the distal segment in relation to the proximal segment.
I believe that in a driven double pendulum, if the proximal segment were to continuously accelerate, the release would be hampered, and it would be hampered more the greater the rate of acceleration. (This assumes no deceleration before the distal segment passes the nadir of the circle.) I think that there is a relationship between the length and mass of the distance segment and the rate of acceleration of the proximal segment that determines the amount of "release."
This is moot in the case of a real golfer, who does not and, under normal swing conditions, cannot continuously accelerate the hands. The physics causing the deceleration of the hands (force acting on the clubhead which travels in one direction while the hands travel in the "opposite" direction) causes the release.
S
|
|
|
Post by imperfectgolfer on Jul 4, 2020 12:30:43 GMT -5
DG, You wrote-: " The physics of the double-pendulum is still applicable in some shape or form to create clubhead speed but cannot , by itself, explain the triggering of PA#2 release." If it cannot explain the triggering of the release of PA#2 then how does it explain the physics of the release of PA#2? Jeff. Dr Mann The physics of the 'release' in the double pendulum model is the MOF that you see in Dr Kwon's graphs and SMK videos. So although you have observed that the hand couple is assisting release, the MOF (ie. the physics that explains the release of the double pendulum) is still mainly responsible for increasing clubhead speed in the late downswing when the hand couple become zero/negative (the rest of the release of PA#2). DG I disagree - because the MoF values seen in the Dr. Kwon and SMK graphs is too small between P5.5 => P6 to induce the release of PA#2. The MoF values only increase a lot in the later downswing when the release of PA#2 is already well underway and they explain the completion of the release of PA#2, but they do not explain what triggers the release of PA#2. Jeff.
|
|
|
Post by dubiousgolfer on Jul 4, 2020 16:50:31 GMT -5
Dave Tutleman has replied to me (see below):
-----------------------------------------------------
Sasho says in this video, other videos, and even a published paper or two, that: * At slow club speeds (that is, early in the downswing), hand couple is the dominant effect. * At high club speeds (late in the downswing, specifically during release), the moment of the force is doing the angular acceleration and the hand couple is just along for the ride.
Sasho and Dr Kwon also mention 30msec before impact as the point where the hand couple has already gone negative, most golfers between 30 and 50 msec. Let's see how this compares to P6. (I don't use that nomenclature nor do most biomechanists, except when working with PGA instructors where the nomenclature originated.) As I remember it, P6 is shaft horizontal on the downswing.
I've looked at a bunch of videos frame by frame, and concluded that good golfers with good clubhead speed get to P6 35-40msec before impact. That means that you have 10msec at most, and no time at all for many, to actually experience positive hand torque during release. Remember that the P-notation is not based on equal time but roughly equal angular movement. The time from P6 to impact is tiny. (Try watching the Tiger Woods swing at <https://www.youtube.com/watch?v=npcdJaYOEKo>; the frame rate is 30fps.)
So here's my position on it. It is consistent with Sasho, and I suspect Kwon would tell me I'm being too generous.
(1) Early in the downswing, for the time that the wrists have not begun to uncock, the swing's behavior is dominated by hand couple. But very little is muscular effort (at least not the hands' effort), but rather "passive torque" due to wrist range of motion limits. The muscles causing this are the big muscles turning the body. The hand and wrist muscles are not trying to uncock the wrist at all.
(2) Later in the downswing, the swing's behavior is dominated by inertial forces -- the moment of hand force on the club. The hand couple goes negative 30-50 msec before impact, and the wrists begin to uncock 35-40 msec before impact. That means some golfers (not the majority) will get some increase in clubhead speed due to hand couple during release, but for 5-10 msec at most. I doubt that's enough (haven't done the math, and don't have time to now) to generate even 2mph of added clubhead speed.
So don't base your speed training or your swing philosophy on positive hand couple.
-----------------------------------
DG
|
|
|
Post by dubiousgolfer on Jul 4, 2020 17:09:36 GMT -5
Dr Mann I'm not convinced about that section I underlined in DT's reply . Isn't there a substantial increase in clubhead speed from P5.5 - P6 in Tour Pro swings? DG PS. Here are screen images for a Tour player on Gears (at P5.5 and P6) and it shows an increase in clubhead speed from 79 - 95 mph (approx). Even SMK's video for that 'multiple major winner' shows an increase in clubhead speed of about 20 mph from P5.5 -P6. Further DT says: "I've looked at a bunch of videos frame by frame, and concluded that good golfers with good clubhead speed get to P6 35-40msec before impact" "the wrists begin to uncock 35-40 msec before impact"That doesn't make sense to me because it is a contradiction and infers that golfers are uncocking their left wrists at P6.
|
|
|
Post by imperfectgolfer on Jul 4, 2020 20:21:51 GMT -5
Dave Tutleman has replied to me (see below): ----------------------------------------------------- Sasho says in this video, other videos, and even a published paper or two, that: * At slow club speeds (that is, early in the downswing), hand couple is the dominant effect. * At high club speeds (late in the downswing, specifically during release), the moment of the force is doing the angular acceleration and the hand couple is just along for the ride.
Sasho and Dr Kwon also mention 30msec before impact as the point where the hand couple has already gone negative, most golfers between 30 and 50 msec. Let's see how this compares to P6. (I don't use that nomenclature nor do most biomechanists, except when working with PGA instructors where the nomenclature originated.) As I remember it, P6 is shaft horizontal on the downswing.
I've looked at a bunch of videos frame by frame, and concluded that good golfers with good clubhead speed get to P6 35-40msec before impact. That means that you have 10msec at most, and no time at all for many, to actually experience positive hand torque during release. Remember that the P-notation is not based on equal time but roughly equal angular movement. The time from P6 to impact is tiny. (Try watching the Tiger Woods swing at <https://www.youtube.com/watch?v=npcdJaYOEKo>; the frame rate is 30fps.)
So here's my position on it. It is consistent with Sasho, and I suspect Kwon would tell me I'm being too generous.
(1) Early in the downswing, for the time that the wrists have not begun to uncock, the swing's behavior is dominated by hand couple. But very little is muscular effort (at least not the hands' effort), but rather "passive torque" due to wrist range of motion limits. The muscles causing this are the big muscles turning the body. The hand and wrist muscles are not trying to uncock the wrist at all.
(2) Later in the downswing, the swing's behavior is dominated by inertial forces -- the moment of hand force on the club. The hand couple goes negative 30-50 msec before impact, and the wrists begin to uncock 35-40 msec before impact. That means some golfers (not the majority) will get some increase in clubhead speed due to hand couple during release, but for 5-10 msec at most. I doubt that's enough (haven't done the math, and don't have time to now) to generate even 2mph of added clubhead speed.
So don't base your speed training or your swing philosophy on positive hand couple.
----------------------------------- DG, I don't understand what DT is trying to state when he states that there is only 5-10 msec for the "hand couple to increase clubhead speed during release". Does he mean that the hand couple must still be positive for it to help induce the release of the club? I thought that the initiation of the release of the club was due to the hand couple becoming negative around P5.5 - P6 while the MoF starts to increase.
Here is another SMK video showing the amount of angular work due to the hand couple. I noted that the CHS increases form ~87mph at P5.5 to 99mph at P6. Also, the hand couple presumably does it angular work when it is positive (which is between P4 => P5.5) and I presume that its "effect" on angular acceleration of the clubshaft, and therefore CHS, is only seen when the club releases (at which time the hand couple is becoming negative). Does DT take that fact into account - that the accumulative angular torque due to the hand couple must precede angular motion, and that the hand couple's angular work output is the area under the hand couple curve (during the time period that it is positive)?
Also, when DT states that the hand couple's positive torque is a "passive torque" due to big muscles turning the body, how can he explain the underlying biomechanics that would cause the "passive torque" to be operating exactly at the coupling point between the hands?
Jeff.
|
|
|
Post by dubiousgolfer on Jul 4, 2020 21:05:43 GMT -5
Dr Mann Imho , I think DT is assuming that 'Release' happens when the MOF and Hand Couple graphs cross (ie. around P6). That after they cross there is still a small amount of positive hand couple that lasts for 5-10 msecs (before it goes to zero) which he's approximated will cause a small 2mph increase in clubhead speed (see the small positive section of the blue graph after the vertical black line below). Personally , I think your observation about the hand couple 'kick-starting' release has been missed by SMK /Dr Kwon/ DT . They haven't looked at the minute detail of exactly when the wrists uncock or even cross-referenced that event on their graphs (because TGM PA#2 release has no meaning to them). I think they are looking at the kinetics of the golf swing in a more general manner rather than getting involved in the biomechanical intricacies. DG
|
|