Dr Mann
I have found 2 differing statements (one relating to Mike Malaska move and the other regarding Jon Sinclairs wrist graph).
"I think that this punch elbow motion, which combines internal rotation of the right humerus together with pronation of the right forearm, does not often happen in professional golfers, and their right forearm only pronates to a much smaller degree much later in their late downswing so that
their right forearm rotates from being frankly supinated at P5.5 to becoming less-supinated, and becoming closer-to-neutral, by impact (where the right palm faces the target, but is still partially under the club handle)."
"The red graph represents the trail forearm supination graph. Note that the
trail forearm starts to supinate during the early-mid downswing and that it continues to increasingly supinate during the first half of that yellow highlighted zone and that the degree of supination peaks just before impact. The trail forearm then becomes slightly less supinated by impact, but it is still frankly supinated at impact."Also
Not sure about this bolded part below in Topic 5 :
"The force being applied by the lead hand = 38.6N, and the total net force
(which includes angular work) = 60.9N. The clubhead speed is 30.1 mph.
Reason: Work done by the Net Force includes the 'work' done by the MOF , not the work done by the 'hand couple' which is separate to linear work.
Here are some other issues I have commented on:
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Angular work is performed to change the angular position of the golf club in space"
Reason: If the club was moving around in a circular path at a constant speed , there is no angular work being done even though the angular position of the golf club is changing . Angular work happens when there is a 'Net Torque' applied to the club which will angularly accelerate the club over an angular distance (the calculation of work will be Torque x angular displacement).
Your statement above is not wholly true from a physics standpoint but you are correct , angular work will also cause a change in the clubs angular position .
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"Having an increased degree of clubhead lag (> 90 degrees) allows a golfer to produce more angular work during the downswing."
Reason: The above statement is correct but there are other advantages. I can imagine Jamie is strong enough in his forearms/wrists to utilise that increased angular distance to apply extra Torque via an active 'Hand Couple' (if he wanted to but unsure whether he does this).
Having so much lag also decreases the overall MOI of the 'upper torso/arms/club' unit which means that for a given upper body pivot torque , the Force applied via the hands will be larger.
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John Dunigan Graph:
"The blue graph line represents the rate and direction of rib cage rotation during the swing"
Reason: I think the graph is Green not blue .
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However, when you look at Jamie Sadlowski's hand arc path, you will note that his left hand moves slightly farther away from the target between P4 and P4.5. Why does his left hand move further away from the target at the start of the early downswing?
Note that Jamie Sadlowski's left hand is vertically positioned above his head at his end-backswing position (image 1) when his left arm is at the 12 o'clock position, and that it then moves well to the right of his head at the P4.5 position (image 2). This indicates that his left hand is moving away from the target between P4 and P4.5. But what is causing that motion of his left hand away from the target at the start of his downswing action?
Reason: I remember having problems understanding what point you were trying to make in a previous post and am still having problems when I read this again. His left hand was further away from the target in the backswing so why shouldn't it be further away from the target in the downswing?
Are you asking the question why is JS's P4.5 hand position closer to the target than his P3.5 position?
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The coupling point (red dot) is a point on the club handle that is midway between the two hands and if the golfer adopts a baseball style grip, where the two hands are not overlapping, the coupling point is located just below the position of the left hand's left 2nd knuckle, and the entire right hand will be positioned below the coupling point. However, many professional golfers adopt a Vardon, or overlapping, grip style (rather than a baseball grip style) and that means that the right hand is positioned further up the grip in such a manner that the base of the right palm abuts against the base of the left thumb at PP#1 (yellow area)
. That means that any push-pressure being applied by the right palm is primarily being applied above the coupling point against PP#1, and it is not mainly being applied against the aft side of the club handle below the coupling point. Any push-pressure being applied by the lower right palm, or right index finger, is being applied against the aft side of the club handle below the coupling point, and it can predispose to a casting-flipping motion of the clubshaft if it is wrongly applied during the early downswing action.Reason : A push force like PP1 or PP3 below the coupling point will not rotate the club unless that coupling point was fixed in space. A 'hand torque' about the coupling point would rotate and cause an early casting motion .
Also individual positive hand torques (or a combination of both) can rotate the club
A net eccentric force applied across the grip could cause an early cast if its direction was in such a direction that it caused a MOF which would cause a counter clockwise rotation of the club (from a face-on view)
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I'll resume tomorrow as I'm unsure about Dr Kwon's graphs.
Dr Kwon graph below :
In your article you have said the following which I think has errors.
"In the left-sided diagram, the green arrow represents the tangential force component and the blue arrow represents the radial force component. The black arrow represents the net force (which is the combination of the two forces)."
Reason: Check out this link below which shows the same figure 3 as above:
www.drkwongolf.info/technotes/mh_kinetics.pdfDr Kwon's description of Fig3 is as follows:
Figure 3. The net MH force (black arrow) acting on the club by the hands.
The green and blue arrows are the
tangential and normal axes of the moving MH reference frame defined on the swing plane. The net MH force
was decomposed to two on‐plane components: tangential (green line) and normal (blue line)
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The image A shows the hand couple forces being produced by the two hands. The left hand is producing a force that is directed downwards-and-outwards. Note that the right hand part of the couple is producing a force-across-the shaft that is outwards directed.
Image B shows the effect of these hand couple forces - they produce a moment (torque) around the mid-hand point that is in a counterclockwise direction, and that hand couple torque can prevent the clubshaft from jack-knifing inwards.
Reason why I think your reasoning is incorrect:
1. Imagine an individual 'net' force vector applied by each hand using the green and blue arrowed images above
2. Then extend the tail end of each vector so that it passed by the COM of the club
You mentioned that the COM of the club will tend to align itself with the force vector. In both cases the COM will rotate clockwise to align with either of those 'net' hand forces. Your above example will not produce a positive MOF to stop the jack-knifing effect but will actually increase it.
Note: For the MOF , the direction of rotation will always align with
the 'tail' end of the 'Net Force' vector.
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Here is a possible scenario for DJ retaining his PA2 angle where the force applied by his left hand is yellow , while the purple force is his right hand. I drew an extension of the tail end of each vector so that is passes by the COM of the club . Can you see how each force will cause an MOF rotation of the club?
The left hand yellow force vector will cause a positive torque and CCW rotation (from a face on view)
The right hand purple force vector will cause a negative Clockwise rotation (from a face on view) .
Theoretically , depending on the magnitude of each force and its 'moment arm' they could cancel out each other which would keep the PA2 angle constant.
I am not saying that is what's happening in reality but it is one of many theoretical possibilities which is why Dr Kwon and SMK cannot provide an answer. I can draw some other vector diagrams showing a mixture of forces and active wrist torques too that could retain the same PA2 lag angle (there are endless subtle combinations ).
I won't go into any more detail concerning the red dotted arrow because its getting too complicated from a physics perspective.
DG