Release action

[BerntR]

BerntR,

I do appreciate it that you spent some time looking at my release post. Whereas you base your critique mainly on what you feel to be right or wrong I did my analysis following a rigorous mathematical procedure. Multi-body dynamics is not readily accessible to intuition, its interactions being complex and highly non-linear. Therefore you might possibly agree with me that it is better to stick to mathematics.

Really???! ;-)

Nice rhethorics, btw. There must be some significant non-linearites in the human efforts in the golf stroke, but I can't see any in your equations. I can't see the imaginary aspects of the said complex situation that you refer to in your paper either. I think you will find alot of non.linearities and a little of complex forces when the kinesiology enters the framework. But what I see in your paper is a 3D problem projected into 2D, where any non-linearities and any complex issues are ignored. The whole release is discussed as a highly linear, lossless and 100% real process. I am fine with that, but why pretend that this is so bloody complicated? You aren't flashing high tech terminology just to impress your audience, are you?

Working forces are the ones doing work and producing net kinetic energy into the system. Non-working forces don't. However when considering one single body, in a multi body system, one can still think of non-working forces doing work locally but there will be no net work done and no 'fresh' kinetic energy created in the system. Only a redistribution of existing kinetic energy – the very basic action in a kinetic chain action.

Of course.

I am fully aware of the particular way centrifugal force has been and still is considered by many. Not all of it has to do with logic but such is human nature. I started by countering each of your arguments since I don't agree with them, but quickly I lost interest, the rebuttal getting way too big. Perhaps it is better to get right away to the essential mistake in your reasoning, since showing it to be wrong takes the steam out of all your arguments.

Fire at will.

Let's use your point of view and show that its implications logically leads to an absurd consequence (reductio ad absurdum).

- You feel that a centrifugal force is exerted on the clubhead.

No I don't.

I feel that a centrifugal force is exerted on the cocked wrist soon to be released. And also on the pulling shoulder.

Let me correct that. I know it. And so do you if you can read your own paper.

- We also know that for the clubhead to stay in its path requires a centripetal force.

- Newton's third law indicates that these two forces are equal and opposite.

Nice try, but no cigar.

Let's for safety sake agree that you only need a centripetal force to the extent that the club head has inertia (mass). If it's massless you can do anything you like with it, without applying any force whatsoever. Or perhaps not, because without mass, the acceleration will hit infinity before any force is developed and your equations will suffer from numerical explosion in the first iteration. I guess that's when the non-linearities comes in and save you (lol).

It's a tragic joke that you even consider explaining the release without including the inertia of the moving mass, which is a key enabler of any physics activity in the model.

- Conclusion the net force on the clubhead is zero.

You should really be more subtle if you want to ascribe me a totally different view than the one I have.

- Hence clubhead is frozen in space incapable of any curvilinear motion.

- Q.E.D. : Your point of view is hence very basically wrong.

Assume a stationary rotation, a mass rotating around a center, without any nonlinearities and without any complex, out of phase forces that may or may not make their presence later (lol). Jut a pure, friction less rotation. Then you analyze any cross section of the lever between the swing center and the mass center. You will see that the downward axial force on the lower section equals the upwards axial force of the upper section. Yet the object is moving. This is contrary to your cheap rhethorics.

And in case you haven't noticed, the wrist cock is located somewhere in the middle between the club head and the left shoulder.


I further advice you to consider that the "system" during the release is not in a stationary state. It is subject to torque and linear acceleration. Unless you introduce a negative wrist torque you can't have lag without acceleration. But you can shut down the engine and then the lag will be released in no time.

BerntR, Your error is not al that uncommon. Moreover you are in good company. Dr Cochran et al in 'Search for the Perfect Swing' also made the same error. It is one of several misconceptions quite common with regard to centrifugal force.

Mandrin,

Your error isn't uncommen either. You present a problem that you're going to dissect. But you do so without stating clearly what you are going to investigate. Then you present a theoretical discussion that is somewhat related to the problem, but where you fail to put an angle on it that highlights the problem. You're confusing shaft flexing with wrist uncocking. Introduce a highly sophisticated set of equations that is overkill with regards to what you need to draw a conclusion. Then you draw a conclusion that is thematic relevant, but in conflict with your theoretical discusion.

I used to tutor bachelor students when they were writing their thesis. I see the same flaws in your papers as in their first drafts. They have a lot of theoretical knowledge about the subject they are investigating, and they are so eager to put all of their knowledge on display, so they write page after page about everything they know about the subject without even getting close to answering the question at hand. There are no limits as to how complicated this can get. I get the same feeling when I read your papers. Reading a true scientific paper is a breeze by comparison if you are familiar with the subject. These kids don't know how to ask, investigate and answer a question in a scientific manner. And signs are, neither do you.

There are many ways to skin a cat. You don't need all those equations if you want to debunk the centripetal / centrifugal release. It only confuses the message. SteveT, which seems to be a disciple of yours is now attacking me because I say that centripetal force doesn't create swing speed. I guess he didn't notice that you stated the same in your paper.

The only effect your unnecessary complication of the matter has is that most people don't even try to read it. They browse the charts and head straight for the conclusion. The inertial forces from the moving clubhead plays at least as big a part in the release as the centripetal force in your own theoretical discussion. You even have a chart displaying a massive release torque from the inertia forces. Yet you fail to acknowledge that in your conclusion. That's an F in my book.

 

[TeeAce]

@TeeAce..... Please read and study mandrin's rebuttal response to 'engineer' BerntR, because you are falling into the same misconception trap.

I think I don't understand your posting and you didn't understand mine. I'm sure only about the first

What the heck is centrifugal force

 

[birly-shirly]

Hey, I'm quite satisfied with my scientifically sound golfswing and I don't need to post a video for analysis by "average golfers" who don't really know much about a golfswing. Besides, Brian has stated several times that you can't judge a golfswing with pics and vids, and in the New Year he will ban such nonsense.

Also, I don't want to lower myself into a gorilla chest-beating contest with you... and embarrass you too.

Where to start?

(1) Don't worry about embarrassing me. How would that happen anyway?

(2) I'm not beating my chest. I'm not claiming to be better than anyone else, or even competent to critique anyone's swing.

(3) You're the guy who once proposed that posters should put up their credentials before joining a discussion.

(4) If I made a claim to have a swing that's the result of decades of scientific research, developing and perfecting - I'd expect to be asked for evidence.

You're the one whose constantly lecturing the forum on the scientific virtues. Isn't evidence part of the scientific method? Where's yours?

(5) As for the validity of video analysis - Brian made the point that video could not discriminate between changes of a degree or two in face angle or clubhead path in a swing that was already tour pro quality.

Are you suggesting that if you did post up your swing, we'd see something similar? Something that looks like a tour pro - maybe just a couple of degrees out in your delivery angles?

(6) Besides - I didn't suggest that you ONLY post up video. I suggested trackman data too - since I expect that such a rigorous scientificist as yourself wouldn't work with anything less.

Since you're so happy to talk about other posters' credibility with the forum, let me suggest that your own credibility as anything more than an armchair theorist, who can do more than just throw some terminology around and who can actually execute, wants some bolstering.

If you want to carry on as you've been doing with any credibility, let's see some evidence.

Post it up.

 

[SteveT]

@"engineer" BerntR .... I see you have attempted to respond to mandrin's rebuttal, and I will let him reply to you.

Now could you respond to my 3 questions at message #44, still outstanding?

You create a centrifugal "force", and this tells me that you are confused between inertial and non-inertial frames of reference. Please don't respond by proclaiming : "I know what I feel."

 

[Chiefbullmarket]

Let's use your point of view and show that its implications logically leads to an absurd consequence (reductio ad absurdum).

- You feel that a centrifugal force is exerted on the clubhead.

- We also know that for the clubhead to stay in its path requires a centripetal force.

- Newton's third law indicates that these two forces are equal and opposite.

- Conclusion the net force on the clubhead is zero.

- Hence clubhead is frozen in space incapable of any curvilinear motion.

- Q.E.D. : Your point of view is hence very basically wrong.

BerntR, Your error is not al that uncommon. Moreover you are in good company. Dr Cochran et al in 'Search for the Perfect Swing' also made the same error. It is one of several misconceptions quite common with regard to centrifugal force. [/QUOTE]



Mandrin, I agree with you that there is no centrifugal force. What we feel as a centrifugal force is just inertia. Someone sitting in the passenger seat of a car as the driver turns left "feels" a force but it is simply inertia and there must be a force (friction, seat belt, inside of door) to make that passenger stay in that circular path.

I did disagree with your argument just not the conclusion.

Newton's 3nd law does not apply when two different forces act on the same object. It applies when one object exerts a force on a 2nd object. By Newton's 3nd law the 2nd object exerts an equal force in the opposite direction on the first. These two forces never cancel because they are on different objects.

When the net force becomes zero on an object it does not stop, it keeps moving at that velocity. No net force is needed for an object to move provided it was already moving.

Chief

 

[leon]

Well I was going to say some stuff, but it looks like I got beat to most of it

I love this place!

 

[BerntR]

@"engineer" BerntR

Now could you respond to my 3 questions at message #44, still outstanding?

There was only one question in your message #44, which I responded to, about my credentials. I have noticed that you aren't convinced....

I didn't feel like commenting your statement about centripetal force in the same post. It would be very difficult for me to do that without giving you negative exposure. If you want any further answers from me, just ask questions. I promise to reply in the same tone as you ask them.

 

[BerntR]

What we feel as a centrifugal force is just inertia.

Chief,

Centrifugal force is per def an inertial force Centrifugal force - Wikipedia, the free encyclopedia.

The never ending CF doesn't exist/ yes it does discussions are quite boring.

Personally I don't care what we call it, as long as it can be referred to without writing three sentences.

 

[OLIVER1]

Well I was going to say some stuff, but it looks like I got beat to most of it

I love this place!

It's fabulous, isn't it. I wonder if any other golf instruction website could engender this much ferocity from what are obviously very erudite individuals? While I'm not a scientist, I can kind of figure out what's going on, and I'm left with the distinct impression that if these chaps could find a little more common ground, then they'd be quite the force...

 

[SteveT]

There was only one question in your message #44, which I responded to, about my credentials. I have noticed that you aren't convinced....

I didn't feel like commenting your statement about centripetal force in the same post. It would be very difficult for me to do that without giving you negative exposure. If you want any further answers from me, just ask questions. I promise to reply in the same tone as you ask them.

Don't worry about "giving (me) negative exposure", I'm quite prepared to defend myself...!!!

Answer the 3 questions which are based on your own pompous declarations in your OP.

Intellectual cowards and frauds avoid accountability for their statements... they just obfuscate while twisting in their own fartuous wind.

Your response to mandrin was a joke ... just your own "snot on your moustache" ... and your hesitancy to answer my 3 questions reveals your inability to provide simple Newtonian physics proofs as it is applied to the golfswing.

BerntR(oger-the-Dodger)... we are waiting... unless you still "feel" like not commenting ... again!

 

[drewyallop]

If those are your credentials for habitually referring to other posters and "the average golfer" as clueless, ignorant and deluded, then post up some video of your scientifically-developed golfswing.

Ideally, a man of your scientific bent would also post trackman numbers, but if that's not possible (for whatever reason) then just video will do.

I agree birly. Steve often speaks down to us "average golfers" from the commanding heights of his superiority and it gets on my tits. But watch the Anti-Summit I video and marvel at the humility of the scientists therein. No arrogance, careful consideration of all points of view, no flaunting of their superior knowledge. A refreshing change from much that appears here.

 

[BerntR]

All real forces must be applied, they just don't spring out of 'feel'. Please explain how the 100 lbs of 'centrifugal force' is generated.

The number was picked because you used that as an example. But when you have 100lbs of centripetal force pulling a rotating object inwards you also have the same centrifugal force pulling on the center pin. And those forces will be present in any cross section of the lever that ties the mass to the center.

Centripetal force is defined as Mass x Tangential Velocity^2 / Radius. V^2/r is known as the 'centripetal acceleration. According to this definition, centripetal force does create 'speed' tangentially.

To put it in plain English, this expression shows you how to calculate the centripetal force whenever there’s an orbital moving mass. There are no causes and effects there. The cause of speed is work. The cause of the radius can be a hinge, a curved wall, magnetic force, gravity or basically mechanism that can produce a force that is at right angles to the motion of a moving mass.

Ever heard about work?

When you increase the speed of a mass you produce kinetic energy. That requires work.

W = F * d. The bold notation signifies vector form. If you don't know what a vector is you can google it. W is work, F is force, d is the distance of the mass while the force is operating.

Here’s the non vectorized version that is applicable to calculating absolute values.

W = F *d * cos (a), where a is the angle between the force and the motion.

Kinetic energy = 1/2mv^2. If you do kinetic work in the golf swing you get increase in swing speed.

With centripetal force the angle (a) is always 90 degree. Cos(90) = 0. No work and no increase in speed. You can do the rest of the math yourself.

You can find the equations here Work (physics) - Wikipedia, the free encyclopedia

This simple work equation shows that the work done by the centripetal force is zero.

To demonstrate the absurdity in your claims of the opposite, let’s take a brief look at the moon.

The moon has been spinning around the earth for quite some time. We're talking billions of years here.

New Moon: 200 Million Years Younger Than Thought - ABC News

It’s the gravity force from the earth that keeps the moon around. Gravity keeps it spinning around the earth, approx. 1 rotation per month. The gravity force from the earth on the moon is centripetal force as good as the stuff that “powers your scientifically sound” golf swing. What should puzzle you is that the moon has had the same speed for a substantial duration, while you produce a vast increase in swing speed within tenth of a second when you apply centripetal force in your swing. I would be rather amused if you could enlighten me on the paradox.

Here’s a little bedtime lecture for you:Orbit of the Moon - Wikipedia, the free encyclopedia

On some areas it would be a blessing if your surreal interpretation of CF had a hint of truth in it. For instance, we should be able to solve the energy problem for mankind once and for all. Where I come from there are a lot of hydropower plants in operation to supply electricity. And magazines filled with water is a highly priced commodity. Other places uses gas, coal or nuclear power. For some reason those ignorants running the power plants believe they that they need energy to drive their turbines. Perhaps you should go and talk to them. Explain that since the turbines are rotary devices, there will be centripetal forces at work. And since the centripetal force produces speed, they don’t need no stupid water or gas or coal or nuclear power. And then you can show them your cf equation and explain to them that the more speed cf creates, the more cf will grow. This is hotter than nuclear power. The power generators must be calibrated to keep the fast growing cf at a manageable level, but that should be doable. We are talking about a perpetuum mobile here, de Luxe edition, that in some magic, mysterious way creates kinetic energy out of nothing.

But why stop there? You could convince the governments to start building roads with more curves. The vehicles will get a speed injection each time they go through a curve, due to your centripetal force. The list of novel causes waiting for your cf magic is endless. You’ve got a world saver at your hand here.

The only catch is that it is pure nonsense. You pretend to have science on your side, but you don’t even know how to read the cf equation you blatantly posted to prove me wrong. I can only say that it is a rare thing to experience so much arrogance, ignorance and rudeness from one person within such a short time span. It is almost as surreal as your claims regarding the magics of centripetal force.

 

[lia41985]

BerntR: Don't mind Steve. Just let him humor you with his absurdity. I'm sure he doesn't mean to be as big of a jack ass as he is and if he does happen to be who cares? I, for one, and I'm sure others on this site, appreciate your contributions.

 

[BerntR]

Thanks lia,

I'll try to remember that.

 

[ZAP]

I think that part of "going normal" is to assist the release of the club thereby creating extra speed. Can't really put it in math terms but you are shortening the "radius" and straightening it at the same time. Call me an idiot if you want. But get in line to do it. lol

 

[birly-shirly]

BerntR - would you give SteveT a pass in "applied mechanics" if he posted up evidence of his scientifically perfected golfswing?

 

[mandrin]

BerntR,

I had another look at your post and here are some additional comments.

It is correct that centrifugal force doesn't create any swing speed, and that is important to take note of.

First of all, the moment diagram, especially fig 35b, shows a very significant positive wrist torque from the centrifugal force. As far as I can see, the work done by this torque (the area under the curve) is bigger in the release interval than the torque created from the radial arm force. I would like to see those two charts superimposed. I bet that cf torques more than the arms pulling, but it is pretty close.

Wrong
1) Fig35a and Fig35b don't refer to centrifugal force/torque.
2) As explained in the text, Fig35b represents the sum of all other torques.

The direction of the axial shaft forces in the diagrams is 180* wrong, btw. They should be pointing towards the clubhead and not the other way.

Wrong.
Your force is actually a centrifugal reaction force.

The resultant force from the arm tangential and the club head tangential would be a backward force on the wrist, a force that works towards slowing down the hands and uncocking the wrists. This would be reinforced by any positive deliberate wrist uncocking by the hands around the coupling point. With or without deliberate wrist torquing, that's the release. A couple of forces - one up the left arm, another down the club shaft - that pulls the hand backwards and stretches out the cocked wrist.

Wrong.
You started off in your post admitting that centrifugal force doesn't play a role in creating clubhead speed, yet you keep introducing it continuously through the back door.

It is important to reckognize that the major part of the radial force in the arm is a function of club head CF towards impact. Without cf, the radial force up the arm would be less than zero. (The force would be a push force and not a pull force) So both those forces that works to move the hands backwards and to uncock the wrists are caused by CF.

Wrong.
You are really fixated on introducing a centrifugal force into the release action. Reactive forces don't come into the picture. That is an important advantage of using the 'Kane', 'Lagrange' or 'TMT' formalism - eliminating all non-contributing forces.

When the club is released, it is mainly because CF wins over the golfer's effort to match the increased club head angular speed with increased hands angular speed. A positive wrist torque will speed up the action, but later it is at best the icing on the cake.

Wrong.
Centrifugal force does not play a role in the releases action. Again contradicting your own opening statement that centrifugal force does not play a role in creating clubhead speed.

Centripetal force doesn't create speed. Because it works at 90 degree angle to the motion. But it enables us to keep the club head close even though it moves in 100 mph. The release doesn't create swing speed either. But the release is also an enabler. It works like a gear shift. Gives increased leverage. It enables the golfer to accelerate[/B] a club head that approaches 100mph with hands that moves slow.

Wrong.
The centripetal force up the arm constitutes the major force in the releases action. You have the simple picture in your mind of a single mass whirling around a center. With linked bodies the situation is a bit more complicated.

 

[BerntR]

Wrong
1) Fig35a and Fig35b don't refer to centrifugal force/torque.
2) As explained in the text, Fig35b represents the sum of all other torques.

I hear you.

In your introduction you write: "Release is taken to be the secondary rotation adding angular speed to the primary one in the impact zone and henceforth causing the club to overtake the arms in the impact zone." In plain English that means that you define the release as the straightening of the cocked left wrist. Nothing more and nothing less. I will get back to this definition further down. For now we can conclude that you can investigate the release by looking at the wrist joint.

And you confirm further down in the text that this is your mission: "To more conveniently grasp the relative importance of the forces / torques acting on the 'wrist' joints, I have derived their magnitude / direction and presented these force vectors and associated torques in graphical form."

So in other words diagram 35a-d display the forces and the torques imposed by the club on the wrist joints. The club is pushing the hands down the hand path. It stands out as the major force for creating hands speed. A little help from the arms, and for parts of the down swing, a bit of help from gravity as well. But the charts clearly states that the club is the main driving force behind the hand path. The club is pushing a wrist joint down the hand path. The tail is wagging the dog. It's absurd.

Since diagram 35 a and c are the only forces imposed on the wrist joint by the club we can use the D'Alembert's principle to see what the wrists are doing with the club. All we need to do is change direction of the forces in diagram 35a and 35c. The wrist is pushing the club up the swing path as far as the radial component is concerned. But since the angular component has the direction required for a downward motion the club head isn't going up nor down the depicted club head path.

More absurdities at impact: when the club is fully released, and where we would expect to see a strong domination of a centrifugal / centripetal force pair, the wrist is pushing the club into the ground. But the swing path and the geometry tells us that the joint must be pulling a centripetal force towards the center.

While this goes to the credibility of your analytical skills it's beside the point. Because most of your theoretical discussion is off topic anyway. It's the same old freshman error where one problem is stated and something else is discussed.

Wrong.
Your force is actually a centrifugal reaction force.

Yes.

You can call it whatever you like, but it is an inertia force that pulls downward and backwards on the wrist joint. Depending on how the wrist joint works this can be a pure axial force or a combination of axial force and torque.

Wrong.
You started off in your post admitting that centrifugal force doesn't play a role in creating clubhead speed, yet you keep introducing it continuously through the back door.

My bad. My intention was to introduce it through the main entrance.

You started off by defining the release as wrist uncocking. But your analysis deals more with how to create swing speed.

Why are you sneaking swing speed through the back door? And why don't you acknowledge that in your conclusion?

Wrong.
You are really fixated on introducing a centrifugal force into the release action. Reactive forces don't come into the picture. That is an important advantage of using the 'Kane', 'Lagrange' or 'TMT' formalism - eliminating all non-contributing forces. ......
Wrong.
Centrifugal force does not play a role in the releases action. Again contradicting your own opening statement that centrifugal force does not play a role in creating clubhead speed.
......
Wrong.
The centripetal force up the arm constitutes the major force in the releases action. You have the simple picture in your mind of a single mass whirling around a center. With linked bodies the situation is a bit more complicated.

Yes I am fixated on introducing a centrifugal force into the release action.

No I am not contradicting my own opening statement. I am only contradicting your hidden assumptions. Your reading is coloured by your own beliefs and you fail to see the implication of what I have stated even though it is there between the lines.

To your last sentence: What do you think will happen if the swing engine is shut down for a brief period? Do you think the wrist cock will be sustained? Do you think the release will be avoided if no "release work" is done?

The biggest problem in your approach is your assumption that the release creates speed. You introduce that as a given early on and proceed on that basis. Then you get so obsessed with work that you fail to investigate whether non working forces does something to the wrist cock.

Any golfer can uncock the wrists without spending a calorie. It doesn't take action and real time work. Non-action will do just fine. You can let the kinetic energy in the club head do it for you. Just shut down the engine, stall the shoulder turn, dead hands, freewheel the second half of the down stroke. DISCONNECT. You know, some of the things that high handicappers do. It will release fast. No action is required to release the club.

In a situation of complete shutdown of the swing engine, there will be a brief period of time where there is neither centrifugal and centripetal forces present (for simplicity, all masses except of the club head is ignored here). The club head will go straight forward until the wrist joint is fully uncocked and the double or triple pendulum is stretched out to max swing radius. Then a new pair centrifugal / centripetal force will reinstall a larger swing radius and the club head will start to move in orbit again - now fully released.

But in a human golfer I doubt that a complete shutdown is possible. There will instead be an effort at the wrist joint to produce more swing speed, small or big. The efforts of the poor golfer to sustain the lag with a forward driving torque is overridden by inertia and centripetal force, and the wrist is forced into a state of release. A good golfer may be able to sustain lag until past impact and can turn on a positive wrist torque in the last instance.

You've got the torque business completely wrong as far as release goes. Torque creates swing speed. Torque delays the release. The release happens because inertia and kinetic energy wins over the torque that creates hands speed and lag, deliberate or not. A release torque is optional but not mandatory. Turn off the torques in your simulator when the club head is parallel to the ground and see the early release blossom. But fix the direction of the club radial force first. You could also try to increase torque 1( the central torque) gradually, to obtain an angular acceleration of the hands that matches the angular acceleration of the club head. Just to see what it takes to prevent the release from happening before impact.

The forces required to sustain lag will create swing speed. And swing speed will increase the inertia forces. In the end, inertia forces will win and force the wrist joint uncocked.

The release works like a gear shift. It's a swing speed enabler. The club head speed / hands speed ratio increases dramatically during the release. Enables the golfer to create more swing speed without moving the hands at 50 mph. I would say that's a pretty huge benefit. There are gear shifting in in cars too. Allows the engine to work with optimal speed regardless of how fast the car is moving. It's the same thing, basically. Yet there are no one who claims that the engine is doing the gear shift.

 

[mandrin]

I hear you.

In your introduction you write: "Release is taken to be the secondary rotation adding angular speed to the primary one in the impact zone and henceforth causing the club to overtake the arms in the impact zone." In plain English that means that you define the release as the straightening of the cocked left wrist. Nothing more and nothing less. I will get back to this definition further down. For now we can conclude that you can investigate the release by looking at the wrist joint.

And you confirm further down in the text that this is your mission: "To more conveniently grasp the relative importance of the forces / torques acting on the 'wrist' joints, I have derived their magnitude / direction and presented these force vectors and associated torques in graphical form."

So in other words diagram 35a-d display the forces and the torques imposed by the club on the wrist joints. The club is pushing the hands down the hand path. It stands out as the major force for creating hands speed. A little help from the arms, and for parts of the down swing, a bit of help from gravity as well. But the charts clearly states that the club is the main driving force behind the hand path. The club is pushing a wrist joint down the hand path. The tail is wagging the dog. It's absurd.

Since diagram 35 a and c are the only forces imposed on the wrist joint by the club we can use the D'Alembert's principle to see what the wrists are doing with the club. All we need to do is change direction of the forces in diagram 35a and 35c. The wrist is pushing the club up the swing path as far as the radial component is concerned. But since the angular component has the direction required for a downward motion the club head isn't going up nor down the depicted club head path.

More absurdities at impact: when the club is fully released, and where we would expect to see a strong domination of a centrifugal / centripetal force pair, the wrist is pushing the club into the ground. But the swing path and the geometry tells us that the joint must be pulling a centripetal force towards the center.

While this goes to the credibility of your analytical skills it's beside the point. Because most of your theoretical discussion is off topic anyway. It's the same old freshman error where one problem is stated and something else is discussed.

Yes.

You can call it whatever you like, but it is an inertia force that pulls downward and backwards on the wrist joint. Depending on how the wrist joint works this can be a pure axial force or a combination of axial force and torque.

My bad. My intention was to introduce it through the main entrance.

You started off by defining the release as wrist uncocking. But your analysis deals more with how to create swing speed.

Why are you sneaking swing speed through the back door? And why don't you acknowledge that in your conclusion?


Yes I am fixated on introducing a centrifugal force into the release action.

No I am not contradicting my own opening statement. I am only contradicting your hidden assumptions. Your reading is coloured by your own beliefs and you fail to see the implication of what I have stated even though it is there between the lines.

To your last sentence: What do you think will happen if the swing engine is shut down for a brief period? Do you think the wrist cock will be sustained? Do you think the release will be avoided if no "release work" is done?

The biggest problem in your approach is your assumption that the release creates speed. You introduce that as a given early on and proceed on that basis. Then you get so obsessed with work that you fail to investigate whether non working forces does something to the wrist cock.

Any golfer can uncock the wrists without spending a calorie. It doesn't take action and real time work. Non-action will do just fine. You can let the kinetic energy in the club head do it for you. Just shut down the engine, stall the shoulder turn, dead hands, freewheel the second half of the down stroke. DISCONNECT. You know, some of the things that high handicappers do. It will release fast. No action is required to release the club.

In a situation of complete shutdown of the swing engine, there will be a brief period of time where there is neither centrifugal and centripetal forces present (for simplicity, all masses except of the club head is ignored here). The club head will go straight forward until the wrist joint is fully uncocked and the double or triple pendulum is stretched out to max swing radius. Then a new pair centrifugal / centripetal force will reinstall a larger swing radius and the club head will start to move in orbit again - now fully released.

But in a human golfer I doubt that a complete shutdown is possible. There will instead be an effort at the wrist joint to produce more swing speed, small or big. The efforts of the poor golfer to sustain the lag with a forward driving torque is overridden by inertia and centripetal force, and the wrist is forced into a state of release. A good golfer may be able to sustain lag until past impact and can turn on a positive wrist torque in the last instance.

You've got the torque business completely wrong as far as release goes. Torque creates swing speed. Torque delays the release. The release happens because inertia and kinetic energy wins over the torque that creates hands speed and lag, deliberate or not. A release torque is optional but not mandatory. Turn off the torques in your simulator when the club head is parallel to the ground and see the early release blossom. But fix the direction of the club radial force first. You could also try to increase torque 1( the central torque) gradually, to obtain an angular acceleration of the hands that matches the angular acceleration of the club head. Just to see what it takes to prevent the release from happening before impact.

The forces required to sustain lag will create swing speed. And swing speed will increase the inertia forces. In the end, inertia forces will win and force the wrist joint uncocked.

The release works like a gear shift. It's a swing speed enabler. The club head speed / hands speed ratio increases dramatically during the release. Enables the golfer to create more swing speed without moving the hands at 50 mph. I would say that's a pretty huge benefit. There are gear shifting in in cars too. Allows the engine to work with optimal speed regardless of how fast the car is moving. It's the same thing, basically. Yet there are no one who claims that the engine is doing the gear shift.

BerntR,

Have you even looked at these equations and perhaps noticed that they contain terms representing inertia forces and torques? Probably not, seeing the strange assertions you make. Just some tidbit of information for you. In these models if you set the central torque to zero just prior to impact, hence free wheeling, there is not only a joint torque remaining, it even increases. Arms slow down quickly and some additional kinetic energy flows to the club. The equations completely take care of external and inertia forces/torques.

And you confirm further down in the text that this is your mission: "To more conveniently grasp the relative importance of the forces / torques acting on the 'wrist' joints, I have derived their magnitude / direction and presented these force vectors and associated torques in graphical form."

So in other words diagram 35a-d display the forces and the torques imposed by the club on the wrist joints. The club is pushing the hands down the hand path. It stands out as the major force for creating hands speed. A little help from the arms, and for parts of the down swing, a bit of help from gravity as well. But the charts clearly states that the club is the main driving force behind the hand path. The club is pushing a wrist joint down the hand path. The tail is wagging the dog. It's absurd. Nonsense.

Above, a typical example of the serious misrepresentation going on. A completely neutral statement about forces and torques is misleadingly interpreted as meaning that I am referring specifically and exclusively to forces/torques imposed by the club on the wrist joints. Subsequently it is then indeed easy to claim things to be absurd and continuing from there on to use this false assumption to ridicule. I am surprised I am not also accused to have introduced some perpetuum mobile type mechanism into the golf swing.

I am done, definitely wasting my time. There is too much misreading (nonexistent graphs 35c and 35d ) and misrepresentation going on. BerntR, feel free to continue discrediting message and messenger in unfair fashion, it does not take away the fact that you simply have opinions as to what you feel it all should be and that I prefer to deal with mathematics. As they say in your part of the world:

Betre å vite rett enn å håpe feil. ​

 

[Jon Hardesty]

Better know rightly than hope wrongly...

Nice.