Release action

[SteveT]

Does this simply mean that the ~100 lbs of centripetal force makes the arm and clubshaft 'go normal' if properly applied when going through impact?

 

[BerntR]

Michael,

The whole release analysis is centered on the torque exerted on the shaft as it determines the release action of the club through impact, i.e., catching up and quickly over taking the arms through impact. This is never really explained and usually it is disposed off erroneously as being caused by the centrifugal force acting on the club.

If one considers the total force acting on the wrist joint than the picture is obscured by the dominant centripetal force acting along the club shaft but not contributing to any release torque. Hence to be able to analyze the release action one has to dissect this total joint force into its various components, associated with the angular and radial (centripetal) acceleration of arm and club, in addition to wrist torque and gravity.

In general to obtain angular and /or radial acceleration for a body requires a torque and hence a force having some moment arm. The magnitude of a torque depends on the magnitude of the force, the length of the lever arm, and the angle between the force vector and the lever arm. Fig1 shows the club, shown as a free body diagram. Since we have taken the club to have a massless shaft and the clubhead to be a point mass, it follows that the moment arm relative to the point of application is simply the distance L between wrist joint and clubhead.

Looking at figs 28a to 33a and/or figs 35a to 42a, one can get a quick global view by looking at the amplitude of the force vectors acting at the joint and the angle they are making with the club shaft. The resulting corresponding torques are shown in figs 28b to 33b and figs 35b to 42b. If you look respectively at fig 29a and fig 36a one notices that there is no angle between the club centripetal force and the club shaft and hence there is also no release torque associated with this very large centripetal force component throughout the release.

However the force associated with the radial (centripetal) acceleration of the arm, having an angle with the club shaft, can exert a torque on the shaft. It is this particular torque associated with the radial (centripetal) acceleration of the rotating arm which is really the dominant factor in the intriguing release action of the club through impact. See Figs 31a and 31b and also Figs 38a and 38b.

I've now spent at least an hour with the release paper.

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

But it is wrong to say that the centrifugal force doesn't play a part in the release. It plays THE major part. For several reasons.

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.

Let me also add that most of the analysis isn't really focused on shaft torque, but on the net torque in the left wrist. All except the radial force in the shaft. And that is a bummer, IMO.

The analysis would have been much clearer if the linear forces and the torques in the wrists had been put into the same picture. We could decompose into forces that creates swing speed and the rest.

* an axial force down the shaft to the club head.
* another axial force up the arm to the shoulder,
* a tangential, forward force along the hand path (this one creates swing speed)
* and optionally, a wrist torque around the coupling point. (this one can also create swing speed)

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.

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.

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.

Towards impact, the only thing working against the release, and hands going in reverse for a brief while is the forward moving hands, the tangential force produced by pulling from the left and pushing from the right.

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.

As long as the angular speed of hands and club head remains the same, the wrist cock will be fully intact. But the overtaking is unavoidable. You have to accelerate as long as you turn with lag and you are destined to hit the speed limit sooner or later.

The smart way is to have enough lag and speed reserves left and keep building hands speed, so that the hands aren't outraced by the club head too early. I just saw on TV that Gary Woodland took it easy from the top and stepped on the gas towards impact.

What matters to the swing speed in the end is how many Newton Meters you put into the club through various torque and forces. There is no magic trick as far as physics is concerned. That goes for the parametric acceleration as well. It creates swing speed because the golfer forces the club to move faster. Any effort that coincides with where the club head is heading at the moment will create swing speed. The real key to swing speed is finding a pattern where you are able to recruit and apply as much force as your body can deliver. Not down THE swing path. Down any swing path.

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 a club head that approaches 100mph with hands that moves slow.

 

[BerntR]

Does this simply mean that the ~100 lbs of centripetal force makes the arm and clubshaft 'go normal' if properly applied when going through impact?

100 lbs of "centripetal" force and 100 lbs of centrifugal force stretching out the wrist cock.

 

[SteveT]

100 lbs of "centripetal" force and 100 lbs of centrifugal force stretching out the wrist cock.

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 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.

Please provide, or explain your assertion. What are your scientific education qualifications to make such an assertion?

Centripetal force doesn't create speed. Because it works at 90 degree angle to the motion.

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

I look forward to your clarifications. Thank you.... ....SteveT

 

[BerntR]

Steve,

I am not going to argue with you whether centripetal force creates speed or not. It doesn't. I could explain it to you, but you don't have the background to understand the explanation. You will have to trust me, learn some physics or ask someone else who understands physics.

But I really think you should be able to sort out for yourself that the force imposed by the club head on the hand in Mandrin's diagram is pulling the hand downwards and backwards, and not upwards and forwards.

I have an MSc degree in engineering, btw.

 

[SteveT]

@BerntR ... I'm not arguing, I'm just holding you accountable for your blatant assertions without providing scientific proof... as does mandrin and even myself.

If you cannot, or will not respond professionally, I question your claimed credentials.

Btw... a TGM MSc degree in golf swing engineering (GSEM) is bogus.

 

[mandrin]

I've now spent at least an hour with the release paper.

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

But it is wrong to say that the centrifugal force doesn't play a part in the release. It plays THE major part. For several reasons.

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.

Let me also add that most of the analysis isn't really focused on shaft torque, but on the net torque in the left wrist. All except the radial force in the shaft. And that is a bummer, IMO.

The analysis would have been much clearer if the linear forces and the torques in the wrists had been put into the same picture. We could decompose into forces that creates swing speed and the rest.

* an axial force down the shaft to the club head.
* another axial force up the arm to the shoulder,
* a tangential, forward force along the hand path (this one creates swing speed)
* and optionally, a wrist torque around the coupling point. (this one can also create swing speed)

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.

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.

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.

Towards impact, the only thing working against the release, and hands going in reverse for a brief while is the forward moving hands, the tangential force produced by pulling from the left and pushing from the right.

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.

As long as the angular speed of hands and club head remains the same, the wrist cock will be fully intact. But the overtaking is unavoidable. You have to accelerate as long as you turn with lag and you are destined to hit the speed limit sooner or later.

The smart way is to have enough lag and speed reserves left and keep building hands speed, so that the hands aren't outraced by the club head too early. I just saw on TV that Gary Woodland took it easy from the top and stepped on the gas towards impact.

What matters to the swing speed in the end is how many Newton Meters you put into the club through various torque and forces. There is no magic trick as far as physics is concerned. That goes for the parametric acceleration as well. It creates swing speed because the golfer forces the club to move faster. Any effort that coincides with where the club head is heading at the moment will create swing speed. The real key to swing speed is finding a pattern where you are able to recruit and apply as much force as your body can deliver. Not down THE swing path. Down any swing path.

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 a club head that approaches 100mph with hands that moves slow.

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.

One of the great advantages of using Kane's equations or Lagrangian's approach to derive the governing differential equations of multi body dynamics problems is that there is a clear distinction made between real forces and non-working reaction/inertial forces. All non-working forces are eliminated from the outset, simplifying considerably the complexity of the governing differential equations.

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.

The figures in my release post are a 'one-to-one translation' from the various parts of the derived governing differential equations. Each part representing a specific force or torque They were done in an attempt to make the solution to the complex differential equations for the down swing visually available in one glance. I can assure you that it took some time and effort.

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.


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.

 

[Brian Manzella]

Great post Mandrin. Thanks for all the hard work.

 

[SteveT]

"Engineer" BerntR has a lot of explaining to do if he wants any credibility here .... believe it!

 

[TeeAce]

IMO the centrifugal force is only reaction, not a real force, but counterforce to centripetal force. It can't be created.

Player can only effect to linear force and centripetal force, and centripetal force is the force which is changing the linear move to arc. If we loose centripetal force, the object will continue its linear move directly. More the centripetal force is overtaking the linear force, more the arc will be restricted, so to achieve the arc, there has to be balance between centripetal force and linear force and centripetal and centrifugal forces are always equal.

So players only way to get more speed to the club head is to produce more linear force and match that centripetal force to that. No way to speed up anything by centrifugal force.

 

[SteveT]

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

 

[leon]

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

Steve, I find your dismissal of BerntR by referring to him as 'engineer' pretty offensive, as if all engineers have no clue about fundamental mechanics & dynamics of motion. What prey tell are your qualifications, if that is the measure by which we are supposed to be judging people?

I think much of the confusion in analysing club forces is the mixing and matching of coordinate systems. Centripetal forces really exist in a cylindrical system, which has a fixed centre. Linear forces are best defined in a cartesian system. Of course you can convert from one to another, but when you want to have time varying forces in both systems at the same time, it gets messy. Plus you've got to consider that the origin of the cylindrical system in which the centripetal force exists is moving in space. It's just messy.

And before you ask, I have a PhD in engineering (modelling sports ball impacts). I hope that makes me qualified to contribute to this thread

 

[SteveT]

Steve, I find your dismissal of BerntR by referring to him as 'engineer' pretty offensive, as if all engineers have no clue about fundamental mechanics & dynamics of motion. What prey tell are your qualifications, if that is the measure by which we are supposed to be judging people?

I think much of the confusion in analysing club forces is the mixing and matching of coordinate systems. Centripetal forces really exist in a cylindrical system, which has a fixed centre. Linear forces are best defined in a cartesian system. Of course you can convert from one to another, but when you want to have time varying forces in both systems at the same time, it gets messy. Plus you've got to consider that the origin of the cylindrical system in which the centripetal force exists is moving in space. It's just messy.

And before you ask, I have a PhD in engineering (modelling sports ball impacts). I hope that makes me qualified to contribute to this thread

FYI... BerntR claims to have an engineering MSc.. if you bothered to read his comments. I found his cavalier declarations and claiming that Newtonian physics back him up without providing proofs to be quite non-professional. Your defense of him with your polar/cartesian coordinate systems is unconvincing and not helpful, particularly since his errors are Physics 101 blunders..!!!

Perhaps you with a lofty engineering PhD can respond to my three question I posed to him and which he seems to avoid broaching (perhaps in shame). Unfortunately, I only possess a lowly engineering BSc... but I have a scientifically-developed golfswing over several decades of research, experimenting and perfecting. Brian has felt the sting of my science many years ago and now he's seeking salvation in science. I support him wholeheartedly, and occasionally I will try to correct him. He's a gem...

Also, our "mandrin" has debunked BerntR rather elegantly and gently too ... so why don't you go after him because I suspect he has a "double-doctorate" ... in physics and engineering....

 

[SteveT]

Folks.... if you want to see "nasty", just watch graduate engineers go after each other ... then golf becomes a blood sport...

Meanwhile pure scientists (like mandrin?) tend to be courteous and gentle... but can also shove the shiv in and twist it...!!!!

Brian can just sit back, watch and chuckle ....

 

[leon]

Steve, I wasn't defending BerntR's post, in which Mandarin quite elegantly identified the major holes. Rather I was taking issue with your character asassination of him and apparent derogatory use of the term engineer. If you are one as well then maybe you can understand why it rubbed me the wrong way.

I was proposing that coordinate systems may be part of the general confusion for some. That and misunderstanding of free body diagrams seems pretty common here.

And whilst I haven't read much of mandarin's stuff (no pdf reader on my mobile) I wouldn't be so bold as to call any of it into question. Clearly his knowledge of the subject matter far exceeds my own (and most everyone here I would expect.)

 

[birly-shirly]

... but I have a scientifically-developed golfswing over several decades of research, experimenting and perfecting.

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.

 

[BerntR]

@BerntR ... I'm not arguing, I'm just holding you accountable for your blatant assertions without providing scientific proof... as does mandrin and even myself.

If you cannot, or will not respond professionally, I question your claimed credentials.

Btw... a TGM MSc degree in golf swing engineering (GSEM) is bogus.

Steve,

I can only respond professionally to someone who are capable of understanding the message. So far I haven't seen any signs that you are capable of separating the snot from the mustache when the discussion gets technical.

 

[SteveT]

Steve,
I can only respond professionally to someone who are capable of understanding the message. So far I haven't seen any signs that you are capable of separating the snot from the mustache when the discussion gets technical.

I dare you to say that to mandrin who exposed and utterly destroyed your fallacious swing concepts, and forum credibility too!!!

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

Don't bother attempting to respond to my questions challenging your own statements... because you can't - you're scientifically incompetent according to mandrin.

 

[SteveT]

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.

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.

 

[johnnymarlboro]

This is pathetic Steve T. You sit here and call out people to produce evidence of "fill in the blank" then when called out yourself you pull the old, oh I don't have to because of of how superior I am at "fill in the blank." If anyone should be embarassed here it's Manzella at having you spoil his site with your self indulgent tirades, and temper tantrums. Scientifically speaking, you're a d-bag.