Release action

[mandrin]

Golf kingdom is permeated with the idea that centrifugal force plays a cardinal role, specifically in the release of the club through the impact zone. This notion is really omni present in golf instruction, books, articles, posts and even in golf science.

I have analyzed the various torques acting on the club due to angular and radial acceleration of club, arms and shoulders to find out exactly what constitutes the main source for the release torque acting on the club through the impact area.

The analysis shows that the release torque is primarily generated by the centripetal force, associated with the arms, and exerted through the butt end of the club. Hence speed and path of hands are important parameters in generating release torque and not some centrifugal force acting through the clubhead.

I have been putting this material together off and on over a fairly long time period. I got sidetracked and let it collect dust. Seeing however the recent surprising interest in the matter of release I felt motivated to post it up and have it contribute hopefully to a better understanding of the release action in the golf swing.

For those who have made centrifugal force one of the key elements in their method, it might perhaps not be what they particularly like to hear but I am confident that many will appreciate a scientific analysis of this most tenacious centrifugal force myth embedded in golf and still very much alive today.

 

[GeoffDickson]

Thanks Mandrin. First, two gumby questions: Radial acceleration of the arms/hands...is this simply the rotation of the hands/arms? Torque..when I hold the golf club and rotate my arms/hands, I am said to applying torque to the club (i.e. torque = 'twist' force)?

And now to paraphrase/summarise your argument: The rotation of the arms/hands on the downswing creates the release. If the arms/hands do not rotate, then the club would not release.

 

[natep]

Mandrin

Thanks for working that out and posting it up.

 

[jmessner]

Mandrin,

Regarding radial acceleration of the hands, can you remind us about the importance of "when" the hands accelerate and if they actually decelerate during the time just before impact as described in the kinematic sequence stuff by Phil Cheetham and company.

 

[dbl]

Mandrin, great stuff. Over in the giant Release thread, I answered about centrifugal force in post 812 and then replied in more detail in post 818, saying "If I (or anyone) would give an overview, there would a 100 page argument over it." And you started off with a GIANT overview and explanation, almost on cue . Yours was (in Word) a 17 page intro before the analysis! I like your resolving the forces down in Fig 14c and 14d, and will study the rest after dinner. Thanks for sharing your work.

 

[hp12c]

Mandrin love your work/analysis. Being a non scientist/mathmatician I cannot agree/disagree Im not equiped to do it.

 

[mandrin]

Thanks Mandrin. First, two gumby questions: Radial acceleration of the arms/hands...is this simply the rotation of the hands/arms? Torque..when I hold the golf club and rotate my arms/hands, I am said to applying torque to the club (i.e. torque = 'twist' force)?

And now to paraphrase/summarise your argument: The rotation of the arms/hands on the downswing creates the release. If the arms/hands do not rotate, then the club would not release.

GeoffDickson,

When a object moves along a curvilinear path one can at each moment of time along the trajectory imagine a local osculating circle and hence an associated instantaneous radius of curvature. There are two accelerations to consider at the 'contact' point of trajectory and local circle - tangential and radial, i.e., the latter along the instantaneous radius. Radial acceleration can be either centrifugal or centripetal acceleration. Centrifugal is outwards, centripetal is inwards and radial can be either, specific direction not being specified.

Whenever you want to rotate an object about a center you have to exert a torque to get it into motion. When you pass through a revolving door, you exert a force on the structure some distance from the center, hence creating a torque causing the door rotate.

 

[lia41985]

Is invoking a linear force, acting along a suitable curvilinear path, sufficient to explain the vigorous release action felt by a golfer in the impact zone ? Or is there still more to it ? There is indeed. We have taken the club in isolation but in real life it is connected to the arms through hands/wrists. Very quickly in the down swing a rapidly increasing centripetal inward force is exerted through the arms/hands onto the handle. This the definite crux of the release issue. More on this below.

The beautiful free-wheeling action in the swing of a Bobby Jones through impact looks like there is no torque being exerted on the club since the golfer seemingly simply holds on. However that is a bit like the motion of a duck on water - all the vigorous activity beneath the surface is hidden from a casual onlooker. When the golfer lets go, there is a fairly large inertial torque at work making it appear like the golfer is just getting something for free.

That is beautiful, mandarin. Not only do you have a brilliant technical mind but also a grace to your writing. Thank you for your continued efforts.

 

[mandrin]

Mandrin,

Regarding radial acceleration of the hands, can you remind us about the importance of "when" the hands accelerate and if they actually decelerate during the time just before impact as described in the kinematic sequence stuff by Phil Cheetham and company.

jmessner,

The inevitable counter part of a release torque acting on the club is an identical torque acting in the opposite direction on the arms.....Newton's third law. This is always the case. It simply happens, for both swinging and hitting.

You can accentuate it by letting go prior to impact and use it to your advantage having some of the kinetic energy of the arms flow into the club before impact. If you muscle the club through impact you actually try to negate any deceleration of the arms, hence not being as efficient.

 

[footwedge]

Mandrin is your analysis of the release through the impact area include or exclude the squaring of the clubface and what torques are used and what forces are present or not present in the squaring of the face? Thanks in advance.

 

[mandrin]

Mandrin is your analysis of the release through the impact area include or exclude the squaring of the clubface and what torques are used and what forces are present or not present in the squaring of the face? Thanks in advance.

footwedge,

The aim of the analysis was to study the role of the centrifugal force in the release action of the golf club. The squaring of the clubface and associated torques, certainly very interesting, is not part of the analysis.

 

[footwedge]

footwedge,

The aim of the analysis was to study the role of the centrifugal force in the release action of the golf club. The squaring of the clubface and associated torques, certainly very interesting, is not part of the analysis.[/QUOTE





Is cf present in any part of the squaring of the clubface or anywhere through impact and beyond? The reason I ask is because of these terms cf swing and cp swing in describing how the swings are different due to the way the face squares up, one is supposedly a faster closure rate than the other and the direction of the path is different. Seems to be misnamed by the analysis that you have done?

 

[James Marshall (Hogan1953)]

Does this imply that the "handle draggers" mentioned in the "release thread" release inappropriately because they are pulling with their arms too early?

 

[drewyallop]

There are two basic errors:
1) The centrifugal force is not fictitious but instead very real indeed.
2) Moreover one can't have a centrifugal and a centripetal force acting both on the same object - a mistake frequently encountered.

However, in general, the simple fact that centrifugal force is readily measured, as illustrated in Fig 5, should be sufficient to discard this quite common erroneous notion of centrifugal force to be not real, to be fictitious.

This is confusing Mandrin. You say that it is an error to think that centrifugal force is not fictitious and at the same time state that it is erroneous to think that the force is fictitious. To be sure, you probably meant something else but your writing can sometimes be confusing.

In any case, I am still waiting for a drawing of the vectors for centrifugal force that was requested some time ago by SteveT in your thread (paraphrase) "It is real this centrifugal force".

Also, Aaron Zick has stated that there is no centrifugal force at play in the golf swing. Have you shared your analysis with him and if so what is his response?

To be honest, I don't think your work has any relevance to swing science unless you can defend it against legitimate challenges.

BTW how did you find Chalmers?

Drew

 

[footwedge]

This is confusing Mandrin. You say that it is an error to think that centrifugal force is not fictitious and at the same time state that it is erroneous to think that the force is fictitious. To be sure, you probably meant something else but your writing can sometimes be confusing.

In any case, I am still waiting for a drawing of the vectors for centrifugal force that was requested some time ago by SteveT in your thread (paraphrase) "It is real this centrifugal force".

Also, Aaron Zick has stated that there is no centrifugal force at play in the golf swing. Have you shared your analysis with him and if so what is his response?

To be honest, I don't think your work has any relevance to swing science unless you can defend it against legitimate challenges.

BTW how did you find Chalmers?

Drew

The two basic errors you quoted , was Mandrin's rebuttal to those. Mandrin can speak for himself but I read it that way.

 

[drewyallop]

Sorry footwedge I don't follow. What are the two basic errors that I quoted?

Drew

 

[footwedge]

Sorry footwedge I don't follow. What are the two basic errors that I quoted?

Drew

This:


There are two basic errors:
1) The centrifugal force is not fictitious but instead very real indeed.
2) Moreover one can't have a centrifugal and a centripetal force acting both on the same object - a mistake frequently encountered.



However, in general, the simple fact that centrifugal force is readily measured, as illustrated in Fig 5, should be sufficient to discard this quite common erroneous notion of centrifugal force to be not real, to be fictitious.


In all Mandrin's statements he's saying that cf is not ficticious from what I'm understanding.

 

[dbl]

I think Mandrin is arguing it is not fictitious, but also not as usually presented. Hence when he resolved the forces down to two in figures 14c and 14d I thought he'd made a great step toward in analysis.

 

[mandrin]

Is cf present in any part of the squaring of the clubface or anywhere through impact and beyond?

footwedge,

MJ's third video mentions the large possible deflections in the shaft during the down swing prior to impact caused by forces acting through the com of the clubhead.

You are curious as to what exactly might be this large force - is it a centrifugal force as is usually assumed?

To give you in the simplest possible way an idea of how centripetal/centrifugal forces act on the clubhead, I have put together a graphical explanation.

Imagine a mass M connected via two light slender rods to pivot A and the ensemble rotating around this point A. See Fig1a. At point B there is a solid connection.

Usually one assumes erroneously a centrifugal force to act outwards on mass M, and a centrifugal torque acting counter clockwise around B, Fig1b.

Instead, as shown in Fig1c, there is a centripetal force acting inwards on the mass M and a centrifugal force of equal but opposite direction from the center A.

How do we now derive the counter clockwise torque we know from experience to act on section BC? Let's look at Fig2.

We view section BC as a free body and look at all the external forces acting on it. There is, ignoring gravity, only the external force F, transmitted through rod AB, acting on section BC at point B, as shown in Fig2a.

A force can be replaced by a force and a couple as illustrated in Figs 2bcd. Fig2c and Fig2d show a centripetal force acting through C and a centripetal torque acting on section BC in a counter clockwise direction.

The force and torque acting respectively on mass M and arm BC are both the result of a real force F acting at point B. Centripetal and centrifugal forces are inertial reaction forces caused by curvilinear motion, disappearing when absence of motion.

Hope this helps.

 

[footwedge]

footwedge,

MJ's third video mentions the large possible deflections in the shaft during the down swing prior to impact caused by forces acting through the com of the clubhead.

You are curious as to what exactly might be this large force - is it a centrifugal force as is usually assumed?

To give you in the simplest possible way an idea of how centripetal/centrifugal forces act on the clubhead, I have put together a graphical explanation.

Imagine a mass M connected via two light slender rods to pivot A and the ensemble rotating around this point A. See Fig1a. At point B there is a solid connection.

Usually one assumes erroneously a centrifugal force to act outwards on mass M, and a centrifugal torque acting counter clockwise around B, Fig1b.

Instead, as shown in Fig1c, there is a centripetal force acting inwards on the mass M and a centrifugal force of equal but opposite direction from the center A.

How do we now derive the counter clockwise torque we know from experience to act on section BC? Let's look at Fig2.

We view section BC as a free body and look at all the external forces acting on it. There is, ignoring gravity, only the external force F, transmitted through rod AB, acting on section BC at point B, as shown in Fig2a.

A force can be replaced by a force and a couple as illustrated in Figs 2bcd. Fig2c and Fig2d show a centripetal force acting through C and a centripetal torque acting on section BC in a counter clockwise direction.

The force and torque acting respectively on mass M and arm BC are both the result of a real force F acting at point B. Centripetal and centrifugal forces are inertial reaction forces caused by curvilinear motion, disappearing when absence of motion.

Hope this helps.

Thank you for taking the time and trouble of doing that, much appreciated.