Release

[lasse]

The conclusion imposes itself now very clearly:

Centrifugal torque doesn’t play a significant role during the release phase of the down stroke.

So what on earth then is energizing the typical rapid release action?

Perhaps the earlier posts start taking on a new meaning.

First of all, really nice explanation about how the CF does not play a significant role in the release, thanks.

But can i guess again what does?

Could it be the shortening of the radius you talked about earlier?
Standing up on your toes like Laura Davis did, shortens the radius due to the lead shoulder moves upwards with the whole body, but the continuous rotation of the shoulders also moves the lead shoulder upwards and should therefore shorten the radius and accelerate the club?

 

[mandrin]

Michael,

Thanks for your compliment and thanks for posting on this subject. I like your synopsis. Teaching golf and science are both close and very far apart. One can be a good teacher whilst being wrong on science. But human nature is geared to strive for clarity and knowledge.

1)the inner center (i believe Search for the Perfect Swing and others refer to it as a hub) anyway, the hub movement plays a huge role in speeding up or delaying the outward fleeing of the club which indeed leads to a lot of confusion amongst a lot of physics and mathematic models that create conclusions based on "models" with rods and fixed centers.

In “Search for the Perfect Swing” the model used is that of a simple double pendulum (2 rods and fixed center), whereas they use the concept of ‘hub’ primarily as a visual alignment image. Sort of like a swing plane for the arms. I don’t see the confusion. A small advantage I can see using the image of a hub is that it emphasizes visually more the trajectory of the hands in space.


Interesting that you did not use even once the adjective, ‘centrifugal’, in your post. Centrifugal force, however, plays a very, very special role in golf. May instructors have made it explicitly the cornerstone of their teaching. Just to name a few, Ernest Jones, George Knudson, Manuel de la Torre, Bob Toski, Jim Flick, John Redman and so many more.

Suppose I came to you for a golf lesson and chit-chatting on the subject of golf, I asked you a question such as below:

Michael, I have possibly read all there is written of significance about golf, including publications by eminent scientists. They all refer to centrifugal force/torque to explain the rapid release action of the golf club. On Manzella's forum, there is fellow, mandrin, saying that all are wrong. Want do you think? Is this guy full of beans, what is your view, and are you aware how is it viewed in the Manzella Matrix?

 

[mandrin]

First of all, really nice explanation about how the CF does not play a significant role in the release, thanks.

But can i guess again what does?

Could it be the shortening of the radius you talked about earlier?
Standing up on your toes like Laura Davis did, shortens the radius due to the lead shoulder moves upwards with the whole body, but the continuous rotation of the shoulders also moves the lead shoulder upwards and should therefore shorten the radius and accelerate the club?

lasse,

Thanks for expressing yuor appreciation. I discussed your question in post #31 reproduced below. It is indeed a contribution but only a minor one.

James,

Some instruction wants you to extend the clubhead through and beyond impact out towards the target. Anything along this nature, in my opinion, does not make up for a natural and sound golf swing.

Brian, I think, is strongly advocating swinging left beyond impact. Another teacher who is very strong on swinging left is Mark Evershed. A natural swing, especially through impact, should be on-plane and hence goes inwards and upwards, beyond impact.

A rather different move, re to swinging sharply inwards, but mathematically equivalent, is to stand up through impact such as done by Laura Davis. They can both be analyzed as causing a ‘shortening of effective swing radius’.It does not take all that much to gain a few percent in club head speed.

Curving inwards/upwards is most effective pumping energy into the swing when the club has obtained high speed hence, primarily, just before impact. Perhaps when you will hear now on TV a comment that a golfer is snapping his knee(s) straight through impact, it might take on perhaps a different meaning.

James, the trail arm per se can push in various ways. Perhaps it is better to concentrate on continuing to pivot through and beyond impact. Another useful idea perhaps is to keep the lead upper arm glued to the chest.

You might want to play around for fun with doing part swings with only two thoughts in mind – back swing, trail elbow slides backwards along trail hip and mirror like for through swing - lead elbow slides back along lead hip.

 

[nmgolfer]

We've been through all of this before but just to clarify for those who might be new to the discussion....

Centrifugal force, as the term is commonly used in golf in particular and in life in general is imaginary... not real... fictitious. All golf instructors use the term in this generally accepted (imaginary ... not real) way... Golf Instructors use the term centrifugal force explain something they don't really understand and cannot otherwise (ie by using Classical Mechanics) explain.

The only ligitimate use of the term centrifugal force, other than as a layman crutch, is by a person a person performing a dynamical analysis using a non-inertal (i.e. rotating) coordinate system. In that rare instance the fictictious (centrifugal force) term must be introduced in order to arrive at the correct answer. Think of it as a necessary "fudge factor" in that rare case.

Centrifugal torque is a term that Mandrin has invented. By definition the centripetal force (a real force btw) acts in a direction towards the instantaneous center of rotation (always). Any force who's line of action is through the center of rotation cannot create a torque about the center of rotation. Its an impossibity.

 

[Michael Jacobs]

In “Search for the Perfect Swing” the model used is that of a simple double pendulum (2 rods and fixed center), whereas they use the concept of ‘hub’ primarily as a visual alignment image. Sort of like a swing plane for the arms. I don’t see the confusion. A small advantage I can see using the image of a hub is that it emphasizes visually more the trajectory of the hands in space.

I understand what you are saying for search for perfect swing but i was more referring to others such as Steven Nesbit - his 3 D approach and studies of actual golfers of varying levels was brilliant

I like your CF questioning, I'll have a good post for you on that one --

 

[Bronco Billy]

We've been through all of this before but just to clarify for those who might be new to the discussion....

Centrifugal force, as the term is commonly used in golf in particular and in life in general is imaginary... not real... fictitious. All golf instructors use the term in this generally accepted (imaginary ... not real) way... Golf Instructors use the term centrifugal force explain something they don't really understand and cannot otherwise (ie by using Classical Mechanics) explain.

The only ligitimate use of the term centrifugal force, other than as a layman crutch, is by a person a person performing a dynamical analysis using a non-inertal (i.e. rotating) coordinate system. In that rare instance the fictictious (centrifugal force) term must be introduced in order to arrive at the correct answer. Think of it as a necessary "fudge factor" in that rare case.

Centrifugal torque is a term that Mandrin has invented. By definition the centripetal force (a real force btw) acts in a direction towards the instantaneous center of rotation (always). Any force who's line of action is through the center of rotation cannot create a torque about the center of rotation. Its an impossibity.

Hey Nm.... I read this Thread 10 Times and for the Life of Me I can't Figure out Where the Hell Mandrin is Going with all This Drivel....Do You Have Any Idea?

 

[thefuture37]

Hey Nm.... I read this Thread 10 Times and for the Life of Me I can't Figure out Where the Hell Mandrin is Going with all This Drivel....Do You Have Any Idea?

Mandrin wants you to have a nice day with your new found knowledge Surely you understand that...

 

[Bronco Billy]

Mandrin's New Found Knowledge......

Mandrin wants you to have a nice day with your new found knowledge Surely you understand that...

Actually I was More Concerned about Mandrin's New Found Knowledge....He Seems to Be Keeping it from the Rest of the Known Universe...... Have a Great Day......

 

[thefuture37]

Unless you have at least a masters in physics, the vast majority of this thread is useless for the purpose of actually playing better.

 

[Bronco Billy]

UnFound New Knowledge.....

Unless you have at least a masters in physics, the vast majority of this thread is useless for the purpose of actually playing better.

That's Why I Asked Nm He Knows EveryThing....... Have a Great Day....

 

[mandrin]

Prof. Jorgensen in his book, “The Physics of Golf”, when discussing the various torques acting on the arms and the club, refers to the centrifugal torque acting on the club during the down stroke.

Dr Steven Nesbit, an expert golf scientist, in his research article, “A Three Dimensional Kinematic and Kinetic Study of the Golf Swing”, published in the ‘Journal of Sports and Science & Medicine’, refers to centrifugal acceleration pulling the club outward and through impact.

Dr Cochran, a reputed scientist, in his study, “SEARCH FOR THE PERFECT SWING, The Proven Scientific Approach to Fundamentally Improving Your Game”, refers to centrifugal force pulling and throwing the club outwards, and speeding it up.

I do agree with these eminent scientists that there is a centrifugal force acting in the golf swing. I also do agree that that there is a centrifugal acceleration/torque in the golf swing. However, I don’t agree that there is a centrifugal torque, or centrifugal acceleration acting, during the release phase, speeding up the club head, and responsible for take-over at impact.

As I have mentioned before centrifugal acceleration/torque would require an angle between centrifugal force vector and club shaft, such as shown indeed in Fig1, a faithful reproduction of Fig 2:3, as it appears in “The Search for the perfect Swing”.

As shown in Dr Cochran's study it would indeed produce a large torque and produce effectively a large centrifugal acceleration of the club shaft. But it is basically wrong. It is a rather subtle affair. There is indeed a centrifugal force but it is not acting during the release phase.

The centrifugal force vector should not, as shown in Fig 1, point towards the inner center but towards the second swing center. Then there is effectively no angle and hence no centrifugal torque/acceleration produced during the release phase.

Let’s do the following thought experiment applying mathematics, using a double pendulum model. To isolate the centrifugal force from the various other forces present we will assume the swing to have no active torques, we ignore gravity, and assume some suitable initial angular velocity conditions.

To be more specific. The rods are initially at 90 degs, the connecting revolute joint (hinge) is ‘frozen’, and the ensemble is given a certain angular velocity at t=0 sec. A short period thereafter the hinge is freed. The results of this thought experiment are shown in Figs 2 and 3.

In Fig 2 shows the centripetal force, acting on the clubhead, instead of the centrifugal force, since it has the same line of action as the centrifugal force and it shows more readily the geometric relationship between line of action and the two swing centers. Fig 3 shows the same information for the centrifugal force, as acting on the distal end of the club shaft.

Notice how first the lines of action pass perfectly through the inner swing center whereas as soon as the hinge is freed, there is an immediate shift of the line of action to the second swing center. Therefore during the release phase the centripetal/centrifugal force is aligned along the club shift and can’t produce any significant torque or acceleration.

There is indeed a centrifugal torque present and acting in the down swing; it can indeed be quite large, but it is restricted to the very first part of the down swing when arms and club behave like one solid object.

The centrifugal force once aligned with shaft can’t produce a release torque but it still contributes to some centrifugal shaft stiffening and due to the com offset of the clubhead produces a shaft bending torque.

 

[nmgolfer]

Bronco Billy, I'm not sure where he's going... only that he's off to a bad start... again

Afterall we went over all of this last year. Apparently none of it sunk in... especially the part about there NOT being a centrifugal force (or centripetal either for that matter) acting on the club (CG or head). Disregarding for the moment the small contribution due to gravity, the only force acting on the club is that which the golfer imparts at the grip... period... blamo.....

Here's what I think: Centrifugal... which means "center fleeing".... is sometimes used as an adjective by eminent scientists (the list of which does not include Cochran and Stobbs as indicated by those blatantly wrong diagrams above as well as other evidence) to describe forces imparted by golfer at the grip. That does not mean it is a real force acting through the center of gravity of the club or anywhere else for that matter, in the commonly accepted (webster's definition) sense of the word: Force.

Infact it is the very absence of a centripetal force (the exact opposite of which would be centrifugal force) which enables the angle between the golfer's forearm and the club shaft to increase (state another way... the absence of a centripetal force allows for "the release" to happen).

Furthermore if there were a real "centrifual force" then mandrin ought to be able to point out the term or terms in differential equations generated by his math package that make up this ellusive (I say non-existant) centrifugal force. That he has not done and cannot do.

 

[mandrin]

The impressive emphasis on the centrifugal aspect in all of golf, golfers, instruction and science alike, has gradually and strongly created the impression to be found everywhere, that the main force making the club catch up with the hands, i.e., the release action, is originating form the centrifugal force acting on the clubhead. We have shown that this is not the case.

The real source for release can hence only come form the only contact we have with the club and that is through the hands. Perhaps it will be clear now why I posted in the beginning of this thread about simple linear pulling of the club and showing that it produces nevertheless very much a normal release type of behavior. And also why I touched a bit on influence of hands trajectory.

This was done purposely to suggest that centrifugal force, strongly associated with pivoting and circular motion isn’t really required to explain release action and moreover also to suggest that motion and force are inputted via the hands on the grip end. Also transfer of energy, power and momentum from the proximal core parts to the distal clubhead end can only pass through the hands.

Hence pending interest and also if some peace can be maintained so that I keep a minimum of motivation to continue spending my time, I could touch over time on subjects such as the real release mechanism, the influence of the trajectory of the hands on the club head speed, shortening the swing radius, the relation between normal and tangential acceleration versus angle retention and clubhead speed and why the power delivered to the club head is originating from passive joint reaction forces.

 

[Bronco Billy]

The impressive emphasis on the centrifugal aspect in all of golf, golfers, instruction and science alike, has gradually and strongly created the impression to be found everywhere, that the main force making the club catch up with the hands, i.e., the release action, is originating form the centrifugal force acting on the clubhead. We have shown that this is not the case.

The real source for release can hence only come form the only contact we have with the club and that is through the hands. Perhaps it will be clear now why I posted in the beginning of this thread about simple linear pulling of the club and showing that it produces nevertheless very much a normal release type of behavior. And also why I touched a bit on influence of hands trajectory.

This was done purposely to suggest that centrifugal force, strongly associated with pivoting and circular motion isn’t really required to explain release action and moreover also to suggest that motion and force are inputted via the hands on the grip end. Also transfer of energy, power and momentum from the proximal core parts to the distal clubhead end can only pass through the hands.

Hence pending interest and also if some peace can be maintained so that I keep a minimum of motivation to continue spending my time, I could touch over time on subjects such as the real release mechanism, the influence of the trajectory of the hands on the club head speed, shortening the swing radius, the relation between normal and tangential acceleration versus angle retention and clubhead speed and why the power delivered to the club head is originating from passive joint reaction forces.

Force via Hands on the Grip.... I Could be Wrong but it Seems to Me that You and Nm have some Accord Here...... Maybe the Debate Can Continue without Discussing CF and Maybe Not..... I for One would Like to See Your Theories Expanded..... Have a Great Day...

 

[jmessner]

Keep it going...

Sorry if this has been linked previously, but this thesis paper discusses these concepts and includes a diagram similar to mandrin's related to line of action. Especially note tangential and radial force discussion starting on page 17 (page 32 of pdf).

Jay

 

[nmgolfer]

Here's what I don't agree with:

"On one hand there is a small fanatic group who simply denies centrifugal force to exist - the flat-earth people."

They/we arn't fanatics and we arn't "flat-earth" people either. The truth is: some schools still teach that the reaction to a centripetal force is a centrifugal force. Example: Brian grips toddler's wrists and swings toddler in circle... Brian exerts centripetal force on toddler which is needed to keep toddler orbiting him; toddler exerts "centrifugal force" on Brian... Action/Reaction... get it? That is a fair use of the term "centrifugal force" which is still taught in some schools. The only other legitimate use of the term pertains to a specific type of dynamical analysis involving non-interial coordinate systems (That one need not concern anyone).

Here is an example of the misuse of the term "centrifugal force": Car driver enters curve and glasses sitting on the dashboard slide to opposite side of vehicle... layman says "centrifugal force" acted on the glasses causing them to move. Here is another misuse: Golfer swings club and it releases. Layman says: "centrifugal force" caused the club to release. In that sense (which is the same sense the term is used in the vast majority of the golf literature "centrifugal force" does not exist... its fictitious... its a layman's crutch. (btw Crazy Jack Kuykendall which mandrin disparaged along with our own Ringer last year... has always had it right) Not all golf literature got it wrong. Just most.

If CF is the wrong explanation what then what did cause these things to happen? The car moved underneath the glasses. There wasn't enough friction to hold the glasses in place on the dashboard as the car began to deviate from straight line motion underneath them. The golf club released because the equations of motion: F=MA an M = I *alpha dictate that it does. NO CF necessary. Indeed its time golfer's got it right.. no more crutches.

I'm going to make a prediction. Those who what to see where this discussion is going need only read last year's thread in the archives. Kinematics (hand path) is paramount and that coupled with dymanics (velocity profile along said hand path) dictate when/where/how of the release. Kinematics what separates wheat from the chaffe.... hacker from pro... flipper from _______. What's desirable is a reducing radius inner hub (hand path) (think of a contracting spiral). This is what Tiger's snap is about. This is why Bubba goes up on toes etc. etc. so-forth. What's desireable is a continuous acceleration of the hands (No slowing of the hands is required or even beneficial as Dante and others I will not mention would have had you believe.

 

[Bronco Billy]

Continuous Acceleration of the Hands......

What's desireable is a continuous acceleration of the hands

.

 

[rwh]

What's desireable is a continuous acceleration of the hands (No slowing of the hands is required or even beneficial . . . )

Don't the stroboscopic photos show that the hands are slowing down before impact?

 

[Bronco Billy]

Inefficiencies of the Human Machine

Don't the stroboscopic photos show that the hands are slowing down before impact?

If it Does Show the Hands Slowing Down this is Probably attributed to the Inefficiencies of the Human Machine(The Golfer)..... The Physics Models Depict the IDEAL Situation.... The Closer the Golfer Conforms to the Physics Model(ie. the Less Slowing Down of the Hands) the more Club Head Velocity is Produced Etc...... Have a Great Day with Your New Knowledge.....

 

[nmgolfer]

>Don't the stroboscopic photos show that the hands are slowing down before impact?

Nesbit's measurements show the better golfer has a positive hand acceleration (meaning increasing hand speed) all the way up to impact. Dante (4 Magic Moves) had stroboscope pictures of one golfer showing his that his hands did slow down prior to impact.

I'm not saying a person's hands can't/won't/don't slow down. I'm not suggesting that a slowing of the acceleration (i.e. a decreasing jerk or rate of change of acceleration) might not be unavoidable, a least by human (as apposed to mechanical -- iron byron) golfers as is alluded in that thesis jmessner linked, either... I'm only saying that slowing hands are not necessary in order to "release" the club. Nesbit's data proves it. I'm saying slowing hands do not contribute to club head speed and are therefore to be avoided. That's all.