Acceleration of clubhead

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I am trying to relate this to an actual golf swing. Should the wrist hinge be as loose as possible? Maybe Brian can answer.

mb,

Well, the Jorgensen model (I think I'm reading it correctly), actually says that applying reverse torque on the wrists at the beginning of the downswing is a better way to add clubhead speed. This basically prevents any early uncocking and applied to the extreme produces a further cocking action (Sergio Garcia, Davis Love III style). What's the TGM term for that.....float loading? So, loose wrists are not preferred at that stage of the swing.

I'm guessing if mandrin added that to his model, the same effect would be demonstrated.
 
This may or may not be related, but while I was watching TV yesterday, the Golf Channel had a special on Johnny Miller's swing (hosted by Jim McLean). Anyways, the one interesting thing that I heard while watching the show was that Miller claimed there was a study done, and he was the only pro to have ever been recorded with a golf swing that was faster after impact than just before.

Mandrin, Brian, anyone, thoughts on this?

Stew
 
mb,

Well, the Jorgensen model (I think I'm reading it correctly), actually says that applying reverse torque on the wrists at the beginning of the downswing is a better way to add clubhead speed. This basically prevents any early uncocking and applied to the extreme produces a further cocking action (Sergio Garcia, Davis Love III style). What's the TGM term for that.....float loading? So, loose wrists are not preferred at that stage of the swing.

I'm guessing if mandrin added that to his model, the same effect would be demonstrated.
jmessner,

I have posted on this subject.
 
This may or may not be related, but while I was watching TV yesterday, the Golf Channel had a special on Johnny Miller's swing (hosted by Jim McLean). Anyways, the one interesting thing that I heard while watching the show was that Miller claimed there was a study done, and he was the only pro to have ever been recorded with a golf swing that was faster after impact than just before.

Mandrin, Brian, anyone, thoughts on this?

Stew

I saw that show awhile back and I couldn't believe what I heard. There is no way that the club could be going faster if he indeed actually had an impact with a golf ball. However, I have a feeling he really meant that his maximum clubhead speed was located past the typical impact location if he swung without hitting a ball. That might be believable, but would indicate an extremely well-timed release.

Jay
 

nmgolfer

New member
nmgolfer,

Since you are firmly denying credence to my ideas I am obliged to expose the fallacy in your arguments.

You argue that:

“Centrifugal and centripetal share a common line of action and by the principle of transmissibility are an equal but opposites pair (action/reaction). Therefor they/it cannot cause a torque.”

Let’s analyze this statement more closely since it involves a very fundamental error made quite frequently, even by those with a background in engineering or science. Fig1 shows pictorially, with a simple arrangement, the argument employed by nmgolfer. On first look it appears that nmgolfer is correct, yet he is totally wrong. ;)

freebodydiagram_1.gif



Anyone with a basic knowledge of physics is aware of free-body diagrams. Free-body diagrams are diagrams used to show the relative magnitude and direction of all forces acting upon an object in a given situation.

Figs 2a and 2b show these free body diagrams for our situation. There is only one force acting on the point mass M and there is only one real centrifugal inertial force acting on the ‘crooked’ segment. Gravity is ignored.

freebodydiagram_2.gif



In Fig3a shows the decomposition of the centrifugal force and Fig3b shows the resultant centrifugal toque acting on the ‘crooked’ segment. People will likely recognize the cog of the clubhead in our simple setup.

Hence, in conclusion, I have shown very clearly nmgolfer’s argument to be false and moreover I explained clearly the reality of the existence of a true centrifugal torque operating in a golf swing.

There is nothing fictitious about my arguments as used. There is no invoking of some mystical non-Newtonian and or imaginary “centrifugal torque as nmgolfer's claims I do. On the contrary I simply used common high school physics. :p

The other arguments in your post are equally basicaly wrong. Just hang on, you won’t miss anything waiting. When finding some time I will come back to your post and decorticate it with delight to show the errors made.

Nice Try But No Cigar. :D

Nice diagrams mandrin... but why do you ignore the torque caused by f1? Is it because it cancels out the torque caused by f2 when you consider moments about the axis of rotation, thereby disproving your claim? Anyone versed in mechanics should be familiar with the difference between:

Internal and external loads

The torque you have show acting on the "carpenter's square" arrangement is of course real an the load path (through the square) had better be sufficient to react such a moment or it would most definitely break... BUT.... it is not a torque that can increase omega (angular velocity). That is the point.

We're talking about what causes release and it ain't "centrifugal force". Because the line of action of the centripetal/centrifugal combination is through the axis of rotation, it causes no torque which would make it rotate faster (i.e. release).

Yes... a golf club experiences that internal load because the shaft and the cg of the clubhead are not collinear.... It causes toe down deflection and the forward bend in the shaft often observed at impact.... but that has nothing to do with what causes the club to release (about the golfer's wrists).
 
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nmgolfer

New member
Mandrin's model reminds me of the model used in Theodore Jorgensen's "The Physics of Golf". Jorgensen was pretty successful in getting the model to match the dynamics of a pro's swing, so I think the simplifications used don't inhibit its usefulness.

In any case, NM, I think the centrifugal force does indeed drive the release and you were using the centripetal vector whereas it's the opposite centrifugal vector that is acting on the shaft. Here's another article that I've seen in the past that describes this behavior (he references Jorgensen)

http://www.tutelman.com/golf/design/swing1.php?ref=

Think what ever you like jmessner... but Tutelman is wrong as is mandrin. Jorgensen let the hub translate... and it "came close" yah. right... I don't believe it.

The absolute best job modeling the golfswing was recently done by Nesbit using highly capable modeling software... everything else (including mandrins simple pendulum) pales in comparison.
 

nmgolfer

New member
Hi nm

How the Hell are You :D ..... If What You Say is True Why does it Take One Full Quadrant for the Release to Start to Occur?

Cheers

Fine thank you :) BB.

Tell that to a "caster"... he/she wishes. It all depends on the dynamics of the individual's golfs swing (both kinematics and dynamics that is).

PS turn on you PM please... I've got something to tell you.
 
Think what ever you like jmessner... but Tutelman is wrong as is mandrin. Jorgensen let the hub translate... and it "came close" yah. right... I don't believe it.

The absolute best job modeling the golfswing was recently done by Nesbit using highly capable modeling software... everything else (including mandrins simple pendulum) pales in comparison.

To mandrin....
We're talking about what causes release and it ain't "centrifugal force". Because the line of action of the centripetal/centrifugal combination is through the axis of rotation, it causes no torque which would make it rotate faster (i.e. release).

The Nesbit article has been discussed here before, but I haven't read it (yet). I'm glad to see that there are new efforts into modeling the golf swing - no intrinsic reason why we should continue to rely on the older models. However, that said, more complicated models aren't always better as they can put more demands on input quality.

I'm still not seeing the point about CF not forcing the release. You said the centripetal/centrifugal combination is through the axis of rotation - but which one? I'm infering you mean the axis of rotation through the stationary hub of the swing and of course the combination does not provide a torque on the hub. But, it's definitely not in line with the axis of rotation at the wrists (until the club and arms are in-line for a brief moment after impact) and therefore does impart on torque on that axis which is where the release occurs.
 

nmgolfer

New member
The Nesbit article has been discussed here before, but I haven't read it (yet). I'm glad to see that there are new efforts into modeling the golf swing - no intrinsic reason why we should continue to rely on the older models. However, that said, more complicated models aren't always better as they can put more demands on input quality.

I'm still not seeing the point about CF not forcing the release. You said the centripetal/centrifugal combination is through the axis of rotation - but which one? I'm infering you mean the axis of rotation through the stationary hub of the swing and of course the combination does not provide a torque on the hub. But, it's definitely not in line with the axis of rotation at the wrists (until the club and arms are in-line for a brief moment after impact) and therefore does impart on torque on that axis which is where the release occurs.

We're talking about release.... that's when the angle between the club and the lead arm increases. The release is responsible for the bulk of clubhead speed. (Vclubhead = Vhands + ClubLength*w where w is angular velocity or omega).

Look, its really simple.

The direction (remember... acceleration is a vector quantity having both magnitude and directon) of centrifugal/centripetal component is by definition... perpendicular to path. It therefore cannot contribute (anything) to acceleration along the path... ever!

In the Tutelman/mandrin make-believe world of a CF powered release all rotating objects would just continue to (angular) accelerate forever. Everybody knows that does not happen.

Newton long ago provided the equations of motion:

F = MA and
M =I * alpha

where alpha is angular acceleration and I is the (club) moment of inertia about the grip end. What you need to ask yourself is what causes the M (moment) required to make the club accelerate (alpha).

Mandrin showed you the acceleration on the clubhead... his mathcad or whatever the toy he's playing with gave the right answer... I'm not disputing that... where he (and Tuttelman) go wrong is in ***interpretation of results***

When you sum moments about the grip end of the club (for any snapshot of the club in the diagrams mandrin provided... it doesn't matter which instance you choose) what you find is centripetal acceleration (fig. 4) acts to retard alpha not increase it! The tangential component is solely responsible for the release of the club about the golfer's wrist and that's NOT centrifugal force.

Tuttelman's picture http://www.tutelman.com/golf/design/swing1.php?ref= is so typical.... so typical and so very WRONG! There is no CF force out there pushing on the club causing it to release as he depicts. Its not there! (This one of the major gripes we technical folks have with TGM btw.)

The only forces acting on the club (not withstanding the small contribution due to gravity once the clubshaft passes vertical) are those which are imparted to the club via the golfers hands.

This isn't the first time so-called "scientists" got it wrong. Cochran and Stobbs evoked the now busted "COAM myth" in their oft touted classic. Even mandrin admits they ... those "great british scientist golf researchers" got that wrong. I'm sure eventually most (including mandrin) will accept the truth... but as Schopenhauer said... its a process.

First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident.
Arthur Schopenhauer
German philosopher (1788 - 1860)

P.S.

Tuttelman and mandrin (and practically everyone else) are in good company. (I believe) Nesbit wrongly attributes the release to "CF" too... other than that, his research is impeccable. There's much to be learned in his reports by the discerning golfer.
 

PBH

New

Doesn't centrifugal force act on the golfer and not on the clubhead?

When you sum moments about the grip end of the club (for any snapshot of the club in the diagrams mandrin provided... it doesn't matter which instance you choose) what you find is centripetal acceleration (fig. 4) acts to retard alpha not increase it! The tangential component is solely responsible for the release of the club about the golfer's wrist and that's NOT centrifugal force.

The golf swing only resembles a simple circular motion like a rock on a string when the shaft is in line with the left arm. When the left wrist is cocked 90 deg there is no force towards the center acting on the club head. Centripetal force can not increase the wrist cock at that point and probably not later either.
 

Brian Manzella

Administrator
Nm....

So...finish this sentence for me...

The release of the angle between the lead arm and the clubshaft is in small part due to gravity as the club passes vertical, and in large part to________________________________.


(If I have you correct, you are saying it is the force of the golfers hands).
 
“Centrifugal and centripetal share a common line of action and by the principle of transmissibility are an equal but opposites pair (action/reaction). Therefor they/it cannot cause a torque.”

nmgolfer,

You deny with statement above clearly the possibility of centrifugal torques to exist. I took the time, using a very simple model of a golf club - point mass on shaft with some offset - to disprove your assertion. Given some time I will do the same with your other arguments. Just hang on.

I would suggest for enlightenment that you take a good look at the following –

-1- Newton’s Third Law.
-2- Point of application of forces.
-3- Free body diagrams.
-4- Instantaneous center of curvature.

BTW, I don’t have to admit anything since I am the sole source for the busting of the "COAM myth". Just check archives. You keep mixing and side stepping everything, try to keep your bearings straight.
 

nmgolfer

New member
Wrong...

I busted that myth long before you did... Ask George Hibbard on GEA about the guy who gave him heck for it then later on fgi. Only later (much later) did you chime in.

On another note...Mandrin you are one condescending SOB. Its apparent that I and a whole lot of others are much better educated than you on matters scientific. Let me guess... you're a "drafter" or tech-aid like homer was..

Now mandrin explain why you elected to ignore the torque caused by F1 on your diagram. NO! You cannot do that... reality does not "pick and choose". I cannot believe you don't understand the concept of "line of action" and how it relates to what does and does not cause a torque. Who prey tell is feeding you answers mandrin?


“Centrifugal and centripetal share a common line of action and by the principle of transmissibility are an equal but opposites pair (action/reaction). Therefor they/it cannot cause a torque.”

nmgolfer,

You deny with statement above clearly the possibility of centrifugal torques to exist. I took the time, using a very simple model of a golf club - point mass on shaft with some offset - to disprove your assertion. Given some time I will do the same with your other arguments. Just hang on.

I would suggest for enlightenment that you take a good look at the following –

-1- Newton’s Third Law.
-2- Point of application of forces.
-3- Free body diagrams.
-4- Instantaneous center of curvature.

BTW, I don’t have to admit anything since I am the sole source for the busting of the "COAM myth". Just check archives. You keep mixing and side stepping everything, try to keep your bearings straight.
 

nmgolfer

New member
Sorry Brian... I don't do guessing games. YES! The force (the swinger's linear and the hitter's torque) is in the golfer's hands.

So...finish this sentence for me...

The release of the angle between the lead arm and the clubshaft is in small part due to gravity as the club passes vertical, and in large part to________________________________.


(If I have you correct, you are saying it is the force of the golfers hands).
 

nmgolfer

New member
The golf swing only resembles a simple circular motion like a rock on a string when the shaft is in line with the left arm. When the left wrist is cocked 90 deg there is no force towards the center acting on the club head. Centripetal force can not increase the wrist cock at that point and probably not later either.

In order for ANY object to follow a circular (curvilinear) path there must be centripetal acceleration present. This is call the centripetal force requirement: http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/circmot/cf.html Centripetal force never causes wrist cock to increase (or decrease). That's the CF myth were busting here and now.
 

JeffM

New member
Unfortunately, I cannot really understand Mandrin's and NM's technical arguments. Can anyone summarise them for non-engineers (like me)?

I am particularly interested in whether the release is due to the tangential/straight line force imparted by the weight of the clubhead. It would seem to me that in the early part of the downswing, the hands/club grip gets pulled down towards the ball by the downswing body pivot action. The clubhead has intertia, due its weight, and it presumbaly has a certain resistance to downward/forward motion. However, the clubhead is attached to the clubshaft, so it has to move in the same general direction as the hands/club grip. However, later in the mid-downswing, the clubhead has acquired considerable momentum (force) and I presume that this momentum causes the release (clubhead to catch-up to the hands/club grip) in the latter part of the downswing. One can see that natural release happening in the PingMan machine, and the PingMan machine has PASSIVE hands/wrists that cannot ACTIVELY induce a release (cannot hit with the hands). Therefore,when Brian asks-: " The release of the angle between the lead arm and the clubshaft is in small part due to gravity as the club passes vertical, and in large part to________________________________", surely it cannot be a hand-induced force.

Jeff.
 
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Bronco Billy

New member
One can see that natural release happening in the PingMan machine, and the PingMan machine has PASSIVE hands/wrists that cannot ACTIVELY induce a release (cannot hit with the hands). Therefore,when Brian asks-: " The release of the angle between the lead arm and the clubshaft is in small part due to gravity as the club passes vertical, and in large part to________________________________", surely it cannot be a hand-induced force.

Jeff.

Hi There

I Too Sure Hope nm Addresses this Free Hinge Robot Problem :confused: ....

Cheers
 
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