Miura - parametric acceleration

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Mandrin,

I believe he is referring to this diagram that MJ posted earlier in a different thread.

mpa.jpg

That is it Mandrin.

Drew
 
Mandrin,

Thanks for the work on parametric acceleration.

I am having trouble understanding the diagram from the Miura paper that Mike Jacobs posted here. If you have time would you provide a fuller explanation? Specifically, what are hands doing during the periods of tangential and centripetal force shown in the the diagram.

Thanks,

Drew
Drew,

The diagram you refer to is not from Miura but rather from Dr. Williams, the first golf scientist. :)

The forces, as shown in the diagram you referred to, are those calculated by Dr. Williams, based on the golf swing of Bobby Jones, using a driver. The diagram show the tangential and centripetal force component in the down swing. You ask what are the hands doing? The answer could be as simple as that they are really simply holding on and not exerting any active torque. If you start the down swing dynamically than eventually inertial forces take over and diligently run the show.

Look at Figs 1a / b and Figs 3a / 3b where the same information is displayed as in Williams' figure. They are quite similar in nature. However the simple overall picture is that very soon from the top the force acting through the wrist joints aligns itself along the club shaft and remains so for the remaining of the down swing. Therefore initially this force is tangential to the hand path and closer to impact virtually normal to the hand path.

I like to mention that showing the forces/torques, such as determined either in a math model or measured, can be quite confusing for the average golfer. When showing such derived forces acting through the wrist joints one could quite likely take this for the actual forces/torques exerted directly by muscles of wrist and hands. However these forces/torques are largely determined by the dynamic interaction of arms and club, hence inertial forces/torques. We are, for instance, barely aware of the large centripetal force developed being too short in duration.
 
Mandrin I have a question what happens when a small mass that is connected via a rope, chain or arms and hands , to a large mass goes/travels in the opposite direction that the larger mass wants to travel in? Does the large mass travelling in a different and opposite direction exert a pulling force on the small mass and win the tug of war?

Also if they were travelling in opposite circular directions would the small mass catch up to the large mass if the large mass suddenly or slowly came to a stop? How about if the large mass wasn't moving and a small mass travelled around it and then the larger mass started to move in the opposite circular direction, what would happen?

footwedge,

You have to give a bit more specific information for me to be able to give an answer to your questions. It looks like you want to learn more about particle mechanics. :)
 

footwedge

New member
footwedge,

You have to give a bit more specific information for me to be able to give an answer to your questions. It looks like you want to learn more about particle mechanics. :)


Isn't that what the golfswing is?:D O.k. Why do galaxies have that spiral look to them?
 
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Drew,

The diagram you refer to is not from Miura but rather from Dr. Williams, the first golf scientist. :)

The forces, as shown in the diagram you referred to, are those calculated by Dr. Williams, based on the golf swing of Bobby Jones, using a driver. The diagram show the tangential and centripetal force component in the down swing. You ask what are the hands doing? The answer could be as simple as that they are really simply holding on and not exerting any active torque. If you start the down swing dynamically than eventually inertial forces take over and diligently run the show.

Look at Figs 1a / b and Figs 3a / 3b where the same information is displayed as in Williams' figure. They are quite similar in nature. However the simple overall picture is that very soon from the top the force acting through the wrist joints aligns itself along the club shaft and remains so for the remaining of the down swing. Therefore initially this force is tangential to the hand path and closer to impact virtually normal to the hand path.

I like to mention that showing the forces/torques, such as determined either in a math model or measured, can be quite confusing for the average golfer. When showing such derived forces acting through the wrist joints one could quite likely take this for the actual forces/torques exerted directly by muscles of wrist and hands. However these forces/torques are largely determined by the dynamic interaction of arms and club, hence inertial forces/torques. We are, for instance, barely aware of the large centripetal force developed being too short in duration.

Thank you mandrin.

I will check out the figures you suggest.

I don't think you have the provenance of the diagram correct. There is a citation at the bottom of the diagram that leads to the Miura article in "Sports Engineering", here: Sports Engineering - Volume 4, Issue 2 - May 2001 - Wiley Online Library

Drew
 
Thank you mandrin.

I will check out the figures you suggest.

I don't think you have the provenance of the diagram correct. There is a citation at the bottom of the diagram that leads to the Miura article in "Sports Engineering", here: Sports Engineering - Volume 4, Issue 2 - May 2001 - Wiley Online Library

Drew

Drew,

I verified and indeed it is Miura and not Williams. Recently seeing a figure in 'The Dynamics of the Golf Swing' by Williams, with a similar way of presenting forces, is likely the reason for the confusion. I dislike making this kind of mistakes but memory is a faculty which does not always perform as desired. :eek:
 
Why do you think Brian and the scientists don't understand the difference between 2D and 3D? Because of that one model that was discussed earlier? He already answered that is just one model used in their research. As Brian said there is a lot of information that he has not talked about yet.

That not what he is saying. TeeAce can defend himself but he is simply asking about the way the measurement have been done. He seems to own a lot of data and explained that in the process of trying to extract information out of the data he found out that you need to pay attention how you measure angles.

If the Bman team is willing to answer his question he then is able to compare his information with the information that has been shared here freely by the Bman and his team. And as far as I can tell from his posting he is even willing to share his data and knowledge here as well.

That all, a simple question of the procedure used to measure the angles.
 

TeeAce

New member
That not what he is saying. TeeAce can defend himself but he is simply asking about the way the measurement have been done. He seems to own a lot of data and explained that in the process of trying to extract information out of the data he found out that you need to pay attention how you measure angles.

If the Bman team is willing to answer his question he then is able to compare his information with the information that has been shared here freely by the Bman and his team. And as far as I can tell from his posting he is even willing to share his data and knowledge here as well.

That all, a simple question of the procedure used to measure the angles.

You get me 100% right.

I'm really open and interested about this case and asking because I have tried myself to find same kind of correlations. First I found it easy, then I noticed more things and was very confused. No I've stepped few steps ahead, but there is still lot of open questions and variations.

I give an example based on 3D data of the release point:

First it seemed to be clear that players with flat shaft and lot of "Sergio move" had lot of angle for certain point of dsw. The angle was then released about same point and it is just where the hands reach their closest point relative to the target line. All those guys so seems to have ch much inside of the hands at that moment.

Then I found that same thing is happening with some players with steeper swing, but not at all of them and that confused me. When splitting that steeper group to two, I found that bigger handicaps had that point but it was very early, but I found the group of better players who had later release, but also steep hand path and ch not that much inside. Sometimes even quite close to hands.

I also found that the wrist angle was not so big (with this I mean sharp because You can think it two ways) as it seems to be from face on view with those players who dropped the ch much more inside.

So after confusing explanation some conclusions that might have some information. Not yet proved or researched enough, but as said, there might be some explanation.

Bigger handicap players with OTT, release it too early with upright swing. Better players (not the best ball strikers IMO) who drag the handle also to the ball are releasing it very late and have often problems to square the face or keep the rotation on. They quite often slow down much of the and speed to get the release happen, and loose actually quite much from the chs also.

Then the group which is most interesting in my teaching. They are somewhere between those two and when asked, they all say they don't release the club. It just happens naturally. And it happens totally different way and different direction relative to the hands move. As they have their ch so much more inside, they release it much more perpendicular to the target line, but they also rotate more open at impact and their hands are moving much more in at impact area. I think they also got much more force to the direction of Brian's normal, because they are throwing the ch more away from their body.

So I think there is great possibility that BM's team is totally right with this case and I believe they are. I'm just digging deeper and try to find things that got effect to that and explanation why it works better somehow.
 
Drew,

I verified and indeed it is Miura and not Williams. Recently seeing a figure in 'The Dynamics of the Golf Swing' by Williams, with a similar way of presenting forces, is likely the reason for the confusion. I dislike making this kind of mistakes but memory is a faculty which does not always perform as desired. :eek:

Me too mandarin. My memory is good but not long.

Drew
 
Very nice diagrams and graphs illustrating a closer to real golfer parametric acceleration.

Would the acceleration of the club head be different from the swing center moving horizontal forward if the swing center moved horizontally backwards?
 
S

SteveT

Guest
When watching tour pros swing on TV, I try to spot their lead shoulder rotation with respect to impact. This should indicate when they 'go normal' to establish their peak centripetal force. Add to that the straightening of the lead knee and the impression becomes complicated.

Intuitively, I would think that maximum shoulder torque is achieved when the shoulders are level and the largest shoulder torque radius occurs. However, some pros seem to unleash their 'normal' impact position when the shoulders have rotated beyond level, particularly with the mid to long irons. Also, if they tilt their torso back as they lash through the 'level' position changes. With the driver the impression is that the shoulders are level and perpendicular to the torso rotatory axis. It all goes by so fast.

Then their is the dipping of the entire torso at the end of the backswing and/or the start of the downswing, and the subsequent upward thrust together with a change in the spinal configuration from 'S' to 'C'. To fully determine the sources of the parametric displacement and acceleration things gets very complicated and then it becomes an anatomical assessment of each golfer's swing and their physical capabilities.

Another factor in the shortening of the radius approaching impact is the "left arm displacement" that Jacobs has mentioned in his video (still on his x-golf website), whereby the left arm is drawn in tighter to the body at impact than it was at address. This will also shorten the radius from the clubface to the rotatory axis.. by not much but some. In the face-on view, a straightening of the lead arm and club shaft occurs, but in the side view there remains an obtuse angle between the arm and club.

Your analysis suffices to demonstrate the consequences of various movements of the swing center, and the remaining complexities must be left to the golfer and his swing coach, if any. Meanwhile we plebes must apply the old reliable trial and error and error and error mode of advancement... and the lottery winner is .....!!!!
 
Very nice diagrams and graphs illustrating a closer to real golfer parametric acceleration.

Would the acceleration of the club head be different from the swing center moving horizontal forward if the swing center moved horizontally backwards?
spktho,

Forward...............51.55 m/s
Zero....................51.57 m/s
Backward.............52.01 m/s


Backward motion gives a somewhat greater clubhead speed re to forward motion of center.

If you are particularly interested I could produce the figures as well, but give me some time.
 
S

SteveT

Guest
Backward motion gives a somewhat greater clubhead speed re to forward motion of center.

Interesting, and this may explain why some of the pro and LD golfers seem to rear back with their shoulders through impact, while their hips have cleared and moved forward.... as they lash out at the ball. Go figure ...
 
spktho,

Forward...............51.55 m/s
Zero....................51.57 m/s
Backward.............52.01 m/s


Backward motion gives a somewhat greater clubhead speed re to forward motion of center.

If you are particularly interested I could produce the figures as well, but give me some time.



Thank you for your work on my question.

I had an inkling that's what the result would be.
 
Interesting, and this may explain why some of the pro and LD golfers seem to rear back with their shoulders through impact, while their hips have cleared and moved forward.... as they lash out at the ball. Go figure ...

Not just in a golf swing.
 
I had a hunch also that this would increase clubhead speed...

Mandrin, could you expand on swinging left adding to clubhead speed? I think this component doesn't get the attention that it deserves.

Thanks again for all your contributions on this site. Much appreciated.
 
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