A HELPING HAND

[Mike O]

books

Mandrin- Quote:
"This idea is expressed in various ways such swinging one’s weight into the ball or swinging slowly and ‘heavily’. It is supposed to increase the effective mass of the club head, resisting impact deceleration, etc. What I would love to see is some solid evidence by those who believe in these ideas. I do not, but am always open to reasonable arguments."

If you haven't seen Stanley Plagenhoef's book "Patterns of Human Motion" 1971- you might want to buy it - doesn't cost much and seems like it would be right up your alley and maybe have something interesting for you. I'm not saying that it would support or not the above idea but again it seems to analyze and look at golf in a similar light as yourself.

 

[mandrin]

feel vs real

[size=-2]Mandrin- Quote:
"This idea is expressed in various ways such swinging one’s weight into the ball or swinging slowly and ‘heavily’. It is supposed to increase the effective mass of the club head, resisting impact deceleration, etc. What I would love to see is some solid evidence by those who believe in these ideas. I do not, but am always open to reasonable arguments."

If you haven't seen Stanley Plagenhoef's book "Patterns of Human Motion" 1971- you might want to buy it - doesn't cost much and seems like it would be right up your alley and maybe have something interesting for you. I'm not saying that it would support or not the above idea but again it seems to analyze and look at golf in a similar light as yourself.[/size]

Mike O, thanks for the tip, I placed an order. You mention golf being analyzed, did you perhaps mean tennis?

Mindy Blake a wel educated and respectable engineer puts it as a central idea in his two books – a quick ‘high-speed swing’ vs his slow ‘high-pressure swing’

Ike Hardy is another author who believes in swinging slowly and heavyly. Very adamant about it - the slower and heavier the swing the more clubhead speed obtained.

TGM seems to also entertain notions along the same line as above.

I can’t reject these ideas based on feel but physics seems to tells me that these ideas have no value to them.

 

[golf2much]

golf2much,

BTW, would you be so kind to explain to me what ThinkingPlus possibly meant with,

“Lag pressure maintained through impact will result in a collision that is more inelastic (less lossy) than if one had a clubhead moving with a constant velocity (my assertion, et al.).”

and also tell me if you agree with the ideas contained in her statement.

ThinkingPlus is a big girl. If she has more to say on the subject I'm sure she will. Whether I agree with the statement is not relevant to our debate. We have enough to sort out without draggging others into the fray.

I'll get back to you
G2M

 

[mandrin]

Cross-fertilization

golf2much,

I had thought innocently that one stimulates thinking, not so much by focusing too narrowly on an idea or concept, but rather by opening up to other points of view.

 

[golf2much]

Don't disagree

golf2much,

I had thought innocently that one stimulates thinking, not so much by focusing too narrowly on an idea or concept, but rather by opening up to other points of view.

Don't assume that I'm not thinking about the comments you referenced, just that I wanted to work through the current debate before we start another. I think I know ThinkingPlus' intent, but since she is alive and well, and can speak for herself, (unlike Mr. Kelley), I'd prefer to let her do just that.

G2M

 

[blehnhard]

Theoretical Test

Mandrin & G2M -

If it was possible to conduct the following test, would it prove / disprove either side of your arguements?

1. An object (shaped like a clubface with x* of loft & with the same mass as an average driver head) is accelerated down a path to reach a speed of 100 mph. A golf ball is positioned on the path. One millisecond prior to impact the force that accelerated the the object is removed (the object is now under no influence other than friction which would be negligible for 1 ms. Speed of the ball is measured just after impact. This would be an approx. duplication of the argument that nothing we can do thru the impact interval can influence the impact interval conditions.

2. The same scenario above except that the force that accelerated the object (now constant as we only wish to maintain 100 mph) is maintained thru the impact interval. Ball speed is measured. This would duplicate the agrument that continuing pressure would influence ball speed.

Would there be any difference. Is the premise valid. Not a science guy - just wondering.

Bruce

 

[golf2much]

Different Debate.....

Mandarin & GTM -

If it was possible to conduct the following test, would it prove / disprove either side of your arguements?

1. An object (shaped like a clubface with x* of loft & with the same mass as an average driver head) is accelerated down a path to reach a speed of 100 mph. A golf ball is positioned on the path. One millisecond prior to impact the force that accelerated the the object is removed (the object is now under no influence other than friction which would be negligible for 1 ms. Speed of the ball is measured just after impact. This would be an approx. duplication of the argument that nothing we can do thru the impact interval can influence the impact interval conditions.

2. The same scenario above except that the force that accelerated the object (now constant as we only wish to maintain 100 mph) is maintained thru the impact interval. Ball speed is measured. This would duplicate the agrument that continuing pressure would influence ball speed.

Would there be any difference. Is the premise valid. Not a science guy - just wondering.

Bruce

Bruce,

Actually Mandrin and I agree that you cannot influence impact deceleration in and of itself. Our current debate is whether this is consistent with the writings of Homr Kelley. However, to the scenario you raised...

If the club has released due to the inertial forces exceeding the golfers ability to retain lag, the golfer would not have the ability to apply any additional force to the club during the impact interval. The force/pressure the golfer feels, the heavy feeling so often described is the clubhead rebound from impact and/or interaction with the ground post impact. It's not a bad thing to "think" about maintaining lag pressure through the impact interval, but if you've properly released the club at maximum velocity, the pressure you want to feel is actually felt after the ball is gone.

On the other hand, IF you could continue to apply force, then you would not have reached maximum velocity at impact, but at a point slightly after impact. Since the ball derives its speed from the clubhead speed at impact, having less than maximum speed at impact results is less ball speed. There is an argument that if you are accelerating through the impact interval, that the "extra" velocity detracts from the impact deceleration. (I think I actually said this in an early post), but as Mandrin correctly points out, this would be negligible given the extremely short time frame and the very small amount of "extra" velocity that might generated in this scenario. The kinetic energy transfer that results in a particular ball speed is related only to instantaneous velocity and the mass of the two objects involved in the collision.

Where we are in disagreement now is whether Homer Kelley effectively said this when he wrote sectin 2E. I think he did, Mandrin thinks otherwise.

I'll have more to say on this in a few days.

G2M

 

[mandrin]

common sense

[size=-2]Mandrin & G2M -

If it was possible to conduct the following test, would it prove / disprove either side of your arguements?

1. An object (shaped like a clubface with x* of loft & with the same mass as an average driver head) is accelerated down a path to reach a speed of 100 mph. A golf ball is positioned on the path. One millisecond prior to impact the force that accelerated the the object is removed (the object is now under no influence other than friction which would be negligible for 1 ms. Speed of the ball is measured just after impact. This would be an approx. duplication of the argument that nothing we can do thru the impact interval can influence the impact interval conditions.

2. The same scenario above except that the force that accelerated the object (now constant as we only wish to maintain 100 mph) is maintained thru the impact interval. Ball speed is measured. This would duplicate the agrument that continuing pressure would influence ball speed.

Would there be any difference. Is the premise valid. Not a science guy - just wondering.

Bruce[/size]

Bruce,

An experiment quite similar to the one you are proposing has been done quite some time ago by English scientists (Search for the Perfect Swing - Cochran et al) in a very elegant way. They used two #2woods, with one having a small free hinge incorporated in the shaft just above the head.

The text associated with the high speed picture sequence of impact shown in ‘Search for the Perfect Swing’ for the #2wood with the free hinge:

“Despite being completely free, the hinge is hardly bent back at all and the shot flies just as well as one hit with a normal club.”

Bruce, one really does not need any complicated theoretical or experimental science, only a bit of common sense.

Clamp a driver’s shaft on a table and hang a small 2lb dumbbell on the hosel and measure the deflection. I measure about 2 inches.

Let’s assume, for arguments sake, that the shaft bends backwards at impact about 4 inches.

Hence, as a ballpark figure, we are exerting, for the conditons above, a force of 4lbs onto the ball.

The impact inertial force, exerted by the clubhead onto the ball and vice versa, is very large, 2000 lbs.

Therefore our estimated 4 lbs is really not up to the task to compete with this large inertial impact force.

If we further consider that the shaft actually bends forward, not backwards, at impact, further reinforces the idea that a golfer doesn’t exert any appreciable force during impact.

 

[Mike O]

Golf or Tennis?

Mike O, thanks for the tip, I placed an order. You mention golf being analyzed, did you perhaps mean tennis?

Mindy Blake a wel educated and respectable engineer puts it as a central idea in his two books – a quick ‘high-speed swing’ vs his slow ‘high-pressure swing’

Ike Hardy is another author who believes in swinging slowly and heavyly. Very adamant about it - the slower and heavier the swing the more clubhead speed obtained.

TGM seems to also entertain notions along the same line as above.

I can’t reject these ideas based on feel but physics seems to tells me that these ideas have no value to them.

He analyzes golf in "Patterns of Human Motion" and other sports- that's the book that you want. He also wrote a book called "Fundamentals of Tennis" although that's not the one that you would want to get.

 

[mandrin]

Patterns of human motion

Mike O - “Patterns of human motion” is indeed what I have ordered. Thanks.

 

[mandrin]

cogitating?

golf2much,

Still meditating why you did paint yourself into a corner?

Why don’t you have a look also at 2-M-1 and 3-F-6.

2-M-1: ---- and the sustaining or driving actions of the above mentioned Thrusts - all of which contribute resistance to Impact Deceleration (2E).

The same idea is expressed differently and more intuitively, with the notion of increasing the effective mass of the clubhead.

3-F-6: ………Clubhead lag can give the hands a heavy Clubhead to drive (or swing) against the ball…...

Looking forward to any comments.

 

[golf2much]

Nope, just playing golf...

golf2much,

Still meditating why you did paint yourself into a corner?

Why don’t you have a look also at 2-M-1 and 3-F-6.

2-M-1: ---- and the sustaining or driving actions of the above mentioned Thrusts - all of which contribute resistance to Impact Deceleration (2E).

The same idea is expressed differently and more intuitively, with the notion of increasing the effective mass of the clubhead.

3-F-6: ………Clubhead lag can give the hands a heavy Clubhead to drive (or swing) against the ball…...

Looking forward to any comments.

Nothing new to report yet. Look for a PM from me.

 

[mandrin]

Time

An essential factor to consider when discussing impact of clubhead with golf ball is TIME.

If you put your hands gently onto a water surface there is little resistance. However doing it progressively faster and faster there comes a time that the water just does not have the time to get out of the way and it starts behaving like a solid surface.

Next imagine a large coil spring on the ground and exerting a force on it. The same force will be felt on the other side of the spring. Imagine that we are able to progressively apply this force over a progressively smaller time interval. Do we have still the same force at the other side?

Well it takes time for a disturbance to travel through the spring. Eventually the time interval the force is applied will get smaller than the time it takes for the disturbance to travel through the spring. The whole dynamics changes completely

Now we have to use a special branch of mechanics for the analysis i.e., ‘continuous systems’. Here we don’t have anymore a rigid object with a well defined center of mass but have to take mass to have a time dependent spatial distribution throughout the system.

When the golf ball is fully compressed against the clubhead the disturbing force has just barely traveled up the shaft and reached the golfer’s hands. Just imagine that the impact interval is half its usual value than ball is already separated from the clubhead before the force disturbance has even traveled up the shaft.

Perhaps one can start to sense hat the clubhead, for the duration of impact, starts perhaps behaving more like a free object. And if so how can we than possibly influence the impact dynamics? Just something to think about.

 

[golfbulldog]

An essential factor to consider when discussing impact of clubhead with golf ball is TIME.

If you put your hands gently onto a water surface there is little resistance. However doing it progressively faster and faster there comes a time that the water just does not have the time to get out of the way and it starts behaving like a solid surface.

...

When the golf ball is fully compressed against the clubhead the disturbing force has just barely traveled up the shaft and reached the golfer’s hands. Just imagine that the impact interval is half its usual value than ball is already separated from the clubhead before the force disturbance has even traveled up the shaft.

Perhaps one can start to sense hat the clubhead, for the duration of impact, starts perhaps behaving more like a free object. And if so how can we than possibly influence the impact dynamics? Just something to think about.

is an impact between 9 iron and ball (ie. where ball is compressed between clubhead and planet earth) different to the SFTPS experiment where the clubhead ( 2 wood) compressed the ball against air ( ball being teed up and struch at the shallowest point of arc)??

In a descending short iron style impact, does the planet exert a reactive force on the clubhead when the ball is trapped between the two? Is this a force worth resisting ( unlike your estimated 4 lbs) and hence impact alignments and sustaining compression may be of benefit?

I know that there is no time for there to be a conscious effort to resist impact deceleration once impact has begun... but would correct impact alignments and sustaining the line of compression ( all set up before impact) resist the planetary reactive force that i suggest above and hence maximise the clubhead speed at seperation?

How do you explain the variation in Smash factors for different players?

Do you believe the people who say that Hogan's impact just "sounded different" - other people had his clubs and balls, similar clubhead speed at impact and played from the same grass - what else made his sound energy signature different to the other players - some guys ( i think Jackie Burke or Ben Crenshaw ) get quite misty eyed about the sound of his impact on a video i have about Hogan!

Looking forward to having my incorrect assumptions and physics pulled out of me!! Thanks Mandrin - I am always better for it afterwards!

 

[azgolfer]

I don't think the ball is ever actually "trapped". It seems to me the only downward motion of the ball would be caused by friction between the downward travelling clubface and the ball.

 

[golfbulldog]

SFTPS states in chapter 22 that "...the clubhead travels while in contact with the ball...more like three-quarters of an inch"

If the ball and clubhead travel 3/4 inch in contact together and the club is a 9 iron on descending path... the ball travels down into the ground...

maybe "trapped" is not good word but during impact interval ( 0.0005 seconds) the clubhead is touching the ball and the ball is touching planet earth - simultanously. Trapped / sandwiched ... whatever... does the earth exert a reactive force , through the realively solid ball , back against the clubhead?

 

[azgolfer]

I think that is 3/4 " sideways, rather than vertically. I guess the question would be, if a pro tees up a wedge, can they spin it back ? If so, the ground isn't really involved.

 

[mandrin]

[size=-2]is an impact between 9 iron and ball (ie. where ball is compressed between clubhead and planet earth) different to the SFTPS experiment where the clubhead ( 2 wood) compressed the ball against air ( ball being teed up and struch at the shallowest point of arc)??

In a descending short iron style impact, does the planet exert a reactive force on the clubhead when the ball is trapped between the two? Is this a force worth resisting ( unlike your estimated 4 lbs) and hence impact alignments and sustaining compression may be of benefit?

I know that there is no time for there to be a conscious effort to resist impact deceleration once impact has begun... but would correct impact alignments and sustaining the line of compression ( all set up before impact) resist the planetary reactive force that i suggest above and hence maximise the clubhead speed at seperation?

How do you explain the variation in Smash factors for different players?

Do you believe the people who say that Hogan's impact just "sounded different" - other people had his clubs and balls, similar clubhead speed at impact and played from the same grass - what else made his sound energy signature different to the other players - some guys ( i think Jackie Burke or Ben Crenshaw ) get quite misty eyed about the sound of his impact on a video i have about Hogan!

Looking forward to having my incorrect assumptions and physics pulled out of me!! Thanks Mandrin - I am always better for it afterwards![/size]

Golfbulldog, you must be aware of the advice - hitting down to get it up. Have a close look here at what happens during impact with an iron hitting down onto the ball. The ball immediately travels upwards. It does not really get trapped against mother earth.

Your question regarding the sound made by impact is something which intrigues me also very much. There is indeed a very particular sound associated with a well struck ball.

It is seemingly said of Hogan’s sound that it was very distinct and included the hitting of the ground, a deep thump included with a sharp crack and that one could actually feel the ground vibrate.

One can have a muddy thump, a sharp crack, a clicking sound, there is indeed a quite a range of sounds.

One could think of impact as being an impulsive loading of a resonance system consisting of shaft and clubhead, the sound lasting considerable longer than impact duration.

The position of the hands, their tightness, force/torque exerted, and contact of clubhead with the ground might be possible factors affecting the particular sound(s) and vibrations at impact. Hitting it close to the center of percussion is however likely the most important factor for producing that very peculiar distinctive impact sound.

It could be interesting to measure the sound spectrum and the vibrations associated with impact. It is even possible to envision an acoustical biofeedback system. The sound being a guide to a well struck ball, ie., on the sweet spot.

 

[golfbulldog]

i knew you would help

thanks for the video of impact - very helpful. Proves what you and AZgolfer were saying. thanks to you both.

Helps me get the physics straight in my head!

I agree with impact sound. NIck price is another who is sometimes reported to make the ball sound different to others....

Any thoughts as to the why a player's "smash factor" can vary so much ?? what is your interpretation of the physics of smash factors??

Thanks, i look forward to the "Mandrin impact sonic biofeedback range mat "- with purity of impact sound being conveyed by smilies ! for perfect and for awful!

 

[mandrin]

Smash factor

[size=-2]thanks for the video of impact - very helpful. Proves what you and AZgolfer were saying. thanks to you both.

Helps me get the physics straight in my head!

I agree with impact sound. NIck price is another who is sometimes reported to make the ball sound different to others....

Any thoughts as to the why a player's "smash factor" can vary so much ?? what is your interpretation of the physics of smash factors??

Thanks, i look forward to the "Mandrin impact sonic biofeedback range mat "- with purity of impact sound being conveyed by smilies ! for perfect and for awful![/size]

Smash factor – ratio of ball departure speed divided by clubhead speed at onset of impact.

golfbulldog,

I don’t believe in being able to influence ball departure speed during impact hence the only factors affecting ball departure speed, for equal clubhead speed at the onset of impact, are 3D clubhead trajectory and 3D clubface alignment.

A large smash factor indicates efficient energy transfer to the ball; hence primarily impact on or very close to the sweet spot with proper clubhead/face alignments.

Optimum energy transfer to the ball - optimum smash factor - does not necessarily result in maximum carry. Other parameters such as launch angle and spin play a role. Environmental conditions are also important.

Hence optimum 3D club head trajectory and optimum 3D club face alignment for either maximum smash factor and or maximum carry are likely close but not quite the same.

I will send you a beta version and you can design some appropriate attractive smilies for me.