Bio Servo Control

[mandrin]

Something I did a few years ago might be of interest. It shows how the inertial forces are working in the background and very useful if you let the swing take place instead of forcing it.

 

[golfbulldog]

not many replies yet...

Interesting stuff... got my "search for the perfect swing " chapter 7 open... forgive me if my physics is a little rusty - i am from a biological science background rather than physics.

"Inertial forces" - I need a definition .

so far I have :-

"The force produced by the reaction of a body to an accelerating force, equal in magnitude and opposite in direction to the accelerating force. An inertial force lasts only as long as the accelerating force does. "

(from DavidDarling website on astrophysics)

and :-

"inertial forces= In classical mechanics or special relativity: Whenever an observer who is not an inertial observer wants to explain the movements of bodies using the law "force equals mass times acceleration", that observer has to assume the existence of additional forces; these are called inertial forces. For ordinary forces like the electric force, the magnetic or the gravitational force, one can always state which bodies are acting on which other bodies; inertial forces, in contrast, appear to act on bodies "from nowhere".

A famous example for an inertial force is the centrifugal force - an observer riding a merry-go-round needs to introduce that force to explain why he and all other riders are pulled away from the axis of rotation."

from Einstein online website.

Is it therefore correct that , with regard to golf swing, that the inertial forces present at the transition phase - are a result of you trying to accelerate the club longitudinally ( swinging - "like pulling arrow from a quiver") then there is an inertial( reactive) force acting equally and opposite direction?

I have in mind Ben Hogan "Power Golf" photos of him just staring downswing - hips have started to slide towards target, hands have moved away from target and clubhead has dipped below horizontal.

My reading of your figure 2a is that the greater the longitudinal force then left forearm - clubshaft angle is decreased (ie. a degree of float loading - increases wristcock on downswing)

As usual your free wrist hinge( you have stressed before thatyou like the "free wheeling though impact" or "clubhead acts as a free body at impact) on downstroke causes uncocking and fig2a has more to uncock than 1a BUT both must uncock to vertical at lowpoint - hence faster clubhead speed at impact

I am needing help in understanding how one applies correct force to club so that i get the greater negative inertial force seen in 2b - so far i conclude that i need soft wrists at the top and a pronounced "arrow from quiver" longitudinal pull away from target- is this right??

To my mind that sounds like Brian's "Fiddle Drill" which combines nicely with his sit down squat "snead" type video answer??
Thanks Mandrin - once again you always ripple the pond and cause thinking.

 

[Perfect Impact]

The fact that the left hand moves in an arc and the butt end of the club is being pulled longitudinally tangent to the arc is what causes the inertial momentum. The faster the hands move in their arc, the more energy is imparted to the head and its velocity. It is not just the right angle or the acute angle of the hand/clubshaft: it is how much SPEED YOU CAN MUSTER in a CONTINUOUS drawing of the arrow from the quiver.

COAM transfers this to the other end of the system where the clubhead - the lightest member, gets the benefit of the momentum generated.

 

[mandrin]

Interesting stuff... got my "search for the perfect swing " chapter 7 open... forgive me if my physics is a little rusty - i am from a biological science background rather than physics.

"Inertial forces" - I need a definition .

so far I have :-

"The force produced by the reaction of a body to an accelerating force, equal in magnitude and opposite in direction to the accelerating force. An inertial force lasts only as long as the accelerating force does. "

(from DavidDarling website on astrophysics)

and :-

"inertial forces= In classical mechanics or special relativity: Whenever an observer who is not an inertial observer wants to explain the movements of bodies using the law "force equals mass times acceleration", that observer has to assume the existence of additional forces; these are called inertial forces. For ordinary forces like the electric force, the magnetic or the gravitational force, one can always state which bodies are acting on which other bodies; inertial forces, in contrast, appear to act on bodies "from nowhere".

A famous example for an inertial force is the centrifugal force - an observer riding a merry-go-round needs to introduce that force to explain why he and all other riders are pulled away from the axis of rotation."

from Einstein online website.

Is it therefore correct that , with regard to golf swing, that the inertial forces present at the transition phase - are a result of you trying to accelerate the club longitudinally ( swinging - "like pulling arrow from a quiver") then there is an inertial( reactive) force acting equally and opposite direction?

I have in mind Ben Hogan "Power Golf" photos of him just staring downswing - hips have started to slide towards target, hands have moved away from target and clubhead has dipped below horizontal.

My reading of your figure 2a is that the greater the longitudinal force then left forearm - clubshaft angle is decreased (ie. a degree of float loading - increases wristcock on downswing)

As usual your free wrist hinge( you have stressed before thatyou like the "free wheeling though impact" or "clubhead acts as a free body at impact) on downstroke causes uncocking and fig2a has more to uncock than 1a BUT both must uncock to vertical at lowpoint - hence faster clubhead speed at impact

I am needing help in understanding how one applies correct force to club so that i get the greater negative inertial force seen in 2b - so far i conclude that i need soft wrists at the top and a pronounced "arrow from quiver" longitudinal pull away from target- is this right??

To my mind that sounds like Brian's "Fiddle Drill" which combines nicely with his sit down squat "snead" type video answer??
Thanks Mandrin - once again you always ripple the pond and cause thinking.

golfbulldog,

Inertial force is really a mystery, we can define it, see the results but really don’t have any clue about it. Newton himself saw inertia, as defined by his first law of motion as an innate force present in an object resisting change in motion. Modern definition of inertia is not referring anymore to a force but rather to the phenomenon of inertia itself, hence a shift from the cause of the phenomena to the phenomena itself. Inertia is simply considered as a property of matter, not as an innate force as considered by Newton himself.

This shift in interpretation might perhaps explain why we have so much problems with inertial forces such as, for instance, centrifugal forces. Science has even made it even more difficult by frequently defining inertial force to be equivalent to a fictitious force. For the average layman it becomes a hazardous task to start comprehending all this mumbo jumbo. I prefer to think like Jean le Rond d'Alembert and consider inertial forces as real and equivalent to real forces such as exerted by a spring.

Inertial forces are present when there is a change in motion in either the linear or rotational motion of an object. They are present all over the place. All our body motions involve continuously acceleration and deceleration and hence involve inertial forces. We normally are taught that a real force is external to the object on which it is exerting a force such a spring on a mass. Conceptually an inertial force is very different as it is seemingly generated by the object itself when subjected to a change in its velocity.

We have heard so often that 'the sum of forces is equal to mass times acceleration' as expressed by Newton's 2nd law, that we have forgotten that mass times acceleration not only has the dimension of a force but really represents a real force, to be more precise, a real inertial force. It is hence equally true to say that the sum of external forces is equal to the inertial force of the particle, as it is 'resisting' the change in motion imposed by external forces. In this I follow the example of an illustrious scientist, d'Alembert. When two masses collide there only inertial forces at work and they are darned real not fictitious at all. Just have someone drop a heavy object on your head and tell me if this is not real force cracking your skull.

Is it therefore correct that , with regard to golf swing, that the inertial forces present at the transition phase - are a result of you trying to accelerate the club longitudinally ( swinging - "like pulling arrow from a quiver") then there is an inertial( reactive) force acting equally and opposite direction?

Yes, correct. Newton’s third law - forces always come in pairs, an action and a reaction force.

I have in mind Ben Hogan "Power Golf" photos of him just staring downswing - hips have started to slide towards target, hands have moved away from target and clubhead has dipped below horizontal.

The inertial torque acting at the very beginning of a downswing is acting on the clubhead inwards towards the center of rotation. This explains the bending clearly visible in some swings.

My reading of your figure 2a is that the greater the longitudinal force then left forearm - clubshaft angle is decreased (ie. a degree of float loading - increases wristcock on downswing)

Golfbuldog the simple model is really only meant to illustrate the usefulness of the centrifugal force in a golf swing. Don’t read too much into it. In Fig1a we have initially a much larger inertial torque helping to maintain or even increase wristcock but there is way less clubhead speed at impact.

I am needing help in understanding how one applies correct force to club so that I get the greater negative inertial force seen in 2b - so far I conclude that I need soft wrists at the top and a pronounced "arrow from quiver" longitudinal pull away from target- is this right??

You will notice that there is more ‘pinning’ of the hands through impact in Fig2a. This basically is obtained by maintaining the angles deeper into the downswing. There will be then a sudden snappy release associated with larger innertial torques as shown in Fig2b.

I might not have quite answered your questions. If so try again. The basic idea was simply to illustrate that kind of independent of the backswing, if we keep soft wrists, the swing itself will arrange to have correct impact conditions for the clubhead. Very much in support of those teaching a ‘centrifugal type swing.

 

[golfbulldog]

Great reply

Thanks Mandrin, that is an brilliant reply. I know that so much has been written about reactive forces before, especially regarding whether centrifugal force is a "REAL" force or not.... , but you have made a clear argument for its existence.

What would the human golfer feel they are doing differently between the two swing models 1a and 1b? i know that they are models for discussion but other than soft wrists anything else to apply?

Explains most of my queries and very eloquently and erudite... but only one smiley!!! What happen to the old Mandrin!! He( or she?) used to construct the most beautiful prose with barely a letter of alphabet! only and

thanks again - actually i have just found that i can only use 4 smilies!! restriction of free speech expression!! what about your constitution....!

 

[golfbulldog]

PS...

By "pinning " i maybe understand that it means the hands slow down prior to impact more in model 2 than 1 , giving a snap release appearance?

ie. hands look to be almost stationary and themselves act as a hingepin around impact?

I take it that "Pingman" will swing like this?? he ... why no "pingwoman" swing model! Maybe if Ping sign Michele Wie they will address this ...

In "search for the perfect swing" ( SFTPS) chapter 10 fig 10-1-C- they talk about possibly using muscular effort to delay the wrist uncock until later in the swing - in their model it gives more shaft forward lean at impact "but maximum speed occurs once again near impact, and is even greater than the free hinging speed at impact" - i think they mean free hinged natural uncocking rather that the delayed uncock due to muscles - BOTH act as free hinges once uncocking starts.

 

[mandrin]

unspeakably dismal

Thanks Mandrin, that is an brilliant reply. I know that so much has been written about reactive forces before, especially regarding whether centrifugal force is a "REAL" force or not.... , but you have made a clear argument for its existence.

What would the human golfer feel they are doing differently between the two swing models 1a and 1b? i know that they are models for discussion but other than soft wrists anything else to apply?

Explains most of my queries and very eloquently and erudite... but only one smiley!!! What happen to the old Mandrin!! He( or she?) used to construct the most beautiful prose with barely a letter of alphabet! only and

thanks again - actually i have just found that i can only use 4 smilies!! restriction of free speech expression!! what about your constitution....!

What would the human golfer feel they are doing differently between the two swing models 1a and 1b? i know that they are models for discussion but other than soft wrists anything else to apply?

Golfbuldog, nobody can really create an angle as show in Fig2a

One could surmise that the “golfer-1a” would not feel very much of a release action but more of broad sweep through impact. Also “golfer-1a” might feel the swing to be more a matter of applying muscles to the job.

“golfer-2a” is likely very alert to maintain his acute angle deep into the downswing. His feeling might be like swinging to a definite position (impact), not through, and be acutely aware of a fast release around his wrists.

golfbuldog you seem to appreciate my post but someone else has rated it to be “unspeakably dismal”, this being the meaning of a single star rating. Big Grin.

Since you used already 4 smilies none is left for my post. LOL.

 

[mrodock]

golfbuldog you seem to appreciate my post but someone else has rated it to be “unspeakably dismal”, this being the meaning of a single star rating. Big Grin.

With my 5 star rating it is now up to 3 stars. I tried to vote again without luck!

 

[mandrin]

kindergarten

With my 5 star rating it is now up to 3 stars. I tried to vote again without luck!

mrodock, thanks, I really appreciate.

This star system rating reminds me somewhat of kindergarten, a good job got you a little image.

 

[Biffer]

Five Star Plus!

Good post, mandrin. In my opinion, most of your posts are five star. I say most, because I don't understand everything you write.

I took particular interest in figs 1c and 2c, where you show the hands and clubhead speed. Several years ago an engineer friend of mine told me that he had read somewhere that in the impact zone Tiger's hands were traveling about 25 mph. As far as I can tell, there is no mention of hands speed in "Search for the Perfect Swing" and I have been unable to find any reference elswhere on this subject. Any comments from you, or others, would be appreciated.

Thanks,
Lary

 

[mandrin]

By "pinning " i maybe understand that it means the hands slow down prior to impact more in model 2 than 1 , giving a snap release appearance?
ie. hands look to be almost stationary and themselves act as a hingepin around impact?.

Yes, correct. Hands/arms slow down through impact much more in model2. It is an clear indication of a swing where one allows the kinetic energy / momentum of the arms to flow to the clubhead. You can readily see it when pros make a relaxed practice swing with their driver - the ‘pinning’ and whipping around of the club through impact.

In theory maximum efficiency is obtained when in proper sequence the shoulders, hips and arms almost stop for a short while. Brian, for instance, refers in a post that in a good swing the hips slow down through impact, hardly noticeable by the naked eye. In some swings you might perhaps perceive that there is like a little stutter in the downswing.

A totally different way of analyzing the difference between these two model swings is to refer to ‘shortening the swing radius’. As you mentioned in model2 the hands almost act as a hinge pin or a center around impact. Shortening the swing radius increases clubhead speed. In this respect model 2 is almost ideal, whereas model1 is not.

I take it that "Pingman" will swing like this?? he ... why no "pingwoman" swing model! Maybe if Ping sign Michele Wie they will address this ...

It would be perhaps more attractive for the many male members to have a model with a little mini skirt but don’t how to implement it.

In "search for the perfect swing" ( SFTPS) chapter 10 fig 10-1-C- they talk about possibly using muscular effort to delay the wrist uncock until later in the swing - in their model it gives more shaft forward lean at impact "but maximum speed occurs once again near impact, and is even greater than the free hinging speed at impact" - i think they mean free hinged natural uncocking rather that the delayed uncock due to muscles - BOTH act as free hinges once uncocking starts.

For a simple double pendulum model the optimum for wrist cocking is to use a negative torque first to maintain the angle deep into the down swing followed by a positive torque just prior to impact. This is creating more clubhead speed than free hinging where the angle is not maintained as deeply in the downswing.

Trying to maintain the wrist angle forcefully through impact at full throttle is a good exercise to feel the large inertial torques developed in a downswing. You hardly slow down the clubhead speed. It will simple snap out of the applied restraint torque.

But I repeat this is for a very simple mathematical model. A real golfer is sooo much more complex. The important feature(s) of any swing is not its impact clubhead velocity but the trajectory and clubface orientation through the impact zone.

Free hinging when compared to deliberate applied wrist torques is more machine like. You don't interfere with the forces developed, letting the swing do its job.

 

[mandrin]

hands speed

Good post, mandrin. In my opinion, most of your posts are five star. I say most, because I don't understand everything you write.

I took particular interest in figs 1c and 2c, where you show the hands and clubhead speed. Several years ago an engineer friend of mine told me that he had read somewhere that in the impact zone Tiger's hands were traveling about 25 mph. As far as I can tell, there is no mention of hands speed in "Search for the Perfect Swing" and I have been unable to find any reference elswhere on this subject. Any comments from you, or others, would be appreciated.

Thanks,
Lary

Larry, thanks for the compliment.

There is everywhere a great interest in clubhead speed which is readily measured with inexpensive commercial gadgets. Not so for hands speed.

The figs 1c and 2c are interesting to look at as the downward kink in the red trace in fig2c clearly shows the greater flow of kinetic energy from the arms to the golf club. The arms slowing down did not really get recognized till high speed photos could be made of the swing.

However I don’t want to imply that arms slowing down is the optimum way to swing. For instance, free gravity fall followed by full throttling through impact is equally interesting. The golf swing is a deliciously complicated matter, lots of fun for everyone, for a very long time to come.

 

[Spike]

Dear Mandrin,

Thank you so much for this thread!!! I will not pretend to understand all but I'm getting the gist of it. If you wouldn't mind, would you confirm, add, subtract or redefine something for me.

In our golf system we say that the definition of coordination is......

The ability to minimize the active forces and maximize the passive forces.

Active forces being:

Pushing (using the pressure points in the hands)
Hip Action
Uncocking
Thinking

Passive forces being:

Gravity
Momentum
Centrifugal force
Understanding

I'd really appreciate your thoughts!

You also made a statement that I really like because it is close to the essense of our golfing system....."The inertial torque acting at the very beginning of a downswing is acting on the clubhead inwards towards the center of rotation."

It was a huge paradigm shift for me when I stopped using the "inside to move the outside" as the initial source of motion. My hands are now the "source of motion" and I haven't looked back.

Again, thank you very much,
spike

 

[mandrin]

Dear Mandrin,

Thank you so much for this thread!!! I will not pretend to understand all but I'm getting the gist of it. If you wouldn't mind, would you confirm, add, subtract or redefine something for me.

In our golf system we say that the definition of coordination is......

The ability to minimize the active forces and maximize the passive forces.

Active forces being:

Pushing (using the pressure points in the hands)
Hip Action
Uncocking
Thinking

Passive forces being:

Gravity
Momentum
Centrifugal force
Understanding

I'd really appreciate your thoughts!

You also made a statement that I really like because it is close to the essense of our golfing system....."The inertial torque acting at the very beginning of a downswing is acting on the clubhead inwards towards the center of rotation."

It was a huge paradigm shift for me when I stopped using the "inside to move the outside" as the initial source of motion. My hands are now the "source of motion" and I haven't looked back.

Again, thank you very much,
spike

Spike,

It is difficult to comment on your post being such an open question.

I don’t really feel that any system is superior over another. Be it swinging or hitting or anything else.

However one feature of a solid sound system is to be coherent and hence to create a clear mental picture in the minds of students.

Letting the swing take place as much as possible by itself is indeed a sound way to approach the swing.

This approach, funny enough, makes it more machine like and hence more consistent and repeatable.

 

[Spike]

Spike,

It is difficult to comment on your post being such an open question.

I don’t really feel that any system is superior over another. Be it swinging or hitting or anything else.

However one feature of a solid sound system is to be coherent and hence to create a clear mental picture in the minds of students.

Letting the swing take place as much as possible by itself is indeed a sound way to approach the swing.

This approach, funny enough, makes it more machine like and hence more consistent and repeatable.

Thanks Mandrin,

Do you have any add ons to the list of Passive Forces that i may be missing out on?

 

[mandrin]

Thanks Mandrin,

Do you have any add ons to the list of Passive Forces that i may be missing out on?

Spike,

One uses the expression active and passive forces specifically when applied to muscles.

Could you give me a general definition of a passive force?

Perhaps your definition is any force not generated by muscular activity?

I did not think you were using strict scientific terminology, but momentum is not really a force.

 

[Spike]

Spike,

One uses the expression active and passive forces specifically when applied to muscles.

Could you give me a general definition of a passive force?

Perhaps your definition is any force not generated by muscular activity?

I did not think you were using strict scientific terminology, but momentum is not really a force.

And thus my limitations....scientific...anything :-(

I didn't know that about momentum. Is it just a condition?

I guess then my list would be narrowed down to gravity, centrifugal force and understanding (as opposed to thinking being an active force).

Yeah, muscular forces being minimized for a swinging type action.

I am trying to be more accurate in my teaching and I'm thinking these definitions would help me be a better teacher.

Thanks Mandrin,
spike

 

[mandrin]

bio servo control 2

The swing manages not badly if left alone. Have a look.

 

[Spike]

The swing manages not badly if left alone. Have a look.

I get the gist and am a believer for sure. I just don't know what a Nm is.

 

[mandrin]

I get the gist and am a believer for sure. I just don't know what a Nm is.

Spike,

Nm means ‘ Newton meter’ and has the dimension of torque. Torque as you probably know is a rotational force, it makes things rotate. It is the force applied to a lever multiplied by its distance to the lever’s fulcrum.

A force of 1 N with a lever of 10 m is equivalent to a force of 10 N with a lever of 1 m. Both produce a torque of 10 N m. A golfer is really only producing torques with his body, arms and hands.