[BerntR]

Bernt - thanks for posting your opinion. I am always

I am not sure what you mean by longitudinal force. Consider nm golfer's mathematical explanation. He stated that the hands are always changing direction and speed at every moment of the downswing. Do you regard that as a longitudinal force, a G.O.L.F force?

As a few other terms I used in the post, I could certainly have picked a better one. I should have used the term tangential force, ref my other post above.

I agree that the hands are always changing direction and speed. In addition, the hands transfer radial and tangential forces.

Secondly, he stated that if the hands are pulling the grip end of the club in the same direction that the hands are moving, and at the same speed as the hands are moving, that the clubhead end of the club would be angularly accelerated at every fractional time-point of the downswing, and that the cumulative effect of many thousands of time-points of angular acceleration inputs would cause the clubhead end of the club to progressively speed up.

I was confucing "angular acceleration" with radial acceleration. Sorry about that.

I basically agree with the above, but I think it makes sense to decompose angular acceleration. Angular acceleration is created by radial acceleration and tangential acceleration. But it is only the tangential component that increases the swing speed.

There are basically two ways of generating tangential acceleration.

1) By applying torque (as in trying to bend the shaft)
2) By partly pulling the club in a direction that has a tangential component as well as the radial component.

Secondly, nm golfer's mathematical explanation doesn't state anything about "conservation of energy" because there is not a "fixed" amount of energy in his hand/clubshaft system. The hands can constantly receive additional energy throughout the downswing from a variety of power sources (eg. release of power accumulator #4).

You also wrote-: "In a pure swing, the swing center is shifting. It is always moving a little ahead of the rotation center."

"Swing center" was another one of my ill-defined terms. Unfortunately, I don't have a good expression available at the moment. But what I mean is that the total force applied to the club (tangential and radial force) is not pointing at the rotation center. An offset is required to generate a portion of tangential force. This offset could be the location of left shoulder vs. head/neck which is likely to be the rotation center.

But may I restate that radial force only changes direction and conserves the velocity energy that has been transmitted to the clubhead so far in the swing.

You seem to be implying that there is longitudinal force component that causes the increase in clubhead speed. What is this longitudinal force component and where is it operant in the PingMan machine's swing?

The pingman machine has its mechanical left arm attached to a mechanical shoulder. This shoulder is rotating arount the center of rotation, so that an offset is created.

If you are implying that the left shoulder socket is moving left-laterally in space,

It is moving in an arch. How close this arch is to a circle probably varies from golfer to golfer. But the point is that the pulling must stay "ahead" of the swing center to increase speed. There i said it again. I meant center of rotation. "Swing center" is probably an equally correct phrase. But since I've already abused the term "swing center" i will try to let that rest at least in this thread.

But regardles of swing technique, somewhere in the body, torque must be applied. In a pure swing, torque is applied to rotate the left shoulder. And this torque enables the left shoulder to generate radial and tangential acceleration up on the club by simply pulling the arm.

how can the hands "know" what percentage of their force of forward movement comes from the movement of the left shoulder socket in space versus the rotational movement of the left arm?

I don't understand this question.
[quote]

Could you please explain what you see in Tiger's swing at 9 o'clock?
QUOTE]

When the clubhead is around 10 o'clock, it is loosing speed beween two frames. If the illustration is correct. 10 o'clock as seen from our side, that is. I'm wondering whether there's some downstroke loading going on.

But it could as well be just an inaccuracy in the illustration.