[Jeff]

Bernt - thanks for posting your opinion. I am always interested in reading other people's opinions, because I may learn something "new" that will change my mind about an "issue". Unfortunately, I first have to understand another person's opinion before I can change my mind, and I cannot understand many points that you seem to be expressing.

To start, you wrote-: "Angular acceleration does not increase the speed of whatever is being rotated. Angular acceleration doesn't do anything but change the direction while conserving energy. It is only longitudinal force that can increase the club spead. Or shoud I say: "Geometrically Orienteted Linear Force" - G.O.L.F."

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? 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. In other words, he is seemingly implying that angular acceleration doesn't only change the direction of the clubhead's movements, it also causes the clubhead end of the club to speed-up. Do you disagree? 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."

Could you please define "swing center" and "rotation center". I cannot develop a mental picture of your developing argument. You further wrote-: "This shifting of center is creating a longitudinal force component in addition to the centripetal force component of the "pulling string". The pulling string is used to pull & rotate at the same time. The longitudinal force component is what increases speed."

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? If you are implying that the left shoulder socket is moving left-laterally in space, while the left arm rotates from the fulcrum point of the left shoulder socket point, and you are implying that the constant movement of the left shoulder socket in space represents the longitudinal force, 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?

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

Thanks.

Jeff.