[pistol]

Yoda - I strongly suspect that you are not going to like this answer.

I think that the concept of the left arm-clubshaft combination being equivalent to a taut string connecting the sweetspot to the left shoulder socket only applies to a very small part of the clubhead arc - when the left arm becomes straight-in-line with the clubshaft post-impact. In the early downswing when the clubhead is lagging well behind the hands (>90 degrees) - prior to the release of PA#4 - there is essentially no independent rotation of the left arm around the left shoulder socket joint, and the left hand is essentially traveling along the straightish part of its U-shaped arc - so there can be no centripetal force involved. During the release phase of the downswing - after release of PA#4 - it is only the left hand that is rotating in a circle around the left shoulder socket (which acts as the fulcrum point), and a centripetal force only applies to the relationship between the left hand and the shoulder socket, and not between the clubhead sweetspot and the left shoulder socket. In fact, during the release phase the clubhead sweetspot is actually in a state of centrifugal release, which by definition means that it is essentially free of any centripetal influence. When the clubhead catches up to the hands and the left arm becomes in line with the clubshaft, then the clubhead sweetspot moves at roughly the same rpm as the left hand, and under those conditions a centripetal force applies to the relationship between the clubhead sweetspot and the left shoulder socket, with the left arm and clubshaft structural unit acting as a taut string connecting the sweetspot to the left shoulder.

If you are seriously interested in a detailed explanation of my personal opinions, then I may consider preparing a detailed post.

Jeff.

You got give some credit guys...its a surgical answer with precision