Originally Posted by Jeff (Post 53214)

From my reading of the TGM book, I gather the impression that HK believed that the club released in the downswing because of a change in direction of movement of the hands from a straight line path to a curved path, and that the endless belt model explains the release phenomenon. Conceptually, the endless belt model theorizes that the club will travel at the same speed as the hands until the hands enter the pulley section of the endless belt model. Then, as the hands turn around the pulley, the club will accelerate relative to the hands and this represents the release phenomenon. However, this conceptual model is dependent on there being a straight line path movement of the hands in the early/mid downswing followed by a curved hand path later in the downswing, and "reality" doesn't seem to confirm this fact. If one looks at the hand path of professional golfers, their hand path is always curved and there is no straight line section. Here are two examples.

Bobby Jones strobe photo.



Tiger Woods photo



I used the slow motion Nike commercial swing video of Tiger Woods to produce this image. The red lines represent the clubshaft. The yellow lines represent the left arm (and I only plotted the left arm's location in the later downswing so as not to have too many lines cluttering the image). The green line is a hand-drawn line that plots the sequential movement of the hands over time. Point X is the point when release of the club is definitely apparent, although there is seemingly a small degree of release earlier.

Note that the hand path in both these images is near-circular, and there is no straight line path. Therefore, "reality" doesn't support HK's endless belt concept as explaining the release phenomenon.

Surely, a much better explanation is this mathematical model, which demonstrates that the club develops angular acceleration at all time points in the downswing when the pull on the grip is at an angle to the COG of the clubshaft.

http://nmgolfscience.tripod.com/release.htm

Jeff.

Originally Posted by Jeff (Post 53230)

Donn

I posted this photo



You then responded as follows-: "The picture of Tiger, sure shows the Impact Circle Axis and the Left Shoulder Center of Impact Circle that V.J. presents in his book."

You are making a big mistake. In constructing my composite photo, I only used one image of Tiger Woods, and superimposed the yellow lines on that photo to show the general change in position of the left arm in the downswing time sequence. However, those yellow lines do not point at the same point, because the left shoulder is always changing position.

Here is the true reality.



I used a spline tool to trace the movement of Tiger's left shoulder during the mid/late downswing. You can see that his left shoulder continuously moves upwards and to the left as the downswing progresses - see the three white dots with interconnecting red lines. VJ's representation of Ben Hogan's left shoulder socket as being a single fixed point in space is an oversimplification, and it doesn't represent true reality. It is a gross over-simplification - equivalent to representing Ben Hogan's downswing clubshaft plane with a single plane line when the clubshaft is actually changing planes continuously as it moves down from the turned shoulder plane (at the end-backswing) to the hand plane (at impact).

Jeff.