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Release - uncocking & roll

The basic model used for the 3D analysis is shown in Fig1. The club is modeled as consisting of an uniform shaft and an offset point mass, representing the clubhead. The best way to look at the information given is to think in terms of an Iron Byron modified to fit the mathematical model.

Fig1

For the first portion of down swing, segment ab (lead arm) and segment bc (club) remain in the plane ABCD. ab stays constrained in the plane ABCD, whilst bc can move out of this plane. The angle θ is the roll angle about axis ab, the angle α represents rotation around pivot a, in plane ABCD, whereas the angle β represents the uncocking motion, contained in plane abc, around b.

When somewhere in the down swing roll action is initiated, given by the angle θ , it will cause a slight out-of-plane motion for the clubhead cd. The analysis leads to some interesting findings with regard to the behavior of the release of the roll angle. This can clearly be seen in Fig2. A small roll torque is initiated at t=0.2 sec. However nothing really happens till t = 0.28 s, when, with club and arm virtually aligned, a very rapid release action takes place.

Fig2

There is an interesting auto-regulation process taken place - the occurrence of roll release is not so much a function of the time the roll torque is applied and/or its amplitude, but rather a function of the angle β between arm and shaft  - actually when β near 180 deg, ie., for almost in-line condition for club and arm. The release timing of the roll angle θ is hence seemingly determined by the centrifugal force.

Fig3

Fig 3 gives an idea why the application of a small roll torque initially does not do very much. With  β=π/2 the moment of inertia,re to axis ab,is maximal. When uncocking takes place it decreases however very rapidly and the applied roll torque suddenly leads to a much larger roll acceleration/velocity of the club.

Fig4

It is more interesting to display the information more pictorially as is done in Fig4. The view angle is chosen above and behind our 'Iron Byron'. The white dot is the projection of the end of the shaft on the swing plane. The small segment ending in the red dot represent respectively the radius of gyration and the center of mass of the clubhead. Nnotice that the clubhead is gradually moving out of the swing plane without any rotation of the clubhead followed by a very rapid release of the roll angle very close to and through impact.

Fig5

Fig5 does show exclusively the trajectories of the end of shaft (white), its projection on the swing plane (blue) and the COM of the clubhead (red). Notice the motion of the clubshaft when the quick roll release takes place. The rapid dip indicates that the end-of-shaft moves around the COM of the clubhead. Notice however that the COM does have a slightly curved motion, out of and subsequently into the swing plane.

Fig6

Fig6 show the respective motions of end-of-shaft and COM clubhead out of the reference swing plane. It illustrates the same information as in Fig5 in a different way. Notice the sharp 'dip' in the motion of the end-of-shaft. There is indeed a movement of the shaft around the COM of the clubhead. Where red and blue lines coincide the roll angle is either 0 or 180 deg. When they are separated, rotation due to roll takes place.

Conclusions:

The mathematical analysis seems to confirm what happens in a real golfswing in that it shows an almost automatic release of the roll angle, occurring very rapidly when club shaft and lead arm are very close to the in-line condition. It is this feature which makes a high quality golf swing more readily possible since a precise 100 % conscious timing of the roll angle would very difficult to perform.

The analysis seems to confirm the old adage to 'give up control to gain control'. It is indeed an interesting paradox that more one lets go more a swing resembles a machine swing.

mandrin