Posted by: JJA () on Sat Nov 6 09:31:43 2004

Here are two clips from Jack's 1st video:
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> http://webpages.charter.net/nickkio/HandPath/

Nick,

Thanks again for taking the time to make the clips.

Clip #1 is a wonderful example of the whip effect. It's exactly what Adair is illustrating in his book. To first order, forces are being applied to the bat directed along the length of the bat directed out the knob of the bat. This force vector has a circular path, but isn't caused by any torque at the hands or wrists. (Though it is caused torque in the lower body/torso, which is why the feet tend to roll over during a swing. These are the torques of the body being transmitted to the ground.) It is the force you feel in your bottom hand at the knob as it pushes against the knob.

Clip #2 is an excellent of example of why rotation is required to make the whip effect work. There is no whip effect without rotation. This shouldn't be surprising to anyone. Try to make a a real whip work by thrusting the base of the whip linearly. Won't work. You need to make a semi-circular path with the hand and wrist to make a whip work.

So again, these clips and Jack's accompanying commentary makes our positions much closer than I realized. I believe the only difference between us now is whether top hand and bottom hand torque supplements this whip effect (circular hand path in Jack's terminology) to an appreciable degree.

I would appreciate a refresher on Jack's experiments with rotation and bottom hand torque. (Again, without search capability on this site, this is difficult.) How much bat speed did you generate with clip #1 (using a real bat of course, and with bottom hand only so that top hand and bottom hand torque cannot be a factor), and how much did you generate with bottom hand torque? A clip of the latter experiment, I believe, is crucial for resolving our differences.

In addition, if I have some time, I'll put together a Matlab computer simulation that will illustrate what I believe is happening. Once I get it done, I'll send it to Nick to post if he wouldn't mind, or maybe I'll post it on hitting-mechanics.org.

Thanks again Nick.

-JJA