Posted by: JJA () on Sun May 9 13:14:59 2004

> Thank you for the kind words, but unfortunately I don’t think you’re going to like the conclusions I’ve reached. I think by our recent discourse, we’ve agreed on the following:
>
> 1. Early on, you hypothesized that torque applied to the bat was a significant generator of bat speed.
>
> 2. You then performed the experiments described earlier in this thread that demonstrated that significant bat speed could be generated by applying torque to the bat handle via differential forces of the hands, either top hand or bottom hand.
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> 3. By these experiments, you thus proved your hypothesis that a primary contributor to bat speed was torque applied to the handle via differential forces in the hands.
>
> I believe and hope that I have provided a fair description of precisely what you did. If I haven’t, please correct me where I have gone astray.
>
> If this chain of reasoning is a fair representation of your position, I unfortunately conclude that point 3 does not necessarily follow from points 1 and 2. Although your experiments did prove that torque applied to the bat can provide significant bat speed, it does not follow that torque applied to the bat is actually present in a real, non-experimental swing.
>
> You hypothesized earlier in this thread that torque is applied to the bat evenly throughout the swing. Unfortunately, your experiments showed (proved?) that whenever torque is applied to the bat, the wrists were elongating or possibly contracting. Since we have agreed that in good swings the wrists do not elongate or contract except just before contact, it follows that we reach the opposite conclusion, that little torque is applied to the bat by the hands throughout the swing.
>
> There is no question torque is a major contributor to good swing mechanics. The rotation of the body is achieved by strong torque generated by the torso that is ultimately transmitted to the ground via the feet (which is why the front foot sometimes rolls over in the swings of power hitters.) The issue here is whether torque is applied to the bat via differential forces in the hands. I believe your experimental data is insufficient to prove this point, and in fact points to the opposite conclusion that little torque is applied to the bat via the hands in the swing of good players. Your experiments have helped validate – rather than repudiate – Dr. Adair’s swing model.
>
> -JJA
> Ph. D. Electrical Engineering, University of California, Berkeley
> Senior Engineering Fellow, major aerospace firm
> Several patents and papers in the area of dynamics and controls <<<
>
> Hi JJA
>
> Being a Ph. D. Electrical Engineering, University of California, Berkeley, I would have expected a much more compelling argument for the nonexistence of torque in the swing. Since you present no test data, this is a conclusion you have reached based on your belief the wrist must elongate in the real swing to apply torque as they would in the way I set up the test swing.
>
> You are simply wrong. The test was strictly a palm-up/palm-down movement with no body rotation. In the real swing, applying torque does not elongate the wrist. The wrist (like an oarlock) and forearm rotate as torque is applied. The palm of the top-hand rotates in an arc from a vertical position to the palm-up allowing the wrist to stay straight as torque is being applied.
>
> JJA, three Physics Labs (two were chaired by Ph.D Physics) evaluated Adair’s book and my research paper and concluded torque to be a major factor in generating angular displacement of the bat. Adair’s swing model caused many eyes to roll. I have also had correspondence with many engineers who have come to the same conclusion. A couple said they felt Adair made his no-torque judgement based his misreading of a Bat Companies bat/ball collision test conclusion – a force at the handle is not transferred to the point of contact. They pointed out that this statement referred to the bat/ball collision and had nothing to do with how the bat was accelerated.
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> Jack Mankin
>

Jack,

If you have additional experimental evidence, or could point me to the research paper you mention, then I will be happy to re-evaluate your findings. My conclusions are based solely on the evidence you presented in this thread, which is unfortunately insufficient to prove your hypothesis.

-JJA