Posted by: Dan (daniel.miechels@gmail.com) on Wed Jun 16 21:29:07 2010

> >>> I like your work a lot and I like Chris O'Leary's work a lot too.
> Both of you have helped me a ton. But, I have to believe you are more correct on the hand torque issues because I do see the video evidence, even on Chris' web pages where he refutes THT. <<<
>
> Hi Joe
>
> One of Chris's quotes you posted states, "In a rotational swing, the hands, wrists, and forearms do not generate any force;"
>
> If I read the meaning of his quote correctly, he is saying the arms, wrist and hands serve only as linkage to the rotating shoulders with no ability to impact the bat's acceleration on there own. I would agree that providing linkage to the rotating shoulders is a major function of the arms. This would be especially true of the lead-arm which remain in a fairly fixed position in relationship to the rotating shoulders.
>
> However, the direction of pull and rotation of the back-forearm and hand can provide torque that greatly impacts the bat's acceleration and trajectory. -- I read a thread on another site where Chris and other posters were discussing these mechanics. They were addressing a demonstration video that showed the bat-head sweeping rearward at a much greater angular rate than shoulder rotation - similar to the trajectory in THT.
>
> Below are few of Chris's Quotes from that thread.
>
> ##
> "It's sweeping the bat head rather than whipping it. Notice how early the barrel comes away from the shoulder and the hinge angle changes."
>
> "This is sweeping the bat head. The wrists and arms are turning but nothing else is. I see it all the time in my 2nd graders and in my bad 4th graders, but not in good hitters."
>
> "The bat head is moving away from the back shoulder from the start of the swing, which is completely wrong."
>
> "I teach rotating the back shoulder as the first move, not opening up the hinge angle early and sweeping the bat head."
>
> "the barrel stays in the same position relative to the back shoulder as the shoulders turn."
> ##
>
> I am placing below a video clip that shows the initiation phase four hitters with what I deemed as exhibiting "Good" mechanics and also four hitter's mechanics I deemed as "Poor." The video addresses the first 4 frames (60 fps) of their initiation and note that the "Good" hitters shoulders rotate about 30 degrees while the bat-head rotates (or sweeps) rearward over a 100 degrees. According to Chris's statements, this is what he would expect to see in "my 2nd graders and in my bad 4th graders, but not in good hitters."
>
> Chris states that in a "Good" swing, "the barrel stays in the same position relative to the back shoulder as the shoulders turn. -- Well, that's about what we see in the batters with what I call "Poor" initiation mechanics. Note that their shoulder and bat rotate about the same of degrees during the initiation phase - little THT being applied.
>
> <a href="http://www.youtube.com/profile?user=MrBatSpeed#p/u/1/1f2SwCoFRgI">Four "Good" & "Poor" - THT</a>
>
> Jack Mankin

Hi Jack,

Recently I have done a lot of careful reading of scientific studies/papers such as the previously mentioned:

http://www.physics.usyd.edu.au/~cross/PUBLICATIONS/44.BatSwing.pdf

According to what I have read:
Nearly all of the bat speed can be attributed to a circular hand path causing the bat to undergo the type of acceleration displayed in a double pendulum. The role of the torque applied to the bat by the hands is to control the timing of when the bat flings through. When the shoulders start to rotate, a torque (ie. "THT") is required to stop the bat head from moving the wrong way (ie. cocking further forward). Further into the swing, a negative torque is required to actually hold the bat head back and stop it coming through too early. (This is not the case in golf, where the club is longer with a higher moment of inertia and the negative torque required is neglible).

The question is how does THT (that actually moves the bat head backwards) benefit the swing if the batter has to restrain the bat head later in the swing ? (Personally I find that THT/PLT does work very well for my swing). I would expect that when the bat is restrained, the momentum would be retained into increasing the acceleration the CHP (and then into the bat when the bat is eventually released). So applying THT/PLT should help the swing get a smoother stronger start as the shoulders start to rotate and contribute to the final bat speed. Timing it all is the hard part.

PS. I was skeptical about the 'restraining' torque required on the bat - as the swing happens so fast I can't feel if I am doing it. But the math all makes sense, and the bat does swing through too soon if I swing hard while holding the bat with the top hand in such a way that I can't put much negative torque on the bat.

Dan