Posted by: JJA () on Sun May 30 19:36:10 2004

JJA-
>
> Thanks for the reply.Looking at lots of video of great hitters leads me to generalize that
> the hitter typically cocks the bat somewhat vertically,then uncocks the bat by sweeping the
> bat around toward the catchers as it turns in a more horizontal plane in preparation for
> continuing into the developing swing plane which will be roughly perpendicular to the
> momentum plane of the torso.This action has the potential benefit of assisting the torso in
> stretching/coiling/loading with respect to the hips that begin circling open about the
> same time that the bat starts circling backward.The torso then can be aided in turning/
> staying back as a link in betwen thesmore proximal and distal links.This also has the
> advantage of getting the bat turn underway while still keeping the bathead inside the arc
> of the handpath prior to the hip turn decelerating to transfer momentum and more fully
> energize the torso.Much of this conjecture fits with motion analysis which can chart joint
> position,motion and angles as the swing unfolds.For example,the quicktime motion
> analysis files of Griffey posted at the peaveynet.com site show the hinge angle (angle
> between lead arm and bat) to gradually increase and stabilize rather than decrease as the
> torso starts turning.the hinge angle then widens substantially only after the back foot
> begins to reactivley drag as a sign that hips have decelerated and transferred momtnum to
> torso.In this manner theoretically(or as Nyman would say-totally unsubstantiated
> guessing) you can account for how the torque action might asssist in degree of coiling of
> the body as well as in efficiency of uncoiling being transformed into batspeed/quickness.
>
> This can have application in the development of teaching instruction and swing amalysis
> by including useful descriptions of the grip and hand action/feel as detailed by Jack,for
> example with THT.
>
> BHT on the other hand seems to me to be more a factor related to the shapng of the
> handpath so that the axis that the bathead turns around shrinks as it comes onto and up
> the handle of the bat.

Sir,

One more followup on your question regarding the double pendulum example. You made a very keen observation about Nyman's simulation.

You are indeed correct that his double pendulum simulation did not adequately address the beginning of the swing. In reality, his simulation really started at the launch position. Therefore, anything prior to that in the swing was certainly not addressed by that simulation. Indeed, it is not possible to address those effects by a 2 dimensional simulation. Good observation.

Your second good observation was the hinge position of the wrist. You correctly noted that the hinge (wrist) position changed during the simulation. Very good observation. You noted it went in the opposite direction of what Sheffield does at the start of the swing. However, the simulation doesn't apply there, only from launch.

Next, remember in the simulation that the wrist is thought of as a perfect pin joint, i.e., it can rotate 360 degrees. Of course, a wrist can't do that! My wrist can only move 90 degrees or so.

Why I like your observation so much is that if from launch I swing the bat, I do feel a little pinch in my wrist trying to cock it in a little further than the 90 degrees my wrist will allow. In other words, if my wrist angle is in a good 90 degree "L" position, it stays there with pure rotation, and actually feels like it wants to pinch in further. Maybe other guys out there feel differently, but that's what I feel. This is what the simulation is showing!

I wouldn't read a lot into such a simple simulation, but at least in my case you helped me understand the simulation even better.

-JJA