Posted by: al_Oha (p3d0n6@hawaii.rr.com) on Thu Jun 17 10:47:33 2010

Tom,

The test subject in Cross' paper is interesting: I wrote the author curious to know what the hitter's swing looks like: This is what he had referred to me:
http://www.physics.usyd.edu.au/~cross/Bren14.mov.

I would say that the test subject is not a prime example in the Mankin mold. In fact, the batter appears to be a more linear type of hitter than a rotational one. This was my communication to him in generating his response, which I will not include here.


........ Your experimental data identifies a positive coupling at the initiation of the swing.
In the same way, Mankin describes "top hand torque" as an important factor. Here, the top hand accelerates the bathead rearward towards the catcher in acquiring early batspeed. Your model defines uniform acceleration through a logarithmic spiral, in a roughly similar way Mankin emphasizes motion through a circular hand path. At the
instant just prior to ball contact, Mankin posits "bottom hand torque" in which the knob's end is pulled back towards the catcher.

In your model, you determine a large negative couple is generated for proper bat alignment with respect to the ball in the terminal phase of the swing. You note that this element "is not only counterintuitive, but inconsistent with the action of the arms".

The following is a post on Mankin"s website of an overhead shot in Pete Rose's swing, in which there appears to be a pull with the bottom hand on the knob of the bat just before ball contact.

http://www.youtube.com/profile?user=MrBatSpeed#p/u/13/4gRiRiTvbCU

I am trying to reconcile my understanding of the negative couple The confusion probably relates to this counterintuitiveness, but I am willing to embrace it understanding that what I see will not always correlate with what is measured. To help settle this, my questions
are:

1. Is Pete Rose's swing at the point of ball contact consistent with your model? i.e. Can I expect a similar swing from your batting subject? In your illustration of body segments in the swing (Figure 7), I note that the batter's chest just before contact opens to face first base, where the lead shoulder subtends an angle approximating 45 degrees incident to the ball.

In Pete Rose's swing, his chest is open to the pitcher, or about 105 degrees angle of incidence relative to the ball upon contact.

2. Might there be significant difference in the terminal couple generated by your subject relative to what might be measured in Rose's ? Mankin makes a point that one of the distinguishing features separating high level hitters from the common batter, is the ability to generate bottom hand torque by pulling the lead elbow with the massive muscles of the back and lead shoulder.

I predict that in your subject, the lead shoulder is marginally pulled back, that his elbows are fully extended or "locked" to meet the ball as most typical batters do, for a "less-than-optimal" couple. The symptom results in this "half turn" to first base demonstrated by the test subject.

3. What would a positive couple look like, if one were to exist, or can it based on conservation of torque within the system?