Posted by: Jack Mankin (MrBatspeed@aol.com) on Sat Jan 21 15:51:55 2006

>>> Once again, Jack, there are statements made by you that are in direct conflict with each other.

“Normally, rotation is initiated as the lead-heel drops.”
http://www.batspeed.com/messageboard/output/25356.html


“Lateral and rotational movements of the body do not occur at the same time.”
http://www.batspeed.com/research04.html

It is my opinion that the body is still moving laterally “…as the lead-heel drops.” (If you disagree with this, please prove it with at least a visual example)

For a further opinion, please see:
http://www.batspeed.com/messageboard/24359.html
and I would again ask two questions (to which I know that I will not get an answer [from Jack]):

1. When does “weight shift” stop?
2. When does “rotation” begin? <<<

Hi Ray

You ask;
“1. When does “weight shift” stop?
2. When does “rotation” begin? “

If by “weight shift,” you are referring to the forward movement of the body “mass,” then “weight shift” would approach zero (or stop) as the lead-heel drops and rotation is initiated. Therefore, “Lateral and rotational movements of the body do not occur at the same time.”

If by “weight shift,” you are referring to the transfer of which leg is most responsible for supporting the body’s mass at different points of the swing, then one could say that “weight shift” and rotation could occur at the same time.

You stated, “It is my opinion that the body is still moving laterally “…as the lead-heel drops.” (If you disagree with this, please prove it with at least a visual example) --- Ray, there is often a slight delay (a couple 100/sec.) from heel drop to initiation of the swing where the hips may slide a couple inches as the pelvic cocks open a few degrees. But, there is no linear movement once rotation is fully initiated. As just one example, I would refer to the following clip of Ted Williams. http://dmcmillan.topcities.com/Williams03.mpg

I chose this clip because it is used in discussions on another board of how the blockage of linear momentum is supposedly transferred into rotational acceleration. It appears this clip was shot at about 100 fps. --- During his stride, toe touch was at about frame #31, heel plant about #37 and rotation was initiated at about #41 or 42. At frame #41 (initiation of rotation), I placed the edge of a card to line up with his spine - middle of the neck to the crouch (center of mass). From that frame to contact, there was no lateral movement of the spine (center of mass).

At Frame #41, the hips had just slightly cocked open and all forward movement of mass had ceased -- linear velocity = zero – had been “blocked” -- or however one wishes to call it. Since momentum is the product of mass and velocity, there was no linear momentum available to aid in rotating Ted's hips the final 80 degrees or so.

Jack Mankin