Posted by: Jack Mankin (MrBatspeed@aol.com) on Thu Jan 3 15:22:45 2002

>>> The paradox is that in your documentation you relate batspeed to a strict function of dual shoulder torque about a central axis. If you have modeled the arms and bat as rigid in accepting torque from the shoulders, it follows that the instantaneous velocity of the bat must be strongly correlated with the instantaneous velocity of the shoulders. If, in fact, the shoulders are at zero velocity on contact with the ball, it follows that the shoulders must have decellerated themselves, and the bat to some extent, prior to contact with the ball. Thus, assuming legs are critical to delivering torque to the waist and shoulders, batspeed cannot be maximal if shoulders are at zero velocity on contact with the ball.

Do you see the paradox? On the one hand, you claim shoulder torque is essential to deliver maximal batspeed, but you only consider positive shoulder acceleration. You never consider shoulder decelleration prior to contact as being detrimental to batspeed.

How can the shoulders speed up the bat when they rotate faster, but not slow down the bat when they rotate slower just prior to contact with the ball? Thanks, Mike <<<

Hi Mike

I think what Major Dan stated in his post, "The arms/hands/bat is not a rigid unit, nor is it inextricably linked to shoulder turn" depicts the difference in a swing model you are referring to and the model that exhibits the mechanics of a great hitter.

There is a swing model, I refer to it as the "welded wheel," where the rate of angular displacement of the shoulders and bat are closely related. In the "welded wheel drill," the batter holds the bat in a fairly fixed position (as if welded to the torso) and rotates around a fixed axis. This produces a corresponding rotation of the bat-head. Although this is a good drill to teach a principle of rotational mechanics, this model has limited capabilities of generating bat speed and is not the model I was describing.

The model used by the top hitters also uses rotation around a stationary axis as the energy source but the transfer mechanics does not use the direct-drive (or fixed) principle. This model is based on the principle of transferring (or depleting) the body's rotational energy (momentum) into generating angular displacement of the bat-head. So bat-head acceleration is more inversely proportional to rotational momentum. As bat-head speed approaches maximum, rotational momentum approaches zero.

With efficient transfer mechanics (circular hand-path plus torque as the site describes) and timing, the total transfer (or depletion) of rotational momentum and maximum bat speed will occur as the bat reaches contact. Any retained momentum will be wasted. --- A study of the video frame just prior to (or at) contact (1/30 sec.) will bear this out. The bat can rotate through 70+degrees and attain 50+ percent of is angular velocity while the shoulders finishes it's rotation with about 10 degrees of displacement.

Only the better hitters are able to attain the above. The transfer mechanics of most hitters deplete rotational momentum 1 or 2 frames before the bat is brought to contact. This means the bat is lagging 30 to 80 degrees behind as shoulder rotation ceases. The smaller muscle groups of the arms are left to bring the bat to contact.

Jack Mankin