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Dr. Yeager's Whip Theory

Posted by: Jack Mankin (MrBatspeed@aol.com) on Thu Jan 6 16:47:40 2005

Hi All

Shawn has posted on his Discussion Board ( http://s6.invisionfree.com/Hitting/index.php ) an article by Will Carroll regarding Dr. Chris Yeager's theory of the baseball swing. Dr. Yeager's "whip" theory sounds very similar to that expressed by Professor Robert K. Adair in his book "The Physics of Baseball." I thought it would be interesting to discuss the fundamental differences in principles of the "Whip" theory and the "Rotational Transfer" model.

As I am sure most of you are aware, in the rotational transfer model I developed, torque (forces applied at two points from opposing directions) is a major factor in generating bat speed. However, for this discussion let us set aside the torque factor and concentrate on how the two different models transfer the body's rotational energy into bat speed by applying a force at a single point on the handle.

Dr. Yeager concludes that hip and shoulder rotation is generated from the transfer of momentum as the front leg stops the body's forward movement. Although I disagree with that conclusion, I do not wish to make it a point of debate at this time. Let us just acknowledge that the batter is rotating around a stationary axis and discuss how that rotation is transferred into bat speed.

Other than the torque factor, I think the primary conceptional difference between the "whip" and "rotational transfer" models can be shown by examining Dr.Yeager's following statement.

"If forward momentum is not stopped and if body segments turn at the same time, maximal energy transfer will not result. If one were to attempt to crack a whip by rotating in a circle without stopping the hand, and therefore not transferring energy, the goal of cracking the whip would not be attained. However, if we stop the whip and then allow the whip to sequentially stop down the line, then we'll get the desired result."

This is a very different concept than the principles governing the angular acceleration of the bat-head with the rotational transfer model. Bat-head acceleration in the rotational model is based on the same principle as swinging a ball around with a string. An angular displacement rate of the hand-path induces an angular displacement rate of the ball or bat-head.

As Dr. Yeager points out above, with his whip theory there is no transfer of energy until the hands stop. With rotational transfer there is constant inducement of bat-head acceleration from initiation to contact as long as the hand-path is undergoing angular displacement. The greater the angular displacement rate of the hand-path, the greater the bat speed induced.

A frame-by-frame analysis of a great hitter's swing shows the hands do not come to a stop as required with Dr. Yeager's whip theory. Just before contact, there is reduction in the radius of the hand-path where the bottom-hand is being pulled back around a slower moving top-hand. Some refer to it as the "hook" in the hand-path where the angular displacement rate reaches its peak. However, the hands as a unit continue a sweeping path unlike the motion used to crack a whip. -- Also keep in mind that a bat can not uncoil down its length when the hands stop like a bullwhip.

Jack Mankin


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