Posted by: Jack Mankin (mrbatspeed@aol.com) on Wed May 5 23:30:48 2004

>>> First of all, it will be difficult for me to say this, but after looking at various information, including re-reading Adair yet again, I came to the conclusion that BHT and THT are both fallacies.

They are reactory forces, like centripetal force. <<<

Hi BHL

I would assume that your other reading is Paul Nyman. I would further assume Nyman is also in agreement with Adair’s swing model, which denies torque as a factor in generating bat speed.

The difference between Adair’s swing model and the swing model presented at BatSpeed.com goes to the very heart of the Linear vs. Rotational controversy. The model presented in his book, “The Physics of Baseball,” is linear mechanics in its purist form. Adair not only believes that torque is not a factor in generating bat speed, he also believes the axis of rotation must move forward during the swing approximately 18 inches at approximately 7 mph in order to generate the kinetic energy required for the swing.

Below is an excerpt from his book:

“As the swing begins, the batter strides forward transferring his weight from his back leg to a stiff front leg. As the hands accelerate, the force from the reaction of the bat, transmitted through the hands and arms, slows down the body's forward motion and rotation. As the body slows, the hands that had been accelerated to approximately 15 MPH, also slows to a near stop. The body's kinetic energy is then transferred to the bat as forces uncocks the wrist. During this time (as the hands slows and wrist uncock) the kinetic energy that was stored in the body is transferred to bat. This kinetic energy transfer accelerates the bat head from about 40 to 70+ MPH.”

In 1991, I wrote Professor Adair (and also spoke with him on the phone) that my study of the baseball swing showed that although there is forward movement of the body during the stride, all forward movement ceases before rotation begins and the swing is initiated. I explained that during the swing the body rotates around a stationary axis. Professor Adair told me on the phone that rotation around a stationary axis was impossible. He stated, that in order to generate the kinetic energy required, the axis must be moving forward during the swing.

In response to the research paper I sent to him on this subject, Professor Adair replied (a direct quote from his letter) "And any batter who would use your 'stationary axis' model, taken literally, could not hit a ball past second base."

Professor Adair also stated in his book, "A player swings a bat very much like a weight on the end of a rope. Conversely, a force at the handle is not transferred to the point of contact." -- While discussing these principles with him, he further explained that all energy for the swing was directed down the length of the bat and therefore any force applied by the hands at the handle was not a factor in bat head acceleration. In other words, he was saying that torque applied at the handle was not a factor in generating bat speed.

In the research paper I sent to Professor Adair, I agreed with him that there is a component of the swing where the energy is directed down the length of the bat (with the CHP -- like swinging the bat with a rope). However, I explained that when we isolated the different forces acting on the bat that induce angular rotation, we found that opposing forces supplied by the hands at the handle (torque) was a major factor for generating bat speed. He disputed this and reiterated the whip theory.

To prove that torque, not the whip effect, was a major factor in generating bat speed, we isolated the angular displacement produced by linear weight-shift and extension of the hands (the whip effect). We eliminated torque by attaching a steering wheel knob to the bat handle. We eliminated the CHP by keeping the hand-path fairly straight. We found that no matter how much weight was transferred or how fast the hands extended, there was no bat speed generated as the hands slowed to a stop. There was no quick acceleration of the bat, menaing that there was no whip effect because the bat does not uncoil like a whip. The bat is a solid, rigid object that is not capable of uncoiling.

We then eliminated all factors other than torque from being applied to the bat. We had the batter assume the contact position with the bat-head against a heavy bag. While holding that position, the batter kept the lead-hand stationary as he pulled the bat 70 to 80 degrees away from the bag by pulling the top-hand back with the elbow. The bat is now stationary (has no momentum), the batter’s body will not rotate or move forward, the hand-path will not move forward. And BHL, there is no "reactory forces, like centripetal force" occurring. The only force that will act on the bat to accelerate it to the bag is torque. As the bat-head accelerated to the bag, it was evident that torque was a major factor in generating bat speed.

A few years later, a motion study computer gave bat speed readings of 35 to 42 mph on this test. Similar readings were obtained when the top-hand was held stationary and the bottom-hand was pulled back by the lead-shoulder.

Note: Professor Adair was a consultant on scientific affairs for the National League. When he told me that he was preparing a second edition of "The Physics of Baseball," I sent him a number of frame-by-frame clips of Major League batters rotating around a stationary axis. He acknowledged that the hitters on the videos used the stationary model with success. I told him it would be helpful for baseball if he made changes in his second edition that reflected what those clips revealed. He didn’t, and his linear principles are still being taught.

Jack Mankin