Posted by: Jack Mankin (MrBatspeed@aol.com) on Tue Apr 22 16:01:23 2008

>>> I'll take another stab at this and see what Jack thinks.

the physics/mechanics underlying both golf and hitting are similar.

here is a popular golf model from PHYSICS OF GOLF, Jorgensen:

http://www.tutelman.com/golf/design/swing1.php?ref=

In all high level/total body swings,golf and hitting, there is forward momentum of the torso, torque of the torso, and wrist/handle torque. The simplest physical model is a double pendulum with appropriate modifications to account for these as well as mass of body parts/bat and a 2 handed connection from the torso to the bat handle, see ironnymans for the hitting swing:

http://www.setpro.com/stuff/rotational_simulation4.wmv

http://www.setpro.com/stuff/rotational_simulation5.wmv

Note: this baseball swing model eliminates the forward momentum of the torso, but do demonstrate torso and handle torque/effects.

As Jack has described here, handle torque is a very important aspect of the swing as is a handpath shape ("CHP") that retains connection between the 2 "pendulums" - 1-the turning torso/shoulder/lead arm mass and 2- the bat.

The connection between the two is primarily the wrists, but to some degree may include the lead forearm as a compound (more than double) pendulum.

the body creates and transfers momentum. the transfer mechanics of CHP and handle torque transform this momentum into batspeed (quick acceleration without "drag" starting well behind the hitter/"early" in the swing plane) adjusted for a well lined up/timed collision with the ball.


Jack's definition of linear/rotational is the most straightforward and useful in my opinion based on how well the transfer is made by CHP and torque so that the momentum of the body drives the swing quickly/adjustably. This is usually where hitter's mechanics are most defective/need the most work/pay the most benefits when improved.

A lot of the controversy comes more "theoretically" in how the linear/forward momentum of the whole body relates to/blends with the rotational momentum of the twisting torso.

Is the linear momentum "converted" to rotational momentum or not and what is meant by conversion ?

Or does this linear momentum play some other role in positioning/priming the body/muscles ?

or both or something else.

Another person who has studied the swing carefully that disagrees to some degree with Jack is Dr Yeager who has a list of definitions here that could be a basis for hashing things out at some point if this would add value:

http://z6.invisionfree.com/Hitting/index.php?s=a6ee494dc4de1fba524e34e7dcc61651&showtopic=60

and see also

http://www.dryeagersbaseball.com/dryeager.asp

Jack's focus on "transfer mechanics" is the most useful and practical application/interpretation of "linear vs rotational" I have seen. <<<

Hi Tom

Your summation covered all the important issues. I find nothing I would disagree with.

Jack Mankin