Posted by: Jack Mankin (MrBatSpeed@aol.com) on Sun Oct 17 14:18:30 2004

>>> Jack-

My layperson's model/understanding is that the double pendulum and flail are specialized models of whipping.

I do believe that you can increase the power soucrce by creating linear momentum with the forward motion of the body and use the body's muscle and elastic tissue as well as body positioning (rotate into toe touch then block forward motion at foot plant)) to transform this into to additional coiling of the torso which can then uncoil with additional rotational momentum that good "transfer mechanics" can transform into batspeed.

Furhtermore, developing linear and coiling motion at the same time, then blending them to improve torso coil may not be just a nice added wrinkle, it may actually be necessary for the body to be able to coil and uncoil efficiently. The main support I have found for this is Bobby Jones analysis of the golf swing where he found that the body had to move forward on a line before the hips began turning open to coil the body to avoid "spinning" and getting effective rotation to transfer/transform into clubspeed. Empiricaly, me found this action and sequence essential.

When you look at the purely passive double pendulum whipping type action, it seems that the "hinge angle" wants to greatly narrow before rapid angular acceleration of the final pendulum, but this does not seems desirable for batting with its requirement for dealing with limited reaction times. Do you find that torque needs to be applied to prevent passive hinge angle narrowing among othher things ? <<<

Hi Tom

In reading your post, I think we are dealing with two separate issues. Linear motion as it pertains to flail (double pendulum), and the theory that the body’s linear momentum is transferred into rotation around a stationary axis.

We have discussed the theory that the body’s linear momentum is transferred into rotation around a stationary axis extensively in the past. Below, is a post from the archives that sums up my position on Weight Shift/Rotation. However, I would say that a small hip slide (Bobby Jones or Barry Bonds) prior to rotation is more to clear the hips and set the axis angle than to develop linear momentum.

I would also point out that as the power hitting numbers have risen the last few years, the amount of linear body movement of most Major League hitters has decreased. If, in fact linear momentum is efficiently transferred into rotation around a stationary axis, we would see hitters like Bonds, Sosa, etc., with substantially more forward body movement prior to rotation (as in the Adair model). However, many of today’s best hitters pick up the front foot and place it forward with little to no forward movement of body mass.

Note: I still fail to see the distinction between “spinning” and rotating around a stationary axis.

Tom, I am not sure we have disagreements regarding the principles governing “flail”, CHP and the double pendulum. They all require an angular displacement to induce an angular displacement of the “swipe” or bat. I do have a problem with those that represent flailing (double pendulum) as a linear movement. Little displacement of the “swipe” (or bat) occurs if the tip of the “long stick” (or hand-path) is accelerated linearly. – “Pendulum” by definition infers angular displacement of both sticks.

I would appreciate your thoughts to the following question that I posed to Manny and Hitter earlier.
>> Do you see a difference in the mechanical principle of a Flagellum and a bat swung with a “steering-wheel knob” attached to the handle? The lead-arm, “left shoulder to the batter's wrists,” would be the “long handle” and the bat would be the “stick.” The steering-wheel knob would allow the bat to “swing freely.” <<

You asked, “Do you find that torque needs to be applied to prevent passive hinge angle narrowing among othher things.” – Although I have not actually thought of applying torque for that purpose, you may have an excellent point.

Jack Mankin
##

Weight-shift / Rotation
Posted by: Jack Mankin (Mrbatspeed@aol.com on Thu May 10 09:15:23 2001

Hi All

A business trip has kept me away from the computer for a few days. Since returning I have read most of the e-mails and new posts to the board and will try to catch up as soon as time will allow.

Over the past couple of weeks there has been a lot of discussion regarding linear weight-shift and its relationship to developing body rotation around a stationary axis. There have been many examples given of how a linear motion can be diverted to add to an athletic movement such as high-jumping or similar activities. Diverting a linear motion into a different direction (or vector) is well covered by the laws of conservation of momentum, and of course, I would have no objection to them. But I do have a problem with the explanation given for how linear hip momentum is transformed into rotation around a stationary axis (the spine).

This certainly is not the first time I have debated this subject or those similar to it. For those readers who go back a few years, you will probably recall that Paul and Mad Max from Setpro, Jeff, Steve T and others have discussed this very topic in some detail. I am sure Paul remembers our discussions and drawings of “The runner that tripped.” --- I think it might be a good idea to revisit that discussion as a point of reference. It certainly has more validity than the argument currently being presented.

One of my first disagreements with the theory that converts linear momentum into bat speed was the “weight-shift and extension” theory. The theory basically contended that if a batter shifted his weight forward and extended the bat lengthwise (knob first), and when the hands slowed, the bat-head will come flying through like “the crack of a whip.” --- For those of you that have my video, you saw the results of the test that disproved that contention. This theory is also discussed in “Test the ‘Crack of The Whip’ Theory” from the site map.

When the hands came to a stop after the batter shifted his weight forward and accelerated the bat (knob first), the bat-head came to rest with no angular movement. The barrel was still pointing at the catcher. The laws governing the conservation of momentum that kept the bat-head from rotating in that test are the same laws that keep linear hip movement from being transformed into hip rotation. --- In the case of the bat, the linear momentum vector is directed “in-line” (“n” factor = 0) down the bat’s length and was absorbed in the hands. In the same way, the momentum vector of the hips is directed into (and absorbed by) the lead leg. --- Shift your hips into a wall and see if there is any tendency for them to rotate.

We can now revisit Paul’s “runner that tripped” analogy. --- Here we have both feet of a runner coming to a sudden stop after striking a solid object. Would not the linear momentum of the runner’s body be converted into angular displacement as the torso arced downward? – Yes, this is in agreement with the conservation of momentum laws. But here, we are not speaking of linear motion that has “in-line vectors” as was the case with the bat or hip-slide. The linear vectors of the runner’s feet and head are “in-parallel.” The batter would need to stride with the hips fully open (front and back hip moving parallel with each other) for the runner analogy to be a valid comparison.

As I said earlier, Paul’s position does have some validity. In that, if the batter should stride with the hips (say) 20% open, then about 20% of the hip’s linear momentum could be converted into hip rotation. --- It is important to note that in this case the center of rotation is not the center of the body. In this case, rotation is around the lead-hip. --- The argument now being presented has the momentum of a linear hip-slide being converted into rotation around a stationary axis (the spine). The laws governing the conservation of momentum will not support that argument. I will give my reasons why this is true in another post.

Jack Mankin