View Single Post
Old 01-01-2011, 09:09 PM   #32
Erick Mead
Erick Mead's Avatar
Dojo: Big Green Drum (W. Florida Aikikai)
Location: West Florida
Join Date: Jun 2005
Posts: 2,619
Re: Direction of Groundpath

Mike Sigman wrote: View Post
Erick, you are assuming that because something is spiralling, in the original statement, it is forces.
No. Stresses, not forces. Moments before movement.
Mike Sigman wrote: View Post
That is not clear because it was not explicitly stated as forces. So my question is "what is spiralling?".
Not forces. Stresses. We only perceive the stress. Until a force results in stress we do not perceive it. I can put you in a airplane and do a constant 1g loop and you will have rotated 360 deg. vertically and if your eyes were closed you would not have known it, becuse the stresses in your body were constant.

Opposing unaligned forces in a structure create shear, and create a potential for rotation between them. Holding those forces from creating movement causes torsional shears, which when released cause movement. The stresses can be imposed externally by outside forces, or generated by the body holding a configuration internally without any external load, or the combination of the two.
Forces can result from release (relaxation) of the stresses to actuate movement, or -- when external forces are applied, they can be USED to develop these stresses in this configuration, so as to then apply them.

An applied compression (push), IF received in the compression spiral can be released by an extension in the tension spiral, without pushing back and simply compounding the compression. That seemingly unrelated release creates an imbalance of stresses in the pusher, resulting in a rotation which compromises balance or an uncompensated moment which reduces the force of the push.

If I apply it along the critical shear line in the other guy so as NOT to create the perception of stress changes, I get free rotations and loss of balance -- the source of which is difficult for him to locate, like trying to say when the plane is upside down in the loop with your eyes closed.

Mike Sigman wrote: View Post
Until that is answered, shearing forces is looking for a nail when you are a hammer. Whenever someone asks me a questions nowadays that I don't know the answer to, I always say, "It is either angular momentum or shearing forces." Inside joke.
Since they are both aspects of the same thing, I am glad we both appreciate such self-deprecating humor.


Erick Mead
  Reply With Quote