Mike Sigman wrote:
So why not verify and let us know what you find. Here... do something simple. Analyse the simply thigh or chest pushes O-Sensei does on this video clip in terms of "gyro-dynamics".
They are pretty simple moves, yet they are the heart of kokyu-nage and without the spinning and turning of gyro's. Let's see some analysis.
OK. Not the best images for kinematics of hip gyration, but hey, what the hell ...
First- the attack is set in uke's Anterior/Posterior plane and it is oriented at a slight angle up from the ground.
I see five distinct movements by O-Sensei, all fundamentally part of kokyu tanden ho.
1) A set of the upper torso forward (and thus of the hips slightly back) which, is also a set of the hips slightly off line to O-Sensei's rear.
This slight teeter is rotation in uke's Medio Lateral M/L (cartwheel) plane, in which his attack is not oriented. It cannot be easily seen from the video, but my experience tell me that uke's attack is now slightly offline to his left, i.e. -- the vertical plane of his attack has been shifted left (counter clockwise) about the horizontal plane, by virtue of a rotation in the M/L plane. As a result his balance center is now left of the line and forward.
2) A horizontal gyration (tenkan) of the hips creates a draw rotation of uke tipping him forward toward kuzushi and left (on one limb of the hips' natural figure eight pattern);
This rotation by O-Sensei is in uke's horizontal plane, in which his attack is not oriented. It creates an increase of the A/P moment forward, which leads to further precessional aggravation of the left rotation of the line of attack. Uke is precariously in the edge of kuzushi to the left front.
3) The set of the hips is brought forward again as O-Sensei's torso straightens, warding uke's balance center from collapsing left of the line but closing the center line from recovery forward and right.
This slight reverse teeter is, again, rotation in uke's M/L plane, in which his attack is not oriented. This creates an opposite moment in uke's horizontal plane of rotation (clockwise) from the first teeter but now uke's balance is yet further forward and the rotation moment primarily brings his rear balance component in line along the left edge of that balance envelope. Uke now has virtually no moment arms against the ground to resist further rotations.
4) Then the natural return gyration (irimi - the other limb of the figure eight balance envelope) tips uke into rearward kuzushi and carries uke around out the back of his balance envelope along the left edge along the ikkyo line of the body in a rear roll, to effect the projection outside of his balance system.
The reverse of the first rotation in uke's horizontal plane yields the reverse rotation about the A/P plane, a toppling moment backwards.
5) O-sensei gives a firm irimi closure lean of the thigh out the ikkyo line to ensure the projection and "send him on his way."
Mike Sigman wrote:
I can do and explain these things without resorting to angular momentum in any meaningful way, yet I don't consider myself particularly skilled. Perhaps I am just simple and ignorant... alas.
OK. Do that, please. Five easy pieces. No Japanese other than irimi tenkan and kuzushi. Not just what happens but why. Your turn.
Meanwhile I will work on the chest push. I can see it is the same, but the descriptioin needs to be laid out.