Tim Fong wrote:
I have been following your discussion with some interest. I tried to draw diagrams to understand what you meant but I'm not sure that my physics ability is good enough to do it justice. You seem to talking about the resultant forces from geometric motions?
I am trying to work through concrete examples of the principles that I see. I have elsewhere tried to describe (very poorly, I might add) how the inputs and resultatns function for a "basic" shomenuchi ikkyo. http://www.aikiweb.com/forums/showpo...6&postcount=61
Tim had asked for a "free body diagram" in that discussion That is very difficult to do in this environment, but a careful description can accomplish much the same thing.
I will try the same kind of description of a "basic" katatedori kokyu tanden-ho movement. A couple of things I would like for people to keep in mind as I do this. First, consider nikkyo application, which I think makes a few things very explict that are otherwise implicit in all kokyu movement. The wrist is classically at 90 deg to the forearm, the elbow at 90 from the upper arm and the arm at the shoulder 90 from the torso.
We thus have a structure that is oriented in all three planes of rotation. The wrist rotates in the sagittal or vertically oriented anterior/posterior (A/P) plane; the forearm rotates in the medio-lateral (M/L or cartwheel) plane, and the shoulder rotates in the horizontal plane.
Nevertheless, the actual rotation of that structure in any plane need only be very, very small when applied with firm connection. With proper application this affects balance directly -- much less dependent on tension pain compliance component that we all know -- and have learned to LOVE. It is lovely, of course, but actually an incidental effect.
Place your partner in nikkyo and rotate the wrist gently about the joint toward your partner's head. Do not restrain the elbow at this point so that you can see the body's natural, unrestrained reactions. What you will see is that the application of the vertical A/P plane rotation at the wrist, creates the mediolateral rotation of the forearm about the elbow joint as the system attmepts to find a lower energy position (entropy). As the wrist rotation continues, its tension increases -- so does the elbow tension, and thus its rotation inturn in a perpendicular plane. Now you will begin to see the upper arm begin to rotate at the shoulder joint in the horizontal plane, which eventually carries the upper torso out of the supporting hip orbit, and giving kuzushi.
All of these planes of rotation are simultaneouly shifting orientation relative to the constant force vector of gravity. However, if technique is applied consistently throughout the movement and rotations, the relative orientation of induced forces in uke's body barely changes at all as the imparted rotation continues.
What you are seeing is the development of the ikkyo path in the body. What you are also doing is gyroscopic manipulation of the joint/body complex in three planes simultaneously.
Now the katatedori kokyu-ho movement is precisely the same, but done dynamically at a single point of contact, rather than with the more obvious semi-static cranks defining the orientation of rotation in all three axes. An initial linear offset is created in the wrist connection. This is the implicit equivalent of the wrist crank of the nikkyo. Then the kokyu movement of the arm follows the same spiral three-plane tumbling path of successive joint rotations from wrist to elbow to shoulder into the center of the body, creating the same ikkyo path progression.
I hope this helps visualize the rotations and perpendicular transformations that occur. These physical forces are not easily described by other by other than gyroscopic means. Essentially, the inital rotation creates precessional rotation in another axis which does so in turn to the third, which does so in turn to the original input axis at which time a three dimensional reorientaion of the plane system has occurred. This successive iteration of precessional transfromation on perpendicular axes occurs almost simultanwously throughout the entire motion of the technique.