Re: What is "Aikido"?
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? Have you tried motion capture or something like that, or any attempt to actually measure the forces you're talking about? Not trying to be antagonistic, I'm genuinely curious.
Re: the pressure/spring stuff. I don't actually look at the pressure stuff as a model. Rather it is a feeling in the body that is recreatable . Unfortunately, no I don't know how to measure it, or even what is causing it. What I do know, however, is a method that another person could use to recreate the same feelings, and then, using that feeling, perform a technique which he/she otherwise could not perform. It's more a training method than an analytical model.
Again, I want to re-iterate-- it is NOT a model or even an analogy, but a way of training. I would certainly like to find out how and why it works.