I'll see if I have the bobbin mechanism around. I have a few machines here for parts, but I can't remember if any of them are self winding. If they are, I can either try a disassembly, with pictures, or send you the mechanism.
I like the idea of the twist apart, as emptying a bobbin, but I wind more often than I manually empty. It was good though when my dad bought me a machine and I had 3 bobbins only.