jabbado:
I was hoping you'd see it.
Saved the link to my favorites. Thanks for sharing it! I could picture that mechanism in my head because I have seen it before on coil-widing machines, but couldn't remember how it reversed direction.
The only limitation to it is that the OP mentions variable widths. This could be solved with a square shaft that he can slide on different lengths of these at different points depending on how many piles he is trying to make and how wide.