[Joe Johnson]

I would laser cut this thing before I tried to 3D print them. But even that seems a bit sketchy to me. As I recall (I have only held one in my hand once and it was years ago), the reason the device is a hoop and not a disk is that the hoop structure allows it to become an ellipse and thereby add some springiness to the system. As slack becomes available the ellipse gets more round and takes up that slack.

Bottom line, this thing flexes. I think a 3D printed version is doomed to destroy itself over time.

Dr. Joe J.