TurboTurtle said:
See #8 ("Ghost" or "Phantom" Chainring) on this site and tell me what is happening here. What keeps the CR in place?
Simple chain tension is holding the ghost-CR in place. The idea is that you use the ghost-CR as a wedge to tighten the chain to a point where it won't jump off the ghost-CR's teeth. When you pedal, the top of the ghost-CR is pulled toward the pedals, while the bottom of the ghost-CR is pulled towards the hub, which causes the ghost-CR is rotate in place.
I'm not sure if this technique would work with a regular track or road frame, which have rather tight chainstay clearance. It works on a MTB because they have rather wide chainstays.
