Originally Posted by
genejockey
I'm trying to imagine what you'd have to put on the inside of the big ring to lift the chain from 34 to 70 teeth.
I'm imagining something like a wooden clockwork, except the ring of pins coming off the big ring would spiral outward. It'd be hard to do it with a ramp pressed into the side of the ring (if anyone would dare bring to market a mostly solid ring that big) without pinching the chain and jamming it between the ring and the derailer.
For a grin, think of the possibility for massive chain suck and jams on a rig like that!