Originally Posted by CHenry

Perhaps I was not clear to your reading. My comment about chain wrap pertained to an actual 54-22 double, not to the Schlumpf Mountain Drive. Having owned a Brompton with such a driveset now 10 years, I am aware how it is constructed, and its weight and operation. But thank you. As far as overlap on a 9x3, I have seen those gear-inch calculations and am well aware of the redundancies in those setups. But those have 27 steps from which a sequence can be selected to make reasonably even progression without excessive cross-chain stresses. With 12 "gears" across 550% gain (thinking the Brompton with a standard 3x2 + Schlumpf) avoiding redundancy is more important if you want to keep the spacing between gears reasonably short and even (the way other IGHs do--thinking Rohloff and Alfine 11 or 1x 9-12 setups do.)