I put the Schlumpf for Brompton Mountain drive in my M3L .. the big reduction gear is 150%

so the AW3 hub is run through twice.. a 50t acts like a 20t in low range..

but for real Bottom of the frame gearing you may look at the Pinion.

It has more in common with motorcycle transmissions than planetary variations of the old 3 speeds.

http://pinion.eu/en/ 18 speeds, frames are made around the gearbox, centered in the BB area, like

http://www.en.tout-terrain.de/bicycles/silkroad-xplore/

http://www.en.tout-terrain.de/bicycl...ricana-xplore/

the guys that developed it were with Porsche , I read.

Schlumpf has transferred the Manufacturing of his stuff across the border to Germany

as the CHF , home of the secret numbered bank account was stronger as the rest of the continent
was pushed into Austerity plans , which makes Swiss Exports over priced.