Strida single speed - upgrade to 2-3 speeds possible? Would it be possible to upgrade a single-speed Strida to 2-3 speeds?
I know there is a Strida model with 3 speeds but the frame is different with respect to the one of a single speed. In particular, the 3-speeds model has a bottom bracket shell suitable to fit a Sturmey Archer KS3 (https://stridacanada.ca/product/sturmey-archer-ks3/).
Do there exist commercially available alternatives to fit in the bottom bracket sheel of a single speed?
Someone did it already, but they are unreachable. This is the post (in italian): http://stridaroma.it/it/works/kit-upgrade-2-speed/. This is the google translate version. If only I could de-focus this picture!

This is a closeup of the bottom bracket in place and the frame of a single-speed Strida.

Thanks,
Luca
3-speed is possible, but not at bottom bracket without heavy modification to the frame. The usual location for 3-speed gearbox is the rear hub. As far as I can tell, one could rebuild the rear wheel with suitable 3-speed hub. Running the shifter cable to the hub might be complicated with the folding frame, but I don't see how it would be more difficult than running it to the bottom bracket. Some models already have disc brakes, which also suggests that you can run a cable to the rear hub. If disc brake is not required, another option would be kick shift 2-speed hub. These things have a coaster brake and shift gears every time you brake, no cables required.