Originally Posted by happycheapskate
It would be much easier to design a 2 speed internal gear hub (like a mirror of the conventional sturmey archer type), that took a standard BMX RH freewheel on the RH side.
In fact its possible that some existing planetary hubs can be reversed or modified, and threaded to take a standard freewheel . I saw a article called The Dancing Chain about a wierd bike that had 2 chains and used a modified IGH like that.
This would eliminate the VERY dangerous proposal of a left-handed rear mech and the large freewheel necessary. (The larger a freewheel cog), the "more" it wobbles!
Sturmey Archer S3X 3 speed drives backwards and forwards and can use a Cog, not threads( it can use threaded freewheels too) , on the left side.
YOu could not only get three speeds, but you get a bumpstart out of it too.
Also, if you remove the brake chucks or use a freewheel 3-speed, you can drive them backwards too.
Nexus tricycle transmission jack-shaft for the win!