Originally Posted by bostontrevor
........What about extra deep threads so that you can run two cogs (ok, so your chainline would be messed up, but...)?
For an engineering challenge, why not bring back a 2-speed fixed hub? You could have your 2 cogs (effectively) without screwing up the chainline. Make it so the gear change is done by a small lever or knob on the hub (I can't see many fixie riders adding a shifter and cable to their clean bikes). Naturally you wouldn't be able to shift while riding but it would still be easier than changing cogs.....and cleaner looking.
Jim