I finished building my long-planned 2 sprockets on a Sturmey hub experiment last night, using 2 x 3/32" Shimano Nexus sprockets, a basic derailleur chain and an old '70s Huret mech as I couldn't find a '50s Cyclo derailleur at a sensible price to use a 1/8" chain like I would have preferred.
All seemed to work very well last night so went for a test ride this morning and I was really pleased with the results and the gear change was surprisingly crisp despite the use of sprockets which aren't supposed to be used for a derailleur. I was busy congratulating myself when the spring in the mech to hold the tension in the chain decided to snap leaving me with a loose chain that wouldn't stay on and a 5 mile walk home in the rain. GRRRRRRRRR!