If you had a Thorn Nomad Mk1 with a Rohloff and it failed catastrophically in a far flung third world country, could the Nomad Mk1 bike be converted to take a front and back derailleur system at the local bike shop, or were the frames designed specifically for the Rohloff?
Except for some frame detail changes (i.e. sus-fork compatibility), my 2012 Nomad's drivetrain is essentially the same as a Mk1's so the following suggestions should work for you with one exception: I chose to have the disc brake cap fitted to the left side of the hub to "future proof" it so I more easily convert to a rear disc brake someday. This allows an additional emergency option I will detail below.
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Initially, I shared your concerns because I often ride in the remote parts of America's Great Basin deserts and Oregon's Cascade, Coast and Calapooya mountain ranges, Nevada's Pueblo and Ruby mountains, and northern California's Warners where there are no bike shops and those around the periphery have only the most basic supplies. I have also ridden pretty extensively in Eastern Europe and found shops there often stock only the most basic supplies and even things like 26in touring tires can be hard to find outside the larger cities, though you can usually count on finding a 26in knobby of Chinese or Russian manufacture.
Early in my Rohloff days, I carried one of these:
https://problemsolversbike.com/products/drivetrain/universal_-_21655 . Coupled with a thumbshifter/clamp-on downtube shifter or bar-end shifter, some cable ties, a long run of cable housing and a rear wheel with a freewheel or freehub from even the most basic bike shop, it would allow fitting a rear derailleur. Unlike some emergency derailleur hangers, the Problem Solvers one has a couple of grub screws that can be threaded in from the back side to catch on the dropout's edge to prevent the hanger from rotating around the hub's quick release until it is tightened. The hanger itself replaces the quick-release nut, so the grub screws are more a convenience than a necessity when fitting the derailleur and hanger to the bike before the hub q/r is closed.
As for the front, it is possible to fit a front mech and its own shifter to match the rear -- I did both as a trial and managed to get good shifting in my workstand when I had the same concerns as you. Depending on your crankset, you might need to replace the crankset's chainring sleeve nuts and bolts to accommodate a second chainring and your crankset might not have the inner lands to mount a third chainring. My Nomad has a 73mm wide BB shell and some front mechs don't have the range to fully shift across a triple crankset unless they are designed for a BB shell of this width. A wide-range "1x" setup with no front derailleur would make a more straightforward conversion.
I also found a small 4-bolt chainring can be fitted to mounts on the disc-specific left hand Rohloff hub cap if the hub is so equipped, allowing the bike to be used as a fixed-gear in case the hub's innards pack it in entirely. To do this, the hub must have the external shifter; the disc cap cannot be fitted if the hub has the internal shifter. The chainline is close enough to work when the wheel is removed and reversed left-for-right in the frame's dropouts. In field use, the eccentric can be shifted laterally slightly to improve chainline. Riding Fixed means you cannot coast, so that is something to keep in mind. I ride my fixed-gear road bike a lot even off-road, so this is not so foreign to me. If things really went bad, riding Fixed sure beats pushing a loaded tourer over some distance.
Of course, I always carry an 8mm socket wrench (one is part of the stainless multitool supplied with my Nomad that also includes a pedal wrench/eccentric bolt wrench and pin wrench) so I can manually change gears on my externally-shifted Rohloff in case a cable lets go. I also carry spare cables, cutters, and a little brass tube to size a replacement cable for making a replacement at a more convenient time.
Echoing PH, over time my confidence in the Rohloff drivetrain has grown so now I generally leave the PS Universal Derailleur Hanger home, though I will still sometimes fit the chainring to my hub's disc mounts...depending in where I may be traveling. Some of the roads I ply are traveled by car only once every six months to several years according to the District ranger stations, so it can be important for my peace of mind to have a backup I know will get me out in the worst of breakages. Knock wood, so far I've had
no problems of any kind with my Rohloff drivetrain.
I don't think you'll ever find it necessary -- because it is so unlikely a Rohloff drive will pack in completely -- but yes, in my experience it is possible to fit a rear derailleur or other emergency drive option to a Mk2 Nomad and it seems likely you could do the same for a Mk1.
Best,
Dan.
