3d Printed SRAM TT500 Friction Mod

Download this design at Thingiverse here:
http://www.thingiverse.com/thing:507900

So - about a year ago I bought a touring bike - a Novara Randonee.

I had just assumed the included SRAM TT500 bar end shifters had a friction mode. Having the option to friction shift is one of the big reasons touring bikes tend to have bar end shifters.

Friction shifting is nice because:
- It's less prone to have issues with adjustment
- It's tolerant of minor mechanical issues like worn cable housings, stretched shift cables and event bent derailers.
- If needed - you can even swap out whatever cassette you can find in the middle-of-no-place - and still shift it. 7-speeds? 10-speeds? Friction shifter don't care.

So - I was disappointed to find out the SRAM TT500 does not support friction shifting. In fact - it's really intended for go-fast "time trial" (TT) bikes. To boot - it seems to not be totally-rock-solid. I've broken a "spring" - and have read multiple reports of others doing so online.

It's almost like Novara chose the TT500 shifters so they could sport the touring look. Thanks Novara.

Enough complaining - how can I fix this?

I figured since I previously 3d-printed a pretty-good friction shifter from scratch - it should be possible to modify an existing index shifter for friction mode.

Several OpenSCAD fugue-states and a few 3d-prints on my Replicator 2 later - and I had a working design.

Download this design at Thingiverse here:
http://www.thingiverse.com/thing:507900

I've put about 200 miles on this mod with no adjustments. I suspect it's probably good for a couple-thousand miles with periodic adjustment. Certainly good enough for use as a backup option.

The TT500 is a 10-speed shifter - and it might not be intuitive that a friction-shifted 10-speed would work well. In my testing - I had few problems with it. I landed between gears about as often as I did friction shifting 7-speeds - and correcting was easy. When things are working well - I prefer indexed shifting for 10-speeds - but really like knowing I have friction as a backup.

I printed my design out of Taulman Bridge Nylon. Taulman Bridge is a great filament that's nylon-tough - but much easier to print with than other nylon filament. Specifically - it seems to have fewer issues with platform adhesion / warping - and is more resistant to moisture problems.

There are two parts to the design - I suggest printing them separately as nylon tends to "string" a bit.

I also did a test print out of PLA - which worked fine. Suspect the nylon version will last longer - but you can always print a couple if you're concerned about durability.

I'm back to indexed-shifting for now - but I store the friction shifter mod parts in my headset - so I always have it if needed.