Two-cable IGH spring return a viable option?
Refer to the diagram below. For a NuVinci n360 you have two shifting cables, the underdrive and overdrive. It seems to be it is possible to use a spring or counterweight to pull the underdrive and then use a conventional shifter for the overdrive (may require modification/consideration for full length of pull). Is there a fundamental reason this couldn't work? Have people tried? A few Googles turned up fruitless.
The difficulty I can see is the 120mm draw length of the cable. The system may need to be a bit more elegant than a single spring.
Open to suggestions (I hope this has been done before, success or otherwise)
your lever would need a capstan circumference of 5 inches or take multiple revolutions... (that 12cm)..
how about a pully , 2 housing frame stops, and a loop of cable.. will do the job, I suspect ..
use a bare cable run and attach a ball to it to pull /push
or a big ol' stingray shift lever to pull .. with the distance to lever pivot say 3~4x the cable pull ..
of course, a servo motor could turn that capstan and then you just need a rocker control button
or up/down pair. and a battery ,,
Last edited by fietsbob; 01-21-14 at 09:47 AM.