Introduction: Quick Fix for Broken Shift Cable on NuVinci CVT Hub Using a Hair Tie
The NuVinci® hub is an innovative and low/no-maintenance continuously variable transmission (CVT) gear system for bicycles. For its functioning see the manufacturer's website at www.nuvinci.info. Worth to mention here is that not only the hub is innovative, but also the handle, which gives user feedback through a cyclist in a changing landscape, see the lower-right picture above. According to the manufacturer's website “the name NuVinci (is) a tip of the hat to Leonardo Da Vinci, who sketched in 1490 what many believe to be the first CVT transmission”.
In the rare case where the shift cable is snapping off, the gear settles in its preferred position: the low gear. This is really uncomfortable, since only low cruising speeds can be attained while pedaling at high revolutions per minute.
This Instructable shows how the hub can be fixed in its high gear position, using only a hair tie. In this way it is more easy to get home or to reach a bicycle repair shop. This quick fix can be performed while being on the road, no workshop is needed.
If you are riding a bicycle equipped with a NuVinci® hub the take-home message of this Instructable is to never leave the house without carrying a spare hair tie, for example by wrapping it around the handlebars. Riders that are less risk-averse in nature can use the information in this Instructable as an original conversation starter in the streets, in the uncommon event of a snapped cable (and not having a hair tie or rope at hand).
The approach has been tested on an NuVinci® N360(TM) hub in an Urban Arrow® cargo bike, but is likely to work as well on other bicycles.
In this Instructable Step 1 explains the positions of the gear shifter, Step 2 explains how exactly to fix the hair tie and finally Step 3 dedicates some words to the license of this Instructable.
Step 1: Positions of the Gear
The NuVinci® hub is a continuously variable transmission (CVT). The hub's control ring can rotate freely over all positions, ranging from 12 o'clock (low gear) anti-clockwise to approximately 5 to 6 o'clock (high gear). When one of the shift cables snaps, the preferred position of the hub appears to be the low gear (i.e. low gear ratio), which only allows low cycling speeds. For riding more fast it is required to fix the control ring with its notch at 5 to 6 o'clock.
The next step illustrates securing the control ring in the high gear position using a hair tie. In this way it is more easy to get home or to reach a bicycle repair shop.
Step 2: Positioning the Hair Tie
This operation should be performed when the bicycle is in a standstill position and is only easily possible when the construction is freely accessible (i.e. no hub cover in place). First, make sure that a notch is available for placing the hair tie. Remove the control cable if needed, see first picture. Hitch the hair tie in the notch as indicated in the lower-left picture. Wrap it around the frame and then fix it to the axis nut. If the hair tie is too long (i.e. the tension is too low), wrap it around the nut several times as indicated in the lower-right picture. Obviously, the shifter handle doesn't work anymore after this fix because the cables have been detached (at least one of them was broken anyway). After this fix you'll be able to ride only in the high gear. But as already mentioned: this is usually (at least in flat landscapes) more comfortable than in the low gear, which is the preferred position of the hub.
Step 3: License
This Instructable is being made available through a Creative Commons Attribution (CC-BY) license. Republishing this Instructable is allowed, provided it is being attributed properly (cite the name 'openproducts', link to www.openproducts.org or www.instructables.com/member/openproducts or the original Instructable. For other arrangements send a Private Message through the instructables member page (www.instructables.com/member/openproducts).
The pictures in this Instructable show two commercial and registered objects: a NuVinci® N360(TM) CVT hub (www.nuvinci.info) and an Urban Arrow® cargo bike (www.urbanarrow.com), which have been referred here for completeness but are not part of the CC BY license.
If this Instructable infringes any rights then refer to Article 28 in the Terms of Service (www.instructables.com/tos.html).