Gone Fishin'

HEY!

I'm not actively blogging here anymore. But if you got here because you were searching for something about bikes, you might want to check out my latest project, Vermont Goldsprints. In summer of 2014, I bought a used goldsprints racing setup and have made it a mission to get more bikes in more people's faces by putting on fun races in unexpected places. Come join me!

7.17.2009

Dan's CVT Road Bike VI: Shifty


Author's Note:  I tried to post this earlier via email and it seems to have just gone down the rabbit hole.  Apologies it if shows up again resulting in a double post. -Matt

I got some work done on Dan's bike last night.  I installed the shift pod on to the rear hub (the unit that actually rotates the shift rod inside of the hub) and I ran cable and housing up to the controller on the handlebar.  That doesn't sound like much, but with this hub and on this bike, there were special complications.  

The Nuvinci uses to cables to shift, which allows the shift rod to be turned in both directions without the use of some sort of return spring. The shift rod is rotated when one or the other of these two cables is tightened.  The way this works is that there are two pulleys on the shift rod, and each cable wraps around one of the pulleys with the wraps in opposing directions.  This means that the length of the cables and their respective housings needs to be set carefully, and that I spent some time on the floor of my basement with a steel ruler, trying to get exactly 230mm of cable between the end of the housing ferrule and the outer pulley cable stop.  I got it though. Once the pulleys have been wound and installed, an outer housing goes on over them, and the whole thing takes on the look of a neat little package. The entire shift pod can be removed from the hub without opening the pod up again, which means that a wheel or tire change should not result in any need to adjust the shift cables. 

I mentioned before that because our donor bike started life as a single speed, there aren't a whole lot of braze-on cable stops available to re-purpose.  I installed a full run of housing from the shifter pod to the unit on the handlebars.  I put some of the housing under the bar tape, but alas, the cables supplied with the Nuvinci were not long enough to do a cable run completely under the handlebar tape. I went for the next best thing and ran the housing out under the tape to the down tube, where it will follow that tube under the bottom bracket before making its way out along the drive-side chainstay to the shift pod.  I finally have an excuse to pick up one of those cans of assorted zip-ties at Home Depot!  I'll need to zip-tie this housing early and often to prevent it from slipping around , especially in the region where it comes up under the BB and around the chainstay.  We don't want it getting tangles in the chain, on the fire, or in the cranks!

I tested the whole thing out and it the shifter turns smoothly and offers up the full range of the hub.  Once I get the housing all zip-tied on it will be time for a test ride!

Finally, I'll be rebuilding the rear wheel one-cross for a stronger and more durable wheel.  I'll do that last, though.  Dan may also want wider tires than the stock 23s, and I'm guessing 25's or maybe even 28's would work on here. Maybe we can shop and install when he gets up here later this summer/fall!