Saturday, September 21, 2013

Gear changer repair

The gear changer suddenly started sticking and I wasn't able to change the gear ratio on the Nuvici hub. This is somewhat ironic given my recent post about how cool the Nuvinci hub is with its continuously variable transmission. 

Anyway, the problem was that I couldn't twist the handle. Luckily Organic Transit included the users manual for the Nuvinci Hub which has a good description and pictures showing how to replace the gear cable. 

The first challenge was finding a replacement cable since the ELF has a very long cable. My local bike shop said its called a tandem shift cable but didn't have one in stock so I ordered one from Amazon.   

The next challenge was figuring out how to install it. There are actually two shift cables on the Nuvinci Hub and you have to thread the cable through a hole in the handle and wind it around a guide ridge and pull it all the way through until the grommet is seated in the housing.  I added some oil to the cable housing before threading the cable through to the end of the housing. There is a special clip that needs to be attached to the end of the cable which clips into the hub. The trick is to wait before trimming the cable until after all adjustments have been made. 

It actually took me two tries and a second replacement cable to get it right. The first one ended up getting frayed inside the handle just like the original cable. It appears that if the cables are too loose, they come off the runners inside the handle, and get caught up in the handle mechanism. So the key is to keep both cables relatively tight. The manual says to check the cable tension by pulling on the cable housing near the handle to see how much leeway there is. Then adjust the thumb screws on the handle to keep the cable snug.  I'll be sure to do that often now to avoid more broken shift cables. 

Here's the pagoda I pass on my ride home. It's near the old naval hospital in Silver Spring. 

Saturday, September 7, 2013

Fixing a front wheel spoke

One of the spokes on the front wheel broke inside the nipple so I had to remove the wheel in order to replace it.  It was a really easy operation only requiring removal of 3 hex bolts, one on the wheel and 2 on the brake. The disk brake caliper needs to be removed so that the wheel can be removed from the hub.  Here are some pictures of the front hub and brake caliper assembly after they've been removed. 

I ended up taking off both wheels so that I could have the bike shop check the tension on the rest of the spokes since they were making a creaking sound whenever I turned the wheel sharply.  I also let them replace the spoke which required the brake disk to be removed due to the location of the broken spoke on that side of the wheel.  The bike shop said that the wheel is built with an unusually large amount of dishing to one side and was curious to find out the recommended tension for the inside vs outside spokes.  I'll update this post once I get those numbers from Organic Transit.

After the repair was complete it took a while to get the brakes adjusted just right.  I found that the disk wasn't exactly in the same position on the wheel so I had to do some fiddling with the brake adjustments to minimize rubbing and squeaking.  Now they're working great and the spokes aren't creaking any more either.

Check out the nuvincii hub video

Ever wonder how the NuVinci Hub works?  I didn't think too much about it until my wife asked recently and I had to admit that I really had no idea.  So, I looked it up on the interweb and sure enough it's really cool.  Of course, I'd expect nothing less from Organic Transit!  Check out this demonstration which does a pretty good job of explaining the magic:

And here's a link to the full site:  Fallbrook Technology NuVinci 360