One rattle down, one to go

It's amazing what a small thing can cause a rattle, and how hard it can be to find. After I shimmed the rack piece as described in the prior post, the rattles were reduced. However there was still a bright little chnk! from the back on every pavement irregularity. And we have plenty of irregular pavement.

After wednesday's ride to the gym I spent some time pounding the rear rack with my fist again. There is a tiny bit of movement in the battery on its track, but that didn't seem to be the source of the higher-frequency noise. Eventually I found my way to the lock.

The battery has this lock whose only purpose is to secure the battery in its rack. You can't pull it out without unlocking it. (It isn't an "ignition" lock to enable the system; the system is enabled anytime the battery is mounted.)

So it turned out that the cylinder in the center of the lock has a fraction of a millimeter of play and it makes a noise when it vibrates. I proved that by shimming it with a bit of post-it note:

That shut up the high-pitched rattle, making today's ride quite a bit less noisy. There is still a lower-pitched clunk on the heavier bumps, which I need to investigate further. I suspect it may be coming from where the rack is braced to the Cobra seat braces. (I am coming to realize that the BionX rack-mount battery, although a tidy and esthetically pleasing design, has one problem: it places the heavy battery directly over the rear axle, where it gets the hardest ride and most vibration.)

Anyway the remaining noise is not as annoying. I don't know quite what to do to permanently stifle the lock, either. That purple post-it can't be a permanent fix.

Oh, another mechanical issue. Wednesday while I was drinking coffee at a coffee shop on the way home from the gym, and out of sight of the bike, somebody or something caused it to fall over. I found it on its side when I came out.

No obvious damage was done, but when I righted it and sat down, I found that the chain had hopped off the chain ring and jammed itself inside the small ring. (Might not have happened if I wasn't riding without a chain idler. The new idler came today.)

I yanked the chain out and got it back on the middle ring and rode home, thinking nothing of it. But today I noticed there was no cadence read-out on the computer. And a quick check revealed that the cadence magnet that I had so cleverly installed on the inside of the small chain ring was absent. It probably got forced off when the chain was jammed. So now I have to replace that.