I have several KH/Schlumpf geared unicycle hubs. They allow me to have two different speeds, and really have been a game changer for unicycling. One of my older hubs started to have bearing failure, causing it to rock back and forth in the wheel. This problem was fixed in later versions of the hubs, but I didn’t want to get another one and the hub is way out of warranty. But by chance I happened to have a set of good bearings (long story), so sometime last year I opened up the hub and replaced the bearings. No problem!
I finally got around to getting the wheel built up (thanks Ken) and setting it back up in my KH24. During my first ride, the shifter was occasionally getting stuck half way through the shift, causing the unicycle to freewheel. This is quite bad! I popped open the hub again to see what was wrong (luckily, the wheel doesn’t have to be unbuilt):
I’m not giving away any trade secrets by posting these photos; the hub was featured in “how it’s made” a while ago.
If you look at the shaft, it has a small hole on it on both sides. In each hole there is a ball bearing and then a spring. The spring is held in place by a sleeve over the shaft. I think when I took off the sleeve I didn’t notice that there were two springs, and one disappeared. So, I was missing a small spring.
I couldn’t find the exact spring, but Mc Master Car had one pretty close:
9434K12 Music Wire Precision Compression Spring, Zinc-Plated, .250″ Length, .12″ OD, .016″ Wire, Packs of 5
About $5 for a pack of 5, but I also ordered a stainless one too. This one is a little tight, but worked well enough, and I think it fixed the problem (I’ll find out when I ride again)