Aviner unicycle with stripped hub?

Got a 20 inch Avenir Muni last summer. Was riding it recently and trying some ground tricks and suddenly I go down like brick. The cranks slipped inside the hub (I think). I’ve done several searches on the web to see if this is a common problem, however, I haven’t been able to find anything except one thread and I don’t know how that was resolved. I am mechanically inclined, but it requires special tools to take apart. But I’m not really sure what I would find inside anyway. The cranks aren’t completely free to spin in the hub… there’s still significant friction, but under higher loads it slips again. Any advice or links to this subject or problem would be greatly appreciated!

Ouch, hope you didn’t get hurt too badly.

I strongly doubt the hub is repairable as it has slipped. If the hub is welded together, the welds have failed. If it is splined, the splines are worn down to the point they will slip.

My personal recommendation would be to either replace the hub or the wheelset. Replacing the hub would be time consuming but cheaper plus wheel building is a useful skill.

With any replacement, measure the outside of the bearings. Unicycle frames are designed for specific bearing sizes (40mm for cotterless, 42m for ISIS and occasional wierd ones).

I have one of those unicycles, the hub is junk. After just a little light riding I had already twisted the axle so that the cranks weren’t lined up anymore.

I replaced it with a UDC hub which has been fine for a couple of years now. I don’t ride it hard but I do hop up and down curbs and such with no problem.

Replacing the hub does require rebuilding the wheel; a bike shop could do it if you aren’t comfortable doing it yourself. The hub isn’t expensive, and the rest of the unicycle is still doing fine, so I’d say it’s worth it.

Pictures of the hub would help a lot.

What is slipping exactly?

Is it a spool type hub with a spindle that goes through a spool that has flanges on it?

Is it a more traditional hub with flanges welded to the spindle, or that “should” be welded to the spindle?

If it is a spool hub there is probably a key way, and you may be able to replace the key, and use a little loctite made for press fit keys.

If it is the more traditional type the flanges can be welded to the spindle. You would have to take the wheel apart to do this, and it could result in weaker flanges.

Pics of Aviner hub

Thanks all for your quick replies:
Hub is stamped with “yongling”. Bearings are 40mm. Pics attached.

Options seem to be:
1/ get a new hub and rebuild wheel. Any recommendations on hub?
2/ try to repair the current hub

Either way it seems I need to invest in a crank puller and something to remove the bearings

If you want a quick, dirty, and probably won’t work for long solution, you could try dripping some LocTite green sleeve retainer (#680) into the interface between the through axle and the hub.

from the pictures it looks like you may be able to pull the bearings and weld the flanges to the spindle without taking the wheel apart. That would be a pretty quick repair, and it should fix the problem for good.

I have no idea what it would cost to have it welded, but if you know someone with a welding rig it might be somewhere between cheap and free.

Yes, you should have a crank puller anyway! I started using mine a lot more often after I began unicycling, and at that point I also discovered that a crank puller without a handle is better: it takes up far less space, and it doesn’t require you to remove your pedals every time you remove your cranks.

A bearing puller would probably be a good thing to have as well, but I don’t have one, so I won’t preach.

As far as the other questions you ask, you seem to already be in good hands here. From info available on this forum (plus a few links), I learned how to build a good strong wheel, and it almost never even needs truing, so if you do decide to go that route, do not fear!

Bearing puller (45mm at jaws) £3.48p = $5 appx
http://www.ebay.co.uk/itm/2-65mm-Two-Jaws-Gear-Puller-Bearing-Disassembly-Tool-Spiral-Technology-QW-/322356301947?hash=item4b0deed07b:g:C0QAAOSwiDFYQN4T
Note - take the retaining bolts out and hold the puller with your hand when fitting the puller around the hub spindle

Crank puller £2.50p = $3 appx
http://www.ebay.co.uk/itm/Bike-Crank-Puller-Bicycle-Cycle-Wheel-Repair-Extractor-Remover-Pedal-Tool-UK-/111988905827?epid=1368298424&hash=item1a130f1763:g:hkkAAOSwSclXLI1K