Oh dear, oh dear oh dear oh dear.

Hello,

A couple of days ago i tried some different crank lengths, and of course managed to **** ** the threads on the hub. My almost new UDC Max Traction… sob
Well, if i was an optimist i could always think that this is a great oppertunity to learn to ride long-distance one-footed, or wheel-walk and some gliding. But i’m not…

According to my bank account my options are:
A. Weld crank to hub and rebuild wheel when my wallet is big enough for new hub and cranks.
B. Fix the threads. (No idea how).
C. Become an optimist…

Any tips or suggestions? I can’t be the only one who have messed up this?

/Kenny

I’m afraid I’ve got no experience with fixing threads, but I was wondering what you did to damage them as it may help others to avoid doing the same thing.

Re: Oh dear, oh dear oh dear oh dear.

Definitely not; I think I’ve actually heard of more people destroying / damaging hubs this way than bending them. I did it to my Max Traction, by forgetting to remove the nuts before trying to remove the crank with the crank remover. Overtightening of the nut will probably do the same thing.

If you get the crank(s) welded on, sooner or later you will have to replace the lot for one reason or another, including the price of a new set of cranks. I’d definitely try to find some way of getting hold of a new hub, even if it’s a cheaper one rather than a suzue; if you’re not doing big drops I don’t think there’s any difference.

Phil

Either i tried to tighten it to hard, and/or the bolt wasn’t properly in place when i tightened it.

Never underestimate the damage a hungry and tired Kenny can do…

Take it in to your local bike shop and see if they can help you out. In my early days working at the bike here I stripped the thread on a crank arm and Gary fixed it for me.

Good luck,
Andrew

you’ve had it

welding will knacker the heat-treatment.

Either buy a new hub or possibly get an engineering company to braise-up the threads with some high-strength nickel-bronze rods and re-cut the thread.

Re: Re: Oh dear, oh dear oh dear oh dear.

Yep, that’s how I did mine. I was getting a click on one side. I thought it was the crank, so I torqued it. Must have been the pedal or a spoke.

I stripped some of the threads on the hub and most of the threads on the nut. The hub will still hold a (replacement) nut, but now I’m nervous about changing cranks, since that would put the remaining threads to the test.

I never managed to strip b*cycle cranks/bottom brackets, but I guess the materials are different.

Re: Re: Re: Oh dear, oh dear oh dear oh dear.

Most bike crank spindles have internal threads and a retaining bolt. While most unicycle hubs have external threads and a retaining nut. A unicycle hub with internal threads (like the QU-AX hub) would be less likely to have the threads strip.

I’ll attach a picture (that I stole from Jagur) of the QU-AX hub with internal threads to show what I’m talking about.

e_mnabe.jpg

Kenny

if there is still a couple of threads left at the bottom that are still there,you may be able to beat or press the crank arm on with a wooden mallet/clamp just far enough to catch the last of the threads with the nut.

before i learned to beat them on every time then tighen the nut,i did just what you did.the threads on uni hubs seem weak and the chroming process makes them brittle.

Is there a good reason for this? The bike system of having internal threads seems more logical to me, maybe it’s just because it’s what I’m used to.

Edit: Of course, one of the advantages of internal threads is that you can’t leave the nut attached whilst using a crank extracter :wink:

Bike crank spindles used to be made with the external threads. It’s an older design. Then the bikes switched over to the internal threads. My guess is that the unicycle hubs just haven’t bothered to make the redesign yet. It may also be cheaper and easier to make unicycle hubs with the external threads. Since companies like Suzue already have the machining and tooling set up to make the external threads, why change?

I do hope that companies like Suzue change over to the internal threads for their unicycle hubs. It’s a better design. Maybe one day…

That one day is today! Cokers have internal threads. Yet another reason for its superiority over a 29er :stuck_out_tongue:

But you can leave the washer in place once you have removed the bolt… I would have thought :roll_eyes:

nick

only some of them,another reason for better resale value when selling it for a 29errrrrrrrrrr.

I made the uni.5 axles with internal threads because I could tap them MUCH deeper than the external threads on an axle extend. This gives alot of pulling strength to that connection and, since the threads are internal, if the bolt is kept clean for installation it’s likely to stay clean. I have three times the thread length contact with the internal threads as opposed to the unicycle standard external threads. Removing material from the end of the axle and replacing it with a bolt weakens that area somewhat.

I (probably erroneously) thought that it was a cheaper way to go also. Steve Howard told me that for production purposes it would be easier and cheaper to make the axles with external threads. I think bicycles went to internal threads to keep them from being constantly exposed even though the production process may be more costly.

most of the low-end bykes still come with threaded axles,i have a bucket full of them.

It will be possible to drill and tap the end of the hub, then just use a bolt, but you’d need to find a ‘better than average’ machine shop who can handle hard cutting (machining heat treated materials). A good machinist should be able to do the job without taking the hub out of the wheel. Ask around a few engineering firms, and you’re bound to find someone. (hopefully someone who’ll do it much quicker than the bloke I use!!)

it’s got to be the cheapest option, so it’s worth a try first

I can ride it again. :slight_smile:

The local ‘better than average’ machine shop had a rubber hammer… I’ve always wanted one of those, now i’ve got an excuse for getting one… :wink:

/Kenny

it’s the fact that the whole axle is hardened as one that makes the threads brittle. They’re as hard as the faces of the square taper, they shouldn’t be.

Chroming it makes no difference at all.