Uh-oh, I think I’m in trouble. You know the part of the crank arm that the crank puller threads into?
The crank arm has been dinged at this whole after several crashes.
The metal from the dings has pushed into the threads.
The top couple of threads have deformed segements.
The tool is unable to screw into the crank.
WTF do I do now?
What size of a thread-making tool (if this would even be possible) would I need?
Thanks
I think I would try to do it with a two-armed bearing and wheel puller rather than trying to rethread the crank while it’s attached to the axle and hub. Also, I don’t know what that thread dimension is. If you can get it off with the bearing puller by grabbing it from behind then you can throw the crank in the trash where it probably belongs or get it rethreaded then.
Thanks for the reply. But, could you please go into some detail about the two-armed bearing and wheel puller? what it is? how is it used? Where I can one be found? Thanks
Here are some images of wheel and bearing pullers available in most autoparts stores for not too much money. Maybe you can borrow one from a shop or a friend. I think the one in the upper left hand corner is a two arm. A three arm might work but I think the long part of the crank might get in the way.
http://drp.localweb.com/images/133.html
Or, maybe rent one?
Unicycle.com also sells a bearing/pulley puller.
http://www.unicycle.com/shopping/shopexd.asp?id=419
I use this tool to remove my splined DM cranks and Profile cranks. Should work just fine to pull off square tapered cranks. A good bike shop should have a similar bearing puller on hand.
After you manage to get the crank removed it should be possible to get those threads retapped to clean them up. A good bike shop should have a tap of the right size. It’s not unusual to strip those threads so a good bike shop should already have the tools.
If the threads are really chewed up it might be necessary to use a helicoil. I’m pretty sure there are standard helicoils for that thread size. But if you have to go through the trouble of putting a helicoil in then it might be easier to just get a new crank if it’s not an expensive crank. And again, a good bike shop should have the right helicoil and be able to install it.
john_childs
Oh oh, I got the tool (thanks guys) now here’s problem #2
The bottom of the crank - that the 'armm’s of the tool fit onto are rounded. there is little room between the bearing and the crank. the tool ceeps slipping. resting the ‘legs’ on the other side of the bearing would fit, but this will pull the bearing and crank off together (in theory)
My limited experience doesn’t allow me to decide on my own if this would be hazerdous to the bearing.
Any other techniques to get that in there?
Is it a good idea to just try and ‘cut’ the crank arm off? Maybe a grinding disc, or juigsaw? I’m thinking a cut down to the spindle to the top spindle flat, the the right. This would take off the whole corner , and, in theory, have the crank fall off.
Problems:
2)I don’t want ot risk cutting into the spindle.
Any ideas?
Re: Crank on Permanently?
To get a crank off without a puller …
Take the retaining nut off and ride your unicycle until you feel the crank
start to work loose by itself.
High pressure in your tyre will help you notice the right moment.
Leo W
The only problem with riding it now…
The reason I need to get the crank off is the pedal hole is wrecked.
(note to everyone) Check the tightness of your pedals! Not even just when you put them on. Mine had been on for months, and I guess they were loosening off.
My pedal fell off, leaving a hole with no threads in it!
I can’t get a pedal on, and I can’t take the crank off! 
If you can’t use pedal motion to loosen the crank you could try alternately tapping each side of the crank end with a rubber mallet to mimic pedal pressure. Make sure it’s made of rubber, plastic or leather and not metal - I know you no longer care about marking the crank but a metal hammer could stress the axle and cause it to break later. Don’t wallop it hard assuming one blow will fix it, just use medium weight and lots of taps to slowly work it loose. Be patient and the taper of the pyramid axle will work the axle off.
If the mallet doesn’t work then you will probably have to pull the crank by pulling the bearing as well. You might get lucky and not damage the bearing. But even if you do, a bearing is not that hard to replace - much easier and cheaper than a new axle.
Of course if its a profile splined axle you could bang away at it all day and it’ll never come loose this way - only the bearing puller will work.
Bad idea to use any kind of saw. Too easy to misjudge or slip. Put a notch anywhere on the axle and you’ll set up a weak point where the axle will eventually break.
Noel-
What about one of those tool marking etchers? You know, the ones that vibrate and make a hellacious noise and then scratch your name onto hardened metal tools. I wonder if that would work the crank loose. I think maybe all of the energy would be dissipated at the surface because the frequency is so high. Maybe an orbital sander with just the pad. That’s a longer stroke and lower frequency and larger surface area.
OK, Sofa. Get something wedged in between the bearing and the crank to pre-stress the crank. A wooden wedge maybe. Then press an orbital sander pad up against the crank and vibrate the hell out of it.
Re: Crank on Permanently?
You may be able to clean up the threads with a
“thread restoring” or “thread repair” file, followed
by a tap.
You’ll probably want a “hand tap”, one without
the pointy end on it. You need to measure the
hole diameter with inside calipers, and the
thread pitch with a thread pitch gauge in order
to select the correct tap/file size. Most of this
stuff should be available at auto parts stores.
It may be less hassle to take the Uni to an
automotive machine shop and have them
do the job. I’d expect they could do it
for $20-$30, about the cost of the tools
you’d need.
Well, I’m gonna call an auto shop or something. I’ve been hammering away for about 2 hours now. You see Castaway when Tom Hanks finally gets the fire going? Well it’s like that…but with no fire!
Re: Crank on Permanently?
Did anyone mention that maybe you should try simply riding around with the
axle nut off, it should come off eventually. Drops would speed it up?
Sometimes auto repair shops think unicycles are cool and will help for free.
I still like the idea of vibrating it off. If you have someone to help you and you don’t like the wooden wedge idea to pre-stress the crank, try this as a vibrating aid. Have your assistant place the blade of a large (largest possible) screwdriver against the INNER race of the bearing. There should be a stop on the axle so the bearing won’t go in towards the hub. Pry between the INNER race and the crank while you vibrate it. I think it will work loose like that in a jiffy (where a jiffy is an undefined but reasonably short period of time).
Re: Crank on Permanently?
I did grind off a crank once. It took forever and I had the use of a good 4
1/2 inch angle grinder. I did it with a sanding disc because that is what I
had handy. I was careful to only grind just far enough to not quite hit the
spindle. I found I did not have to quite grind through the crank as the
grinder made so much heat that the crank worked loose before I was actually
grinding on the spindle. I do not recommend this method except as a last
resort. I do not know what the heat of the grinding might do to your bearings,
although bearings can be replaced. My bearings were not harmed. It was a
Schwinn unicycle.
A propane torch might be better. Try some Liquid Wrench or other penetrating
oil.
Good luck,
Idaho Joe
Yay, I took my unicycle to my friend’s house. He has a mapgas(something like that) / oxygen torch. He heated the crank up for about 1 minute. 3 or 4 bangs with a hammer, and it was off.
Man, I hate not knowing anything!
Thanks everybody for your input, now I have some hours to make up!
Later