crank comes loose all the time!

Unicycles and Equipment
1

this is really starting to irritate me. I know unicycle cranks have a tendancy to come loose and I’ve read posts here on how to deal with it. But my left crank comes loose after about 20 minutes of riding without fail. I am constantly tightening it and even worse I’m constantly riding with it loose. My right crank is just fine, hasn’t loosened once.

I applied some loctite to it, and at that time also tightened it a tad more than is probably normal. That kept it fine for a little while. I guess the loctite wore off.

Is this normal? Do I need a new crank? It’s a schwinn 24" that I bought brand new about 3 months ago, everything on it is stock. I used to ride a schwinn 20" many years ago and I don’t remember the crank ever coming loose on me.

If nothing else, it’s very frustrating.

2

I doubt the Loctite is relevant as it will only stop the nut unwinding on the thread. Given enough persuasion, the nut will loosen anyway - it has to otherwise no one would ever use Loctite because they wouldn’t be able to remove the nut later if they wanted to.

My guess is that either you are not seating the crank properly on the tapered end of the axle, or the taper is damaged, worn, or faulty.

Try this two-pronged approach:

  1. Remove the other crank and refit it at 90 degrees to its original position. (Do it in this order so you have a reference point.)

  2. Remove the offending crank and fit it appropriately - i.e. at 90 degrees to its original position, and at 180 degrees to the new position of the other crank.

(My theory being that if the taper is worn, faulty or damaged, this will have been exacerbated by the constant loosening during use, and the wear will be distributed on the taper in one direction because the pedaling force is always in the same direction.)

  1. Now, before tightening the nuts, find a large block of wood and a heavy soft mallet - ideally wooden or rubber, but copper faced might do.

  2. Using the block of wood as an anvil, and perhaps asking a friend to hold the uni straight, position the uni so that the axle is vertical, with one crank resting on the block of wood.

  3. Now wallop the top crank at the centre to drive it onto the taper. The important thing with the hammer is to use the weight and balance of the hammer to deliver the force, and to strike confidently ‘through’ the target, rather than tapping away at it lots of times.

  4. Tighten up the nut for the crank you’ve just walloped on.

  5. Now flip the uni over and do the same for the other crank.

(What you have now done is realign the cranks by 90 degrees to counteract any uneven wear on the taper, then seated the cranks very firmly on the tapers, then tightened the nuts up to draw the cranks on fully.)

  1. Leave the dust caps off for now, and carry a 14 mm socket or use the crank tool and a spanner. Ride for a bit, idle for a bit, but don’t wait for the cranks to feel loose. Then nip the crank nuts up just that bit tighter.

(You will find that crank nuts come loose every few hours of riding anyway. I seldom ride anywhere without the necessary tools, because riding with a loose crank is annoying, and it damages the crank or, worse still, the taper.)

Good luck.

3

Re: crank comes loose all the time!

tortoise wrote:
>
> this is really starting to irritate me. I know unicycle cranks have a
> tendancy to come loose and I’ve read posts here on how to deal with it.

With all this talk of loose and worn cranks, I am wondering how long I
can expect before I need to perform some maintenance on my own. Since I
am just learning I will probably stick to the pavement for the remainder
of the summer. However, next summer I would like to maybe get a MUni and
give that whirl.

So is the crank problem a MUni thing, a Uni thing, or both?

4

Re: Re: crank comes loose all the time!

Both. Cranks can come loose just from road riding. MUni and trials activities will tend to loosen them faster.

5

I’ve not had a problem with cranks coming loose so far; I’ve had a pedal come loose twice, it did no damage but clanks annoyingly.

Phil, just me

6

Mike gave a good procedure for pounding the cranks on. You do need to be rather forceful when pounding them on. I had problems with my cranks getting loose and I discovered that it was mostly because I was being too timid when pounding them on. I was just tapping them on with a rubber mallet. Use a hammer, a block of wood, and a good wallop. You may need to drill a recess in the wood block to allow for the bolt on the axle.

Two things that I do a little differently. I use a little grease on the taper to help the crank slide on the axle. Then I use Loctite in the nut to keep it from vibrating loose.

john_childs

7

RE: crank comes loose all the time!

> With all this talk of loose and worn cranks, I am wondering
> how long I can expect before I need to perform some
> maintenance on my own.

> So is the crank problem a MUni thing, a Uni thing, or both?

Both. MUni puts more stress on, but any form of unicycling stresses the
cranks more than average bicycling. This is because we stress the cranks in
both pedaling directions, so the cranks have more of a chance to be worked
loose.

So it’s a good idea for any unicyclist to check the tightness of your
cranks from time to time, especially if you haven’t done it lately (or
ever):

  1. If you have plastic dust caps, be careful removing them or you’ll chew
    them up. Somebody the other day suggested the pull rings from aluminum drink
    cans. That sound like an even better tool than coins. Obviously if yours has
    a six-sided hole in it, neither of those will work.

1a. Why use dust caps? They are there to protect the threads on the crank
hole (they don’t keep dust out). You need those threads to take the cranks
off with a crank puller. So if your caps stay on, put them back afterward.

  1. If possible, use a 6-sided socket wrench rather than a 12-sided one. They
    grip the nut much better, and are less likely to slip off, rounding the nut
    and doing bad things to your knuckles. If you don’t have a 6-sider, you
    should get one because it’s one of the most important tools on a cotterless
    unicycle.

  2. Point the unicycle against a wall or other non-moveable object, and
    tighten the side that’s on your right. Make sure the pedal is to the rear,
    so your hand can’t hit it if anything slips. If you can’t get the nut to
    tighten any more, you’re in good shape. Otherwise, tighten as much as
    possible.

  3. Rotate the unicycle 180 degrees and tighten the other side.

Lately, I haven’t found the need to pound on alloy cranks. I haven’t done
much with steel lately though, and I think those are the ones where you need
to get the hammer. With alloy cranks, I just crank them on good & tight,
ride it for a minute, and tighten again. Then I ride for several minutes,
and tighten again. Lastly, I bring the wrench on at least the first proper
ride after changing the cranks. Check the tightness at least once during the
ride.

If you have been riding on a crank that was loose, and it subsequently won’t
stay tight, you probably need to replace it. Riding with it loose tears up
the hole (hopefully not the tapers on the axle).

Occasionally you get a bad set of cranks. I’ve heard of cranks that just
didn’t stay tight from day one, and this may have been due to a defect in
manufacture. The tolerances on those square holes are fairly strict for a
tight fit, so they’re not always perfect.

Breaking lots of axles? Time to start saving up for a splined crankset…
:slight_smile:

Stay on top,
John Foss, the Uni-Cyclone
jfoss@unicycling.com
www.unicycling.com <http://www.unicycling.com>

“This unicycle is made all from lightweight materials. But it uses a lot of
them.” – Cliff Cordy, describing the very heavy new prototype unicycle he
brought on the Downieville Downhill

8

Re: crank comes loose all the time!

Mikefule <Mikefule.6rhzb@timelimit.unicyclist.com> wrote:

This is an excellent description of how to put on cotterless cranks.
Please allow me to make a few comments based on my own experiences.

>I doubt the Loctite is relevant as it will only stop the nut unwinding
>on the thread. Given enough persuasion, the nut will loosen anyway - it
>has to otherwise no one would ever use Loctite because they wouldn’t be
>able to remove the nut later if they wanted to.

The crank must be pounded on tightly. The nut is really only able to
keep the crank on tight, the nut itself is on very tight.

>My guess is that either you are not seating the crank properly on the
>tapered end of the axle, or the taper is damaged, worn, or faulty.

>Try this two-pronged approach:

>1) Remove the other crank and refit it at 90 degrees to its original
>position. (Do it in this order so you have a reference point.)

>2) Remove the offending crank and fit it appropriately - i.e. at 90
>degrees to its original position, and at 180 degrees to the new position
>of the other crank.

>(My theory being that if the taper is worn, faulty or damaged, this will
>have been exacerbated by the constant loosening during use, and the wear
>will be distributed on the taper in one direction because the pedaling
>force is always in the same direction.)

If the crank hole for the axle is no longer square (is more rounded than
its original square shape), toss it and buy new crank arms.

>3) Now, before tightening the nuts, find a large block of wood and a
>heavy soft mallet - ideally wooden or rubber, but copper faced might
>do.

In my experience, a rubber mallet is too soft to get the crank on tight
enough. A wooden mallet should work fine (or hardwood block and steel
hammer combo). A copper faced or brass mallet should also work fine.
The brass mallet might be a bit too hard for this application, so some
restraint in its use would be advised.

>4) Using the block of wood as an anvil, and perhaps asking a friend to
>hold the uni straight, position the uni so that the axle is vertical,
>with one crank resting on the block of wood.

>5) Now wallop the top crank at the centre to drive it onto the taper.
>The important thing with the hammer is to use the weight and balance of
>the hammer to deliver the force, and to strike confidently ‘through’ the
>target, rather than tapping away at it lots of times.

>6) Tighten up the nut for the crank you’ve just walloped on.

I’d repeat steps 5 and 6 about three times for each crank arm. Doing
this properly will likely tighten the crank on the taper so well, that
it may never come loose (until the nut is loosened).

>7) Now flip the uni over and do the same for the other crank.

>(What you have now done is realign the cranks by 90 degrees to
>counteract any uneven wear on the taper, then seated the cranks very
>firmly on the tapers, then tightened the nuts up to draw the cranks on
>fully.)

>8) Leave the dust caps off for now, and carry a 14 mm socket or use the
>crank tool and a spanner. Ride for a bit, idle for a bit, but don’t
>wait for the cranks to feel loose. Then nip the crank nuts up just that
>bit tighter.

I’ve never had to do this step for any crank in which I repeated steps 5
and 6 at least three times total.

>(You will find that crank nuts come loose every few hours of riding
>anyway. I seldom ride anywhere without the necessary tools, because
>riding with a loose crank is annoying, and it damages the crank or,
>worse still, the taper.)

If both the crank arm and crank retaining nut are both made extremely
tight using the above procedure, neither the crank or its retaining nut
will ever come loose.

To remove crank arms: Loosen the retaining nuts each about a few
rotations. Do some hard idling or riding until both cranks feel
slightly loose, being careful that the retaining nuts don’t become too
loose. If one crank becomes too loose, its retaining nut has become too
loose and should be tightened a bit. When both cranks are slightly
loose, a cotterless crank removal tool should easily finish the job.
[Due to the force used in pounding the cranks on, using only the crank
removal tool could strip out the corresponding threads in the crank, so
please use the loosening up procedure at the beginning of this
paragraph.

Sincerely,

Ken Fuchs <kfuchs@winternet.com>

9

Re: crank comes loose all the time!

the key thing I’ve found with loose cranks is to make sure you have a long
socket, 10 inch or so to do it up and a decent fitting socket on the end of
it.

Also, if you spray wd40 on the crank and the taper before fitting the crank
it’s much easier to get the nut done up tight enough and the crank on far
enough.

Joe

10

Thanks for all the advice. I need to get a day off and run out and buy a crank remover tool, and give this a go. In the meantime I’m just not gonna ride :frowning:

I was looking at cranks on unicycle.com and was pleased to find them pretty reasonably priced. Is it just the crank arms that are likely to receive damage? Do I need to be concerned about the axle? Can I just get any ol’ axle and/or cranks if the need arises or must my schwinn use specific parts (as usual all the schwinn stuff is out of stock).

Oh and to the person asking about muni vs road uni and loose cranks, I just ride on the road. The most treachorous thing I do is ride down a flight of 3 steps every once in a great while.