Old Schwinn 24" - crank fell off.. how to repair?

I just learned to ride my dad’s old 24" Schwinn last summer. A couple days ago, one of the nuts fell off the right crank, and it started wobbling when I peddled (which is why I noticed). So, I went w/ my dad to the Schwinn bike store in Boise (they happen to be the only unicycle.com dealer in the area, so I figured I’d take a look around while I was at it). We bought a $2.50 hardened steel nut.

We went back home, I put on the nut and tightened it as hard as I could. I test it out a couple days later, the nut starts to come loose in five minutes.

So, I try tightening it again. Same thing again. I figured maybe the crank just wasn’t on tight enough, so I used a hammer and lightly tapped it around the edges some so it could go on a bit farther. Put on the nut, tightened, and tested. Same result - falls off after about 500 ft of riding.

I’m not quite sure what to do now, so I’m asking for help from the knowledgeable people of this forum.

Note, I don’t know the difference between cottered and cotter-less cranks (I happen to have searched a bit on the forum, so I’ve read the term - don’t know what it means).

I took several pictures. Here they are:

^^ The crank w/out the nut on it ^^

^^ Crank and the new nut ^^

The bare shaft

The other crank (still has the original nut on it)

W/ the nut put on (not tightened)

A side view

The new nut

From another view


You’ve got cotterless cranks.

Here’s a past thread on installing a crank: Cranks (yet more)

It gets a little involved with grease, Loctite, torque wrench, and all that. You can get by without all that, but doing all that makes it more sure that the crank is going to stay on.

What is probably happening is that you’re not getting the nut on tight enough. 40 foot-pounds is a lot. If you’ve got a socket wrench with a 6 inch long handle you’d have to put 80 pounds of force at the end of the handle to get 40 foot-pounds of torque on the nut. If you had a socket wrench with a 1 foot long handle you’d need to put 40 pounds of force at the end of the handle to get 40 foot-pounds of torque on the nut.

The other possibility is that the taper on the crank or the taper on the hub is damaged. If the taper is worn or bent or otherwise damaged it can be impossible to get the cranks secure so that they won’t come loose.

You could take it to a bike shop and have them show you how tight the nut needs to be. Once you get the feel for what 40 foot-pounds feels like then you’ll be prepared for next time when you do it yourself. Let the bike shop know that 40 foot-pounds is the suggested torque for unicycle cranks. The bike shop can also look at the taper and tell you if there is obvious damage that may be keeping the crank for staying tight.

Riding repeatedly on a loose crank will cause the connection to become larger, so it won’t fit no matter how much you tighten it.
This may not be your situation. Blue lock tight on the contact face of the nut may help. Three small dots should do it. Allow this stuff to set up for a few minutes before connecting the two surfaces first. A light, very light, application of grease on the taper will also help.

Re: Old Schwinn 24" - crank fell off… how to repair?

On Fri, 10 Dec 2004 17:59:46 -0600, “aurum78” wrote:

>I’m not quite sure what to do now, so I’m asking for help from the
>knowledgeable people of this forum.

I hope you didn’t ride when the crank was wobbly. That can ruin the
taper (hub and crank) pretty quickly.

Wow, your crank and nut have been properly photo-documented! In the
picture of the other crank, I seem to notice that you have a plywood
surface on your pedal. Did I see that correctly and (if so) why is it?

Klaas Bil - Newsgroup Addict

“Deflating pi does not reduce calories, it just concentrates them. - billham”

Looks to me like it’s just a white plastic pedal.

Nope, that’s just the orange reflector on the side of the pedal.

I did actually ride some while it was loose - I wasn’t quite sure what was wrong with the unicycle until a bit later. I’m pretty sure it can still be fixed though - I’ll probably be taking john’s advice on the torque wrench and loctite.

Thanks for all your help guys!

Well, since I’ve received all the help I’ll probably need / get, I’m taking the images off of my server (coneff.org) - i.e., all the images will be broken.