1 piece crank woes
 

My bike is rocking / running a one piece crank...(I know)
I felt a little slippage when trying to slow down, thought it was my lockring...
Tightened it, and still have this "little slip"

After staring at the drivechain for about 45 seconds I realized that it is likely that it is my one piece crank...

The drive pin is smaller than the drive pin hole so the sprocket / crank moves a very small amount!
I can totally feel it... it bites.

Is there some common way to fill the gap so that there is no movement?
http://www.sheldonbrown.com/images/opc-chainwheel.jpg

Its a cheap frame / bike so im not going to do a bottom bracket conversion / 3 pc crank...
Im saving up for a better frame / etc... and just looking for a way to stop this from happening in the meantime.
Thanks for any ideas

-Jake

Maybe fill in the extra space with super glue or something of the sort that can stand up to the pressure

Really, $10 junker BB and bulletproof cranks. Short of welding nothing will work. I'd suggest JB Weld but it cannot stand the physics of this application.

bulletproof cranks>1 pc cranks

I have the same issue...i'm going to weld it at some point. or just take another crank out of my junk pile.

Some chainrings fit the pin better than others. Another possible solution is a shim. I did that on my fixie, making a shim from a piece of steel, grinding it into a wedge-like shape. Seems to work OK. I wonder if it'll fall out one day?

So hook yourself up some car batteries and do something dangerous!

http://www.youtube.com/watch?v=8tHJ0NSjZnM

(3:45)

Go a muffler place and give the guy $5 to put a few tacks of weld on there for you.

he might even do it for free.


Or like shecky suggested a metal shim with JB weld will do it too.

or you can ride it like that, its not like anything is gonna happen.

Thats exactly what I am gonna do... Muffler shop!
I know its a minor issue really, but I find it really annoying.
I dont care if the bike IS cheap, but it cant have slack in the drive train... feels r.e.t.a.r.d.e.d.

He he... -Jake

My friend had the same problem except with 3piece bmx cranks. Since the BMX chainring also has a slightly bigger hole for the arm it kept moving around and slipping. He tried everything and after a month he just switched to a proper track crankset. I've seen some others use bmx cranks on fixed gear bikes, I wonder how they keep it from moving around.
Good luck.

Good to know that...
I Dont want to eventually "upgrade" to another slippery situation.
-JAke

That crank and pin setup were only designed to move in one direction. Why not just go single speed and avoid the danger till you save up for your new ride?

...Or you can wait for it to fail on you. And keep in mind that it's not gonna break when it's sitting in your living room. It's gonna break when you are either accelerating or braking on the road. Not a good idea.

With respect, as im sure you know what you are talking about.... I cant imagine that the pin is going to break off or tear thru the chainring... you think thats possible? They are both made of steel.
I have had whatever number of BMX bikes with 1 piece cranks and never seen or heard of this happening.

[edit] Thanks for warning me BTW... If you know something I dont would you please elaborate? ... Im just resisting the idea of having to go back to SS!! [/edit]


P.S. I went to the local muffler shop and asked the mechanics about welding it...
Three spanish guys came out and talked about it for 5 minutes in their native tongue then said "Tomorrow"
Its just down the block, so I was game and asked them how much "Just $35"
I started laughing, and then they did too... I said "really...how much" (more spanish) "$25"
Ha! "Nada Amore amigos!" I yelled and rode off to buy some of this ($5.99):

http://www.jbweld.net/img/jbweld_lrg.jpg

Gonna try it tonight.

Those Spanish guys will have the last laugh when you lose all of your teeth...

Would you mind switching into "trying to help a fellow biker" mode and help me understand why I will lose my teeth? I would really rather not do that.

JB welding a cog is one thing but JB welding a crank doesn't seem to be a great idea....it is a part of the bike that is under a lot of stress.

Check out this thread for some neat photos: http://www.bikeforums.net/showthread.php?t=512579

You're misunderstanding. The hole in the chainring is too ovalized and now the crank slips in it a bit. It might get worse but certainly not bad enough to fail (unless the chainring folds, which would be unrelated).

What I'm saying is the JB Weld will probably loose bondage on the second or third application of backpressure. It's just not designed for that application.

OK fellas, not arguing with you, just making sure that we are all on the same page here...
Judging by some of the answers / comments in this thread I am not sure that we are all talking about the same thing.

http://www.sheldonbrown.com/images/opc-chainwheel.jpg

PROBLEM:
On my one piece crank, the drive pin is smaller than the drive pin hole, resulting in slight "slack" (movement) when decelerating / skidding.

MY SOLUTION:
Filling in the gap with JB weld, thereby closing this gap and eliminating the slight movement.

MY COMMENT:
I am not REPAIRING the crank, or sprocket with JB WELD

FINAL QUESTION:
Are you guys saying that I will lose all of my teeth from using a one piece crank on a fixed gear bicycle because they are known to fail in this application?

Thank you very much for your patience with me on this...

-Jake

No, I go it, I just think that, as a whole, the thing is pretty sketchy. I've ridden plenty of 1-piece cranks and even had a problem similar to the one that the OP is having but I had brakes in the front and rear so it didn't matter. 1-piece cranks are junk and are crafted out of cheap metal because they are not meant to bear an undue amount of stress....the OP is putting an undue amount of stress on them. I hope he is running a front brake, that is all.

On my old beater, I just dealt with it. I cranked down the lockring/race that holds the chainring on really well and called it good to go. Short of welding/shimming, there isn't really an easy solution. I could have welded it (have a welder) but just got used to it.

Absolute nonsense. One piece cranks like the one pictures are made out of cheap metal. That's because steel is cheap. However, they are about as durable as cranks get. The forged one piece cranks simply don't fail unless you're doing some crazy BMX stunts with them. BTW, one piece cranks are common on BMX bikes because they are cheap and strong. They do fine backpedaling, too. Consider, they are very common on coaster brake bikes, which require backpedaling in order to stop.

Jakerock, if it really bothers you, I would just spend a few bucks to get the pin tack welded to the hole on the sprocket, like EatMyA** suggests, presuming it's a steel chainring. It won't significantly weaken anything. No sense in spending the $$$ on three piece cranks unless you must cut about one pound, which is what you'd lose by going to aluminum cranks.

The only one piece cranks I would avoid are the ones that look like a S-shaped bent piece of rebar. These were usually reserved for the lowest end bikes. The drive pins on these are bonded on, not integrally forged like the one in the pic, running the risk of breaking off at inopportune times. And they are just kind of crappy all around.

I was thinking about caving and buying a us / euro conversion BB and new cranks there for a second, but ultimately Im with Shecky on this.

I have owned / ridden alot of bikes and most of them have had 1 piece cranks...
In my BMX days there was a massive amount of skillful / unskillful, generally abusive riding / flying / crashing going on and I never even saw one of these things bend, nevermind break. I cant imagine that one, heavy, solid piece of forged steel being less hardy than a modern multi component crankset / BB.... Maybe not as "refined", but certainly as strong.

I cannot find ONE case of a real "horror story" about 1 piece cranks on this vast interweb. A whole lot of hearsay about three piece cranks being stronger and better, but not much of anything by way of evidence, or even stories. As far as the safety issue in using a 1 piece in the drivechain of a fixed gear bike... If the crank isnt bothered by all of the forward motion stomping and stress it has endured as a SS, it will not have any prob dealing with the occasional leg powered deceleration or skid involved in fixed riding.

My only complaint is the little bit of movement, which seems easily remedied by a shim or some kind of welding... The bike was cheap and having already spent much more on mods and upgrades than the bike originally cost, it is dialed in to my needs pretty nicely!

Im gonna make it work with the crank thats on there, as in my opinion the whole issue of safety seems unfounded!

Much respect and thanks to all who chimed in on this!!!
Ride safe...

Best, Jake

Dude, Take the thing apart, including the nut that holds the chainring down to the crank, give everything a GOOD cleaning, put the chainring in place, replace the nut that holds down the chainring (be sure to add some LockTite) be sure to get the pin centered in the pinhole, then take it down to the muffler shop and have the guy fill in the pin hole gap. Itll last for the rest of your life! Problem solved. :thumb:

if its just the ring they are cheap clik this bunch on ebay