JB Weld on wobbly/deformed crank arms. Anyone tried this?

[trail-blazer]

The story begins with me having a frame that I want powder-coated but had pitting all over it. I didn't want to remove too much material with blasting etc so I sanded it down (after stripping the paint) and looked for a product that would fill the pits but withstand 400 degrees. I was pointed in the direction of JB weld which is a steel epoxy.

After smothering the frame in this grey goop and leaving until the next day to cure, I then had the tedious task of sanding it back to remove the high-spots which covered up the pits pretty well.

Anyway, I had a little bit of this stuff left and thought about trying it on something else - a wobbly Sakae SA crank arm. This thing was ruined due to some numpty riding around with a loose crank arm - not me BTW. This stuff sets really hard so I thought it had to be better than a coke can shim.

After keying the affected area of the crank arm, I greased the tapered axle lightly before applying the JB weld to the crank arm before sliding it on and tightening. JB Weld can be runny so I left the bb in a frame and placed it on the floor so gravity would take it's course.

I knew I would be removing my crank to inspect it but you could miss this step out if you were fitting the crank to the bike it came off etc.

Mine came off the axle clean and it has filled the gaps perfectly - I have no idea how long this bodge will hold up but it has to be better than a shim...

My pics aren't brilliant but they will give you a rough idea of what the JB Weld has achieved. I need to trawl through Photobucket to find a before picture - back soon...

I have the drive arm to match and really didn't want to chuck this arm away so I thought it had to be worth a shot...

 

[trail-blazer]

Before pics - this crank arm was wrecked and heading for the bin so no biggie if it isn't a permanent solution...

 

[rooksfoot]

lots of people have tried lots of things in the past I used to shim the faces out with little squares of steel drinks cans ..... but all these are very temporary bodges sometimes measured in metres - not miles...! that shud be used only will u save up 4 some new cranks......... the basic rule is.. once they wobble, or creak it will only ever get worse.

 

[trail-blazer]

lots of people have tried lots of things in the past I used to shim the faces out with little squares of steel drinks cans ..... but all these are very temporary bodges sometimes measured in metres - not miles...! that shud be used only will u save up 4 some new cranks......... the basic rule is.. once they wobble, or creak it will only ever get worse.

I mentioned coke can shims earlier but this product has replicated the exact shape of the BB axle which must be better. The biggest question mark is regarding how hard this stuff sets and will it compress or not.

I have plenty of other crank arms BTW - was just looking to find a new use for what was left in the tube...

 

[rooksfoot]

no worries (i only skim read ur text) if it does work u will be a legend among your peers

 

[trail-blazer]

if it does work u will be a legend among your peers

This is only meant for a bike that gets used lightly every once in a while - as is the case with a lot of old bikes. I wouldn't dream of trying such a bodge on an everyday bike...

I just like playing around with stuff if truth be told.

 

[Robbied196]

Re:

JB Weld

Its like a trade secret you've exposed! I've used it for years and it genuinely seems to become as hard as steel and definitely harder than aluminium.

Nice result, but now everywhere is going to be sold out :facepalm:

 

[trail-blazer]

Re: Re:

JB Weld

Its like a trade secret you've exposed! I've used it for years and it genuinely seems to become as hard as steel and definitely harder than aluminium.

Nice result, but now everywhere is going to be sold out :facepalm:

Cheap as chips on eBay - £4 delivered and they have tons of it. I probably had enough to prep two pitted frames and forks TBH.

I haven't seen the guy who is going to powder my frame yet but I've read a lot of stuff saying that it is absolutely fine for using as a filler for powder coating. It is meant to be OK up to 500 degrees apparently..

 

[Woz]

Interesting. But it beckons the question if indeed the cranks were set in the correct plane / position if they were wobbly
to begin with - I mean there was no longer a properly machined interface right?

Eitherway, for a corner shop errand bike there's nothing to loose so keep us posted how it holds up!

 

[trail-blazer]

Interesting. But it beckons the question if indeed the cranks were set in the correct plane / position if they were wobbly
to begin with - I mean there was no longer a properly machined interface right?

Eitherway, for a corner shop errand bike there's nothing to loose so keep us posted how it holds up!

Most of the deformation was at rear of the tapered interface. The machined interface was generally good at the narrow end/front of crank so this product just built up that area. I

I had the JB weld sitting there and a duff crank arm and thought, why not...