tonyfourdogs

Hi folks

I was wondering if anyone can advise a poor cack-handed would-be vintage bike restorer. On my latest and most difficult project so far, the drive side crank arm was stuck on so hard to the bottom bracket axle, that I resorted (in my stupidity) to trying to improvise a wedge to remove it (the thread for the crank removal tool was stripped).

It wasn't until the folks at my lbs finally took it off for me that I noticed I'd bent one of the spider arms in my previous efforts. No problem, thought I, I'll just bend it back - carefully.

I didn't realise aluminium was so easily bent. In short, I applied too much force, and now it's cracked/ split along one side of the hole for bolting on the chainrings. I've seen people on youtube fixing cracked aluminium with araldite (I think it's called JB Weld in the states?). I would like to repair the crank arm to get the bike up and running at least, even if it means replacing it if/ when I realise I have a bike worth riding. But I'd prefer not to die while I'm test riding it.

Logic (and Sheldon's website) lead me to think it's probably OK as the load is spread across the remaining 4 undamaged chainring arms. Anyone else worked with a crank in similar condition, or do I just need to chuck it and find another?

Thanks in advance

Kontact

Would you consider a bike with globs of gray epoxy "restored"?

I doubt the repair would hold up to much actual use, unless your chainrings are unreasonably stiff.

CliffordK

If it has both stripped threads and a cracked arm... it is time to throw it into the recycle bin.

Head off to your local bike co-op and look for a similar used crank. Right & Left only have to be close, they don't have to be a 100% match. Get the right length, and one that is similar.

You can probably test-ride it with 4/5 bolts, but it will put strain on the rings, and you'll still need to get the crank arm off again when you find a suitable replacement.

Better to just replace now.

tonyfourdogs

Thanks fellas. Haha no, I wouldn't consider it restored in that condition. Just don't want to spend money on something that turns out to be a crappy ride.

Sadly I don't have a local bike co-op. If someone doesn't start one soon I guess it will have to be me

CliffordK

Where do all the dead bikes go?

Your LBS may have some take-off cranks. E-Bay? Craigslist?

I realize you don't want to spend much money on the bike until you decide you like it. And, you may be able to get it to work with 4/5 bolts. If you want it welded, then use a welder.

But, you still remain with the hassle of removing the crank in the future.

Trakhak

On the bright side, you're probably no longer a "cack-handed mechanic"---i.e., you've been given a lesson in the dangers of overestimating material strength that all mechanics have to learn, and it didn't really cost anything, since the crank arm was already damaged and ripe for replacement.

tonyfourdogs

That is true... Although I wasn't planning on riding it for much, probably just a week. Lbs wrench seemed to think I'd be able to get it off again with my hammer.

But now I think about it in more detail (thanks to this thread) I realise I'm just creating more work for myself. A replacement crank arm it is! Really hope I can get one to fit my chainrings - they're one of the best features.

Also, eBay is expensive! Who pays 50 quid for a 25 year old Japanese crank arm for goodness sake?

Maybe I should just strip it for parts and get rich instead

FBinNY 

One thought.

Jacobs chuck removal wedges.

Kontact

You can also sometimes ride a crank off with the bolt loosened.

FBinNY 

Yes, this works best if you ride far from home.

Just a reminder that bolt loosened means it's still on. This is an important point because you want the crank to pop loose, but not come off completely under load.

sweeks

Hahaha! I think my sarcasm detector just blew a fuse.
Steve

CliffordK

Oh, also Thrift Stores. The County Dump? Although, one may have to wait some time to find the right deal.

And, yes, there is stripping, or hunting for a donor bike to strip.

In fact, our local bike co-op strips about half the bikes that get donated. Not my choice, but it works for them.

tonyfourdogs

Oh I can assure you, I am still a cack-handed mechanic and human being in general. But thank you for the well chosen words of encouragement. A lesson has been learned!

As for the wedge (sorry don't know how to quote two separate replies in one post) I appreciate the suggestion. However, I think I saw a better solution from rj on YouTube: a 3 claw puller.

dsbrantjr

Stick with the chuck wedges.

tonyfourdogs

Bike is from the local dump Sadly, they very rarely have road bikes there. Everyone in my neighbourhood throws away mountain bikes (not that I blame them ) I found a couple of bikes there with the right length cranks, but none of them compatible with 2x chainwheels or the actual chainwheels I want to use.

Thrift around here is even worse. Bikes are all cheapo mountain bikes with more suspension than a motorway bridge. Disgusting.

@dsbrantjr - what's wrong with the 3 claw puller? Chuck wedges look kinda brutal by comparison.

Good news is, I've found a crank arm that probably fits. Got to travel an hour to pick it up, but it's better than Ģ50 on ebay.

Thanks for all your help here folks

79pmooney

Just to be contrary here, I bet a JB Weld repair done right would do just fine, probably for a long time. If done right, it could be a very smooth (though quite substantial) lump on the spider. I'd probably use Gudgeon Bros boat building epoxy and some kevlar stands, a less brittle end result. But I wouldn't bother until I had in hand a good means for removal and that might well cost much of a used spider. (Haven't looked into drill chuck wedges yet. Harbor Freight probably has the 3-prong pullers.)

In fact, the spider might go a long ways on just 4 bolts. I wouldn't chance it, at least now as I am reaping the consequences of the many crashes I did over the years.

Ben

bikeman715

Another tool that can be use is what they call a pickle fork , you can fid it at any auto part store . IT what we mechanics would use back in the day when all else would fail at removing the crank .

wschruba

The reason people are suggesting the chuck wedges is because they are the less brutal option. 3-claw pullers have a tendency to skip/damage crank arms (which you'll notice, don't have 3 equidistant points built into them by design), and you'll typically only get one, maybe two (if you're lucky) chances to get it right. Steel cranks, of course, don't have the problem with the claws pulling material out of the arm.

Chuck wedges, on the other hand, are used [with the wedges] facing each other, and you, the mechanic, get to choose which part, if any, gets scuffed up--you simply hit the one that is directly pressing against the part you don't care about. If you want to preserve both parts, you can even back them up with a thin piece of cardstock (cereal box, for example). You should still leave the bolt screwed in a few turns, to keep the crank from flying off when it breaks loose.

NB, the 'right way' to use them is actually to tap each one (gently!) alternately until the taper breaks loose. Even better would be a large ductile-iron screw clamp, but they often don't fit.

maddog34

A three jaw puller will just add frustration to a simple job... the jaws will slip off the back of the crank arm and the hooks may not fit behind the spider very well... and will probably not even begin to pull theleft crank arm(if anyone was thinking of trying).

automotive "pickle fork" tie rod end removers will work, but may cause damage to the BB spindle, or even the frame... same for the jacob's wedges, or DRIFTS actually...... the drifts and pickle forks come in various sizes, so consider that factor.

another tool to have is a PROPANE TORCH... aluminum expands much fast and farther than the steel spindle... Heat is your Friend!!!! watch to make sure you don't heat the FRAME, or paint will be damaged. A little heating goes a long way.....

a rather grumpy old M/C mechanic i used to work alongside had two sayings... "Heat is your Friend" and "Use some Patience on it!"... "Patience" was the name he'd given to a 5 lb. dead blow hammer that hung in the shop... it never gathered any dust! Lots of Salt corroded ATV's came through that shop......

maddog34

my favorite wedge setup? Two similar sized pickle forks from opposite sides.... presents flat faces to both sides of the equation!

tonyfourdogs

Brilliant advice and suggestions in this thread. Thanks to everyone who's chipped in.

The plot thickens though... A friend has just offered to weld the crank for me. I know the threads are still stripped, but I'd be interested to hear any opinions on welding.

wschruba

All things been equal (post-weld heat treatment to restore the hardness of the metal, for one), you would still need to re-mill/face the arm mounting point in question, since welding distorts the object being welded.

As practice for the welder, it has merit. As a repair? Unless you're talking about a 30-40 year-old aluminum crank that is irreplaceable...no.

Kontact

Welding will work better than glue. The heat affected area will be far stronger than any other repair method, heat treated or not.

I would weld it using the chainrings to hold the arm in place. 2 tacks then fill. Weld both sides and it shouldn't wander much.

Reynolds 

I wouldn't bother with gluing it. Either replace it or use it with 4 bolts if it holds.

WizardOfBoz

Umm. Glue - 3000psi tensile strength (on a good day, on a clean, dry, well-mated joint. For a cracked or broken piece, the effective strength is lowered. A 6061 forged aluminum crank has a tensile strength of 45,000 psi or so.

Welding a 6061 forged Al crank will reduce strength in the heat-affected zone by about 80%. You could weld, then heat-treat to get back up to T4-T6 (full strength) conditions.

I'd find an old crank of the type you want. I don't think eBay is that expensive for the off-beat stuff. For some highly desirable and rare stuff, yeah, the bidding keeps the prices high. But if you're restoring something high-end and desirable, you probably won't get off cheap in any case.

If the crank doens't have an internal thread, the chuck wedges are the way to go when removing cranks. It puts the force nearer the center mass of the crank hub. With a bearing puller, the hooks are more outboard - leaving you with the possibility of doing the same type of damage that you wrote about.