Help! Cracked frame-mount derailleur hanger - '92 Trek 2100. Heart sunk.
 

Any there any frame builders/repairers that can repair this frame-mount derailleur hanger?
OR perhaps a recommendation for a talented metalworker that can repair this?
(See photos below)

Cost no object!
OK not literally but I know this is NOT a trivial "$50" repair and I'm happy to compensate someone for thier expertise and time.
I really, really want to keep this bike.

The derailleur mount was first bent last week when I peddled hard after the chain bounced out of the pulleys.
(I had walked my bike down some stairs and I didn't notice that the chain was tangled in the pulleys - when I peddled hard it pulled the derailleur inwards and bent the frame mount hanger).

Then, it cracked after I tried to fix it. I actually ordered and used the correct Park Tool for the job, the DAG-2.2 - and I carefully read instructions and watched the video.
Unfortunately, the force need to realign was just enough to crack the piece.
(Ironically, the piece was pretty close to alignment when it cracked).

Note that I did find posts with similar issues - with varying levels of encouragement and recommendations - including the first link with reported success with TIG welding (and starting from with a brand new piece - presumably more difficult) on an aluminum frame. In any event, I'm very much leaning towards finding an expert shop for a professional repair.

Other posts:
https://www.bikeforums.net/framebuil...ar-repair.html
https://www.bikeforums.net/bicycle-m...destroyed.html
https://www.bikeforums.net/bicycle-m...ounting-2.html

Thanks for any recommendations!

https://cimg0.ibsrv.net/gimg/bikefor...61438939d3.jpg
Derailluer hanger bent after chain mangled in pulleys.

https://cimg0.ibsrv.net/gimg/bikefor...bc8b98d22f.jpg
Used the Park Tool to straighten - Read and followed the instructions!

https://cimg3.ibsrv.net/gimg/bikefor...6d45f8dcd3.jpg
Cracked! Just as it was getting into alignment, it cracked on one side.

https://cimg2.ibsrv.net/gimg/bikefor...ce0a7629d2.jpg
(Aligned? Ironically, the Park Tool works well. Although cracked, you can see that the hanger is now pretty close to correct alignment)

https://cimg8.ibsrv.net/gimg/bikefor...04e43ce5cf.jpg
"Half" Cracked? I'm hoping that a repair might be more feasable or easier because the structure is still intact. (This is not, at the moment, moveable by hand only.)

Are you sure, it doesn't look aluminium, and they usually have replaceable hangers? He might just be referring to some other frame in some other thread.

Even if it is it could be TIGed (and of course you could easily do that on a metal frame as well). The only difference is you need to find someone with an AC/DC TIG.

I just deleted two posts where I said dumb things.
When I said "never buy aluminum frames", that was meant as a joke. But even if you get that I'm joking, it's not funny, so Fail either way.
Fact is I'm just too ignorant of welding aluminum to have anything smart to say. Apologies all around.

My welder is AC/DC, so maybe I should try welding alu one of these days... Feels like going to The Dark Side though. ;)

I really want a welder but keep holding off on getting one. I was thinking about it last night, and thought about building an aluminum bike. Because when aluminum came around as the preeminent material for bikes, I felt inadequate because I couldn't build an aluminum frame. But I have come to accept my inadequacies. I still might try building in Ti, dunno.

As far as the OP's bike, it looks like toast to me. You could get a welder to weld it back up and then tap the hole and get it to work for a while. The crack isn't in the worst possible place, in fact I wouldn't expect it to crack there. I don't think I would bother finding someone that welds on bikes. Just find out what alloy that frame was made from and go to a welding shop with a lot of broken down trucks around the building and have them zap it back together.

The 1992 Trek catalog doesn't say what alloy the stays are made from, but it doesn't matter that much on a non structural component like this. 5356 filler will work with 7005 and 6061 alloys. The weld will almost certainly melt into the threaded hole, so it will need to be cleaned up and re-tapped. It's going to be tough to weld that without having it melt away. If a stainless M10 bolt could be threaded into the hanger, that would go a long way toward preventing damage to the threads and acting as a heat sink to prevent it from melting away.

The early Trek Al frames didn't have a replaceable hanger. That was one of the "deal killers" in my mind, back then.

Very few framebuilders work in Al. But they shouldn't be too hard to at least find and ask. There have been various lists published in different forums over the years. But a skilled and motivated welder/fabricator could repair this too. If the hanger hole part is too damaged or small to weld on consider cutting it off completely just under the axle slot and grafting on a replacement sourced from a tossed out frame. Cut off the doner at that same spot and angle... Andy

All good, bulgie! I appreciate your eagerness to help and the quick response!

Really appreciate everyone's input here…looking like this bike might survive after all...


AC/DC TIG Welding. That sounds like the plan! Thanks for the encouragement, Guy!

Agree. The derailleur mount is not subject to great force under normal mechanical conditions. I admit there was some great force involved in bending this in the first place (Instinctive superhard pedaling from stationary – without realizing the chain was mangled in the pulleys)
Lesson Learned. I will DEFINITELY be more careful from now on when chain has jumped the sprockets, or is jammed in pulleys or when the drivetrain just isn't acting normal – on ALL my bikes!


Cool I know a talented general body shop metalworker guy that I can ask…

So noted 5356 filler.
Good thinking on the bolt. Will suggest that to preserve the hole/threads.
Will also bring the Park alignment tool to the shop – so that the hole can be properly aligned. (I also plan on bringing a M10X1mm thread kit/helicoil kit – I guess metal shops would have these things, but just in case).

Cool. Good to hear that there are folks that can do this.
I’m imagining that welding the existing structure and the redrilling / retapping would be more efficient that grafting - but reassuring know that even grafting is possible.
TY!

For reference, the link to catalog and the page on this bike:
http://www.vintage-trek.com/Trek-Fis...d/1992trek.pdf

https://cimg7.ibsrv.net/gimg/bikefor...10d07f3a35.jpg

Maybe show it to Dave Levy at Ti Cycles. I've seen him do some pretty nice welding in alu, tho of course his bread'n'butter is Ti. He's smart and conscientious and knows bikes better than your neighborhood welder, if that matters.
Since it's a bonded frame, the DO might not be a weldable alloy. Based on the theory they'd use the cheapest option that's good enough, and the part looks cast, who here knows what's the most likely alloy? i.e. what would you use for a cast part like this that was going to be bonded not welded?

I found Ti to be pretty easy to learn, coming from pretty much brazing-only prior experience. I did take a Ti class from Gary Helfrich, which definitely shortens the learning period because you don't have to learn every single thing from your own mistakes. But the actual welding part was pretty easy, after maybe a couple dozen hours max of TIG practice on steel before I took the Ti class. In some ways I found welding Ti to be easier than welding steel. There's just the stricter requirements for the argon purge with Ti, and fanatical cleanliness required. But my Ti welds came out much better looking than my steel welds. I think I've said it here before but I can't help myself, I frikken LOVE welding Ti, while I'm doing it. The molten puddle is just beautiful.

I say go for it, playing with Ti is fun, and even if you don't end up making a whole frame with it you'll find other uses for a welder.

Mark B

I'd be somewhat worried about the heat causing issues with the bonded joint if attempting to weld it.

I've been using Shimano Hone/Saint axle mounted downhill bike derailleurs to fix frames like this. Not exactly fitting for a road bike, but it works.

There is always the option of turning it into a replaceable hanger. Pick a hanger that has a simple mounting scheme and file/dremel the dropout into shape, and probably duplicate a mounting hole or two.

I see Dave Levy on the internets. Looks like a total pro. West Coast, though. Could be a lot of shipping miles from NYC but I will inquire.

I totally get it. Could be some guesswork involved in the materials and how to approach this.
I also have a hunch the bicycle uber professionals might be more risk averse if they have concerns...I might need to sign a legal waiver - or just end up with the local metal worker.


That would be ideal, actually - as I'd have a sacrificial piece instead of frame to deal with if this ever happens again. (no doubt why the industry went to replaceable hangers).
Also beyond my skill level but will ask about this as frist option. A couple of sites seem to have every derailleur hanger ever made:
https://derailleurhanger.com/
https://wheelsmfg.com/derailleur-han...facturers.html

PS - what the bike looks like - and the juncture of the aluminum and carbon fiber tubes...

https://cimg8.ibsrv.net/gimg/bikefor...a80ae9b04a.jpg
Took off the shifter, cabling and dangling chain.

https://cimg4.ibsrv.net/gimg/bikefor...13ba02d910.jpg
I think this was the first generation of carbon fiber bikes... basically, crude, thick, straight tubes glued into lugs.

Get a welder. But the AC/DC ones are quite a bit more expensive. For steel (or Ti) frames you only need the cheapest DC-only machine because you don't need a lot of current. But you do need a foot pedal, a nice CK torch with a flexible lead, and a couple of Furick No 10 gas lenses. Then you're all set.

Back in the day I had a Vitus cyclocross bike break its non-replaceable hanger. A local shop/framebuilder cut it off and put a replaceable hanger on there and it went on to provide many more years of service. I do recall that it was never as secure as the original and required period re-aligning, but I'd think the same should work here.

It's an epoxy-bonded aluminum dropout, and it pre-dates replaceable derailleur hangers.

I've been very happy with my AHP AlphaTIG welder. The 225 is currently $750 and does AC/DC, hi-frequency pulse, come with a nice foot pedal and runs on either 120 or 240 volts. You'll have to get a smaller torch for bicycle work, since it comes with a 26 torch.

Thanks, I was trying to remember who had recommended a welder here. The one I have my eye on right now is the Primeweld TIG225X as discussed recently on the framebuilder's list.

Mostly to do stainless sculptures, not bike frame shaped sculptures.

That is a very nice machine and Primeweld has a pretty good reputation for customer service.

Mine is an "R-Tech" which is the UK version of what's branded "Everlast" in US. Chinese but reasonably good. The solenoid failed and they sent me a warranty replacement. The display just shows random numbers (but the display is pointless anyway since you're looking at your weld). Also the HF start is sometimes a bit unreliable especially it seems in cold and damp weather. Might need new contacts or something. Apart from all those things it performs flawlessly :) It has pulse but I very rarely use it.

What size argon tank do I need?

I purchased an "S" Argon tank from my local welding supplier and take it back for exchange when it gets empty. I think the last time it cost me $48 for an exchange. The S size tank is 154 SCF and is the largest size that my LWS would sell.

Bigger ones usually work out cheaper.

I got an 80 ft^3 tank some years ago and it's adequate for my level of farting around, but looking at prices now it appears the 125 ft^3 tank is hardly any more expensive = better buy. Especially if you're welding more than I am.

BTW when I needed a CO2 cylinder for my MIG welder recently, I got one cheap on Craig's. The steel is the expensive part, refilling cheaper, so consider getting a cheap-ass bottle. As soon as you exchange it once, the bottle is someone else's problem and any advantage to brand new flies out the window. Mine even had an expired date on it, LWS where I exchanged it didn't care, didn't even look.

One quick mention of Chrome-6 (hexavalent chromium): in case you haven't heard, welding on SS can cause cancer, so just "keeing your head outta the plume" may not be good enough. My wife's Day Job, before she retired, involved teaching small businesses about worker health risks from chemical exposure. They made a video using "video exposure monitoring" (whatever that is) that showed the weldor was getting too much chrome-6 even when welding outdoors. Maybe this is really only an issue for someone spending long hours at it, I dunno, not an expert. I haven't read up on it because I almost never weld SS.

Mark B

Good reminder. I'll have to look into it a bit more. I have a respirator with filters for welding, but I'm not sure it's good enough for that.