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Old 09-07-09, 01:06 PM   #1
estasnyc
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Cracked Dropout Repair?: Epoxy Or Weld?

If my Panasonic Sport 500 were a motorcycle then this would be my rat bike: something I used for commuting around NYC such that I wouldn't care if it should get stolen or become broken. Nevertheless, I've managed to keep this going for some 20 years now.

Anyway, I now have a cracked dropout (photos attached) that I suppose should be repaired although it hasn't affected my cycling in any way that I can recognize now.

Will epoxy resin be enough to repair the crack or should it be welded?

Now for the history of this bike:

I believe that this crack is the result of a botched repair a few years ago at an LBS that is now a tattoo parlor. The original freewheel needed to be replaced and I was offered an entire rear wheel for reasonable price.

(This site and Sheldon Brown's are great - I spent the last several weeks getting up to speed on bicycle tech)

Turns out that my original wheel, with 5-speed freewheel, probably had a 120mm O.L.D. while the newer wheel, that I'm still using, has a 135mm O.L.D. hub. The shop screwed up the cold-setting by bending the rear frame triangles, near where the rear brake mounts, AWAY from the freewheel (now cassette) side and bending the rear frame triangles, near the dropouts, TOO FAR TOWARDS the freewheel side.

Anyway, it was when I recently discovered Sheldon Brown's website that I took a second look at this and recognized how badly that this repair had been down. Using a 2 x 4 and Sheldon's web page on bicycle frame spreading as a guide, I was able to bend the frame into a better alignment. Not perfectly aligned. My estimate is that it's still off by about 2 to 3mm but is much better than it was before.

It was when I was doing this repair that I discovered the crack in the dropout.
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File Type: jpg CrackedCloseUp.jpg (49.5 KB, 68 views)
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Old 09-07-09, 01:09 PM   #2
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Will epoxy resin be enough to repair the crack or should it be welded?
Should be cleaned, a fillet ground in, and welded. Epoxy gives no penetration and won't ever be as strong in a repair of that nature.
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Old 09-07-09, 01:58 PM   #3
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Should be cleaned, a fillet ground in, and welded. Epoxy gives no penetration and won't ever be as strong in a repair of that nature.
I understand this but will that strength be needed?

I'm by no means 100% sure but I suspect that I relieved much of the stress that created the crack when I bent back the frame-spacing. The direction of the crack actually leads me to believe that my weight on the bike may actually compress the broken ends together rather than pull them apart. I think that hitting something like a pothole with my rear wheel will be when I get screwed.

If welding costs (much) less than $50 and I knew where to go, I would do it.
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Old 09-07-09, 02:10 PM   #4
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I understand this but will that strength be needed?

I'm by no means 100% sure but I suspect that I relieved much of the stress that created the crack when I bent back the frame-spacing. The direction of the crack actually leads me to believe that my weight on the bike may actually compress the broken ends together rather than pull them apart. I think that hitting something like a pothole with my rear wheel will be when I get screwed.

If welding costs (much) less than $50 and I knew where to go, I would do it.
Epoxy? are you serious? That needs to be welded.
It might be cheaper to just find another junk frame and transfer the components over.
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Old 09-07-09, 03:27 PM   #5
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I understand this but will that strength be needed?
Yes; it was stronger than epoxy *before* it broke, after all. Either weld it or pull the whole dropout and braze a new one in. Welding is probably cheaper.
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Old 09-07-09, 04:52 PM   #6
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You can probably just braze some brass onto that dropout and fix it.
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Old 09-07-09, 05:09 PM   #7
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Epoxy would be the equivalent of duct tape on the hull of the Titanic. Have it welded or a doubler plate brazed on.
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Old 09-07-09, 07:59 PM   #8
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I took the bike for a spin this afternoon, looking constantly down at the rear wheel, and I could clearly see that there's no way around having the dropout welded.

Google located a single bike shop in Manhattan specializing in frame welding while the yellow pages turned up welders all over the place for boilers and such.

Is there any specialized knowledge needed for welding the dropout that will make going to this bike shop a necessity? They probably will charge a premium being the only one nearby occupying this niche but I could be mistaken.

If this turns out to be costly then I'll probably hit craig's list instead for a replacement frame.

I only considered using epoxy because it would have become a DIY project.
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Old 09-07-09, 09:14 PM   #9
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Being that its on the dropout, which is fairly thick, any GOOD welder should be able to do it, Particularly someone who welds sheet metal. Should not be too expensive if you prep it for them.

Might be cheaper yet to buy another frame/bike off craigslist.
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Old 09-07-09, 09:25 PM   #10
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May just need an I-bar saddle

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Old 09-09-09, 02:56 PM   #11
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Wen to a local welder, who apparently works on iron fencing among other things from the looks of his shop, and he arc-welded in less than 30 seconds - for $5

Come see what a $5 weld will get you
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Old 09-09-09, 03:19 PM   #12
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Wen to a local welder, who apparently works on iron fencing among other things from the looks of his shop, and he arc-welded in less than 30 seconds - for $5

Come see what a $5 weld will get you
You got the right fix. I had a crack like that on a very nice frame, did the same thing, had it arc-welded. Worked great. I would never use a torch since you would heat up the joint too much and the solder would melt out.
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Old 09-09-09, 04:19 PM   #13
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Grind it down some and put on a rust resistant primer until you're ready to paint.
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Old 09-09-09, 07:40 PM   #14
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Wen to a local welder, who apparently works on iron fencing among other things from the looks of his shop, and he arc-welded in less than 30 seconds - for $5

Come see what a $5 weld will get you
Since that's a mild steel stamped dropout you will likely be O.K. It may last forever. Then again, don't be too shocked if it cracks again right in the same spot. That's a lot of heat in a very small area and without heat treatment it just might crack... or not.
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Old 09-10-09, 09:20 AM   #15
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I think you mean annealing.
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Old 09-10-09, 07:10 PM   #16
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I think you mean annealing.
Yes, as a form of heat treatment.
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Old 09-10-09, 08:18 PM   #17
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You got the right fix. I had a crack like that on a very nice frame, did the same thing, had it arc-welded. Worked great. I would never use a torch since you would heat up the joint too much and the solder would melt out.
A torch and brass would have worked fine.
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Old 09-10-09, 09:42 PM   #18
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a weld will be quicker and easier than a braze in this circumstance. I could probably have fixed that in about 30 seconds with a little mig (minus 20 minutes of prep, of course)
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Old 09-11-09, 08:08 PM   #19
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BTW, did the welder grind a V-notch into the crack before welding? On both sides?
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Old 09-11-09, 08:42 PM   #20
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BTW, did the welder grind a V-notch into the crack before welding? On both sides?
He did use a power grinder before welding. Whether it was to grind a V-notch at the crack or, perhaps, to simply clean the immediate area surrounding it, I just don't know. He did grind it on both sides.
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