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Small crack in seat cluster

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Small crack in seat cluster

Old 09-27-22, 03:46 PM
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Small crack in seat cluster

Hello! I'm in the middle of restoring this beautiful 1975 Colin Laing touring bike. I found a small crack where the right hand seat stay is brazed onto the seat tube lug. The crack seems contained to the silver. It's about 12mm and the rest of the joint seems fine.
I have a torch set up so I could repair it while the paints off. What do you think the best course of action is?

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Old 09-27-22, 03:52 PM
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Repair it with your torch while the paint's off
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Old 09-27-22, 05:50 PM
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The problem that builders have with that style of fastback attachment is not getting penetration and then filing a nice sharp line at the joint. Because nobody wants a big fat fillet there. It looks to me that this bike has been repaired before and the repair failed.

I know this is very conservative, but what I would do is replace the seat stays. Or at a minimum pop that stay loose so you could clean things up. It's going to be difficult to clean out that joint to get clean surfaces. So it's just going to crack again if you just braze it again. .
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Old 09-28-22, 08:15 AM
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Are you sure the filler is silver? Were the stays to be replaced or the cracked one pulled back enough to clean up the area well I would consider using brass/bronze filler to reattach the stays. Silver filler does noy like big gaps and this miter is not the easiest to make in the stay end, the stay wants to touch the tube and the lug surfaces and the step between the two can be hard to create in the miter. Andy
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Old 09-28-22, 01:15 PM
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Simply remelting the existing filler and maybe adding a bit more (after thorough clean-up) doesn't have the highest likelihood of success, as unterhausen pointed out it might just crack again later. But on the other hand, it might not! And it's super easy to try.

So "You've got to ask yourself one question: 'Do I feel lucky?' Well, do you, punk?"

If the cost of a paint job is too high to risk and/or you need a bike that'll never ever crack, then the quick'n'dirty repair is not for you.

If it were my bike, I'd probably just re-flow it. Maybe even for a customer if I could trust him when he says "I won't blame you if it doesn't hold".

Also in favor of the quick re-flow is that fact that this is a totally low-stakes place for a crack. It absolutely will not throw you to the ground even in the worst-case scenario.

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Old 09-28-22, 01:30 PM
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Originally Posted by Andrew R Stewart View Post
Are you sure the filler is silver? Were the stays to be replaced or the cracked one pulled back enough to clean up the area well I would consider using brass/bronze filler to reattach the stays. Silver filler does noy like big gaps and this miter is not the easiest to make in the stay end, the stay wants to touch the tube and the lug surfaces and the step between the two can be hard to create in the miter. Andy
I'm not sure the filler is silver or brass, is there a good way to tell? Once I know the material Is it impractical to just heat the joint up, melt the filler and add some more, even build a small filet? I'm nervous about popping off the stay because I don't have any frame fixtures to hold it. Though I guess it wouldn't be to hard to make something if it's nessary.
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Old 09-28-22, 01:54 PM
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As Mark B said trying the just remelt as a first effort makes sense.

Brass/bronze is, well, brassy colored. Silver is a grey color. you could lightly run a hacksaw blade along the crack and see the bright color that shows. Ideally any dirt/grime/oils in the crack should be removed best possible anyway before a remelt is tried.

Hopefully the filler is brass/bronze as with the higher heat to braze and the flux being more reactive (compared to silver flux) will make any remaining contaminate not be a problem.

Mark's comment about any repainting and associated cost is a good one too.

For just remelting the joint no added fixture should be needed. The other stay and the brake bridge are doing this already. Andy
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Old 09-28-22, 07:00 PM
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Originally Posted by bulgie View Post
Also in favor of the quick re-flow is that fact that this is a totally low-stakes place for a crack. It absolutely will not throw you to the ground even in the worst-case scenario.
Mark B
Waterford apparently had a problem with this kind of fastback because I have seen 4 of their bikes with this style and 2 of them were cracked. I looked at one in the hotel bike storage room before we started PBP and noticed it was cracked. After we had ridden halfway across France and back, I asked if anyone knew whose bike that was because it was cracked. People were outraged I didn't tell the owner before. But I figure I did them a favor because it wasn't going to break all the way and there was nothing they could do about it then anyway. AFAIK, they finished, although if they didn't it wasn't because of that crack. Riding 1240 km in less than 4 days isn't that easy.
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Old 09-28-22, 08:49 PM
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Originally Posted by unterhausen View Post
People were outraged I didn't tell the owner before. But I figure I did them a favor.
Yep, you did the right thing!

I got in trouble once for pointing out a fatigue crack. It was at some organized meet, I forget what but not a race, Seattle-To-Portland or a century or some such. A couple of racers were showing off their racing tandem made by a local framebuilder, and predicting whatever scary-fast time they were about to do the ride in, with a small crowd around them listening, a half dozen or a dozen maybe (this was 40 years ago, forgive the vagueness). I said, loud enough for everyone to hear, "what about this fatigue crack?" The guys riding the tandem were his friends and they were outraged that I would point out the crack in the frame, or at least that I would do it so publicly. OK, it was a bit of a dick move on my part, but the local FB who made the bike was giving all custom FBs a bad name IMHO because his workmanship was so awful. I hardly ever saw one of his frames that didn't have a crack somewhere. I probably should have told them quietly, away from the crowd though.

Another tandem he made was on a Glenn Erickson organized tandem ride I was on, and the captain's pedals started scraping the ground when they guy stood up to pedal. The front seat tube had broken clean off from the BB shell and the frame sagged down opening up a big gap between the tube and the shell. The frame was practically new, too. Capn was a top local racer, had been US National (amateur) Road Race Champion actually, turned pro right after that. Someone who should have known better, Just goes to show ya, being able to ride fast doesn't mean you can tell a bad bike when you see one.

Speaking of people who should know better, this FB got a reputable bike shop to sell his frames, and they made a display that had info about him, like the fact that he'd apprenticed under Bruce Gordon. Except when Bruce himself dropped in for a visit and read that display, he threw fit, yelling for the manager, threatening to sue etc. Turns out BG had never heard of this guy! Ross Shafer was with Bruce at the time, he's the one who told me the story. "Man you shoulda seen him, he was on fire!" or words to that effect. Ross says Bruce showed the shop manager everything that was wrong with the frame they had on display, and it was a long list. The shop owner apologized, took down the display and promised not to sell those frames anymore, no lawsuit needed.

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Old 09-28-22, 09:32 PM
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Originally Posted by unterhausen View Post
Waterford apparently had a problem with this kind of fastback because I have seen 4 of their bikes with this style and 2 of them were cracked. I looked at one in the hotel bike storage room before we started PBP and noticed it was cracked. After we had ridden halfway across France and back, I asked if anyone knew whose bike that was because it was cracked. People were outraged I didn't tell the owner before. But I figure I did them a favor because it wasn't going to break all the way and there was nothing they could do about it then anyway. AFAIK, they finished, although if they didn't it wasn't because of that crack. Riding 1240 km in less than 4 days isn't that easy.
Ayy that's comforting. If that was my bike I would have laughed and thanked you for saving me some stress!
I think what I'll do is reflow it. I'll get to it in the next few days and post my results!
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Old 10-01-22, 05:30 PM
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Ok so I reflowed the joint and added a little more filler. I determined that it was brass. I built up a little more brass, feel pretty comfortable riding this thing now. Still have some sanding to do, but these photos make it look way uglier then in actually is. I'll upload some decent daytime photos when I finish.


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Old 10-02-22, 02:36 PM
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I think the thing that causes these cracks is tightening the seat post binder bolt. I suggest finding the biggest seat post that fits.
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