A crack in the brazing.

[waterlaz]

A guy asked me if I could help him fix his frame. It has a crack near the head tube. I haven't seen the frame yet, only this picture. The owner claims that there is no sign of a crack from the inside of the head tube, so it seems to me that the brazing had failed.
Of course, I could "fix" it by heating the lug and melting everything back together, but I have doubts about it. Is there a good way to fix it without rebrazing the head tube lug, given that I don't know how to unbraze the head tube without damaging neither the head tube itself, nor the lugs?

[e-RICHIE]

Is there a good way to fix it without rebrazing the head tube lug, given that I don't know how to unbraze the head tube without damaging neither the head tube itself, nor the lugs?

You answered your own question atmo. Don't accept the repair.

[Dancingbear]

What I'm trying to say is that the joint cracked for a reason. No way to determine the reason without taking the joint apart and looking. Hence head tube replacement, minimum.


If the braze failed it most likely has poor penetration,and (or) poor prep, and at this point any un-brazed steel in the joint will have corroded enough that you could never get brazing material to flow through, let alone bond. All you would be likely to accomplish would be to cosmetically flow the visible part of the crack together. A skilled builder could possibly just replace the head tube, but may find that the downtube is not usable once the repair is underway- (may not have been fully inserted, brazed in with miter twisted out of phase, etc)

[EricKeller]

It would be great if you could just pull the headtube and replace it. However, my guess is that it cracked because there is very little surface area between the lug and the head tube, and the miter doesn't fit closely. In any event, there's no way to add surface area. Best to say no now.

[Doug Fattic]

Evgeniy, as you anticipated and has been explained, it won’t work to repair the frame by just remelting the braze. The surfaces are contaminated and silver or bronze won’t stick. However it is possible to take the head tube and head lugs off and put new ones on to save the frame. In the States this is probably more effort than it is worth unless the frame has a lot of sentimental value. Inexpensive used steel frames are readily available. However I fully understand that Ukraine does not have the throw-away culture that America has so it might be worth it to do the repair. And it can be educational too.

It is also really difficult to try and reuse the old lugs. They are easily damaged taking them off and then they probably won't fit right going back on without some serious work. However it is possible. It is just that being an American I wouldn’t want to be bothered. I can bring a couple of new lugs with me when I come in September if you want to try.

By the way I’m really happy with the stainless steel fixtures I have laser cut and etched in Cherkassy (this is a city 200km south of Kiev). I got some samples of a basic one in May and a more advanced one in June. They are really nice. Fortunately for me and unfortunately for you the dollar has gotten a lot stronger against the grivna so I could get them made at a great price.

Doug Fattic
Niles, Michigan but often in Bucha, Ukraine

[waterlaz]

Thank you, I thought that this is not going to be an easy repair.

It is also really difficult to try and reuse the old lugs. They are easily damaged taking them off and then they probably won't fit right going back on without some serious work. However it is possible. It is just that being an American I wouldn’t want to be bothered. I can bring a couple of new lugs with me when I come in September if you want to try.

Doug, thank you, but the owner still thinks that this should be an easy repair =)

By the way I’m really happy with the stainless steel fixtures I have laser cut and etched in Cherkassy (this is a city 200km south of Kiev). I got some samples of a basic one in May and a more advanced one in June. They are really nice. Fortunately for me and unfortunately for you the dollar has gotten a lot stronger against the grivna so I could get them made at a great price.

That's nice to hear. I actually benefit a bit from weak grivna. People don't buy as many new frames as they used to and instead want to fix the old ones.
Since there are not that many people in Kiev that braze bycicles, this gives me a lot of practice material.