I would like a second opinion on the repairability of this crack in the BB-lug (left chainstay). The frame is an EM MX-leader (sort of a barn find) that I had for some time now but only recently discovered not to be intact. My LBS (used to work in the EM factory) says "can't be done without replacing the seat tube". Surely there are other ways to salvage the frame. Or not?

replacing the seat tube is probably the only way, don't know any ways to clean out a rusty lug with a tube in it. Is the drive side chainstay going to break next? Doesn't look great

Well actually I don't think there's much rust around, the frame has a rust-colored primer. Thats what you see under the paint chips.

I'd strip it clean before making an assessment. It may be brass brazed. If it is I'd clean and braze the crack and keep an eye on it. When, and if it happens again- pull the tubes and replace the lug.

CMAW; I am not expert enough to provide a real answer, but first I would want to strip the paint off fully and take close up pictures to inspect. Be sure to take some looking in through the BB shell to see where the tubes are inserted into the shell (discussed below). Do you know what the value of the frame is or how rare it is in terms of C&V aspects.

My gut feel is that the chainstays and maybe all the tubes may have not have been fitted to the ID of the BB shell which will add a troublesome stress ridge to each joint. Also the shells' lugs for all the inserted tubes may either been too short from the OEM or have been widdled down too much by the builder. Both probably, but the goal was likely to make them look more "artsie". The amount of metal to metal looks minimal all around imho.

Fixing it seem dubious to me. I would recommend poking the question to Frank (FTW). He might see that a good TIG welder could run a line of weld down each of the cracks in the shell and get enough penetration to provide at least a minimally acceptable repair. Although I do braze over weld often, I have never welded over a brazed joint. But I think I have heard others say that the brass can polute a weld. I am thinking that I am thinking TIG as it might avoid throwing a lot of extra heat at the larger joints associated with the BB and thus might not disrupt the brass in those areas or reduce the amount of re-brazing needed after the shell integrity is restored by welding.

Anyway, it 110% fact that whatever Frank says is what you should do. Trust the Force.

/K

^^^^ Sorry ksisler, I don't understand a word you are saying, except the part about FTW. I'm sure you're right there. Thus far it looks like my options are: turn this historic frame into a beater and die with my boots on (no appropriate emoticon found). OK, stripping and cleaning around the crack will be my next step.

It's going to be sketchy with the crack in the casting itself between the seat tube socket and the c-stay socket. Replacing the tube will not take care of this.

dave

I fix all the courier bikes around here - they're always breaking their old lugged frames. I fix cracks like that by just doing a decent fillet braze over it. Do it neatly and it looks like it's meant to be there, and it's at least as strong as new.

the reason I said there was rust is that the crack in the shell (which I didn't see before) is leading from a place where someone had a bad day and didn't completely braze the shell to the seat tube. There is no paint in that area to keep it from rusting inside the bb shell socket.

CMAW; Apologies, as I made some assumptions given your post to the Framebuilders forum. But if you got the "listen to what the Frank says" recommendation, that will carry my message well enough. Some other later posts have also posited some other viable fixes which is a good thing also. Hope it works out well...and please post your outcomes...with pictures if possible.
/k

So sloppy brazing was the basic problem that resulted in the chainstay lug cracking? Just trying to understand what happened here.

yes, I'm pretty sure if that seat tube was removed that you would find that the bb shell was not completely brazed. The crack would not have separated the seat tube from the shell like has happened if the joint was completely brazed, the crack would have gone up into the tube.

It's not hard in a production environment to lose track of where you are on a lug. Break whistle could have blown halfway through or film crew could have come through while that bike was being brazed or any number of things could have distracted the worker. You can find pictures and videos of their construction techniques. It would be really easy to screw up.

Thanks all for the input, will keep you posted.