BB shell replacement Qs

[Bim]

Hey guys, So I picked up a frame that seems to have a cracked BB shell (hoping the seat tube is fine). I will be taking it to the builder but I wanted to ask if anyone had any prior experience in having a similar repair done?

I think the frame is worth saving.

Any pointers, ideas on what I should expect the repair will cost, would really help.

Thanks!

[DRietz]

The bottom bracket shell is the hardest part of a lugged bicycle to replace. Expect to pay a substantial amount of money.

A failure like this usually indicates the seat tube was under tension, which would subsequently indicate to me that the frame is not worth repairing (i.e. not well put together)

[Bim]

That's too bad. I'll see what the builder says and ask what sort of assurance he can give me if I went ahead with the repair.

Thanks!

[David Kirk]

So....you have a lugged steel frame that has a broken bottom bracket shell?

If so it can probably be replaced.....it's a big job but it can be done if need be. The tough part may be finding a replacement BB shell. There isn't a universal shell design and it would be best if a direct replacement for the original shell can be found.

Cost - this will vary dramatically from builder to builder. Like I said it's a big job and it will take a number of hours to do properly. Let's call it 4 hours VERY roughly at a shop rate of $100/hr and then add the time to source a BB shell. On top of this the cost of shipping to/from the builder needs to be considered....call that $120ish.

And of course the paint will be toast and that will not be cheap.....and shipping to/from paint.... In the end it will be a minimum of about $1100 to do it. That is assuming that a compatible BB shell can be found.

I hope that helps.

dave

[Bim]

Thanks Dave, that's very helpful! Builder is local and Velocolour is also a few minutes drive. I'll see what the builder says.

I would post a pic but the file is too big. I'll try and upload later tonight.

[Bim]

Not sure if this'll work. I uploaded a couple pics on Google:

https://photos.google.com/share/AF1Q...hLMTY1WENXcGhn

[Mark McM]

Originally Posted by DRietz

A failure like this usually indicates the seat tube was under tension, which would subsequently indicate to me that the frame is not worth repairing (i.e. not well put together)

What does this mean? When does a seat tube never experiences tension (tensile stress)?

[DRietz]

Originally Posted by Mark McM

What does this mean? When does a seat tube never experiences tension (tensile stress)?

Yes, let me clarify. Take for example that the seat tube angle is different from the predetermined angle of the ST socket on the lug, and this is not accounted for well enough in tube prep stages. The ST gets brazed in to the BB at the desired angle, but under “tension” as the BB socket has not been adequately adjusted. You end up with a “stress riser” of sorts, leading to premature fatigue issues.

Does that make sense? It’s just a hypothetical.

[unterhausen]

I would worry a lot less about that with a bb shell than I would with a head tube lug. From what I have seen, the seat tube/bb joint is one of the most likely to fail. Lots of cyclic load down there. And it sure looks like that joint wasn't properly brazed, the shoreline is virtually all cracked. I vote metal recycling

[Black Dog]

Why not just ride it and see if it gets worse? It may stay like that for ever. It will not fail catastrophically. The cracks have just isolated the tongue created by the cut out in the lug.

[ultraman6970]

Im a little naive and because seen the weirdest fixes to bikes ok?

I do not think you need the shell replaced at all. When you mentioned a cracked bb Shell I thought the thing was split in two, thing ive seen in atalas, miyatas and even derosas. When the tube is not all the way down (usually because he shell was not even filed, typical 80s mass produced stuff) the tube doesnt fit down enough and the shell starts stressing and cracks pretty much in the middle, yours is not which IMO is a good thing.

Yours IMO is salvageable, what broke is the little ear on top of the carving, what you need to get is somebody that can fill that crack, even better fill up the crack and the carved hole in the shell all together, repaint and good to go, easier to say than get it done because the area is super small.

I would recommend aaron dykstra for the job but the dude is not working anymore, he was the only one willing to do a weird repair in frame I had.

Just my 2 cents.

As for price no clue, we got shells replaced for pennies in my country and thats the only place I know you can do repairs for almost no money.

Or what dog says... is just the ears... IMo that cracked due to crystallization in that area, probably the shell it self wont crack or explode ever.

[Bim]

The crack goes all the way around the ST/BB joint. Doesn't this mean that the BB shell is now only attached to the DT and CStays?

It would be great if it can be repaired by just re-brazing and filling the joint!

[jtakeda]

Originally Posted by Bim

The crack goes all the way around the ST/BB joint. Doesn't this mean that the BB shell is now only attached to the DT and CStays?

It would be great if it can be repaired by just re-brazing and filling the joint!

If you already know you’re gonna save the frame at any cost I’d just take it to the builder.

Without seeing the frame and touching the crack and getting a good look I don’t think anyone besides Dave Kirk is qualified to make an honest assessment.

That said. Prognosis negative

[David Kirk]

It looks to me like the seat tube has separated from the BB shell. Impossible to tell why without pulling it apart. When the seat tube came loose from its socket part of the rear tang stayed affixed to the seat tube and thus broke away from the shell.

This is not an indicator that the frame was under any undue stress or that the ST was under tension....it was just not brazed as it should have been and it failed.

It's remotely, very remotely, possible that the seat tube could just be re-brazed into the shell and life would be good. The problem is that the area where the braze needs to go is no doubt corroded and full of dirt and grease and one can never get all that crap out and any re-brazing would be compromised and highly suspect. I personally would not waste any time going down this re-brazing road.

If it's worth it to spend real money and time on it I'd have it professionally repaired....if not make a lamp out of it.

dave

[xlbs]

Why not take this frame to Mariposa?

They are capable of assessing the problem accurately, and if they determine that they can repair the frame, they have a good painter on site who will do fine work for considerably less than velocolour.

I've seen Mike Sr. and crew do some wondrous repairs and restoration over many years. I would suggest that they should be your first point of call.