Seat lug crack

[Logan Eiland]

Hello,

I am seeking information about what looks to be a small crack in the seat lug of an orange Quickbeam. The reason I think it’s a crack in the lug and not just the paint is that it is visible from both inside and outside the seat tube. Pictures attached below.

Some questions I have are:
- Am I diagnosing this correctly as a cracked seat lug?
- Is a crack this size and in this location a big deal (I’m assuming yes), and if so, how big of a deal?
- Does this render the frame dangerous to ride?
- Can something like this be repaired? Is there anyone that’s had something similar repaired who can share their experience?

Thank you for any information anyone can share or point me toward.

Logan

[Jeremy Till]

Replying not as a frame expert, but I did work as a mechanic for a while and was often customers' first line of inquiry about frame issues. Take my advice with a grain of salt. The only authoritative source of information on this would be a framebuilder who has been able to inspect the frame in person.  

All that being said: 

-I would agree that that looks like a cracked seat lug. If my understanding of frame construction is correct, that also means the top of the seat tube is cracked, since it extends through the seat lug and is cut off even with the top of the lug. 

-A crack there would be a big deal in that it would eventually cause the frame to no longer be able to clamp the seatpost. The tension of tightening the seatpost binder bolt would tend to expand the crack, and eventually the seatpost would start to slip. Riding it in this condition would probably accelerate the process. 

-I'll let you evaluate what is an acceptable amount of danger for yourself, given the failure mode I've described above. 

-I would imagine that something like this could be repaired by a skilled framebuilder, but the questions would be whether you could find one that was willing to take on the work, and, depending on what they charged, whether the repair would make sense financially. It's a tricky repair being at the seat cluster joint, where four tubes come together, rather that at a joint with only two tubes, or better yet in the middle of a single tube. Given that the crack is also through the seat tube, a repair might necessitate replacing that tube as well, although a framebuilder might be able to cut it off somewhere in the middle of the tube and splice in a new section to run through the seat lug. I don't know where you're located, but as always, finding a local builder who could look at it would be ideal. 

Good luck!

-Jeremy Till (former orange QB owner myself)

Sacramento, CA

[George Schick]

Are you the original owner of this Quickbeam or did you buy it used from someone?  If the latter is true it may be that the wrong diameter seat post was initially used and thus the seat post binder bolt over tightened to accommodate.

[christian poppell]

Amateur framebuilder here...

Id drill a hole to stop the propagation of the crack then TIG weld to fuse the crack. grind smooth to finish. I would try that first before replacing the whole seat lug.

"If my understanding of frame construction is correct, that also means the top of the seat tube is cracked, since it extends through the seat lug and is cut off even with the top of the lug."

Some seat lugs are like that, many lugs used in production have a shelf on the inside where the seat tube would be cut at 90deg then inserted into the lug. (image from torch and file) I believe that is how the lug is on the QB, I can check mine when i get home and report back. 

Are you at U Michigan? If so, there's Doug Fattic (Niles, MI) and Franklin Frames (Newark, OH?) that are closeish. Doug is great, I don't have experience with Franklin but have heard he is willing to take on odd jobs. 

Long live the Quickbeam!

Christian

Phoenix AZ

[iamkeith]

Where are you located, Logan?  Maybe someone will know a builder or repair service near you, that they can recommend.  

It sure looks like a crack to me, and I too would guess that the most likely cause was a too-small seat post.  I also like Christian's idea:  If you're lucky, perhaps a small drill hole to stop it propogating further, and then brazing the crack itself might suffice without a large area of paint damage.  Great that you caught it before it got worse.

Finding a good builder will be the first step.   I wouldn't hesitate to ask Rivendell if they have any ideas or experience.  You're way beyond anything that could be construed as a reasonable warranty period, so be clear that you're not approaching it from a standpoint of expecting something or pointing fingers.  You're just asking for advice and brainstorming. 

[Logan Eiland]

Thank you to everyone who replied with ideas/suggestions.

@Jeremy: The seat lug extends about a millimeter above the seat tube and the seat tube is seated under a short lip at the top of the seat lug. For now, the crack is isolated to the top of the lug.

@George: I am not the original owner. FWIW, when I purchased the frame from the previous owner there was a correctly sized seatpost installed. 

@Christian: I got in touch with Franklin Frames and had a helpful conversation. From Franklin Frames (based on my description): the frame is probably safe to ride given the location of the crack; the crack likely won't grow once it reaches the point where the lug and tube are brazed together (which it has); if the crack does grow it will likely occur slowly, over the course of years; and fixing it would be easy and cheap ($25 or so) compared to the post-repair cosmetic costs.

@Keith: Christian's suggestion of Franklin Frames is within a four hour drive and they were helpful over the phone. I had the same thought about contacting someone at RBW and I received two quick replies after I reached out. I shared the same pictures and description with them that I included in my original post, here. Their recommendations were the same I got from Franklin Frames: probably nothing to worry about and okay to continue riding; keep an eye on the crack for any growth; if the crack grows, contact a frame builder for what should be an easy fix.

Thanks again for all the thoughtful and helpful replies.

Logan

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Logan Eiland

Doctoral Candidate, Teaching and Teacher Education

University of Michigan

eil...@umich.edu