Stripped the paint from a frame I really like and was really bummed to find a crack at the seat stay/seat tube junction:






Frame is a vintage steel Spot single speed. I am trying to figure out what tubing was used now.


Any thoughts, opinions, input greatly appreciated.



Steve

I wouldn't worry about what tubing was used originally. It was certainly some variation of cromoly steel and any current tube of the same size will be comparable. At minimum, you will need to replace the top tube and seat tube, which will likely exceed the value of the frame. If it was mine and I wanted to get some more use out of it, I would just clean the crack really well and weld it.

Don't know if i's use the term "vintage' with the brand Spot. I agree with dsaul that the best repair is likely not worth it, replacing the TT and ST. BTW it looks like the crack is traveling along the weld of the ST and stay. Welding over the crack is one way to repair the frame. Know that some ST distortion is likely to happen and after welding seat post fit might need "massaging". Another method would be to braze on a patch over the crack. The patch would be a piece of steel sheet shaped best possible to fit as tightly as possible. Either way I'd be tempted to drill a small hole at (or just beyond) the ends of the crack in an attempt to limit the crack's continued growth. Andy.

My Guess . as said above a stopper hole at the ends of the crack.

Maybe someone can TiG weld the crack, then ream out the distortion of the seat tube to get a seat post back in.

The Brazing a Patch is Good too , as Long as the filler wire used to make the original TIG weld was Not Stainless

Stainless wire is popular to use , but brass wont stick like it will with plain steel filler wire , then

the use of silver content solders will be better , but they flow thinner and so you need the patch to fit more precisely.

Would you think that is from a seatpost without enough insertion length?

Drill the ends of the crack and fill it with brass. That should keep it from spreading.

I'd probably TIG it starting along the seatstay weld, and continuing up through the toptube.

It is quite possible that the crack does extend through the front part of the seat tube which will be hidden. You might see it by inspecting the inside of the seat tube. It would be hard to repair. Perhaps that is one that could be drill stopped. It may be only marginally structural, but could increase the risk of recurrence.

Otherwise, I wouldn't drill it out of you're planning to TIG. The end of the crack will disappear with the welding process.

I generally don't grind welds, and so the repair will be visible.

As mentioned, with good weld penetration, you'll need to ream the seat tube.

How tall is your seatpost? Good fit? I'd make sure the post extends down at least a couple of inches beyond this junction.