d36csr

Id be really grateful for some advice.

I just bought a Dawes Super Galaxy for spares and repairs, as it has a crack in the seat-tube caused by the previous owner trying to chizel out the old seatpost! So silly! I eventually managed to remove the mangled remains of the seatpost, and was wondering if anybody knew whether it might be possible to save the frame after all, since it was made in the UK from fancy Reynolds 631 steel tubing.

The seat-clamp is intact. I was thinking I could put an extra-long seatpost in it, so that my weight is applied to the frame at the seat-clamp, and far below the crack, rather than stressing the weakened cracked area of tubing in between. Perhaps I could get someone to weld a metal patch over the crack to stop it spreading? There's a local engineering firm that does welding, or I could take it to a specialist frame welder.

The crack is about 1.5 inches long. Please see attached picture.



I'm not bothered about aesthetics, just practical considerations.
Thanks so much for reading.

Ben

lostarchitect 

I would recommend posting this in the framebuilder's forum. Someone there can give you better advice. I have heard of people brazing in another smaller tube inside the seattube to repair cracks like this, which makes the seatpost size smaller.

fietsbob

a TIG weld, to close thecrack, then boring out the ID again.. and touch up the paint,

Are they, the locals, practiced at working with thin wall steel tubing?

davidad

Drill a policeman (hole) at the end of the cut to keep it from migrating. Use a slightly longer seatpost and ride it.

DannoXYZ 

No problems with that crack, most of the load is at the top of the seat-tube when the clamp is tightened.
To keep that crack from spreading, drill a 4-5mm round hole at the very bottom. Similar to the original hole at the bottom of the slot.
Then carefully brush on some primer over the exposed metal edges.

Ira B

Easy fix:

As mentioned, drill a small hole at the end of the crack (although it sounds like it is actually a chisel cut), then carefully dress the cut with a file to match the existing cut of the seat post clamp. Use a longer seat post and be sure it is inserted well past the bottom of the cut. You will probably be the only one who ever notices.

Better, more costly, proper and aesthetically pleasing fix:

Drill a small hole at the bottom of the cut.
If you have done automotive body work and can use a hammer and dolly, use a steel seat post as a dolly and reshape the steel around the cut. Get someone who is good at TIG welding to stitch up what is left and do final clean up with a dremel (inside) and file (outside).

neurocop

I believe that the ST defect could be repaired by silver brazing...If I had the bike I would drill a 1/8" hole at the bottom of the ST "crack" clean up the area with a wire wheel or just emery cloth, flux the margins, and carefully fill in the defect with something like 15% Silvalloy rod. Then I'd smooth out the filler weld inside and outside and refinish to make the repair look good. That's a lot of work, and you could probably get by without the effort, since this "crack" shouldn't really compromize the strength of the frame.

Nick

Kimmo

If I was gonna hit this frame with a torch, I'd convert it to fastback, with the seatstays joining the seat tube right over the damage.

cs1

WOW, can I ask how you got that?

Grand Bois

I think you mean Reynolds 531.

Airburst

Not that it couldn't still be a mistake, but Reynolds made/make 631 tubing as well. I seem to recall hearing that the difference is it's supposedly designed to withstand more heat than 531, to allow it to be used in welded frames. Whether or not that's true, I've certainly seen a frame with a "631" decal on it.

Kimmo

It's Wikislap time.

Michael Angelo 

Simple fix for a qualified frame builder.

d36csr

Wow, I'm so very grateful to everyone who took the time to reply to my question. I think I'll probably just drill a hole at the bottom of the crack, as I'm strapped for cash. Who knows, maybe the tatty look will save my bike from getting stolen!

Grand Bois, You might be right actually. I assumed it was 631 because that's what Dawes use now, but it might have been 531, because now that I look, there isn't a decal.

Yay, I got a galaxy for £150!!