I sometimes use a silver brazed sleeve over the top of the seattube and have always just assumed trying to tig seattays on this sleeve was a bad idea but I’m pretty sure I saw a post (maybe from Rody?) that said this was something that he’d done. Is anyone else doing this? Is it just a case of making sure you don’t get penetration through the backside of the sleeve? I think I’ll make some test pieces up but thought it would be worth asking here too. My gut feeling is that I just can’t see it working.
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I’ve always wondered about this interaction for various places like CS caps, etc!
I’ve done it but with thick sleeves: 1.5mm (.058") or maybe 1.65mm (.065").
I dunno that I trust my skills enough to go thinner.
It seems as long as you don’t penetrate the sleeve, there wouldn’t be any mixing of filler. I’m good at stating the obvious.
I also remember a discussion some time ago with Garro about how he does sleeves. He only adds filler about 1" into the sleeve from each end. He doesn’t fill the whole thing. That might provide you the space with no filler underneath to weld to. If you burn through, there wouldn’t be contamination.
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When I did sleeves slipped over seat tubes I would weld everything out and as the last step wick silver from the bottom of the sleeve. To keep the sleeve in place during the buildout I would center drill one or two small holes in the sleeve and fill it with a plug weld slightly proud of the tube OD (file and sand smooth so you’d never know it was there).
I never tried brazing the sleeve in place and welding from there. I always imagined there’d be some kind of issue with silver contaminating the weld and/or running out of the joint.
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I build my seattube as the first step. I add the sleeve, derailleur tab, bottle bosses and seat binder. I can then index off of those so everything is straight and square.
I’m not sure I understand this part. You’re silver brazing the sleeve after you’ve plug welded it and welded the stays and TT? Without flux?
I use nickel “silver” (SIFBRONZE No2) for the sleeves. Good penetration. No issues.
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And you tig weld SS and TT to the sleeve?
No. I am fillet brazing.
I add flux after welding, prior to brazing. Preheat helps the flux travel into the joint. Full penetration isn’t necessary. Weld penetration through to the seat tube is where the strength is.
Same here. Only difference is the sleeve gets brazed in the end.
The weld goes through the sleeve to the ST? I don’t TIG but, that seems odd, and I would like to understand. Are you purposefully burning through the sleeve so that you weld to the underlying tube? Have you cut many up to see how deep the filler goes into the sleeve?
I agree, it doesn’t have to flow all the way through the sleeve but without flux in there and oxidized from the TIG, I’m curious how much penetration you’re getting. I suppose it depends on the configuration.
I had the same question on my last frame so I decided to try a test piece with some scrap material. Went better than I expected. I sectioned the weld and sanded well enough to see the silver line.
Sorry the photo isn’t better but I didn’t see any silver migration or issues with the weld puddle. I made sure to be extra careful with heat while welding and things seemed to turn out okay.
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I am not a TIG welder so, disregard my opinion but this is what I would expect unless the welder is blowing through the sleeve material (bad). Thanks for getting empirical data! What was the sleeve wall thickness?
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