So this is my first frame, it has a sloping top tube with about 10cm of tube extending above the St/tt joint and another 10 cm of seattube extending above that. A 180 degree crack has formed right above the fillet. I checked seatpost length and it got way beyond the joint so thats not the issue. I suspect it might have to do with the but, im not sure if the joint was on the but or not. Anyway, i want to repair it without changing the seattube because i dont have a jig yet. I was thinking to make a brace on top, to triangulate and disperce the load. I also thought about making a little sleeve to put over the crack but 28.6 ID tubing is really hard to find in the EU. Any ideas?
Peter from Ceeway sells a 28.6 id tube. But I would indeed make a nice sleeve over this crack that also extends below the toptube with a pointy or diagonal end to create the longest possible section.
I would guess you brazed the toptube on or below the butt and the part where the seattube is actually supported so there would be some wiggle room.
I think a 28.6 ID tube likely won’t work, the fit would be too tight, and you need “some” clearance even for silver, to braze.
Personally, I would file the bronze from the fillet away as much and as carefully as possible, and then heat the joint to disconnect the tubes. Then I would take a section of the same tubing I used originally, a few centimeters longer than the top tube diameter, cut a full slot in it, and snap that around the cracked tube and slide it down the seat tube, in between the top tube and seat tube, so that you have a few centimeters above and below the top tube, with the slot on the back side of the seat tube. Flux for silver. Then braze the sleeve in place with silver. Clean that and flux for bronze, and braze the top tube to the sleeve with bronze. You can fill the slot with bronze if you don’t want it visible after paint, and add bronze on the edge of the sleeve that you can smooth out afterward if you want a cleaner appearance. The .7 mm or whatever incorrect top tube length from the thickness of the sleeve likely won’t matter in the real world. This will probably only be a temporary fix, the tube will crack again in the same way again eventually, at the top of the sleeve. Simple answer is your seat tube is incorrectly specified for the application…
Sorry for the confusion, but the tube Ceeway is selling is 28.7 and fits just right when brazing: Spare Tubes
I’d also add a brace to the top tube in one form or another, can make it look nice and provide a lot of support. Otherwise i think it’ll crack down the road again even with the solutions outlined above.
That sounds perfect, so you wouldn’t do the joint again, just slide the sleeve over from the top and make sure it goes down below the top tube a bit too? Thanks for the ceeway pointer, it’s such a shame that since brexit it has become so much more expensive to order from the UK when you live in mainland EU. Maybe ill do a big order one day and ill put in the tube too.
I think I’ll do the brace anyway, this bike is a tracklocross/commuter so I just want it to be up and running again. It doesn’t need to win any beauty contest and ill probably leave it raw metal anyway.
Where are you located? I might have a bit of the Ceeway sleeve in the workshop, and otherwise I am waiting for Peter to finalize my order and I could get it in there.
He! ik zie dat je in nederland woont, ik heb mijn lasspullen in Deventer staan! Studeer/woon zelf in Gent, dus ben op één van die twee plekken. Als ik een stukje daarvan zou mogen overnemen zou dat top zijn!
Ik heb nog een stukje liggen van 110m lang die je zo mag ophalen in Wijchen. Kom je volgens mij vlak langs op weg van Deventer naar Gent.
110 meter lijkt me wat lang, neem aan dat het 110 mm is? In ieder geval super aanbod, ik ga eens kijken wanneer het voor mij uit komt om langs te komen, ben erg druk met afstuderen nu. Mocht dat niet lukken dan misschien verzenden? Dan betaal ik natuurlijk de kosten.
Oh en, waanzinnig mooie fietsen maak je.
Verzenden kan altijd, maar het is natuurlijk veel gezelliger als je langskomt. En idd 110mm.
Dat was ook mijn redenering, Ik zal iets laten weten!