A bit old skool maybe, but has anyone had a cracked tube or joint, on a fillet brazed steel frame?

yes, but not at teh joint.

It's perfectly possible to break a brazed frame.

Yep, I can see now that wouldn't make any difference, perhaps I should have just said joint. The mass of the materials at head tube to down tube and the softness of brass, make me think it could be more durable than say TIG. Be interested to hear folk's experiences – I could be wrong!

🙂

I think the main advantage of fillet brazed frames is that tubes can be replaced relatively easily. I know of a few track frames that have had their top tubes replaced after crashes.

I know of a friend who has cracked a fillet joint, but that was on his first frame building attempt. I reckon a good fillet joint is very strong but how do you know if it's good joint? That has to come down to the skill of the builder.

The mass of the materials at head tube to down tube and the softness of brass, make me think it could be more durable than say TIG

Not really that simple. Here's something I dug out of my bookmarks from years back for light reading 🙂

Fillet, tig, etc.

Bump for the Friday afternoon skivers 😉

Bent a few lugged frames but never at the lugs.

Tigged frames break at welds if the weld was too hot yes, and happens primarily on alu? As brazing uses low temperatures then this is Shirley avoided?

Academic question anyway I'd have thought, steel weld/braze failure is so low.

http://www.singletrackworld.com/forum/topic/steel-gurus-in-da-house-can-i-weld-cracked-853

My reason for asking

In short :Stuff breaks.

Look at the concluding remarks on brazing in:
http://desperadocycles.com/The_Lowdown_On_Tubing/The_Metalurgy_Of_Brazing_Part_4.pdf

"But the fact is that frames do fail, even
ones constructed by the so-called "masters."
I've spent a great deal of time trying
to get failed frames from American builders
to analyze, and have been successful only
twice. Builders are very reluctant to give
frames to me because they fear I'll publish
their names with my results – which would be
bad for business. Because these frames
could teach us a lot, and because naming
names serves no purpose – what happens to
one framebuilder happens to many – the
photos shown in this series don't reveal the
framebuilder or manufacturer. No matter
how skilled the framebuilder is, some very
small percentage of frames will fail for one
reason or another. This shouldn't result in a
negative opinion of a competent framebuilder."

Brazing can be done with an oxyacetylene torch, oxypropane of even propane/air torches: oxyacetylene has a very high temperature flame but low heat, propane has lower temperature but greater heat output.
Reynolds 853 like 531 and T45 and Cro-moly can all be joined by welding or brazing with an oxyacetylene torch.
There is some usefull info in Tony Foale's book Motorcycle Chassis Design.
http://books.google.co.uk/books?id=84hF-qoR5I8C&pg=SA16-PA1&lpg=SA16-PA1&dq=tony+foale+motorbike+weld+book&source=bl&ots=FYD1uNOeRm&sig=VMy2OC81ByzJujsRIFdEW_cbG90&hl=en&ei=ZR6CTMauFsmk4Qb9mO3RCw&sa=X&oi=book_result&ct=result&resnum=2&ved=0CBMQ6AEwAQ#v=onepage&q&f=false

But bronze welding involves neither bronze nor welding, and some of his other comments about oxyactelene welding are surprising.

For info on welding thin-wall low-alloy steels these people have plenty of experience: http://www.tinmantech.com/

🙄 then this is Shirley avoided?

Who's Shirley? 🙄

Its when people do excesive frame realignment that frames end up with some internal stresses, that might end up as cracks.
http://www.youtube.com/watch?v=zsorqEddlMA

http://www.yellowjersey.org/zito.html