Hi, I have just started building bicycle frames and I have used oxy-acetylene for brass brazing, fillet brazing and silver soldering. I am looking for advice on brazing techniques and how you can properly identify if you are overheating the tubes you are welding other than orange is good, red is bad etc.
Are there any forum members in Ireland that can provide advice, tutoring in person in Ireland.
Haven't done much bronze welding for a long time, but did a fair bit a long time ago. If I remember rightly, the less heat the better. You heated it up enough to get it flowing and no more. If you were doing galvanized parts, this was essential, as too much heat and you'd burn the zinc off, the telltale being white smoke. Nasty to inhale, and more importantly, the part was no longer galvanized, so defeating the object of bronze welding it in the first place. We always called it bronze welding incidentally, not brazing, which we were told was something that plumbers did (crusty jugglers tut tut).
The best way to tell when the metal is hotter is that when its red you should be able to let the rod fall through your fingers and once it has started melting continue with your usual practice
Brazing and braze/bronze welding are distinct terms, The AWS (American Welding Society) divides them into those that depend on capillary action (brazing) and those that do not (braze/bronze welding).
In braze/bronze welding, no capillary action is involved, and a relatively large amount of filler is used. Braze welding used to be known as bronze welding, and is quite different to simple brazing.
Braze/bronze welding may be used to weld or repair iron castings as it is done at a fairly low temperature (850 deg) which does not change the mechanical properties of the casting.
Braze/bronze welding was most frequently found in hand built motorcycle frames and early racing/sports car/trials car chassis. I daresay it would have also been used in bicycle frames but I have no experience of that area.
I would suggest if you are thinking of making bike frames practice first, and build choppers etc.
These are all brazed. Better to practice on real frames than nice static joints as you have to think of position.
Having posted a question... never to be seen again
Anyway, just in case - you will find a lot of useful (and dedicated to bicycle frame building) info here: Velocipede Salon