Brazing, soldering lugs…Turbo Torch?

[Applesauce]

Kinda stupid question time, probably… I’m kinda slowly brushing up on my frame-building knowledge after many years away from it. I don’t remember what I don’t know about it all. I’m currently stuck on: why oxy-acetylene/oxy-propane, and not just air-acetylene? Obviously the answer is temperature, but I feel like there must be some more to it than that. Controllability? Obviously the answer is that pure-oxygen flames are superior, because that’s what everyone uses. I’m just curious why?

I’m asking partly because I have an air-acetylene Turbo Torch for plumbing (copper and brass mostly, sometimes some steel), and it seems to get plenty hot. 5500° F ish? And it’s a big, brutish flame that seems to me would be great for lugs, whereby one could get a whole whack of metal up to temp at once. But I know there’s something wrong about this idea, because no one does it. (I’m smart enough to know I don’t have some kind of solution that no one else has ever thought of. ;)) But…why?

Thanks, sages.

[e-RICHIE]

Kinda stupid question time, probably… I’m kinda slowly brushing up on my frame-building knowledge after many years away from it. I don’t remember what I don’t know about it all. I’m currently stuck on: why oxy-acetylene/oxy-propane, and not just air-acetylene? Obviously the answer is temperature, but I feel like there must be some more to it than that. Controllability? Obviously the answer is that pure-oxygen flames are superior, because that’s what everyone uses. I’m just curious why?

I’m asking partly because I have an air-acetylene Turbo Torch for plumbing (copper and brass mostly, sometimes some steel), and it seems to get plenty hot. 5500° F ish? And it’s a big, brutish flame that seems to me would be great for lugs, whereby one could get a whole whack of metal up to temp at once. But I know there’s something wrong about this idea, because no one does it. (I’m smart enough to know I don’t have some kind of solution that no one else has ever thought of. ;)) But…why?

Thanks, sages.

When we started making frames at Witcomb USA we used Turbo Torches for several months. We jettisoned them because they may heat well but lack all other attributes needed to coax the filler material through and around the basic joints that make up the confluences of a typical bicycle frame.

[Applesauce]

I think I get it. So while you might be able to get the whole thing hot, if for some reason you didn’t, you lacked the control to get a smaller region hotter?

[e-RICHIE]

I think I get it. So while you might be able to get the whole thing hot, if for some reason you didn’t, you lacked the control to get a smaller region hotter?

the tips are changed for the heat coverage desired.

how to explain this?

better to just say that the turbo torch process isn’t framebuilding compatible.

one and only one exception might be steering column to crown assemblies.

[Mark Walberg]

I built my first frames in the early 1970s using acetylene and air with a Smith torch that made a pretty big flame. I learned how to do this by going to the local welding shop and asking a guy what I needed to braze a frame. He showed me by brazing a seat lug to a short piece of Reynolds 531 that I had brought with me. This setup worked to build quite a few frames. When I switched to acetylene and air, I found much better heat control, and I was much less likely to cook a joint by getting too hot. It is certainly doable without the O2 though. With practice (like anything else) one can get good at it.