induction brazing

[CSTRider]

Came across this video (https://www.youtube.com/watch?v=NQXdhxSCet8) as i was searching for info about induction stoves.

Pretty amazing - able to uniformly heat a tube and fitting to 1400F in 30 seconds without an open flame. Made me wonder how applicable this technology might be to frame building?

[Lewis Moon]

Wow.

[David Tollefson]

Interesting.

[Kirk Pacenti]

Trek (and probably many others) used that for years, back when they still made steel frames in house.

They would use it to braze 1018 inserts into 4130 seat tubes, head tubes and BB shells as sub assemblies. Because of the thickness of the tubes and/or the high temp brazing alloy used (copper?) they could then weld the frame together, without remelting the brazed areas. The idea was that the cutting tools used to machine said portions of tube could be run much faster and last much longer when cutting the softer 1018 steel. They also used induction brazing to join seatstays and chainstays to the dropout in one operation.


I saw a video of their production line once, where they used in several operations. I'll see if I can dig it up.


Cheers,
KP

[jr59]

I work with jewelry, and I have started to wonder about laser welding for bike tubes.

[Dude]

I believe this is the same as Schwinn's electrofusion process.

[Mark McM]

I believe this is the same as Schwinn's electrofusion process.

Schwinn's Electro Forging process was a flash welding process, not an induction brazing process.

http://sheldonbrown.com/varsity.html

[tigoat]

We do a lot of laser welding and vacuum brazing at work but I don't see why would anyone even mess with other brazing and welding techniques to make a bike frame. In the near future, we should be able to 3D print a whole metal frame, which is somewhat possible now. We also do a lot of 3D printing currently at work but not with metal though.

[CSTRider]

Schwinn's Electro Forging process was a flash welding process, not an induction brazing process.

http://sheldonbrown.com/varsity.html

You're BOTH correct. Sheldon's description says that while the Varsity was mostly electro-forged (E/F), the Varsity seat tube/top tube joint was induction brazed:

Schwinn engineers went to great lengths to create joints suitable for E/F, but one--the top tube to seat tube joint-- always escaped their best efforts. Remember, E/F is an edge-to-edge process, and this joint had only one edge, on the end of the top tube. For years this joint was hand brazed and polished, but finally an economical solution was found. When the end of the tube was mitered ("notched" in Schwinn parlance) its edges were also flared to fit up to the seat tube. The frame was placed in a fixture with the head pointing upward. Surrounding the seat joint were induction coils that heated the seat joint rapidly, melting a preplaced silver brazing wire. Yes, your Varsity had a lugged, silver brazed joint!

[Kirk Pacenti]

We do a lot of laser welding and vacuum brazing at work but I don't see why would anyone even mess with other brazing and welding techniques to make a bike frame. In the near future, we should be able to 3D print a whole metal frame, which is somewhat possible now. We also do a lot of 3D printing currently at work but not with metal though.

Yep: http://www.dezeen.com/2014/02/07/worlds-first-3d-printed-bicycle-frame/

Fwiw, I'm in. I would love to do something with this technology.

Cheers,
KP