Airburst

A couple of months ago, I mentioned to my grandfather (a retired engineer) that I was planning on building a bike frame, and when I told him I was intending to braze it together, he told me that he once bought an attachment for a stick-welder type inverter that would enable it to be used for brazing. He never used it, apparently he was given a load of welding gear by someone, but a small amount of online research later, and I've come up with this http ://www.mig-welding.co.uk/forum/attachment.php?attachmentid=4871&d=1221431165 Apparently, it works for brazing, and my grandfather says it looks like the one he had. Purely out of curiosity, has anyone ever used one to braze a bike together? Not that I'm intending to try it (apart from anything else, I have NO idea where to get one), but might it work?

NoReg

That url didn't work for me.

One can braze with bronze using TIG. Consensus is that the bead laid down is not large enough for a braze alone joint. Whether there is some skillset that would allow pushing that, I don't know. Freddy Parr might know. Main use as I understand it is to cover tig beads so they can be faired where for some reason that is a) desired; b) bondo isn't posh enough.

Or maybe your pic is off an older process. Probably at all earlier times, but particularly during the war, they invented whole processes that started from the point well the X indutry won't get any strategically important Y material, so the boffins would invent a whole new process to get by on that used some stuff we would laugh at today. Note, they won the war. These days the options are represented as only a few. But there are lots of ways of doing stuff, and often even today given industries will be all for one method over another. For instance some high performance industries MIG 4130, others would only TIG it. Another guy who has made a study of this stuff is Kent White.

Airburst

Sorry about the URL. It's just a picture of the tool. Basically, it has two carbon electrodes in it, which you strike an arc between, and move to adjust the gap to maintain the arc as the electrodes burn away. The work isn't part of the electrical circuit, the torch is completely self-contained. You just bring the arc close enough to the metal that the radiant heat gets the whole thing hot enough. It may seem rather crude, but I've seen an older book which references welding aluminium using a "twin-carbon arc torch", which looks rather like the thing above.

NoReg

Interesting. One thing is the heat of the arc which is very high, and the other is the light given off which is also really high. Whether one could get down there to bring both parts to a nice low even heat is the question. One does not want to be making drips of the brass on a "cold" metal surface, as you know.

Airburst

After more research, it's not really a question of "is it possible to braze with this thing" because I've found more stuff online saying it is. It's a question of "would it be the right sort of brazing to build a bike". If my grandfather can find the one he had, and his inverter still works, we'll try and use it and see what happens.

NoReg

That was sorta where I was all along.

Bike fillets are kind a weird area of welding. I am not familiar with too many other processes that use that much filler on such fine walls. Not really an industrially sensible process, which leads one to wonder how many earlier processes that would have accomodated it.

Be careful that you have someone on a kill switch when playing with DC welders, particularly older units and UK input voltages.

Let us know how it works out.

bobbotron

I'd say give it a shot on some practice material, wear good safety gear, and if nothing else, it'll be a fine way to spend some fun time with your grandpa. (Just don't electrocute yourself!)

Oh, and post your photos/carnage. It'd be cool to see how it works or doesn't.

fietsbob

You can get away with stuff on thick plate that will burn holes in thin Bike tubing ,
but practice on scrap is always a good idea..

AndyMann

there's a space between the http and the ":"
I took out the space and got to see the picture.

ultraman6970

This is comming from another web page ok? I was wondering the samething long time ago...

"Silicon bronze TIG rod, and half the amps you would use for steel"

No clue if it will work or how.

Thanks

https://bbs.homeshopmachinist.net/showthread.php?t=40869

tuz

A friend is practising TIG welding bikes, and he told me he was going to TIG weld braze-ons (cable stops, etc.) with a brass rod.

And indeed my local welding shop has some Silicon bronze TIG rod. So it certainly can be done I guess. But for an entire joint vs. a small joint like for braze-ons? No idea sorry.

ftwelder

You can not apply brass with TIG. You CAN however apply silicon/bronze. It's plenty strong for the application. It's a bit more difficult than TIG steel and does not lend itself to weaving or any attempt to flow it out.

I can't zoom and crop but you can see it's about twice the size of E70S2. I used .065 bronze and .045 steel.



IMG_3565 by frankthewelder, on Flickr




IMG_3564 by frankthewelder, on Flickr

mudboy

Hey, FTWelder, are you the same guy as Frank the Welder of Yeti fame?

ftwelder

Yes, that would be me.

As a matter of fact, all the braze-ons on early Yeti frames were done with silicon bronze!

NoReg

Did they last?

ftwelder

oh ya. it's very strong material. It's just difficult to apply smoothly. It also shrinks quite a bit. I can send you a bit if you would like to try it.

ultraman6970

ftwelder, sorry but wich is which ?? the 2nd one is silicon bronze?

ftwelder

No, the first is SB the second is E70-S2. Let me be clear though, they were both applied with TIG process.

ultraman6970

Thanks...

Stupid question, it is possible to build a lugged frame using SB???

ftwelder

no, it does not flow well and has a very high melt point.

Oldpeddaller

Hi Airburst, If you want something to try it out on, I've got three old MTB frames that I'm thinking of using to make a "cut and shut" tandem frame! I was going to buy silver rod and gas braze it together but haven't got past the collecting bits together stage yet. Depends where you are in the UK, but if you're in the South East, send me a PM. Sounds a really interesting process!

fietsbob

I may be missing the topic.. But, seems to me plain steel filler wire in the weld, then brass fillet can be added ,
maybe, but Stainless steel wire is more commonly used in TiG .
its the stainless that wont like brass fill over it

NoReg

Thanks for the offer FT, but I have enough trouble with the processes I am already using! Love to hear about the options, but have to keep it simple for myself.