Carbon arc

[Memmeddu]

So since I'm in lockdown with absolutely nothing to do I was wondering about learning more about carbon arc brazing .
I've read various threads online about this technique but I didn't completely understand how it works
This thread would be meant to put together some knowledge about prior starting another thread in the projects section where I will cover the building of the torch .

So what I've understood is that a buzz box would be the preferred power source for this process , someone says that an inverter welder would work but AC is better in this case (heaven electrodes consumption)
Current settings way lower than carbon arc gouging so my little buzz box would be enough (200A)
But I can't understand which size of electrodes and current settings I would need to use (heating stuff for bending)

Another thing I was reading about is eyes protection
Which shade I should use?
About this I'm thinking to get a traditional aulekro helmet (with double glasses and pc clear lenses inside)

Construction wise I'm searching out for various designs and trying to understand which one would be the best
The clamp holder design seems to be the easiest way to make a torch
This involves a kind of clamp that when is compressed will make the carbons touch together and start the arc
There is also the slide design
This involves to use a sliding element on the handle to adjust the distance between the tips of the carbon electrodes
Another design is the "Lincoln style?" I've seen Lincoln electric arc brazing torches online and those use a mechanism which turns the rod holders to adjust the distance between the rods
This design is the most complex but also the most elegant I might say

Heat shield useful or not?
I've seen some torches use a kind of heat shield between the Arc and the handle ,some others don't .

The rod holders
Various possibility here to make them
But what to use?
Copper isn't an option (too much expensive and hard to find here)
Alluminum tubing (I have some) but the parts that hold the electrode would be steel
So steel might be easier to work with , cheaper , and I can weld it .
Steel rods o steel tubing
Steel rods are easier to weld
Steel tubing I could put the copper strands inside of it


So essentially a lot things in mind but actually not clue of how to proceed
I can buy one already made but where's the satisfaction to use something Made with your hands ?
Thanks in advance and sorry for the long thread object

 

[frank horton]

in the old days my instructor used to take the carbon rods outta torch batteries and used them to localy heat up metal.....
thn I think old WW2 searchlight were carbon rods adjusted for the gap ie light.....

 

[Memmeddu]

in the old days my instructor used to take the carbon rods outta torch batteries and used them to localy heat up metal.....
thn I think old WW2 searchlight were carbon rods adjusted for the gap ie light.....

I'm young but I love old technology ,also because today is cheaper ,and usually old stuff is very reliable and bomb proof

 

[eddie49]

my instructor used to take the carbon rods outta torch batteries

Carbon rods could be salvaged from these large bell batteries:

( They were about 20cm tall ! )

and placed into the carbon arc brazing torch in post #2 of this thread:
https://www.mig-welding.co.uk/forum/threads/carbon-arc-heating-brazing.17798/

 

[the snooper]

The carbon rod holders use a slide to get the carbons close enough to arc and are made from brass

 

[Memmeddu]

So those are the torch designs
The "sliding" one is being found on this forum

 

[eddie49]

The 3rd one is the one I know ( and have ! ). The 2nd one is clever - sliding heat shield also adjusts the rods. The 1st one looks unusable to me - after bringing the rods together and then separating them slightly, they need to be fixed. With that one you could not hold them fixed.

 

[the snooper]

1st one looks cheap and nasty, your hand would soon ache and you would then soon lose control of the arc

 

[Memmeddu]

The 3rd one is the one I know ( and have ! ). The 2nd one is clever - sliding heat shield also adjusts the rods. The 1st one looks unusable to me - after bringing the rods together and then separating them slightly, they need to be fixed. With that one you could not hold them fixed.

Which design I should copy ?
I would like to make the second one but I reckonise that it will be very difficult (but I've enough free time )
I just need to understand the sizes and figure out how it could work
The sliding one would be the easiest to make

 

[eddie49]

I agree, copy the third - sliding - one. However, I would suggest make the adjusting slider smaller, just a button, so that after striking the arc and setting the electrode gap, you do not move it accidentally whilst using the heat. Also, make the heat shield bigger.

 

[Arc Tourist]

Copper sleeved carbon arc rods make the best carpenter pencils in the world.

 

[Hopefuldave]

Copper sleeved carbon arc rods make the best carpenter pencils in the world.

Work OK as electrodes for anodising / rust removal too, once you peel / etch the copper off, but dissolve eventually - I think they're carbon dust/granules in a clay binder?

Dave H. (the other one)

 

[mtt.tr]

Ive still got carbon arc kit, not the most pleasant thing to use

 

[Memmeddu]

Ive still got carbon arc kit, not the most pleasant thing to use

I should mention that I would like to use an Arc-Air torch just to see molten metal flying around
I think to remember that someone said that both are very loud process

 

[Rudi McAnichal]

Brazing external corners using a carbon arc torch is fairly similar to O/A brazing, but fillets are much more awkward -- the torch is quite bulky, and the arc flows between the two carbons (rather than projecting forward like an O/A flame), so it is difficult to heat a small spot.

Somebody who used to post on this forum a long time ago reckoned the best carbon arc torch was the Forney design. You can look up the US patent number 3,012,131 (1961).

I once cobbled together a couple of home-made torches, as per these photos. The left hand pictures show a design where the tip spacing could be adjusted by rotating one of the rod holders. The other model had a hinged mount, with a thumb wheel for adjusting the tip spacing. Both of them worked OK, but of course they didn't solve the fundamental problem of excessive bulk.

 

[RWD3M]

That's a blast from the past. The very first body repair I did as a 19 year old was brazing a front end onto a 1968 1600E that I'd driven into a stone wall up in the north of Scotland.

The car survived my ownership and went on to a new owner. Sadly the carbon arc welding kit didn't. To be honest I can barely remember what it looked like, but I do remember some sort of slider involved.

 

[Memmeddu]

Somebody who used to post on this forum a long time ago reckoned the best carbon arc torch was the Forney design. You can look up the US patent number 3,012,131 (1961).

I once cobbled together a couple of home-made torches, as per these photos. The left hand pictures show a design where the tip spacing could be adjusted by rotating one of the rod holders. The other model had a hinged mount, with a thumb wheel for adjusting the tip spacing. Both of them worked OK, but of course they didn't solve the fundamental problem of excessive bulk.

The forney thing is clever
Tomorrow if everything goes right
I will start drawing a project and may be make a prototype

 

[8ob]

Didnt know folk still used them, I had one fifty years ago I also remember the ones sold as a kit that could be used straight off a truck battery

Bob

 

[BarrieJ]

Ive still got carbon arc kit, not the most pleasant thing to use

Had one years ago (made by Kel-Arc?), like your good self, just couldn't get on with it, gifted it to Mike Cannon the trials car man, I don't think he ever had much success with it either.

 

[dannyp]

i'd advise buying one off the likes of ebay they rock up occasionaly, tbh i wouldnt't put much effort into makeing something not wishing to rain on your parade but it really is a crap prosess, and welderburn central if you do have a go don't show it any skin