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n9viw
03-11-2008, 04:38 PM
Hey, all,

In an attempt to further my abilities, I've been perusing the web and discovered some new old technology- carbon arc torch brazing and welding. Unfortunately, with the advent of OA, these things pretty much went obsolete back in the 70s, and it's nigh unto impossible to find them anymore. The last company to make them was Lincoln, they sold them under their own name and through Sears.

Since I'm poor, I can justify $50 for a carbon arc rig, but not $200+ for OA tanks. I like the idea of being able to braze my frames without having to pay $8-10 per O2 tank for my Oxy-Mapp rig (which might not even get the bike tubing hot enough, anyway!). Those things only last 10-15 minutes, tops, so I'd likely burn through a gross of them putting a frame together.

Does anyone know where to find one of these old things? At a pinch, where can I find the rods, as the handle looks pretty easy to copy and fabricate with brass and wood. In the states, please- no Canadian Tires down here! ;)

Wood Butcher
03-16-2008, 09:23 AM
Nick,

Here's a couple of links to new carbon arc torches:

http://tinyurl.com/36ccxe

http://tinyurl.com/38ecnx

Used torches are available on eBay from time to time. It seems that the prices are reflected by the amount of traffic in metalworking forums at the time--more discussion in forums about them = higher prices on eBay. I found an unused torch on eBay 2 years ago for $15, but I have seen them go for as much as $60 when auction fever takes over.

As you mentioned, they can also be fabricated from common materials. Lindsay Publications features a companion set of three booklets about building a carbon arc torch, a water resistor (powering the torch from a 115v outlet without needing an arc welder as the power supply), and how to salvage carbon rods from small batteries (lantern type, D-cell, C-cell) for use in the torch. The booklets can be found near the bottom of this page:

http://www.lindsaybks.com/bks8/meador/index.html (*)

A few caveats about using a carbon arc torch, some learned the hard way:

1) Wear complete protection when using the carbon arc torch. Don't even think about using gas welding goggles--use your welding hood. The light from a carbon arc torch is extremely bright (this is the same technology used for WWII-era searchlights) and you will get a nasty sunburn on any exposed flesh. This is the voice of experience talking.

2) It will be difficult, but not impossible, to see the color change of the base metal when brazing with a carbon arc torch. This is due to the darker shade of the lens in the welding hood. It will take practice (like any welding process) to be able to get the feel for what you are doing. In the meantime, expect to melt holes in thinwall tubing until you get the technique right.

3) The same flux and filler metals are used for brazing with a carbon arc torch as are used with an o/a rig. Until you get the technique right, expect to boil off a lot of the flux and not have the filler metal stick to the base metal.

4) You will need to be adjusting the position of the carbon rods as you are brazing. This is done with a knob for your thumb on the torch. The carbon rods will be burned away as the torch is used. When you run out of adjustment range (rods become too short), you will need to stop and reposition the carbon rods in the holders

5) The ideal shape of the arc flame is a fishtail. Once you get the flame going and can maintain it, you will see it. The flame burns around 9000°F, which is significantly higher than the flame from an o/a torch, even in the cutting mode.

6) Carbon rods can be obtained online or from your local welding supply house. Chances are that you will only find carbon rods meant for the air-arc gouging torches used for cutting heavy plate. These will work fine. Get the 1/4" diameter rods--they will be around 12" long and will work for quite a while before being complete burned up.

7) Keep an old pencil sharpener around for tuning up the ends of the carbon rods. They become rounded with use, but a beveled end is needed for a consistent flame.

8) Run the carbon arc torch on the AC setting (assuming you have an AC/DC welder). It is possible to run the torch on the DC setting, but the rod on the negative side of the torch will burn up faster. I haven't found any real advantage of using DC with a carbon arc torch.

Kind of a long, rambling read, but I hope it helps.

Mike

* - I have all three of the carbon arc booklets from Lindsay Publications that are doing nothing but gathering dust. I already purchased a torch, have an AC/DC arc welder in the shop as a power supply, and I've got a lifetime supply of carbon rods. In short, I don't need the booklets. If anyone is interested in them, contact me offline and we'll see what we can work out.

trikeman
05-27-2008, 05:32 PM
Speaking of homebrew cargon arc torches, here is an interesting one I ran across;

http://weldingweb.com/showthread.php?t=4090

meancoyote
05-27-2008, 06:36 PM
The rods look the same as the ones my arcair uses, maybe they are the same?
http://www.airgas.com/browse/product.aspx?Msg=RecID&recIds=352064&WT.svl=352064

n9viw
05-28-2008, 02:22 PM
Thanks for your replies, you guys. I liked the one in the WeldingWeb link Trikeman posted, I may make one like that that works more like the Lincoln one (now discontinued).
Coyote, it sounds like the only difference between the gouge rods and torch rods is that the torch rods are sharpened to a point, and are pretty thin, whereas the gouge rods are rounded on the tip and are quite a bit thicker. Still, it's an option.

savarin
05-29-2008, 07:24 PM
thanks for the heads up. I had totally forgotton about these.
I've never used one but always wondered how good they were.
Now I've lost my O/A setup (had to hand it back to the original giver) I must give these a try.
Thanks for the info