Carbon Arc Gods help needed

I really really really really want to make asustained carbon arc, I have tryed using #2 pencil lead from wood pencils down to .5 mm lead. I have at my disposal an indestructible 480 watt 12 volt epoxy sand filled transformer, none of this new SS Sh*t that overloads when shorted.

What sort of carbon bars should I use and what should I expect to happen. So far I have had anything from instant exploding graphite to slowly melting and eventually burning at a spot of high resistance.

When I get the a small enough resistance the carbon glows wonderfully and the point of contact glows into a ball of molten graphite but almost instantly vaporizes and kills the arc. Tomorrow I may try to use some old heavy duty batteries for their carbon rods.

Thanks for anyhelp, the transformer is protected on the input with a 5 amp breaker which has only tripped when I used the unit to head a pool of borax mixed with molten steel and Salt.

Sounds crazy, but I like it.

Like the sound of your transformer. You're more than halfway there.

I have two tips:

Somehow - don't know how - put the carbon rods in a vacuum. This is the trickiest part of the operation.

Second tip - you may get better results if you run the arc on DC.
There is only one reliable way to do this, and that's with a mercury-vapour rectifier. The old-timer's favourite weapon of choice is the 866A tube. Try eBay.


This is a really exciting experiment - with the very first-ever practical form of electric lighting. The carbon arc predated even the carbon filament, but was rejected in the 1900 era in favour of the filament because it produced too many lumens...

I don't have a vacuum container or a vacuum pump so that is out, and I would worry in a vacuum that carbon vapors could build up and kill me when I replaced the carbon or something.

It's a pure DC output transformer, I don't know how it is wound but it has 3 wires 2 - 1 + I think and the 2 negatives go to some small metal leads in a metal plug about 3/8" around which are inserted into a large heatsink. There is also a 600 volt cap (measured that) on there, but that doesn't seem to do much as I have shorted it out, it's AC so the cap doesn't store energy as far as I know, but its a live 600 volts.

LOL, this sounds a lot of fun. The main problem will be the presence of oxygen which will cause the carbon to burn. You shouldn't need a gas-mask for the fumes, but make sure there is ventilation as there will be some CO and CO2 given off. I would advise welder goggles, and keep a fire-extinguisher handy. Keep us posted!

DM51 said:

The main problem will be the presence of oxygen which will cause the carbon to burn.

Click to expand...

Hence the vacuum.

I still don't understand what you mean by "in a vacuum that carbon vapors could build up and kill me when I replaced the carbon or something", perhaps someone could enlighten me.

I didn't write that, and I'm not 100% sure either!

The only carbon arcs I've ever seen burnt in the open. My father was a lithographic plate maker and they used arc lights to expose the plates.
Norm

Carbon-arc is ionised plasma, you need at least some sort of gas to obtain that, otherwise it wouldn't work..

Correct me if I'm wrong: Carbon-arc searchlights indeed always operated their arc's in "normal" air.. Slowly consuming the carbon-rod's which had to be replaced every 3 hours or so..

And don't forget: NASTY ULTRA VIOLET LIGHT OUTPUT !!

Regards,


Ra.

Indestructables had a article about this

http://www.instructables.com/id/Carbon-Arc-Lights/

Popular Science Nov 2006 issue had instructions as well in their
How 2.0 Section



PS.
Norm and Ictorana this is your project for our next meet :thumbsup:

Hello 65535,

Years ago I had a Forney welder. It used a carbon arc torch for brazing. It also had a resistance soldering attachment that was great for soldering generator and starter armatures.

I also ran across a guy that collected old carbon arc movie projectors. We would sit and watch old movies while he tended to the projector. It was fairly easy to maintain a good flame, but the rest of the mechanical apparatus often had issues. The film would jam or break and we would take a break while repairs were done.

Here is a source for carbons.

Tom

the presence of oxygen will make short work of pencil lead...and since pencils use a varying degree of carbon with some other stuff for stability and tint its generally not recommended for running excessive current through pencil leads.

if you want to take part of a short arc experiment, I'd recommend buying carbon rods made for arc welding.

momentarily touch the two carbon arcs together, which creates a short and heats the carbon up pretty good...then slowly move them apart...depending on the power supply that you use, you should be able to create a little arc of light

be careful of UV radiation and VERY VERY BRIGHT LIGHT, eye protection very very important, had someone told me sunglasses aren't enough and recommended using thick cardboard with two cuts using a exacto knife to peek through :thinking:
I'd expect fumes, though I'm not sure what...and CO2, colorless, odorless gas that will kill you slowly if the concentration becomes too high [heres some good info on that]
and last but not least....your going to be working with high current applications...wear gloves and all necessary preparations

EDIT: mount a breaker switch of some sort thats close to you, in the event of an accident, throw the breaker and attack it with WATER....since carbon is solid state and reactive only in terms of oxidation...throwing water on it wont as say a lithium fire.
DM51 mentioned a fire extinguisher, but at that temperature just fire retardant or foam may stop the oxidation process to extend further...but that won't cool down the rods to a safer temperature

About that carbon vapor killing me I was joking that it could build up in a sealed container. Not really serious.

But I got 2 1/8" carbon rods out of old super heavy duty dry cells, I want to try to use a pencil lead feed to maintain the arc and reduce the amount of my battery leads consumption wish me luck I['m going to test it now, thanks for all the info.

Be careful.

I used to own a pair of 1kw movie theater lamp houses and projectors. They operate in open air. Same principle used in spotlights and movie set lights until the advent of enclosed arc lamps like HMI and xenon. The power supplies were full wave rectified 220 vac to 24 vdc at something like 40 amps. The carbons were 6mm diameter (negative) and 7mm (positive) and were copper jacketed. A small motor drive advanced the carbons together as they burned up. A small bit of copper slag remained afterwards. Smoke and toxic gases have to be vented outside. The plasma at the arc is extremely dangerous - extremely bright and full of UV and who knows what else. Even if you use a welder's faceplate, any exposed skin is in danger. I do not know the actual composition of the carbon rods. Larger arc lamps such as drive-ins and searchlight simply used larger diameter rods and more power, sometimes with water cooling for the machinery. A large theater might typically have a 4-5kw lamp.

I assume electric arc welding is very similar.

OK - I'm obviously wrong about the vacuum. Must be confusing myself with plasma discharge.

lctorana said:

OK - I'm obviously wrong about the vacuum. Must be confusing myself with plasma discharge.

Click to expand...

vacuum would be nice nonetheless....

Actually, the xenon arc lamps used in modern theaters are under medium pressure, not vacuum, in a quartz glass bulb. When they poof, they explode. They often are sold with a plastic full face shield. The arc elements are not consumed like carbon rods, of course.

IIRC there is no such thing as a vacuumed bulb, HID arc bulbs require a medium to be super heated be it halide salts or xenon gas, a vacuum would be counter productive current wouldn't even flow.

I was working with the carbon arc today and found that I can burn mineral glass in my arc (more like make the arc out of mineral glass I still can't sustain an arc of carbon) but it produces a very pleasing color output a pinkish orange light. I think the possibilities of carbon arc fuels like salts and other impurities could give some really nice color output. Copper also burns very nicely green.

A side note I found that I can use a carbon electrode to weld steel to copper pretty cool, the copper piece failed before the joint.

If you put other minerals into the arc, you could get some pretty nasty gases coming off when they burn, so I'd be careful. The colors might be nice but you'd need to be a chemist to know what gases might be produced.

Edit: Make sure you get some pics of this set-up and post them here.

Carbon Arcs for fun and danger:


http://members.misty.com/don/carbarc.html