# Carbon Arc Gods help needed



## 65535 (Sep 23, 2007)

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.


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## Nitro (Sep 23, 2007)

Sounds crazy, but I like it.


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## lctorana (Sep 23, 2007)

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*...


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## 65535 (Sep 23, 2007)

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.


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## DM51 (Sep 23, 2007)

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!


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## lctorana (Sep 23, 2007)

DM51 said:


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


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.


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## DM51 (Sep 23, 2007)

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


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## Norm (Sep 23, 2007)

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


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## Ra (Sep 23, 2007)

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.


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## quokked (Sep 23, 2007)

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:


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## SilverFox (Sep 23, 2007)

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


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## Illum (Sep 23, 2007)

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


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## 65535 (Sep 23, 2007)

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.


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## louie (Sep 23, 2007)

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.


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## lctorana (Sep 23, 2007)

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


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## Illum (Sep 23, 2007)

lctorana said:


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



vacuum would be nice nonetheless....


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## louie (Sep 24, 2007)

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.


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## 65535 (Sep 24, 2007)

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.


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## DM51 (Sep 24, 2007)

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.


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## Nubo (Sep 24, 2007)

Carbon Arcs for fun and danger:


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


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## Nubo (Sep 24, 2007)

Melting the unmeltable:

http://theodoregray.com/PeriodicTable/PopularScience/2004/05/1/Scan.small.jpg


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## 65535 (Sep 24, 2007)

Well I am on a hunt for air arc carbon gouging electrodes and then I will be setting up a mount for it all and probably work in my driveway with a fan. I checked a local metal supply they didn't stock the rods so I will order them online, whats a good diameter for 40 amps?


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## tvodrd (Sep 24, 2007)

65535 said:


> Well I am on a hunt for air arc carbon gouging electrodes and then I will be setting up a mount for it all and probably work in my driveway with a fan. I checked a local metal supply they didn't stock the rods so I will order them online, whats a good diameter for 40 amps?



D-cell carbons, sharpened with a pencil sharpener. You'll only need a couple ohms ballast at 115VAC, which a 1-2 KW space heater will do.

Please be careful! (Eye and other protection!)

Larry


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## Ken_McE (Sep 26, 2007)

If you want to run it in an oxygen free environment just run your rods inside a clear container and squirt in nitrogen before you start. I'd suggest pyrex, like the Corning Visions cookware.


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## 65535 (Sep 26, 2007)

Well this week has been pretty busy and I haven't had a chance to work on my carbon arc lamp, but I have been having fun etching and cutting steel parts.


Currently I am awaiting the weekend to order some carbon arc gouging rods via granger, then I need to design a fixture for this, I want to use SS brazed to create 3 areas; a positive, arm a negative arm, and an electronically lifted metal plate middle for anti burn. 

If anyone knows a source for cheap parabolic mirrors with diameters around a foot please don't hesitate to link it up.


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## BVH (Sep 27, 2007)

65535 said:


> 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.



IIRC, some of the high Watt HMI lamps are negative pressure when off and low positive pressure when lit.


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## 65535 (Sep 27, 2007)

I was referring to a complete vacuum of all matter within the tube, yes negative pressure when off would greatly lower the heated temp.

BTW BVH do you know the carbon rod diameter and arc gap in your arc search light?


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## scott.cr (Sep 27, 2007)

Been reading this thread with interest.

Would carbon fiber rods be suitable for this application? McMaster has CF rod stock for cheap, check p/n 2153T52.


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## louie (Sep 27, 2007)

Just a reminder - protect your eyes and all exposed skin from the intense UV from the arc. I'd suggest a welder's facemask, but also cover skin like the neck and hands. No joke! I learned some arc welding in college once, and in maybe 15 minutes of welding, gave myself a "sunburn" on my front neck where my shirt was unbuttoned, below the mask. Lord knows what it does to your eyes.

The way my movie arcs work (exactly the same as the popular "Strong Super Trouper" spotlight of 50 years ago) was straight DC power, about 12 inch, 6mm dia. negative rods and longer 7 mm positive rods (they burn faster). The rods are energized and touched together briefly to ignite the tips, then pulled apart to the perfect arc gap. The rod holders are spring loaded to facilitate this. The gap depends on the current, voltage, rod size, etc. Then the gap is positioned by moving both rods together into the focus of the reflector. A pinhole image reflector shows this on a marked gauge. A small motor brings the rods together as they burn up, and is controlled by a rheostat. A new set of rods lasts about an hour at this power (1kw).

Interestingly enough, part of the supply wiring also forms a large electromagnet, which controls the "tailflame" of the arc.


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## BVH (Sep 27, 2007)

Louie, been there, done that on the throat sunburn. Once only, though. I learned my lesson.

65535, Positive rod is 5/8" diameter, about 21" - 23" long (IIRC but close) non-anodized with Cerium core. Negative rod is 7/16" diameter, solid core, non-anodized and maybe 12" or so. As Louie says, positive burns faster. Initial gap is set at time of rod insertion to about 1/2" to 5/8". The initial gap has to be within a specific area to start with so the automated system can take over. When power is applied, automated feed system takes over and moves rod to strike the arc. Once struck, automated system controls the gap via a small mirror that focuses the reflected light from the arc onto a thermostat. As the rod burns, relative position of reflected light on thermostat changes, causing less heat and therefore, contacts inside the thermostat to close, thereby feeding more positive rod and so on and so on. IIRC, the actual working gap is around 1/8" - 3/16" but I'm not really sure. Part of the probelm is that I haven't run my light yet. Once I have a few runs under my belt, I will be able to talk with more authority.

Part of the fun of running my light will be that I will be burning actual 1940's manufactured National Carbon Co. rods that are packaged in real metal cans which are filled with sawdust as a cushion. It's sad to be using them up but it's part of the fun.


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## DM51 (Sep 27, 2007)

*We* _*want*_ *PICS !!!*


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## lctorana (Sep 27, 2007)

louie said:


> ...(exactly the same as the popular "Strong Super Trouper" spotlight of 50 years ago)...


 
An off-the-shelf arc lamp? That was popular? Wow!

pics?


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## louie (Sep 27, 2007)

Stage union site has a Super Trouper brochure scan. This was a common theater spotlight during much of last century. 1kw carbon arc. If the arena was large, we'd just let the smoke and gas go up the top chimney of the housing. For enclosed spaces, you needed ducting and an exhaust system.

My projectors used the same arc lamp housing.
http://home.comcast.net/~garylouie32/35mm/IMG_1371.jpg


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## lctorana (Sep 27, 2007)

Love it. Thanks!


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## Illum (Sep 27, 2007)

DM51 said:


> *We* _*want*_ *PICS !!!*



here let me help you [this thread is not worthless, but we need pics nonetheless]





considering that now you have a carbon arc going on...have you considered lighting it up while the electrodes are under water?

apparently its a cost effective way to produce hydrogen and carbon monoxide
http://jlnlabs.online.fr/bingofuel/html/bfr10.htm


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## Illum (Sep 27, 2007)

[double post]


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## 65535 (Sep 28, 2007)

I'm still experimenting with the arc, seems my F cell electrodes are full of impurities on the surface that will need to be burned off when I fetch the second set. 

I am working on designs for my permy electrode holder probably using 4 screws on a circular clamp it will look cool enough. I have considered self winding a 30V 60 amp transformer so I am learning how to make a proper transformer, and so far all I know is that I want 240-60 windings a laminated steel core 12 gauge wire on the input and 6 or 8 gauge on the output.

Time to go play some more.


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## Illum (Sep 28, 2007)

65535 said:


> I'm still experimenting with the arc, seems my F cell electrodes are full of impurities on the surface that will need to be burned off when I fetch the second set.



tried fine grade sandpaper?


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## 65535 (Sep 28, 2007)

It appears that there is some carbon oxide or some other oxide that builds up on the carbon that is heated but not burned. Maybe its some sort of Carbonate. Shouldn't be a problem later. If I can make a 1800 watt 30 volt transformer then I don't see any problems coming up.


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## mahoney (Sep 28, 2007)

""If anyone knows a source for cheap parabolic mirrors with diameters around a foot please don't hesitate to link it up.""

We just put a few ellipsiodal reflectors around 6" dia. in the salvage bin at work, and one that was about 10", might be parabolic, might be spherical. If the salvage guy has not picked up yet, I can pull them out for anyone who wants to pay the freight. PM me.


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## DM51 (Sep 29, 2007)

mahoney said:


> We just put a few ellipsiodal reflectors around 6" dia. in the salvage bin at work, and one that was about 10", might be parabolic, might be spherical. If the salvage guy has not picked up yet, I can pull them out for anyone who wants to pay the freight. PM me.


I hope Ra, LuxLuthor, Nitro etc are reading this!

Mahoney, I don't think you will have any trouble at all finding takers for these, especially if there are any parabolic ones.


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## lctorana (Jul 7, 2008)

65535 said:


> It appears that there is some carbon oxide or some other oxide that builds up on the carbon that is heated but not burned. Maybe its some sort of Carbonate. Shouldn't be a problem later. If I can make a 1800 watt 30 volt transformer then I don't see any problems coming up.


 
Hi 65535,

How is your Carbon Arc lamp going now?

1800-watt transformer? Did you have any luck finding a core that big?

I have four questions (for you or whoever is reading):

I gather that 30VAC is your preferred operating voltage - is that some sort of optimum?
If so, and given that DC does present some sort of advantage, would two, or three car batteries do the job?
At 30VAC, what are you using for a ballast resistor?
Has anyone built any sort of automated gap-distance regulator?


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## lctorana (Nov 9, 2008)

:bump:


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## hopkins (Nov 9, 2008)

almost burned down our house doing this as kids.

-extension cord - cut open to allow resistor, just a pyrex measuring cup filled with saltwater to act as a current limiter. The water started to boil in less than a minute when on!

- cut off end of extension cord and wrap wires around 2 carbon cores from D cell
batteries.
-a brick - attach the cabon rods to brick with some heavy wire.\
-just plugged it into a regular wall AC outlet and nudged the rods together with a screwdriver. Surprise, you're now blind!
-don't fire this guy up on a wood deck like we did!!! Its so bright we could not see the wood start to burn. (but we could smell it)


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## Bright Scouter (Nov 12, 2008)

I used to run one of the Super Trooper's when I was in college working in the auditorium. It did have a screw that turned to feed the welding rods at the correct pace. We had to take the reflectors out periodically to clean them off. We did have to replace one set because they got so pitted we couldn't clean them up. 

They were FUN to operate. Had a few (6 or so) color gels in the front to change the color of the light. they also took a minute or so after striking the arc to even out and stop flickering. I always assumed it just was getting up to a nominal temperature. Last time I was in the auditorium, I saw they had been replaced with lamped troopers.


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## lctorana (Jan 14, 2009)

:bump:

I'm just itching to read some more carbon-arc stories.


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## broadgage (Jan 14, 2009)

12 volts is not enough to sustain an arc.
About 24 volts is the minium and from 30 to 55 volts more typical.
In days gone by, carbon arcs were used for street lighting, often about ten arcs in series on a 480 volt supply.

The carbon rods were almost allways operated in air and thus burnt away, the life of a pair of carbons varied from a couple of houres for cinema projectors to a few days for street lights.
Enclosed arc lamps existed, these were not sealed like a modern bulb, but used a small globe of some refractorary material around the arc, small openings being provided for the carbons. The oxygen in this small globe was soon consumed when the lamp was lit, and the arc then burnt in an oxygen free atmosphere, with improved carbon life resulting.

In street lights adjustment of the carbons was automatic, in cinema and searchlight use it was generaly under the control of the operator.

Arc lamps may be operated on AC or DC but DC gives a steady light and was prefered for stage or cinema use.
A drawback of DC though is the fact that one carbon burns away much quicker than the other, this complicates the design of any automatic adjustment.

In order to control the current, an arc lamp requires a resistance in series, or a high impedance source such as a constant current generator.
Sometimes very long series street lighting circuits required no deliberatly introduced resistance, the resistance of the long cables being sufficient.

Arc lamps for street lighting were rendered obsolete by the introduction of reliable high power incandescent lamps, and later gas discharge lamps.

For experiments with arc lighting, a welding transformer can be used, or possibly with care the 120 volt mains supply with a heater etc as a current limiting resistance.

PLEASE TAKE GREAT CARE IN EXPERIMENTING WITH ARC LIGHTING the voltages can be dangerous, and the heat is real fire risk.
An arc emits dangerous UV radiation, which can cause eye damge and skin cancer. The light is bright enough to be dangerous.

This website contains a lot of information about carbon arc (and other) street lighting
http://www.cooksonr.freeserve.co.uk/1880to20.htm

(edited to add link)


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## 65535 (Jan 16, 2009)

This project idea never went anywhere. It ended up being a how many things can I melt that I normally could not.


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