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Carbon arc muffle furnace?

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  • Carbon arc muffle furnace?

    I am looking for ideas for a carbon arc muffle furnace. I am thinking of an oven for heat treating of metal and oven brazing items. I foot cube or maybe a little bigger.

    It seems it would be easy to make a carbon arc heat source using the techniques of the early street lamps where a solenoid drew the rods apart as the current increased (I think that was how they worked? ).

    Power source would be a 240V 140A arc welder, moving choke type.

    Any comments? I am looking for comments on this concept in particular rather than a discussion of the myriad of alternatives.

    Thanks.

  • #2
    Sounds like a cool idea.

    I have no comment on the idea - I AM curious though - what would you be wanting this for?

    Tait
    Hemi-proprietor,
    Esoteric Garage

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    • #3
      Sounds pretty hot to me.

      But why not just nichrome heating elements? Or do you want to get past the 1000c mark?

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      • #4
        My immediate reaction is that you won't get any more heat out of the electrical energy than if you just ran the current through a resistor/heater element.

        The carbon arc was designed to get the energy into radiation. When welding, the arc goes from the work to the rod, so both get heated, which is what you want.

        If all you want is to make heat, which then has time to get transferred to a large box, there's no point in going to the noisy dirty unstable extreme of using a carbon arc.

        The only problem is making sure that the heater wire, and its support material, can take the temperature. If nichrome won't take it, you'll just have to look up to see what will.
        Richard - SW London, UK, EU.

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        • #5
          The thought that occured to me was: 35 mm theather projectors.
          That is a lot of light and UV in adition to the heat. Distribution of the
          heat for uniform treatment may be a bugger. As it is a "more or less"
          point source.
          Don't think I like it very well BUT if you do try it I'd sure like to hear
          about and see it. :-)

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          • #6
            Ennieyelp?

            http://www.google.com.au/search?hl=e...=&oq=&gs_rfai=

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            • #7
              Thanks for the comment everyone.

              As suggested, one of the objectives is to avoid the maximum tempertures of using resistive heaters such as nichrome wire.

              One of the other motivations for this potential project is that I have the welder on hand and I dont think it has felt the surge of hot electrons for about five years or more, but an oven that could braze and heat treat that would be useful.

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              • #8
                So what you want then is a control that brings the carbons together and then pulls them apart and maintains the set arc. When I did the welding gig we actually had such a device. It was used with a gullco track burner that held a fed carbon instead of a torch. You set the voltage on the control box and it does it all. The arc gap voltage is proportional to the distance between the electrodes.

                This would be pretty simple to do with a small microcontroller and stepper motors to feed the rods. Even an arduino. Though you will want some sort of PID loop to stabilize the rods.

                You would use the analog input to monitor the voltage between the electrodes and a cheap hall current switch on one of the lines connected to one of the digital inputs. On start the uC would feed the rods together until the hall sensor sensed current. At that time it would separate the electrodes until the arc voltage matched the preset voltage level. As the carbons burn the voltage will rise and the uC will trigger the stepper to move the carbon in.

                Something like an arduino would be perfect. There are stepper libraries all ready for something like this.

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                • #9
                  Macona, I think it is even easier than that. The old style arc lamps had a solenoid in series with the arc. When the gap was closed current would flow and the solenoid drew the rods apart, when the gap got too big the current reduced and as the solenoid also reduced its force gravity moved the rods back closer together.

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                  • #10
                    Sounds like a cool project -- take pictures!
                    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                    • #11
                      Originally posted by lazlo
                      Sounds like a cool project -- take pictures!
                      .........through my welding helmet!

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                      • #12
                        Originally posted by The Artful Bodger
                        .........through my welding helmet!
                        No kidding, otherwise you will end up like my arm that got too close to a super high pressure mercury arc lamp I was playing with.

                        Not one of the brightest things I have done...


                        Ushio UHP Mercury Vapor Lamp by macona, on Flickr

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                        • #13
                          I am looking for ideas for a carbon arc muffle furnace. I am thinking of an oven for heat treating of metal and oven brazing items. I foot cube or maybe a little bigger.
                          Most work in a muffle furnace is below 1000°CegHardening 650-900°C Tempering 150-220°CBrazing 400-800°C NiCrC (nichrome wire)Chemical Composition: 61% Ni, 15% Cr, bal. Fe Approx. Melting Point: 1350 deg C I don't see a problem, it's- Easy to control (some processes take 24/36 hrs), Clean & quiet .

                          Carbon arc is good for Hi-temps for melting, but is dirty, noisy, needs constant adjustment & replacement of rods + lots of nasty UV.

                          john
                          John

                          I used to be indecisive. Now I'm not so sure , but I'm not a complete idiot - some bits are still missing

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                          • #14
                            Good points Jugs.

                            I thought I would be keeping the temperature down when required by pulsing the arc.

                            Dirty, I thought the idea of a muffle furnace was the work was not exposed directly to the heat source?

                            John

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                            • #15
                              FYI RE: theater 35 mm projectors with carbon arc light houses. Back a few years ago 1954 to be exact I was chief projectionest in a military theater at Ft Bragg. The carbon rods as I recall lasted about 30 plus minutes with an adjustable feed. movie reels lasted 20 minutes to change over. The arc feed moved the rods togeather as they burned. PaulJ

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