How to wind a simple coil reactance that controls the current, protects the fuses, and cuts down greatly the cost of the electric power

By Alfred P. Lane

HEAT so terrific that no known substance is able to withstand it for long can be developed in your home laboratory with nothing more than a pair of electric light carbons, a small crucible, and some means of controlling the flow of the electric current from the house mains through the arc.

Most electrical experimenters attempt to use an old toaster or electric grill in series with the arc. This works all right, but the current flow is limited to three or four amperes and is greatest when the carbons are in contact and the arc is producing the least amount of heat. Adding another toaster or grill in parallel with the first one doubles the current through the arc, doubles the cost of operation, and still is open to the objection that the current flow is greatest when the arc is least effective.

The difficulty is that a carbon arc, operating on the ordinary 60-cycle, 110-volt current, actually requires only about 35 volts. The difference is wasted in useless heat from the grill or toaster.

You can avoid such troubles by building a current limiting reactance to take the place of the makeshift resistances. The reactance upsets the power factor of the line in such a way that the current flowing through the arc actually is in the neighborhood of 10 amperes although the meter runs only as fast as though 3-1/2 amperes were flowing.

The homemade reactance shown was designed especially for amateur arc furnace experiments. The core is made of transformer steel laminations or annealed iron strips measuring 1-1/2 by 6 in. Enough of them are used to make the core 1-3/8 in. thick.

After the core has been tightly wound with four or five layers of friction tape, the winding can be started. Use No. 12 enameled, cotton covered wire. The first layer should be 5 in. long, and the end of each succeeding layer should be stepped- back half the width of the wire. This gives a cone-shaped effect and avoids the use of retaining disks. Continue winding till the outside of the coil measures 3-1/4- in diameter. Then apply several layers of friction tape to protect the winding and keep it from coming loose at the ends.

Be sure that the notches in the upright end pieces of the wooden frame are slightly less than 1-3/8 in. deep so that the toppieces will clamp firmly on the ends of the core.

Connections are made to the coil by drilling a hole in the upright, passing the end of a flexible cord through it, and soldering the coil end wires to the bared ends of the cord. A soldered loop should be formed in each wire so they may be firmly clamped to the inside of the upright by means of small, roundheaded wood screws.

After the reactance is finished, give it a coat of black paint or lacquer.

A handy wiring harness for arc experiments is suggested in the diagram above. The metal or other substance to be melted can be placed in a smaller crucible suspended within the outer one. Obviously, any desired type of furnace may be built to suit the work. Bear in mind, however, that the heat is intense enough to melt iron and porcelain and must be cautiously used. Do not look directly at the arc without wearing goggles.

This reactance is for use only on 60-cycle, 110-volt A. C. current.

  1. MAKE: Blog says: March 20, 20072:09 pm

    Arc furnace that melts anything…

    Handy for arc experiments, Popular Science 1933 HEAT so terrific that no known substance is able to withstand it for long can be developed in your home laboratory with nothing more than a pair of electric light carbons, a……

  2. dave says: January 9, 20086:23 am

    OOOOOOOOOOps..has he still got any eyes left ? well not with the intensity of the uv..NO…sorry..I was looking for an arc furnace..not a method of self destruction.

  3. Mike Mandaville says: May 15, 200912:51 am

    The comments are well put. The word “goggles” doesn’t cover what is required here for safety. A full face shield with the darkest lens available, and every inch of skin covereed on your entire body.

  4. Mike Mandaville says: May 15, 200912:58 am

    Having said that, I would like to add that I like this project, and I plan on building it. Iron wire can be purchased at any Home Depot, and can be dipped in enamel to minimize losses due to eddy currents. Pencil leads or carbon rods from carbon electrical cells can be used.

  5. Matt B says: June 9, 200911:13 am

    Pencil leads contain a lot of clay. I’m not sure how well those’ll work; I haven’t had very good luck. (I tried arc gouging with a “graphite” pencil as an electrode, and the tip of the thing just sort of exploded as soon as I struck an arc.) I think I’d be more inclined to try purpose-made gouging electrodes from a welding supply store.

  6. ocean house says: March 13, 20108:28 am

    AKA, the modern way: enjoy

    This would work even better with an ac type arc welder home depot has one for 220 bux, however instead of building the device mentioned I would just use the transformer out of a large microwave oven known as a “MOT”and for this appliocation you want the tall transformers the little compact ones don’t work as well. The primary coil of a MOT has sufficient reactance to sustain a small arc furnace, or build an arc welder for that matter. I built a MOT arc welder years back, welded up a storm with it and gave it to my nefue, he uses it at his work, still to this very day, the point is MOTS are perfect for making arc devices. The key to using MOT’s is removing the high voltage winding with a hack saw, a hammer and a chisel. The high voltage winding is very dangerous, and must be removed without question. its easy to do without damaging the primary because MOT’s have a 3 volt filament winding and a stack of metal magnetic shunts
    between the 2 coils that serves to protect the primary while are cutting and pinching the the secondary out also if the 3 volt coil becomes shorted just un-short it, only remove it if it can be removed without disturbing the shunts. I would sub-just for ultimate heat using both phases of your household wiring aka 220v, feed each hot leg into its own MOT transformer primary, before going to the carbons, this will impart quite a lot of energy into you arc furnace, at this point you will need a silicon carbide cursible to contain the molten remains of the Denver fire clay crucible (DFC ceramics: google) as pictured above. its worth noting that no one need to take app-art batteries most all welding shops stock copper clad carbon electrodes for the carbon arc cutting / welding process and the are available in a varity of sizes up top 1/2 inch , and are mend for arc processes, they ave very affordable even by kids on lunch money budgets, and fire clay crucibles are the same, in the less than $3 each range, and ofcourse dead microwave ovens are free at appliance repair shops if you ask nicely

    What do shunts do?
    the shunts serve to limit the current that can flow through the primary, dont remove the any of the shunts unless you want more power to your arc, and only remove them one thin strip at a time until the desired power level is reached. however i don’t recommend removing the shunts because the balance the current flow through the primary winding that you are using for ballast I would say that if you want more heat use the 2 MOT 220 Volt (2 opposing hot legs) method mentioned above will probably require plugging to a dryer outlet, unless your like mee and just wire directly to a split phase phase breaker straight from the mains pannel, its real easy, just hook the wires to the breaker then install the breaker (snaps right in) the set the breaker to the on posiation, most servace pannels have enough extra slots abvaible to plug another breaker in, as a power tap.

    BTW if your breaker is on and the 2 mots don’t arc togather, you don’t have a split phase breaker, you have a single phase breaker with 2 trips.

    Have fun and good luck, if i forgot anything just search MOT for the blanks

    Ocean House

  7. Novoltny says: April 7, 20113:12 pm

    haha!! dad with his new hobby, all dressed up with his fancy bow tie and funky hair-do, well hey: he’s just having some harmless fun melting F*CK*NG! STEEL with his BARE hands, UNPROTECTED eyes, and he’s doing it on the F*CK*NG KITCHENTABLE!!!!
    His eyes will be fried withing seconds, then he will SCREAM like no one ever screamed before, completely insane of pain he kicks the white-hot crucible of the table, that will fall in his lap, then he and his house burns down, leaving nothing but some charcoal of this Hero of Science

    whoaaaaHEY! You’ve gotta love these crazy maniacs that made these kind of suicide magazines, those where the days, aint?


  8. stuff says: June 8, 20117:14 am

    The best way to produce more molten steel/iron is to have a small opening at the bottom of the crucible where pressurized air is to be blown through the molten iron. The air will react with impurities, creating heat, carbon dioxide (monoxide as well), and a very pure iron for backyard tech. It’s the hobo Bessemer converter

  9. Thuringen says: July 22, 20114:31 pm

    bessemer converters are sepeate from the furnace – cruicible action. it’s only after the pig iron has been melted down that it is them poured into a seperate, specially designed cruicible for the application of compressed air.

    the cruicible also has to be made of special refractories which are able to participate in the reactions to some extent, depending on the phosporus content of the initial melt and the desired qualities of the final product

    Not to mention that if that were a bessermer converter he were leaning over, everything above his shoulders would be gone.

    though that might be fun too . . . “build an arc furnace/bessemer converter at home, and get to play home mortician for free!”

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