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Bedinis Flux gate Designs

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  • Bedinis Flux gate Designs

    Hello All,

    I thought I would start the ball rolling on a design of Johns not commonly seen these days, the flux gate or G-Flux. For those of you who may not be familiar with the design it can be seen here.


    I have built a preliminary design and done some basic tests, here is a picture of my first model.

    And another with considerably more turns of finer gauge wire and larger flywheel. This design (seen driven by an ac motor) was later driven by a 4 pole monopole. @ 850rpm the peak to peak voltage on my scope was over 400v. I set it to charge a 10000uF cap and discharged it via timed mechanical contactor approx every second into a 12v battery. At this pace the cap would discharge at around 20v

    As you can see it is fairly close to the basic design. I have used transformer laminations as my "iron pole" pieces, however in light of other similar designs like the Kromrey I wonder if this is necessary, perhaps solid iron bar would yield better performance. The rotor is the same, an "x" made from laminations, rotated by a high speed DC brushed motor (first design).

    John was dead right when he said low speed rotor though, this coil produces a lovely sine wave from a very slow speed, my current motor is far too powerful and fast, but it was what I had on hand to use.

    John was also dead right about there being no BEMF force on the driving device, as far as I can tell the only thing the driving device must overcome is the cogging present, which is dependent on magnetic saturation (strength and proximity of permanent magnet) and the air gap between "x" rotor and flux paths.

    I also noted that a Neo magnet like the ones pictured dont offer significantly more output, I was able to replace them with the standard "domino" sized ferrites we are familiar with from our SG endeavours and achieve similar results. And the permanent magnet side of the Gate must be built like John drew it, if one was to use two "c" cores, one with the coil wrapped around the middle the other with magnets strapped to its "back" there is no results. The magnet must bridge the gap between the iron bars, or extend from the back of the iron bar as can also be seen on Johns page where he says "this is how to gate the magnetic flux"

    Can anyone comment on the use of multiple flux paths or phases? I have 6 "c" cores I want to experiment with and have started a simple 3 phase flux gate where an "x" rotor will be used but will only break one flux path at a time (I hope) every 30 degrees. Here is a picture of that assembly.

    As you can see, there are no coils or magnets, or rotors yet, but I have my prime mover ready. If I stick to the original (and just add phases) there will only be three coils, and I will need to cut the middle sections out of the corresponding laminations so the magnets can fit. But I cant help wonder if there is a geometry that will allow for all 6 "c" cores to become coils. With a little guidance from a friend I've been considering changing the design to more closely resemble patent no. 7,109,671, but perhaps it would be best to replicate that patent as close as possible with one coil set first.

    Any advice people?

    Best Regards

    Last edited by Ren; 07-30-2012, 08:53 PM. Reason: rescaled pics for easier viewing

  • #2
    Here is a better pic of the three phase under construction.


    • #3
      Hi Ren,

      I haven't built any of these but I understand the concept. As I understand it the power comes from when you break the magnetic lock. I'm not surprised the neos didn't work out, it is too hard to break that magnetic lock. The same reason why ceramics are recommended in the Kromrey.

      It's not clear in your pictures but I assume you are using a non-magnetic shaft?

      Great work so far, keep it going!

      John K.


      • #4
        Cheers John,

        Yes I agree that the "power" comes from breaking the magnetic lock, I was a little surprised to see the nice sine wave though, I had imagined it to be different in my head. Perhaps it is if just one "x" rotor is used, i.e. breaking of magnetic path instead of magnetic loop? Will have to test that one out when I heal up. Just to clarify, the neos did work fine but all things being the same (i.e air gap) they didnt offer a huge advantage.

        Spinning by hand I could generate a maximum peak of 5vac with the neos inplace, and they are big neos.

        Spinning by hand with the neos removed and the same space filled with domino sized ceramics (7 stack from memory) I could generate just over 4vac.

        This is with a lousy air gap mind you. I was still pretty happy with that though, easy to turn by hand and thats with a commutated dc motor with all its internal friction connected. I think its safe to say that the finer that air gap the more lock, the neos might be more troublesome then. Im also guessing the magnetic lock is dependant on the distance the magnet actually is from the rotor, that is, the length of the iron slug or laminations. You can also keep adding magnets to the back of the iron slug to increase output. So you can have a magnet connecting the northern slug to the southern slug, and also magnets connected to the back of the slugs too, so it would turn a "c" onto a "H" on its side, kinda.

        Im also thinking that if the rotors are axially aligned to the flux path one could get closer tolerances (air gap) easier than radially. But this may limit the ability of multiple phases.

        Also im thinking the more iron the better, bigger pathways anyway. Its all going to be a balancing act as always

        And yes, brass shaft on one, stainless on another. Here is my drive motor for the 3 phase one above. Sorry bout lousy quality pic

        Thanks for your interest.

        Last edited by Ren; 07-31-2012, 02:12 AM.


        • #5
          Yes, I was going to mention your air gap. I think ideally a concave/convex arrangement would give the best results with the smallest air gap you can get.

          Nice 3 coiler!

          John K.


          • #6
            Thanks again JK. Ive put alot of time and effort into that one, its on its 8th rebuild, gets a little better and neater each time.

            In regards to the concave/convex arrangement I agree with you totally, however, its going to prove difficult machining laminations like that I think. Solid iron may be the way to go there, at least on the rotors anyway. All the "C" cores are adjustable in proximity to the rotor, so maybe just some hand filing with a large rounded file will suffice on those, clamp them in a vice so they dont split apart.



            • #7

              its good to see machines other than window motors and SSG's being constructed and tested. Please keep us posted as I am very interested the early JB machines.
              Keep up the good work.

              Best regards