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Thread: New Two Coil Monopole

  1. #1

    New Two Coil Monopole

    Greetings friends,

    I built a new monopole and I wanted to share the build with the group.

    Letís start with some parts listings. I used some non standard diodes on this build. They are ultra fast switching and the main reason I tried them is because they have a lower voltage drop. For beginners reading this, you are better off using standard parts so that you can get help from other members with tuning and troubleshooting. I have gone out on my own with this and cannot say yet if there is any advantage, it is experimental.

    The Collector diodes:
    Rectron 3A 200v 35ns Part# SF34-B


    The B & E diodes:
    Rectorn 1A 100v 35ns Part#SF12-B


    On the base resistors I used ľ watt 274ohm 1 percent tolerance and a 500ohm pot for adjustments.

    The transistors are the standard MJL21194 all matched (8).

    The system has two coils mounted; each has four 18awg power and one 20awg trigger. The second trigger wire is not currently connected to anything. All of the wires terminate on a standard terminal block with ring connectors.

    The wheel is a heavy duty 26 inch wagon wheel (not a bike wheel) with Ĺ inch bearings. I glued the bearings shut and installed a Ĺ inch steel axle to utilize the mechanical energy. The axle is mounted on some roller bearings out at the ends. These are the type of bearings used on assembly line rollers and have a 20 percent self adjusting swivel to prevent any binding on the axle.

    I do not have anything attached to the axle yet but I am thinking of putting a small wheel with magnets to hook up a generator coil assembly, also maybe a fan like Mr. Bedini or a pulley system for doing some kind of mechanical work. I am getting a lot of torque from this setup because of the wheel size and it is also pretty darn heavy which makes for good inertia once it gets up to speed.

    The magnets are the standard ceramic type and there are 16 of them mounted on the wheel. I used JB weld epoxy to glue them on and did a second coat on top of the first.

    I have laid out the circuit in a way to allow a few options for running. The transistors are configured in branch mode with two banks of four. The switches at the top of the board allow for sending all outputs to one side, the other side, or branch (both sides).

    The switch on the lower left is for switching to generator mode and the lower right switch is the primary on/off switch. All of the bus bars are made with 14awg solid wire; the kind used for house electrical. The clip leads are made with 10awg braided and all connectors are soldered.

    Having just completed the build last night I do not have a lot of experience with the system yet but initial testing looks very good. I have been charging up two 75AH batteries in branch mode with no problem. It seems to like to run with a 1A input when in mode 1 operation. That equates to just a little bit of resistance on the pot over top of the base but not much. I may put a fixed resistor in the trigger path on a switch to change over from the pot once I figure out exactly what it like to run on.

    Here are a few pictures of the system.

    new machine1.jpg

    new machine2.jpg

    new machine3.jpg

  2. #2
    Senior Member John_Koorn's Avatar
    Join Date
    Jul 2012
    Melbourne, Australia
    Nice job Bob!

    You may find the collector diodes are under-rated at 200V. I'm using ETX0806 in some of my experiments and they seems to be performing quite well. They are 8A 600V 14nS.


    John K.
    John K.

  3. #3
    Thanks John. Man it is just so much fun when you finish a new build isn't it. I am loving this machine but I already know I may have to adjust a few things.

    So far those diodes are holding up but I know what your saying, at least 300v would be nice. As it is right now a few of them get about 6 degrees above the others and the set of them stand about 15 degrees over ambient temp.

    Another observation is that although I thought that 1/2 inch steel rod would be a great axle it is bouncing slightly, bending you could say. Not much but it does flex. If I had the legs closer together it may not do that but I am thinking abot putting a wider axle on it. The axle and hub can go thicker if I get bigger bearings so I have some room to improve that.

    Over all though I am happy with this thing so far. I have only had it running since last night.

    Another thing I need to look into is when checking the pulse with a led I can only get it down too two. I am not sure if the two coils has anything to do with that or not since it is my first multi coil. Tomorrow I am going to try re-adjusting the coil gaps and see if I can improve it.

  4. #4
    Senior Member Tom C's Avatar
    Join Date
    Jul 2012
    Pacific Northwest

    if you switch from solid rod to a 1/2 inch thick wall pipe the bounce should leave, as long as it is not the bearings off center in the races., please measure freewheel time, you may only be getting to 2 pulses because of rotor speed, and thats all about friction

    Tom C

    experimental Kits, chargers and solar trackers

  5. #5
    Tom I think you are right about the friction and speed.

    I was able to get down to one pulse but at the cost of lowering the resistance on the pot quite a bit and my primary was drawing 2 1/4 amp. I do not want to run the machine on that much juice even though temps were all still good on components I just don't like drawing that much. Down at 1A draw I can only get the 2 pulses no matter what I have tried like re adjusting coil gap.

    I KNOW I have some unwanted friction because of how I am keeping the Axle from drifting. I had forgot to get a good collar with a set screw to put on the axle so I rigged a piece of PVC on the back end of the axle while I am waiting for some collars to arrive. The axle wants to drift forward so I had slipped this little pvc over it and put a zip tie behind that so what happens is when the axle wants to pull the pvc spacer butts up to the rear bearing and then the zip tie binds with it, keeping the axle from drifting.

    It is not ideal at all but I had rig it up that way until I could get a better solution. It is certainly causing a bit of drag and that may be the problem.

    I will try to get a pipe as you suggest for the axle, makes a lot of sense to me now that you mention it. You get that strength from the internal arc of the pipe pushing on itself.

    I am going to keep fine tuning this thing and see if I can get it running exactly how I need it too. Over all it runs pretty good but I need to correct the little details that I couldn't notice until it was running.

    Tell me though how bad is it to have the two pulses instead of one as it runs currently? All of the transistors and diodes are keeping nice and cool and the draw rate is nice with good charging. If I didn't know about the 2 pulses instead of one I would think it was great but I do know that it is double pulsing.

    Thanks for the help

  6. #6
    Ok so I went to the hardware store to get a pipe and the only thing I could find that would fit was "steel tube". I wanted to find heavy duty pipe but they didn't have it with a 1/2 inch outer diameter. I got the tube and got home with it. When I slid it into the bearings I noticed that it was not a good round tube and would not make for a good axle, I like the idea but the material I found was not going to be suitable.

    So I worked on the axle I already was using. I took and drilled a hole in it and slid a cotter pin through along with a few washers. That replaces the PVC/zip tie spacer thing I had on it before. This seems to give much less friction and I also carefully leveled out the axle as best I could.

    new machine4.jpg

    I took out the inner bearings that are glued shut and cleaned them off & re-glued them then presses them back into the hub. Over all it is much smoother now than it was. I may have had one of those pressed in a little crooked or something before, not sure. I used a big socket this time that fit over the whole thing and smacked it in with a hammer and they seem to have set evenly into the hub.

    So I let all the fresh glue dry over night and started playing with it this morning. I am still getting the same result as far as timing goes but it is running smoother mechanically. I made a short video showing what I am up against here. It starts out showing one pulse but the draw is way up at 2 1/4 or so. Then I back it down to where I have been runnig on the two pulse at around 1A draw and also a little lower just to show the multiple spikes.

    I was looking at it and thinking maybe I do not have the magnets spaced close enough? I didn't want to over lap the poles so they are fairly far apart. What do you guys think? In the picture below you can see how they are spaced and I also put one next to the timing magnet to show the spacing if I were to double up on them. I could slip a magnet in between all of them and have it come out even if I wanted too but I'm just not sure if it would help.

    new machine5.jpg

  7. #7
    What shaft / bearings did you use? Did the new rod just fit in after the old one?

    Thanks for the pics!

  8. #8
    Looks like you were constructing part of my answer soon as I was writing it.

  9. #9

    The thing to keep in mind about this is that it is not a bike wheel. This thing is supper heavy duty and super heavy in general. It is one of those wheels you would put on a utility cart. That is why I am using the 1/2 inch axle, to support all the weight. It originally came with 3/4 in bearings which at the time I thought would be too big so I down sized the inner bearings to 1/2 inch and got a steel rod for an axle. The good thing is I can always go bigger because the hub will accept larger bearings.

    Here is the wheel:

    The outer bearings that it spins on are roller bearings, not ball bearings.


    As you can see from the specs these things are self alighning, can carry 1040 pounds, and are rated up to 22k RPM

  10. #10
    Senior Member Tom C's Avatar
    Join Date
    Jul 2012
    Pacific Northwest

    what is the freewheel time with your modifications? run it on one coil..... if it runs faster on one coil than on two then either your magnets aren't exact or the coil spacing is not perfect multi coil machines are hard to tune

    Tom C
    Last edited by Tom C; 12-01-2013 at 07:34 AM.

    experimental Kits, chargers and solar trackers


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