Tesla's Bifilar Pancake Coils

[gyula]

Thanks for the capacitance and resistance measurements. I think the 40nF capacitance value is much better than two normal enameled copper wires of similar length could give when guided directly close to each other, even if they are twisted. The dielectric constant of the pvc material in the mic cable helps increase capacitance, this is one possibility. Another is to use insulated wires with rectangular cross section area to increase the facing surface areas.
All this is for increasing the stored energy inside a coil, by embedding distributed capacitance in it.

Regarding your question, I can only give 'educated' guesses... If you can utilize the two separate EM fields coming from the two coils (placed side by side) in the same way like in case of a single but bigger coil, then it is a viable solution.
Keep in mind that two coils with no coupled magnetic fields normally give less self inductance when they are in parallel, so if you have two coils with 3 - 3mH inductance separately and you connect them in parallel, and their magnetic fields do not interact, then you get 1.5mH resultant inductance, and the copper loss (DC resistance) also gets halved.

If you connect the two smaller pancakes in series, you would have the summed inductance of them, again assuming no magnetic coupling between them, (and copper loss now adds up).

Coils resultant inductances add when they are in series and reduce when they are in parallel (like normal resistors in both cases), provided the magnetic coupling is zero or negligible between them. However if there is a mutual coupling, resultant inductances can vary significantly.
Here is good summary:
Inductors in Series Circuits and
Inductors in Parallel Circuits

[antigraviticsystems1]

Hi buddies, I think that you are getting poor results for the simple reason that the residual capacity between the wires is microscopic, you have to make the coils using flat aluminum strips painted or lacquered, so if you will arrive at positive results .... Greetings .....

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[gyula]

Yes, I agree using insulated metal stripes, tapes. The higher the surface the bigger the capacitance.

Here is an interesting variant:
The HF TRANSFORMER Experiment by Milan Manchich

Gyula

EDIT: I think the resulting magnetic field of such 'pancake' coils with such a height should be explored and compared to the really flat / thin pancake coils, this may depend on application goals.

[wings]

Yes, I agree using insulated metal stripes, tapes. The higher the surface the bigger the capacitance.

Here is an interesting variant:
The HF TRANSFORMER Experiment by Milan Manchich

Gyula

EDIT: I think the resulting magnetic field of such 'pancake' coils with such a height should be explored and compared to the really flat / thin pancake coils, this may depend on application goals.

Milan Manchich HF transformer here

Singe wire conduction - 06/08/01

[Jiffycoil]

I'm going to have to make one of these metal ribbon, or tape coils. I could use 1/2 copper tape. Thanks guys for posting this info. Keep up the good work.

@Wings
That's a very interesting page you posted. Thank you

[Mike2kt]

Hi buddies, I think that you are getting poor results for the simple reason that the residual capacity between the wires is microscopic, you have to make the coils using flat aluminum strips painted or lacquered

Thanks for telling me I just wasted umpteenth hundred dollars on 28 AWG copper magnet wire...

Just kidding, I'm still going for a large bifilar flat coil. I personally thing it would be interesting to see an extremely large (48"+) bifilar coil made from magnet wire....compared to a much smaller bifilar coil made from flat strips.

No idea if the LARGE coil will be a better or worse design...but at least we will have another point of reference to go from (failure or not)!

Failure isn't a bad thing - it's just an indicator that you are moving along the wrong path at the time! Never give up!

[thedude]

Rest of the pancake coil patent.

Hi there all. I'm currently working with a pancake coil in another thread here at Energeticforum. Link is in my signature. I didn't want to clutter and over involve myself with my goings on in this thread with my current line of experimentation.

I did see that we had part of the pancake coil patent but not much of the writings so i put up on my host and thought that i could add it all here for reading as it is only 3 pages. But it does offer some of Tesla's unique descriptive language. :P





Thanks for this thread. I got the coaxial pancake concept from here and although my experimentation is utilizing it a little differently, at low current levels it is offering some very unique efficiency.

[Mike2kt]

Fluke 199C "ScopeMeter" (Oscilloscope) on it's way... Time to scrounge ebay for a DDS Function Generator and an LCR meter. Then the fun starts!

Still having issues getting the glass I want...

[IWD]

sry

just little attachment, my style of coil, Carton, Wire, Needle, thread.
But nothing extraodrinary in electrical measurment.

[Jiffycoil]

Really nice wind on the coil IWD.

[Jiffycoil]

Copper Ribbon tape

I just received the copper ribbon tape to wind the new pancake coil.


Copper ribbon tape by jiffycoil, on Flickr

[Mike2kt]

Update: my oscilloscope (Fluke 199C "Scopemeter" - can also do spectrum analysis) showed up yesterday... Agilent U1732A LCR Meter and Instek SFG-2010 Function Generator should be here late next week! Hopefully things will start moving along now that I will have the right equipment.

I'm starting to give up on the glass coil plan...I thought it would be simple to get the glass I need, but that doesn't seem to be the case (and I'm in one of the top 20 pop. US cities!). I came up with a conceptual idea tonight for mounting the magnet wire on top of plywood...it's basically sticky-site up *electrician's duct tape* (higher temp rating made from vinyl). I'm debating if I should add a layer of real electrical tape w/ two thirds covered with PTFE (Teflon) on top of that for more isolation. I will share more on this build method after I actually attempt it!

On a different path, I'm looking at using 2.5" widealuminum tape with 2-4 copper drains for soldering. I'm thinking one layer of electrical tape or one hybrid layer of electrical tape with two thirds PTFE coverage for layer insulation.

Lots of ideas in my head...and I'm going to try all the ideas I can practically implement. I will focus on builds (and docs/pics how they were constructed) over the next several days in preparation.

All and all, I can't wait to share my builds and hear everyone's feedback on my next "experimental" coils.

[crackahcrackah]

Hi Jiffycoil, this is what lasersaber and the Nathan Stubblefield Earth Battery replicators have been using:

COTTON COVERED Covered Copper Wire
wires.co.uk : Double Cotton Covered Copper Wire

It's interesting to note that Stubblefield used two types of wire (cotton covered copper & iron) which maintain a (seemingly galvanic) potential difference. Tesla refers to the importance of increased potential difference in his patent:

Was Tesla doing the same?

Tesla was doing it to a much greater degree. If you look at the bottom coil, in the pictures, you will see that essentially the coil has built in inductance. It's like a spiral capacitor with respect to the potential difference between the windings which lay side by side.

I think this coild might be great as a secondary with his patent 568,176, which is being discussed under the thread "this is it!"..

[crackahcrackah]

Tesla talks about this in the patent. Does anyone have any idea how to calculate this? I searched google without much luck. Don Smith talks about measuring the capacitance of the secondary with an LCR meter, subtracting the capacitance of the primary, and using that.

However, in the patent, I believe Tesla is referring to adjusting the turn spacing to give the coil the required capacitance without requiring an external capacitor.

Thanks for any info!

I think you want to forget about attempting to measure that. What Tesla did was create adjustable oil filled capacitors. It's far easier to have a few of those and dial in for resonance that way than it is trying to measure and find a combination of capacitors to get it just right.

Look at patent 464,667 for the adjustable oil filled cap.

Look at patent 567,818 for his capacitor "greatly suited to circuits with great rates of vibration".

I think the latter would be the best one to use eeventually, but we must learn to crawl before we can walk. So I recommend looking at the 1st patent, and going that way. That's what I'll do when I can.

[7imix]

Tesla was doing it to a much greater degree. If you look at the bottom coil, in the pictures, you will see that essentially the coil has built in inductance. It's like a spiral capacitor with respect to the potential difference between the windings which lay side by side.

I think this coild might be great as a secondary with his patent 568,176, which is being discussed under the thread "this is it!"..

Did you mean "built in capacitance" here? I think most coils have built in inductance