Tesla's "COIL FOR ELECTRO-MAGNETS".

[synchro1]

Actually, I used  non plated 16 penny nails. We have a guy doing construction at my work. I did do a thin wrap of teflon tape, as the ribbed burrs close to the head of the nail may have scraped the insulation of the wire. I believe for that test to be evident, the coils need many more wraps than described in the article, especially to use a D cell. The author of that site should make changes to that article. Its the right idea, just the wrong ingredients. Sure it may work 'better' with high voltage, but the article doesnt express that.

Mags

Let me add that the series bifilar pancake or solenoid coil has to be CHARGED initially to reach it's full potential. This is done simply by snapping a good spark across the leads. Attempting to charge a single coil is useless. I used a depleted Bedini charge battery that was originally 12 volts, bled down to "D" cell voltage. Too much power will fry those tiny coils in no time! Once fully charged, a small amount of D.C. current will produce the extra magnetic strength in the iron core. High reluctance ferrite with low remanence won't magnetize like soft iron. Farmhand said he had some ferrite lying around. It probably won't work because it looses it's magnetic strength too quickly. Coercivity is another dynamic involving the amount of current required to reverse the magnetic charge. Iron has a low enough coercivity to release the junk on a scrap yard pancake electromagnet. You can get the nail coil to drop the load of paper clips, by inducing a reverse charge too. Higher coercivity alloys like Alnico will retain the attraction.

[Magluvin]

Say we had a BIG coil. 100H coil. 

At 100h  with a cap across it of 70.3nf we get a resonance of 60hz

100H  6.3nf 200hz

100h  100pf  1.6khz

100h  11pf   4.7 khz

Now just imagine all that wire to make that big coil, it definitely isnt going to ring at 5 or 10khz on its own. Not even 100khz

100h  1.1pf  15khz

So the Big 100h coil has a virtually non existent capacitance.  So what would we imagine the capacitance of a bifi coil of the same wire and turns? 

Not saying we need to make 100h coils. It was just an example for understanding.

Mags

[synchro1]

@Gyula,


Quote from Gyula:

"Why do you attribute to Itsu things he obviously did not do?  He did not lower the CMF for DLE to 18,000 rpm with his resonant output coil! In his parallel resonance video the highest frequency from his generator coil output was 206 Hz (this is 12,360 rpm and this latter rpm  occured when he shorted the output), no any higher rpm was demonstrated.  How can you claim he lowered it to 18,000 rpm??   (For the other members: Itsu's video is here: http://www.youtube.com/watch?v=syxL4f2OsPg )"


Look, Itsu's running four magnets at 150 hertz RPM. That's 9,000 RPM equal to 18,000 RPM for the diametric. Now your raising his speed to 206 Hertz which would yield an equivilant of 24,720 for a diametric frequency. Then you ask me how come I'm attributing a rate of 18,000 RPM's to Itsu!


I maintained the critical minimum frequency for a diametric spinner to catch DLE was 25,000 RPM's. Itsu caught it at 9,000 RPM's which would equate to 18,000 RPM's for a diametric magnet, 7,000 RPM's less then where I get it with my spiral output coil and sphere spinner. JLN's spinning at 30,000 RPM with his diametric in his test.

[MileHigh]

Gyula:

Thank you for puling up the YouTube clip with the AM band resonator.  The one I saw was a commercial version, probably manufactured in the late 1960s.  It must be in the "plastic mould graveyard."

Going back to the self-capacitance issue, there is an exercise that anyone can do as an exploration into the whys and wherefores.  Try to estimate the capacitance between to adjacent loops in one of your coils.  You don't have parallel plates.  So you make a reasonable estimate as to how much a long length of wire of a given diameter translates into an equivalent long rectangular metal plate.  What is the approximate equivalent distance between the plates?  Let's keep it simple and assume the relative permittivity of the plastic insulation is one.  That can also be looked up.

So with a few reasonable judgement calls and a bit of punching the numbers in a formula you can make an estimate of the capacitance per pair of adjacent turns of wire in your coil.  Then you can make a quasi estimate the self-capacitance for the entire coil.  Then you can compare the two values, estimated and measured.  Sometimes the estimated value and the measured value for some kind of system are consistently different by some constant or near constant value.  That gives you a "compensation factor" for estimated capacitance so that you can compensate and accurately estimate the actual self capacitance.

There is another way to approach this issue.  I still will pitch light gauge speaker wire.  The two conductors are very close to each other.  You could just put a capacitance meter on the the isolated wire pair and measure the capacitance of the entire spool.  (Note: With that data you could work your way back to approximating the dimensions and separation distance for the equivalent long and thin rectangular plate capacitor.  Once you have the equivalent model for the two adjacent wire loops as a long thin rectangular plate capacitor, you just punch in the numbers and you are done.  So it's also a way of estimating the equivalent long and thin rectangular plate capacitor.)

Then connect up the spool of speaker wire in a series bifilar configuration and measure the self capacitance from the resonant frequency.  Again the question is:  Is there any corelation between the measured isolated wire capacitance and the measured self-resonant capacitance?  Is there a possible compensation factor that you can determine so that you can make a "weighted" or "true" estimate?

MileHigh

[Magluvin]

Let me add that the series bifilar pancake or solenoid coil has to be CHARGED initially to reach it's full potential. This is done simply by snapping a good spark across the leads. Attempting to charge a single coil is useless. I used a depleted Bedini charge battery that was originally 12 volts, bled down to "D" cell voltage. Too much power will fry those tiny coils in no time! Once fully charged, a small amount of D.C. current will produce the extra magnetic strength in the iron core. High reluctance ferrite with low remanence won't magnetize like soft iron. Farmhand said he had some ferrite lying around. It probably won't work because it looses it's magnetic strength too quickly. Coercivity is another dynamic involving the amount of current required to reverse the magnetic charge. Iron has a low enough coercivity to release the junk on a scrap yard pancake electromagnet. You can get the nail coil to drop the load of paper clips, by inducing a reverse charge too. Higher coercivity alloys like Alnico will retain the attraction.

Like I said earlier, testing the 2 coils on a Leedskalnin holder would give definitive data in my opinion. If done properly one could truly measure if there is more field and how much. Part of my tests will do measurements with linear hall sensors.

Still working on the coil winding setup. I only want to do it once without wire breakage.

Mags