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PIRANHA - New Top Load Configuration

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Terry Fritz

Mon Oct 16 2006, 03:25AM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Hi All,

I have decided to try a new topload configuration for my new PIRANHA coil. It will use four 8 inch diameter "gazing balls" like this:

3/8 Brass tubing will interconnect the balls and provide support. The main tubes on the "X" will be 3/8 inch and the balls will have 3/8 inch ID tubing inserted into them. Thus, the balls will ba able to slide in and out in a telescoping fashion. The far end of the tube inside the ball will be epoxied in place. It is fairly critical to get the tube aligned properly. One could tune the coil by sliding the balls in and out.

The electrostatic fields look like this:

The 4 inch radius spheres should arc out at 3MV/m or 305kV which is fine. So It should do about as well as a 24 (or more) x 8 toroid!! The cost is about $100 for the balls and $10 for the brass. You just enlarge the probably existing hole in the balls to 13/32 inch for the tubes and pour a bit of epoxy inside the balls at the opposite end to hold the sliding tubes. The center of the "X" will also be a large brass ball.

The whole coil will look something like this:

I will probably use four little gothic pewter figures like these for the four strike points down on the base rather than the brass balls (I'll use them for feet.):

They can be drilled and taped for 1/4-20 and used as top cover hold down bolts too. The primary coil will probably be hidden under the top cover.

Should be cool!!

Cheers,

Terry

Sulaiman

Mon Oct 16 2006, 06:39AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Looks good except;
if the gothic 'breakout' figures ARE pewter you may fill the air with Lead ions.
(modern 'pewter' is often just Tin which may be ok)

Some breakout would be good - shame to spark-erode those pretty balls.

Steve Conner

Mon Oct 16 2006, 09:20AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Were you inspired by Alan Sharp's "Triodal" toploads at all?

He also did a "Dodecadonoidal" version with 24 stainless steel salad bowls.

Terry Fritz

Mon Oct 16 2006, 06:01PM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Hi,

if the gothic 'breakout' figures ARE pewter you may fill the air with Lead ions.

I checked, and it is "lead free". 90% tin and anitmony/copper. I bet they are just using bulk "lead free solder" ingots. I hope it does not burn off or melt much

shame to spark-erode those pretty balls

Not a problem since there is a nice SS polish

Were you inspired by Alan Sharp's "Triodal" toploads at all?

Cool! I had not seen this! The arc pictures confirm how the streamers fly off the balls and top coil shrouding! A very nice coil that proves out many of the details I was worried about

Still "playing" with the ray tracer (POVray with Moray GUI)

I have to try not to worry about "trying" to calculate the capacitance though.

Here is a good Tesla list post too if interested:

Cheers,

Terry

Terry Fritz

Thu Oct 19 2006, 11:35PM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Hi All,

I got a lot of real parts in now.

For the top load, everything is in but I need to oversize the existing holes and mount the slide shafts into the spheres:

The dragons also arrived today. Four for the corners, and one up top

Also got the box gluing up:

So it really will turn out pretty close to the concept:

There is also a new "official release" of ScanTesla 8.10 at:

Very busy....

Cheers,

Terry

Terry Fritz

Fri Nov 03 2006, 05:13AM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Hi All,

My PIRANHA SISG coil with the sphere top terminal is getting about done. I just need to work some on the wiring and tuning still.

The whole coil is looking like this:

Pretty close to the concept

The secondary will eventually be coated with Envirotex. and the top of the base will have a thin cosmetic cover so the primary and guts are hidden.

The top terminal seems to work very well!

The last picture there is the corona off the top of the secondary under the terminal at 300kV peak. It will not breakout even at that voltage

Things might need a little adjustment there but nothing bad.

The dragons are cute and the primary deck worked out well:

The primary coil is actually under the sheet of acrylic and held by four brackets glued on with 'Weld-On' acrylic cement. The coil is just insulated #4 wire:

The turn to turn voltage is not super high so the coil will be just wound tight in the brackets.

I just transferred the SISG guts to a new base board the fits the new case:

So it really is coming together now

Cheers,

Terry

Hazmatt_(The Underdog)

Fri Nov 03 2006, 09:14AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

I'm a little concerned about the grounded Aluminium fan frame being in close proximity to your heatsinks. I would hate to imagine what a meltdown or flashover would look like at these energy densities.

Terry Fritz

Fri Nov 03 2006, 03:42PM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Hi,

The peak voltage anywere in the primary circuit above ground is about 8kV. The clearance from the fan to the sinks is 0.6 inches (the photo is at an odd angle). So it should be ok

That is over twice the sharp point to sharp point arc distance.

If it were to short on one side it would just fire the primary at 1/2 the Fo frequency. The other side would directly short a 330nF cap which might blow some IGBTs (and cap)... Maybe I should simply put a fuse in it too... Then an internal arc whould just pop the fuse (might still damage IGBTS though). The current draw is a pleasent 10A so that would be easy. A 10 amp fast fuse would be good just to stop it incase something happened.

I also need to arrange some of the wiring on the backside since the voltage is high there. Maybe some poly tubing over the wires.

It is sort of "cool" that there is really no external cooling for the guts. The box has no cooling vents or anything. The fan just blows internal air over the heatsinks that dissipate 24W worst case. At full power, the heat load is around 250W. For short runs that is fine for the big box. All of the parts run practically "cold" now... It would need a small external fanned vent if it were going to run 24/7 though

The base board is neat in that any changes like that are just a matter of changing the $2 piece of plywood around. I wondered if I should just not have the fan, but it is already "stuck" to the capacitor

The coil will be really "silent" now since the fan will be hard to hear (it was very quiet anyway). Of course the guts make no noise other than some magneto constrictive clicking.

The coils goes from dead silent to full power at a chaotic ~~250 BPS "instantly". It's sudden screaming start up is quite a "shock"

It also still has 50% more power I have never used since it is indoors >:-))

It's really cool

Cheers,

Terry

Terry Fritz

Sun Nov 05 2006, 05:58PM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Hi,

The PIRANHA coil is finally going

To fix the corona problem off the top of the coil, I cut the top rod down on the gazing ball top load two inches which seems to have worked fine.

I measured the resonant frequency with varying ball distance from the center..

The chart shows that as I increased the distance of the balls from the center, the capacitance increased "linearly". I could go from 28pF at 23 inches to 35pF at 32 inches major diameter. That gives a 98 to 111kHz secondary tuning range. I will try to center the coil at 103kHz primary 105.5kHz secondary.

For background, the balls are 8 inches in diameter and can be slide from 11.5 inches to 16 inches outside radius. Their center line is 7.125 inches above the top turn of the 6 inch secondary coil. The coil is 73.63mH wound with 1363 turns of #28 and is 20 inches long.

For primary tuning, I set up the signal generator to frequency sweep from 100kHz to 110kHz.

This gave me a nice graph to show the primary frequency:

One "nice cable position" gave me 102.5kHz with is close enough

I then bolted it all together to finish it up (still need to poly coat the secondary coil):

Here it is doing 25 inch arcs at 1/2 power:

I can't run full power indoors. I loose about 10% in spark length due to the hidden primary (lower coupling) but it wants to arc "too far" already

So it turned out real good!!

Cheers,

Terry

Terry Fritz

Tue Nov 14 2006, 03:21AM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Hi,

I got the secondary pretty coated now

The EnviroTex stuff did a great job even though I did not "baby" it at all

)

Remember the dragons:

If there is no breakout point, they corona glow off their wings real cool!!

Best digital picture I could take...

I am not sure if the 8 inch balls are "too big" yet... I can pump a full 300kV into them and they don't even try to break out... But when they do, I am sure it will be "spectacular" +:D I sort of think 6 inch balls might be a better choice for similar ~1kW coils... I will start removing the shorting jumpers in the SISG sections next to pump up the power far greater

))

Cheers,

Terry

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