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Re: PIRANHA - New Top Load Configuration



Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Bart and Stan,

At 08:11 PM 11/3/2006, Bart wrote:
Hi Terry,

It's looking good! Tonight on the way back from dinner, I drove by a house that had ball lights on a pillar in their yard. It reminded me of your topload stack. There were 4 ball lights configured as your topload and about the same size. What was different is that there was a ball in the center of the 4 outer balls.

Looking at the picture you showed where the corona is streaming off the secondary is probably a good indication that a center disc laid on top of the rods and about the inner diameter of the balls would help eliminate that corona.

"Looking at it", the balls are probably too high. I will cut the center rod down about 2 inches. That should fix it.

I guess I sort of disagree about a center ring. The field plots show the voltage stress in there to be very low:

http://drsstc.com/~piranha/PIRANHA/PIRANHA-2/newcoil-01.jpg

The shape of the corona looks like "toroid too high" to me. I made it high at first since it is easier to cut the rod shorter than to "cut it longer" ;-) To bad since the corona is really cool!! It is very bright, pretty, and stable... Very cool that the balls have no problem at all holding off at 300kV!!! Perhaps six 6 inch balls might have been a good choice too... The top dragon can be adjusted at will for a pretty break out point. Taped on nails to the balls work good too... There is a "little" mark left on the balls from the nail contact, but a zero problem there... Those SS glazing balls are super tough!!!


Great job with it all, it looks really nice. Glad to hear your going to coat that secondary (the wrap just doesn't do it).

:-)

I added a 10 amp fast blow fuse incase "something goes wrong". Even at full power, the thing only draws 10 amps at about 105 volts ;-)) But if something shorts or goes wrong, a 10A fuse will pop like a flash cube probably limiting much damage ;-)

I got the guts finished off with the fuse and a big standoff to attach one primary lead.

http://drsstc.com/~piranha/PIRANHA/PIRANHA-2/PIRANHA-Const-011.JPG

The idea is to remove or install the top cover, the lid will be cracked open a few inches and I will reach in there with a nut driver to disconnect the massive primary leads. the primary wire is pretty tough to bend around but once tuned it will never change...

http://drsstc.com/~piranha/PIRANHA/PIRANHA-2/PIRANHA-Const-012.JPG

I need to get some poly tubing to cover the down leads since the voltage there is a bit high for the wire insulation alone. There is good clearance between the fan and all and the heatsinks and other HV parts. The pictures don't show that well...

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 resistors are also finally on ceramic standoffs now. The MMC is still the old underrated in current (prolly voltage too...) one, but I'll wait till it blows up to worry about switching it out :o))

The coil will be 'really' "silent" since the fan will be hard to hear in the box (it was very quiet anyway). Of course, the fully electronic "engine" make no noise other than some magneto constrictive clicking.

The coil goes from dead silent to full power at a chaotic ~~250 BPS "instantly" (like 1uS!!). It's sudden screaming start up is quite a "shock"! It also "still has" 50% more length (2.25X more power) I have never used since it is indoors >:-)) The SISG sections are all still shorted to 600V :D

I was thinking of some sort of dark picture framing matt board to cover the top of the box. Leather was also a thought but it might be too "floppy" unless I glued it down (maybe that super doubled sided carpet tape...). but the matt board could be very easily removed to show the guts... The Weld-On acrylic cement has stuck the brackets on super hard!!! I like that stuff!! It is supposed to kill you instantly and give you cancer, but played with out of doors (Nitrile gloves and safety goggles ) it is zero problem.

It's really cool!!


BTW - Now that others are interested in the design, be VERY aware that the PIRANHA primary circuitry is VERY DANGEROUS!!! There is NO ballast or current limiting for the MOT which pretty much directly connects and drives everything on the primary!!! The 165nF caps hold 4 joules at 7000V and can recharge at 500BPS!!! It is an easy and simple design, but it packs a LOT of "serious killing power"!!! They are "very different" that any other coils...

I have "buried" the primary stuff in the box and the primary coil is insulated and under 1/4 inch of plastic. All the primary HV stuff is impossible to touch. All the external metal is fully grounded... Just don't get silly with these types of potentially "very deadly" coils!!!

Cheers,

        Terry