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Re: Counterpoise Size

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 10:22 PM 4/3/2007, you wrote:

Original poster: "resonance" <resonance@xxxxxxxxxxxx>
I would recommend two short (48") copper rods be driven approx 20 feet apart --- interconnect the two rods and the base of your coil with #2 AWG fine stranded welding cable. The short rods are easy to drive in and relatively easy to pull out. They will not hurt the turf after removal. 

We used this for a "portable ground" and it works great.

Dr. Resonance





I am considering using a counterpoise on my developing traveling Tesla coil
demo.

The coil form is 12" by 62" high plus a base height of 28". Since I hope to
be demonstrating this to High Schools in football fields, I suspect the
grounds people will not appreciate rods being driven into the TLC turf.

I have put together a 3 phase diesel generator to drive a 3 phase radar
transformer for 24-30KV 10KVA DC under control of three 1256D variacs and a
variable 18", 8 pole rotary spark gap (1/2" tungsten). I am hoping to make a
VFD survivable for the 3 phase 3600rpm motor.

Question: would a counterpoise of 12 feet in diameter, 1" chicken wire be
big enough or should I add the base height and make it be bigger?
Add the base height... Why not do something like make a 16x16 or 20x20 ft square that can be easily rolled up. Carpet might not be optimum (sparks might make it catch fire), but if you got some thin plywood (lauan door skins?) or vinyl flooring, you could attach the chicken wire to it. You could make 3x3 ft panels that can be laid out like a lightweight portable dance floor.
The grassy field folks might actually appreciate it, because it would spread the weight out. And, it would be compatible with operating in non-dirt environments, like the running track around the field, or a parking lot. 

it would also provide a clear demarcation of the "close in keep-out zone"



There will also be an 8 foot long exploding wire demo and hopefully a 100KV
Xray transformer driven Jacob's Ladder.

It will be fun getting the liability insurance for this menagerie!

Regards,
Jim Mora