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First firing of 4" coil!




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From:  Alfred A. Skrocki [SMTP:alfred.skrocki-at-cybernetworking-dot-com]
Sent:  Sunday, March 01, 1998 8:08 AM
To:  Tesla List
Cc:  Chris.Stone-at-etak-dot-com
Subject:  Re: First firing of 4" coil!

On Monday, February 23, 1998 3:41 AM Christopher Stone
[SMTP:Chris.Stone-at-etak-dot-com] wrote;

> > I, along with some of my friends did our trial runs with my 4" coil and
> > I have some questions about whether our results are average.
> > 
> > Here are the specs:
> > 
> > PRIMARY
> > 15 turns of 1/4" copper refr. tubing 30 degree inverse conical approx.
> > 21" outer diameter 6.5" inside.  Tapped on turn 14 and 15 for best
> > results.

This is typical for this size coil.

> > SECONDARY
> > 4.2 X 21.5" Secondary wound on PVC/ polyethelyne drain pipe (white
> > outside, black inside) with approx 995 turns of 24 gauge enameled wire.

THe height/diameter ratio of two coil Tesla coils should be in the range of
3/1 to 4/1, yours is over 5/1 which will introdurce too much resistive
losses ie. lower the Q and the output!

> > TOROID
> > 1.75 X 12" foam covered with aluminum tape about 2" above top winding.

Try 3-4 X 12" so you can have more energy built up befor break out occurs.

> > TRANSFORMER
> > 9KV 30mA Franceformer

OK, but the more power the better the output anything larger up to 
15KV at 120 ma. would be a distinct improvement.

> > SPARK GAP
> > Two 1" ball bearings spaced approx 3/16" or less apart (varied during
> > testing).

Poor design, too much losses and poor quenching either go with a Richard
Quick multible cylinderacle gap or at least a multible series gap to improve
quenchinmg.

> > CAPACITORS
> > Salt water bottle caps, started with a value of .005 and found that
> > removing two bottles with a total value of .004 gave the best output.

Ditch the glass it is absorbing too much of your R.F> gow with polyethylene
in mineral oil either the stacked plate design (easiest) or the rolled
design.

> > PROTECTION
> > Safety gap on each side of the transformer spaced about 3/16 of an inch.

Good.

> > Two small toroids with about 18 turns of enameled wire, I know these are
> > probably too small, but better than nothing.

I prefer to use like a pound of #28 for an R.F. choke, yours is just about
useless!

> > GROUND
> > We grounded the secondary to the kitchen faucet which read 0 ohms to
> > some ground rods we had also put in next to the house which were not
> > touching any pipes!  It has been raining for many days and the ground
> > was soaked. We used a 10' 00 gauge welding cable to connect to the
> > faucet!

On a coil of this size a ground is not neccessary.

> > PERFORMANCE
> > Maximum sparks so far are in the range of 5-6" to a grounded wire. We
> > were able to make 2' fl. tubes light about 5' away.  I was expecting to
> > get a slightly longer sparks, is this normal?  What changes should I
> > work on to improve the coil? I am already planning to make a copper
> > pipe/ fan quenched multiple spark gap to improve performance.  Is the
> > limitation with my current set up with my transformer after that?  Can I
> > widen up the spark gap farther?  With the max results the safety gaps
> > were firing almost constantly depending on load (grounded wire, tube,
> > etc.)

I built a similar sized coil many moons ago and with a 12KV 60 ma 
transformer it yielded 2 foot discharges and with a 15KV 120 ma 
transformers it yielded close to 3 foot discharges.

                                       Sincerely

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                                   Alfred A. Skrocki
                               Alfred.Skrocki.Sr-at-JUNO-dot-com
                           alfred.skrocki-at-cybernetworking-dot-com
                      Visit my Do-It-Yourself Aquarium WEB page at;
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