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Re: GOT IT!



Tesla List wrote:
> 
> Subscriber: knardell-at-mailhost.accesscom-dot-net Tue Jan 21 22:42:03 1997
> Date: Tue, 21 Jan 1997 01:26:14 -0600
> From: Kevin Nardelle <knardell-at-mailhost.accesscom-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: Re: GOT IT!
> 
> >Kevin,
> >
> >The changes you're making are improving the "Q" of various pieces of the
> >system, and you're heading in the right direction...
> >
> >Corona will form on "sharp" areas - the top of your coil presents a much
> >better opportunity than the ball, so that's why its forming there. The
> >ball added enough capacitance to make your coil run better, but it isn't
> >positioned large enough to protect the top of your coil. The
> >diameter of the termination (whether sphere or toroid) must be
> >significantly larger (like 2x) than the diameter of the secondary in
> >order to be effective in shielding the hookup wire or the top of the
> >coil.
> >
> [snip]
> It 2X larger, I have a hole blown in the side of the hookup wire and this
> wire keeps getting shorter and shorter. I had to trim it once and the trim
> was more than it should have been, I keep trying to patch the hole but it
> seems to find a way through the patch.
> 
> >When you get your coil tuned properly, using either a toroid or a larger
> >sphere positioned low on the top of the coil, it will perform even
> >better. A properly sized terminal prevents premature breakout, makes the
> >coil run much better, and shields the top of the coil making it less
> >likely for corona to form there.
> >
> 
> >Near-term, lower the ball so that it's just at the top of the coil.
> >Make sure that the hookup wire is a smooth spiral coil coming to the
> >bottom of the ball. If necessary, place a small thumbtack on the top of
> >the ball to aid in getting maximum spark for tuning. Once in-tune,
> >remove the tack and see if it can now break out from the ball. If not,
> >you may need to tape a small wire or piece of foil to the ball until
> >you've reached a sufficient efficiency/power level. Longer term, go for
> >the toroid. You will probably need to add more tank capacitance to do
> >this, however...
> 
> [snip]
> 
> So what you are telling me is that I need more ice-tea bottles? If I add
> more capacitance to the tank it will preform better, would I also have to
> adjust the spark gap? It also might be time for more gap, I run a 12KV 120MA
> neon with a total capacitance of .006uf. Another thing is that my primary
> has 1 inch spacing, would it be better preformance wise if I were to reduce
> the space in the primary or does that not matter? What about going with a
> smaller toroid?????
> Questions qusetions, I am sorry:(
> 
> Thanks!
> 
> >
> >Safe coilin' to you!
> >
> >-- Bert --
> >
> 
>                                        Regards,
>                                             Kevin Nardelle
> 
>    ********************************************
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> My main web page IS UP all TESLA
> related with lotsa pictures and links.
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> **********************************************

Kevin,

Since you're using only 0.006 uF of capacitance, your 120 MA neon is
providing much more current than you really need to adequately recharge
the tank cap. A pair of 12 KV 30 MA's or a 12 KV 60 MA neon may actually
work better since the reduced current will reduce "flaming" in the gaps.
Your coil could actually be driven off a single 12 KV 30, but you'd need
to reduce the gap spacing (since you'd now be near 60 Hz neon-tank cap
resonance).

Adding a toroid is really the only way you're going to stop the corona
from breaking out off the top wire. There is NO insulation that you can
use that will can stop this corona from forming when the electrical
field stress is too high - this is exactly what you're running into. A
toroid stops it by changing the electrical field near the top of the
coil, and will stop corona from forming by reducing the electrical
stress at the top of the winding. You should be able to make one very
cheaply with some small 3" or 4" aluminum dryer ducting and a pair of
pie-plates bolted together:


                             Tack (for tuning purposes)
                           | 
          x                x 
        x   x \--------/ x   x
        X   x /--------\ x   x
          x     |    |     x
                |    |
                |    |

This change WILL stop the corona at the top wire. However, it will also
add some capacitance which will require you too add more capacitance to
the primary circuit. When you make these changes, start out at lower
power levels on the variac, and smaller gap setting. Put a tack on the
toroid as shown, and begin tuning for best performance (longest corona).
Make sure you're in tune before you make major increases in the power
levels or gap spacing! If you start getting flashovers from the top of
the winding to lower parts, you may need to increase the coil height
versus the primary (reduce coupling).

Regarding your primary, the wide spacing only reduces the amount of
inductance you could get in the same amount of space. If its working the
way you have it, you don't need to change it other than for appearance
sake if you wish.

Safe coilin' to you!

-- Bert --