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Re: [TCML] Toroid Problems



Hi Nicholas,

Nothing sounds really wrong from my chair. The cap size is fine for the 9/30 NST. Your calc's are close enough. How high is the bottom of the toroid above the coil? If your getting sparks off the top winding of the secondary, then it's too high. You'll need to lower it.

I got slightly different values for Fr, but that may be due to actual secondary diameter. You said 4". Have you measured that to confirm? The reason I ask is that most of my forms are actually larger like 4.5" diameter. It only makes a little difference in tuning however. If it is actually 4", your probably better off tuning between 9.5 and 10 turns. If actually nearer to 4.5", then about 10.5 to 11 turns.

I don't believe the toroid is too large. My gut is telling me the coil is not liking the spark gap. Can you describe your gap (air flow, electrode diameter, spacing between electrodes, heat of electrodes after a run, etc..?).

Regards,
Bart

Nicholas J. Goble wrote:
I did not wire together various components and hope they'd work together. I did my research and used the calculators listed on deepfriedneon.com. Here are the specs for my coil:

Transformer: 9/30 transformer

Spark gap: air quenched, multi-electrode spark gap. There are five copper pipes, 3.5 inches in length that make up the electrodes. All the gaps fire beautifully. I got the plans off this website: http://www.kronjaeger.com/hv-old/misc/scotsgap/index.html

Capacitor: I used the "Capacitor to Transformer Match" calculator on DeepFriedNeon and found that I needed a capacitance of .0088uF. The Tesla Map construction guide told me that I needed to multiply that by 1.414 to get my LTR capacitance of .01244uF. I bought 12 942C20P15K-F caps that are rated at 2000V and .15uF. I wired them in series to get a capacitance of .0124uF. Correct me if I'm wrong with these measurements.

Primary: 1/4" OD copper tubing spaced 1/4". Inner diameter is 6.5". I did 13 turns just in case, but my calculations show that I only need 11 turns to have the correct inductance. With 11 turns, the inductance of the primary is 40.147uH.

Resonant Frequency of Primary: The capacitance is .0124uF. And the inductance (with some tuning) is .0345mH. That makes the resonant frequency 243.332kHz

Secondary: For my secondary, I wound a 4.5" diameter PVC pipe that was sprayed NUMEROUS times with acrylic spray sealer. I sealed the ends with some PVC caps that I bought at Lowes and used caulk as a glue. I wound the secondary with 24 AWG wire. It was 21" tall. All in all, there were about 950 turns of wire. I sealed the form after winding too. Inductance is 19930uH and self cap is 8.316pF.

Toroid:  Explained in my main post, capacitance is approx 19.137pF.

Resonant Frequency of Secondary: The capacitance of the toroid is 19.137pF, and that of the secondary is 8.316pF. Combined, the secondary circuit's capacitance is .000021453uF. It's inductance is 19.930mH. The resonant frequency is 243.344kHz.

There are the specs. I thought that all those calculations were correct. What could be wrong? There are no wires on the inside of my secondary. If the secondary wire sparks with no toroid, could it just be a problem with my top load? Is it to big? Is my connection not good? I really want to get this thing working well. With a toroid. Any solutions or diagnoses?

Thanks

Nicholas Goble


Lau, Gary wrote:

I see no mention of what you're using for a capacitor, or primary coil.
You have verified that the primary and secondary resonant frequencies match, right? It does sound like they don't match with the toroid in place, but YOU need to gather all the numbers and verify this. One can't just throw together an NST, capacitor, primary and secondary coils, and hope it will all play together. If any one of them is the wrong value, it will be out of tune and won't work.
Regards, Gary Lau
MA, USA

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of Nicholas J. Goble
Sent: Monday, August 04, 2008 1:38 PM
To: tesla@xxxxxxxxxx
Subject: [TCML] Toroid Problems

Last night, I fired up my coil for the first time.  I set everything up
and made sure that all the connections were solid.  When I plugged the
NST in, the spark gap fired, but there were no sparks coming from the
toroid.  I tapped the entire primary, but got no streamers.  At a few
points, the safety gap was firing, so I guessed that the caps were
working.  I thought that the only thing that could be wrong was the
toroid.  When I disconnected the toroid and ran the coil, I got
streamers and some corona coming from the tip of the secondary wire.  I
was able to tune the coil without the toroid.  I got 5-6 inch
streamers/sparks from the wire.

Here are the specifications for my toroid:
4" height
17" outer diameter
9" inner diameter
I took two flimsy 9" pie pans and glued them together.  Then I wrapped
4" aluminum dryer duct tubing around it and secured the ends together
with duct tape.  I secured the tube's connection to the base with caulk
on the rim of the pie pans.  I took some aluminum foil and wrapped it
around the duct taped section, and connected that to the base (pie
pans) with more duct tape.  I drilled a hole in the middle of the pans
and attached a nut and bolt.  I sanded off most of the enamel of the
end of the secondary wire and secured it to the middle of the toroid
with the bolt.

My secondary is 4" dia and 21" tall.  I'm using a 9/30 NST.  Can anyone
diagnose my problem?  I dobut that my toroid is too big.  If anything,
I thought it would be too small.  I used a nail to create a breakout
point on the toroid while it was running and it still failed to produce
streamers.  What's the problem?

Thanks

Nicholas Goble
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