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Re: [TCML] Questions on grounding

Hello Christopher (and everyone else who responded),

I haven't had time yet to fire up the coil at night since I grounded the secondary and nst case to earth ground. Will do tomorrow night. I also relocated my spark gap so I can blow air on it. Right now I am still using the cartridge bolts but I got a 120v 100 cfm boxer fan about 2" away blowing air on it. If it improves the output, I'll look for a blower fan that really cranks and see if that works.

Of course I need to be more exact in my breakout measurements so I am going to mount a grounded wire on a pole and set on a tripod so I can accurate measure the spark length to gauge improvements.

I am also thinking I may be over coupled. The inside of the primary is almost flush up against the secondary form. The primary is about 1" lower than the bottom of the secondary coil. If I try to raise the primary so it is even with the secondary winding, I get sparks. So I may rewind the primary out another inch or two.

Thanks for everyone's input so far.


----- Original Message ----- From: "Christopher Karr" <chriskarr4@xxxxxxxxxxx>
To: "Tesla Pupman List" <tesla@xxxxxxxxxx>
Sent: Wednesday, April 15, 2009 3:50 PM
Subject: RE: [TCML] Questions on grounding

Hello Joe,
The reason that a fan on the spark gap helps improve output of a Tesla coil is that it helps to extinguish the arc and blow out the ions. When the ions are all gone, the gap takes a higher voltage to make it break down, which means that there's more 'bang energy', resulting in more energy transferred to the secondary coil and that means larger streamers on the output.

From: jocatch@xxxxxxxxxxx
To: tesla@xxxxxxxxxx
Subject: Re: [TCML] Questions on grounding
Date: Wed, 15 Apr 2009 14:01:07 -0400

Hello to everyone who has responded so far. Thank you!

Today I went and got a 4' ground rod and banged it into the ground and ran a
wire to the secondary coil and nst case. I used a 4' rod because my ground
here has lots of rocks and I have never been able to go more than about 4'
with ground rods. As you can see from my photos that the coil is on my rear deck, there is no concrete floor. The wire from the coil to the rod is less than 20' long. Tonight after dark I will power it up and see if it helped. I will also connect the ground wire to the end of a pole and see how long of a
spark I can get.

Regarding my spark gap, I always go for the easiest, simplest solution as I
am not that mechanically inclined. I do have some 12v computer fans I was
thinking about placing near the gap to see if it helps. But I wanted to try
the grounding, tuning and adjusting the gap width before adding a fan.
Besides, I have no place right now to add the fan on the base; I will have
to move the gap to somewhere where there is more room. Regarding a 'sucker'
gap, I am not sure what that is, I will have to research that.


----- Original Message ----- From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Wednesday, April 15, 2009 10:36 AM
Subject: RE: [TCML] Questions on grounding

Hi Joe,

When you say that "Right now, nothing is grounded to earth or electrical
ground", this is REALLY bad! The secondary base needs a ground connection. If there is not a good, direct ground connection, the RF current will travel through your hot & neutral wires and wreak havoc with household appliances.

I agree with Bart's reply - that the secondary base is typically connected
to the NST case, and that this case connection should go to a dedicated RF
ground, not the mains ground.  For low powered coils, the mains ground is
often used, but the definition of "low" is subjective.

Regarding the sparks discharging all around the toroid, this may be due to
having a ragged surface on the toroid, so smoothing it out may help. If the toroid is simply too small for the power level you're running at, no amount
of surface prep is going to help, but yours appears to be reasonable in

Looking at your web site, I think the weak link in your coil is the 2
carriage bolt spark gap. It needs forced air flow directly through the arc
(more than just a gentle breeze from a fan), and should be designed to arc
not at just a single point as yours will.  I recommend using a sucker gap,
as it's easy to build and works very well.

Regards, Gary Lau

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of jocatch
Sent: Tuesday, April 14, 2009 9:35 AM
To: tesla@xxxxxxxxxx
Subject: [TCML] Questions on grounding

Hello. I have built my first coil using standard parts and dimensions and
have fired it
up and so far I am producing sparks but only about 12" long. I am using a
12KV nst
with .0125uf mmf, 13 turns of copper tubing as primary and 20" of #28
magnet wire
on a 4" form with aluminum cloths dryer ducting for the toroid

My questions concerning grounding. I have read alot about discharge spark
but not much regarding how to measure it. Above I said 12" discharge spark
that was to a key ring held at the end of a boom stick handle. Should the
object that I am drawing the spark to be grounded? To earth ground? Right
nothing is grounded to earth or electrical ground. The bottom side of the
coil is connected to the metal case of the nst. Should the secondary coil
and nst be
grounded to earth ground?

Lastly, the aluminum toroid is discharging all around its circumference. I
know the
fewer discharge points on the top load, the bigger the discharge length
will be. If I
tape the toroid with aluminum tape to produce a smoother surface, will it

I have a web page showing photos of my first tesla coil before I recently
updated it
to copper tubing and new toriod. The web page shows the old primary wire
coil and
old topload. I will post new pictures of the update soon.


Thanks for your help.


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