Advice

To: "'Tesla List'" <tesla-at-pupman-dot-com>
Subject: Advice
From: Tesla List <tesla-at-stic-dot-net>
Date: Wed, 11 Feb 1998 01:33:09 -0600
Approved: tesla-at-stic-dot-net

----------
From:  Esondrmn-at-aol-dot-com [SMTP:Esondrmn-at-aol-dot-com]
Sent:  Tuesday, February 10, 1998 1:22 PM
To:  tesla-at-pupman-dot-com
Subject:  Re: Advice

In a message dated 98-02-09 05:48:44 EST, you write:

<< 
 Hello all, I have yet again another question.
 
 Since this is my first "real coil" I thought I would run the design by you to
 see how I am doing.
 
 Possible specs:
 
 Power Supply
     4  15kv 30ma NSTs. Controlled with a 15 amp powerstat 120v input.
 
 Spark gap
     RQ type.  1"dia x 3" long copper tubes. 9 gaps spaced .025 between tubes.
     Variable speed 230cfm fan.  Enclosed in 6" PVC.
 
 Primary
     3/8" OD soft copper tubing spaced 1/4" between tubes. ID 7.5" X 23"OD.
15
 degree conical
 
 Secondary
     6.625" X 23" tall.  #22 mag wire.
 
 Toroid
     27" X 8" flexible heater duct covered w/ aluminum tape. (not yet built)
 
 Cap
     Rolled poly .01 uf  (not yet built)
 
 Choke
     Not yet built.  Would value info here.  I have a bunch of #22 wire left
 and would like to use it
     here if possible.
 
 Bypass caps
     Would value input here also. How wired?
 
 Saftey gap
     Will have one to ground
 
 Ground
     The problem here is the place I will be using the coil is on the second
 floor of a friends shop.
     I will need to run al least 80 feet of wire to ground rods outside.  Will
 there be a problem with
     that?
 
 
 Thanks
 Tom
  >>
Tom,

Looks like a good project, similar in size to mine.  I calculate your
secondary at 28.8 mh (if the winding length is 23").  Self resonant at 282 khz
and at 154 khz with the toroid described.  If your primary is not already
built, I would suggest making the I.D. 8.5" to provide adequate clearance from
the secondary to prevent flashover.  I would also suggest making it a flat
pancake primary and using 3/8" spacing between turns - this allows more room
to get the tap lead in and prevent shorting to adjacent turns.  This coil will
produce big sparks and will want to strike down into the primary.  My coil of
this size also uses a saucer shaped primary and I wish I would have wound it
flat.  I don't think you would see any difference in performance with a flat
primary, you will still be able to overcouple it.

You need at least a .015 uf cap and .02 would be good as it will allow you to
go to a larger toroid later.  The 27" x 8" is a good start but this coil will
work good with a toroid as large as 40" to 50".  I am presently using a 40".

Your safety gap should have a center contact connected to your main RF ground.
The description of your RF ground is not good.  You need a good solid (short
path and heavy conductor - copper flashing, etc) ground for this much power.
You might be able to use a large counterpoise such as metal screen layed out
on the floor but I think this works best with smaller lower powered coils.

Ed Sonderman