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Building New Coil

Quoting kasper-at-exo-dot-com:

> My apologies if the questions in this email have been answered
> 10 times over by now.  I just signed on and am building a new 
> coil :)

> Inventory -

> 20 X 5 torroid (from American Welding & Supply)
> 12KV transformer -at- .12A sunk in oil
> .025uf cap rated at 50KV (DC)
> Spool of #26 magnet wire
> Large 3 gang variac

> Questions -

> Secondary Coil:

> The size of the secondary is based upon the size of my torroid.
> According to the TESLAC program, I need 1800 - 4000 watts to 
> drive this properly.  This program assumes that I use a helix 
> that is 8" - 12" in diameter.  According to the TCBA article 
> written by Richard Hull, that diameter is too big.  My thoughts
> are that I should use a 6" diameter form that is 15" in length. 
> Does this sound okay?

Bump your wire diameter up to 22 AWG or larger. Extend you six
inch diam. coil form length from 15 inches to 24 - 28 inches.

> Also, I have heard that gray PVC pipe is reasonable for a coil
> form...? 

Properly prepaired PVC makes an acceptable coil form.

> Main Transformer:

> 12KV -at- .12A is approximately 1440 Watts.  According to the 
> TESLAC program this is not enough power for the secondary and 
> torroid.  

This transformer is just fine for a medium powered coil system
such as this one.

> The transformer is sunk in oil.  I think I can push the power 
> rating of the transformer to at least double for Tesla Coil 
> operation.  If I capacitively load the transformer to double 
> it's rating, will this work? Or will the transformer core 
> saturate and not give better performance? 

There really should be no need to overdrive this power supply. If
you are dead set on getting more juice from it then throw a
couple of neons in parallel.

> .025uf CAP:

> This is a DC cap.  Will this work okay in this type of a
> system? 

Every cap will have a DC rating. You can usually tell how well a
cap will pulse by looking at the terminal mounts. Our pulse
discharging caps (.025 uF) have solid brass threaded studs .5
inches in diam (the standard diam. is .375") extending 1.25
inches out from the body of the cap. If your terminals are inset
for a #10 screw you can bet it will not pulse discharge well.

> Also, The reactance of the cap should load the 12KV transformer
> to around .1A at 60 cycles, if I do not add additional capacity
> will this amount of power drive the secondary system as stated
> above?

Your transformer and capacitor value are pretty well matched. I
would not worry about it.

> Spark Gap:

> I am building an 8 pole stationary gap in a brass housing that
> will be air tight.  I want to quench the gap rapidly and am 
> thinking about pulling a vacuum on the spark housing.  Will 
> this work?  Should I be filling the housing with a "magic" gas,
> or pressurizing the housing?

Static gaps will work well IF your transformer is internally
current limited, such as with a bombarder or heavy neon (this is
what it sounds like). If the transformer requires external
current limiting, then you will need a rotary gap.

As for running the gap sealed, the best way (the Telefunken way)
is to design the gap with a lot of electrode surface area and
good heat sinking, then seal it up. Running the gap for a few
minutes will consume most of the air, then you will get hours
of service in a nitrogen atmosphere before the gap needs to be
opened for cleaning.

You sound like you could use some additional assistance on your
secondary coil design. I would suggest logging into the archive
and downloading the COILBLD.ZIP file.

The Tesla group archive <tesla-at-grendel.objinc-dot-com> is online. The
ftp-site is nic.funet.fi  alias  ftp.funet.fi and this site can
be connected using anon-ftp. The files are in the directory
/pub/sci/electrical/tesla and it's subdirectories.

If one does not have online-ftp it is possible to get the files
using ftp2mail-gateways via e-mail. Some ftp2mail-services:

ftpmail-at-decwrl.dec-dot-com or ftpmail-at-cs.uow.edu.au
bitftp-at-pucc.princeton.edu or ftpmail-at-lth.se
bitftp-at-dearn or to bitftp-at-vm.gmd.de (Europe only)
ftpmail-at-ftp.uni-stuttgart.de
ftpmail-at-grasp.insa-lyon.fr or ftpmail-at-ieunet.ie
bitftp-at-plearn.edu.pl or bitftp-at-plearn (Europe)
ftpmail-at-doc.ic.ac.uk or 
ftpmail-at-sunsite.unc.edu 

In order to get more information on this subject one has to send
mail to an address above and use just "help" as a body-of-letter
to get information on the precise format of the script language
that the particular site uses. If one uses the keyword "ftplist"
one will receive a list of the other sites available.

The information is available via World Wide Web as well - the url
is: http://ftp.funet.fi/ftp/pub/sci/electrical/tesla. This is
just the beginning of Tesla on WWW - there shall be more in the 
nearby future. <FTP tips by Kristian Ukkonen>

Richard Quick


... If all else fails... Throw another megavolt across it!
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