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Re: TC Plans

Calle,

I did take a look at the Tesla coil described at the cudenver site.  Some
observations:

He describes a secondary that is 1.5" in dia with a winding length of about
22".  Tall, candlestick coils like this don't perform well with a spark gap
driven primary.  The H/D ratio is about 14:1.  You want a coil that is in the
range of 3:1 up to maybe 5 or 6:1.  A two or three inch dia. secondary wound
with about 12 to 15" of wire would work better.  #22 wire is overkill on this
small of a coil.  You want a compromise between heavy wire (low resistance)
and small wire (more turns per inch and more inductance).  On a small coil
like this, it is better to go for high inductance and use smaller wire like
maybe 28 guage.

I would suggest to reverse the cap and spark gap.  It is better to place the
spark gap across the transformer, which will add some protection for the
transformer secondary windings.  I would also place a 3,000 ohm 20w resistor
in series with each high voltage lead from the transformer.  A safety gap
will also help to protect the transformer.  I would use a 9 or 12 kv, 30 ma
neon sign transformer.  A spark gap with several smaller gaps will work much
better than a gap with just two electrodes.  Even if you just use bolt heads,
nuts, ball bearing, etc. it would be better to have a gap made with about 4
or 5 small gaps of .020" or .030".

I would not connnect the bottom of the secondary directly to the primary.  It
creates a 60 cycle component in the secondary output which is dangerous.
 Connect the bottom of the secondary directly to a good earth ground, like a
water pipe.

The capacitors he shows are really Leyden jars with salt water inside for the
inside plate.  You normally see salt water caps sitting in a salt water brine
in a metal or foil lined plastic box.  The center electrode of each bottle is
connected together and the other lead comes from the foil on the box.  You
fill each bottle about 3/4 full and the box water level is set to match the
level in the bottles.  Float oil on top of the water in the box and the
bottles to prevent corona leakage.

Be careful,  the high voltage transformer can kill you!

Hear ends my comments on this particular coil.  I would expect his coil to
work about as well as his schematics are drawn (that was supposed to be
funny).  I have built three Tesla coils to date and would not even think of
starting another without spending lots of time on the design and the math to
make sure that it will work when I get done.  The first one, I did not and
the next two I did and they performed as designed at first power up.  There
is no sense in spending time and money on something that isn't going to work
as you have planned when you're done - it is just disappointing.  If you are
justing looking for something to play with and will be happy with any sparks,
give it a try.

Ed Sonderman