Re: advice on secondary

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: jdwarshui@xxxxxxxxx 


Hello Ben

Consider using Styrofoam for your secondary coil form, it will
outperform P.V.C.  You can glue a 3/8 inch maple dowel between
laminations of Styrofoam and use an electric drill for a lathe. (A
steel hook eye in a board makes a good support for the other end of
the dowel.)   36 grit sandpaper against the spinning foam makes for
rapid and precise stock removal. A layer of clear plastic tape on the
surface of the Styrofoam will give a good surface to wind on.

We use the same jig to wind the coil, and to put varnish  on the coil.
(varnish while it is spinning, rub on thin coats.) Carefully twist the
dowel to break it free from the Styrofoam when the last coat of
varnish has dried.
Warning: you must use minimum grain deviation select maple dowels to
be successful with this method, other woods are simply not tough
enough to withstand the torque. (they break when you try to twist them
out of the core.)

The primary circuit should use large O.D. tubing,  it makes a
noticeable difference in performance. Keep all leads as short as
possible and solder all connections. File smooth any sharp edges that
may lead to corona loss and undesired spark nucleation. It is ok to
simply solder leads to your primary using a butane torch, it is easily
tuned this way. The torch discolors the copper but this can be cleaned
up with steel wool.

We make our cylinder primaries by manhandling copper tube around
buckets, tires or concrete posts. Once the tubing has been (carefully)
removed from the form we then weave nylon rope between the winds to
get an even spacing. (you can saturate the rope with polyester resin
or epoxy for rigidity when you are done)

A variation on the same trick works for making pancake primaries. You
wind the coil between two very stiff sheets of plywood held together
with bolts and a spacer. Spring back is considerable so figure on
extra winds and some trimming.

 We prefer solenoid primaries, they are easier to make, more compact,
less prone to being  damaged. (easily replaced, not tied into the
entire structure)

Copper work hardens very quickly, once bent it does not like being
straightened. So either use new tubing or reheat the entire length to
a dull red with a cutting torch. (ideally a water quench from dull red
is desired, but this would require an expensive oven)

Consider trying a variety of different couplings for your primary,
getting the optimal coupling is a bit hit and miss.

Spheres are easier to make then toroids,  they are more compact and
less prone to damage, but some people dislike the way they look.  You
can make toroids  from laminated pineapple rings of Styrofoam. Sand
them round and smooth with 36 grit sandpaper. A mist coat of  77 spray
adhesive on aluminum foil will hold the foil nicely to the foam.
Burnish the foil with a hard object. ( try several different top ends,
the shielding effect of the toroid directly on top of the secondary
tends to reduce the calculated sum of capacitance)

Don't cast your design in stone, do all your mockup work with blocks
of Styrofoam, use clear plastic tape to hold object in position (tape
is a very good insulator). Once your setup is optimized then finalize
your coil.

Old  N.S.T  can get coked with carbon and perform poorly. We would
recommend building a fixed Jacobs ladder to periodically test the
output of the N.S.T.   If the transformer is failing you will be able
to detect it very quickly thus avoiding hours of tuning
frustration.

Do use a safety gap and radio frequency suppression or your
transformer will die a horrible death.  Power correction should not
change the output of the N.S.T, but less line load probably does mean
slightly improved input voltage.

Good luck dont get hurt!