Tesla Coil Builder 2/?

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4) Once the coil is wound, it is sealed to prevent corona leakage
and to help protect against electrical breakdown between turns.
Sealing also prevents the windings from loosening up on the coil
form. I use the same sealers mentioned earlier, those being
petroleum based polyurethane, two-part clear epoxy paint, or
water free acrylic. Coats of sealer are applied with a brush or
spray until there are no ridges and valleys in the wire. In other
words the coats must build up until the wire is completely
imbedded in sealer. A fan and radiant heat source may be used as
required to speed the cure rate of the sealer. Rotating the coil
on the winding spindle will aid in obtaining a smooth coating
that is free of runs and drips.

5) Two plastic disks are cut to match the ends of the coil form.
The plastic should be approximately the same thickness as the
coil form walls. Experience shows that plexiglas is both readily
available and works quite well in this application. Dry fit and
file the caps as necessary until a good match is made to the coil
form ends. I rough up, or score, the matching surface of the
plastic disks where they will be bonded to the ends of the coil
form. This provides a surface around the edges to give the epoxy
adhesive a bite. 

6) Make sure all surfaces are dry, clean, and free of oil. Place
a bead of fresh, good quality, clear two-part epoxy adhesive
around the top of the coil form and the matching end cap, then
cap the end of the coil with the plastic disk. Weight the end cap
down until the epoxy has cured; then flip the coil over and
repeat the procedure to cap the other end. I will stop here to
make an important note: 



Ideally the secondary coil should be hermetically sealed. This
prevents internal electrical breakdowns of the coil and prevents
the uptake of moisture into the coil form when PVC plastic pipe
is used. If holes are drilled into the coil sidewalls, and/or,
the wire is allowed to enter inside of the coil, then spark
lengths that exceed the length of the winding will almost surely
cause the coil to fail. Once a coil has failed in this manner it
is not repairable. One small hole may be drilled into the bottom
end plate to allow the air pressure to equalize, but under no
circumstances should any other holes be drilled. 

7) The first step in constructing a high current ground terminal
is to cut out a rectangle in the sealer at the base of the coil
form just below the winding. The coil winding should end just
above one corner of scribed area. The cut should be about two
inches long and one inch high, minimum. This section of sealer 
is then peeled and scraped away to expose the bare plastic coil
form. Use a blade and deeply score and cut the bared plastic in 
a "cross-hatch" pattern.

8) Cut a strip of copper from some heavy copper sheet. The strip
of copper should fit inside of, and almost fill, the cleared and
scored area on the coil base. Round the corners of the copper
strip, then bend the strip gently until it conforms exactly to
the curvature of the coil form. The rounded and curved strip of
copper should fit neatly on the coil form in the prepared area.
If copper sheet is not available the ground terminal may be
constructed by splitting open a section of copper water pipe and
peening out the proper shaped terminal. 

9) This next step requires a piece of steel (with a flat surface)
and a small hammer. Gently pull the base wire of the coil free
from the sealer. Pull the wire up all the way to the beginning of
the winding. Once freed, trim this wire, leaving a 2-1/2 inch
length. Scrap the base wire clean of all sealer and enamel

Next, carefully wrap some heavy plastic or cardboard around the
coil to protect the winding from dings, but leave the base wire
extended and exposed. Position the coil so that the base wire may
be laid out flat on a small steel block or plate, then gently
peen the wire out with a small hammer. Copper wire is very
malleable, it will be possible to peen the round wire into a thin
flat strip. Trim the length again if required.

10) Clean and tin the inside curved surface of the copper strip.
Clean and tin the peened out base wire from the coil. Using a
clothes-pin, or other small clamp, position the flattened base
wire diagonally across the inside curve of the copper strip.
Solder the two together with a very hot iron. Avoid clumps or
blobs of excess solder. Clean the soldered area thoroughly with
solvent to remove all traces of rosin, oil, and dirt. Sand the
soldered area gently with abrasive paper to smooth out any rough
areas and high spots. Clean the soldered area a second time.

11) Using a cloth or lint-free wipe, clean the scored rectangle
on the coil form base with solvent, carefully removing all traces
of oil and dirt. Wipe down the copper ground terminal one last
time. Prepare some strips of waxed paper and an assortment of
rubber bands. Mix up a small batch of clear, two-part epoxy.
Smear the scored rectangle on the coil form with epoxy, then
smear the inside curve of the copper ground terminal. Fit the
ground terminal into place, cover with strips of wax paper, and
secure with a couple of rubber bands around the coil form. Allow
sufficient time for the epoxy to gel firmly, but do not allow a
complete cure. Remove the rubber bands and the wax paper strips. 
Gently scrape away excess epoxy from the surface of copper ground
terminal, then wipe the terminal surface clean with solvent. 

If attention has been paid to detail and technique, the copper
ground plate should be nearly flush and firmly attached to the 
bottom of the coil form just below the winding. Sometimes it may
be necessary to fill in a low spot or two with a second tiny
batch of epoxy.

12) This figure shows how effective this ground terminal is in
practice. It is quite easy to connect one inch SMOOTH grounding
strap directly to the base of the coil with a couple of rubber
bands or a long strip of electrical tape. This connection is
ideal for removing the heavy RF current produced at the base of
the coil. This ground terminal is also nice in that it may be
quickly connected and disconnected, offering flexibility and ease
of setup. This system is also efficient if the base terminal is
to be used to feed RF current into the bottom of the coil, as in
the extra coil of the Tesla Magnifier. 

Being flush mounted without drilling holes into the coil form,
this terminal preserves the electrical strength of a sealed coil
form. Without protuberances typical of other terminal types,
there is nothing to break off or damage. The same lack of pro-
tuberances makes it easy to store several coils close together
without worry of scratching or cutting the finishes. This
terminal is clean and professional looking.

13) If the preceding directions have been adhered to, the
completed Tesla coil (RF resonator) will closely resemble the
diagram in figure 13. The coil form is hermetically sealed. There
are no holes into the wall of the coil form. The wire never
enters inside of the coil and all connections are made externally
where they do not compromise the electrical integrity of the
construction. The base wire has been cut, peened, and connected
to a high current ground terminal. The other end of the coil, the
air terminal, has been left untrimmed.

14) This shows how the air and ground connections are made to the
completed coil. A stand-off insulator is placed on the top of the
coil. A TOROID discharge terminal is placed on the insulator and
the wire is air-wound around until it contacts with the bottom
plate of the conductive toroid. These air wound turns are widely
spaced, but the diameter is kept as close as possible to that of
the secondary winding. Once contact has been made to the bottom
of the toroid, the wire may be held in place with a small piece
of tape, then the winding is discontinued and a bared section of
wire is connected directly to the center of the toriod with a 
nut and bolt clamp, tape, etc.. Excess length may now be trimmed. 

The exact length of the stand-off insulator, and therefore the
height the toroid discharge terminal sits above the secondary
resonator, can only be determined by experiment. This varies with
the size of the toroid, the size of the coil, and the input power
into the system. Due to the number of factors involved, this
insulator may require frequent adjustments/changes. For this
reason I do not permanently mount a stand-off insulator on the
coil. I keep a selection of square cut sections of PVC plastic
pipe that I use for stand-off insulators. The toroid is elec-
trically connected as indicated above, then it is simply set on
top of a PVC pipe stand-off insulator. The system is now ready to
be fired. If desired, after some experimentation, the insulator
can be permanently mounted: the end cap should be scored with a
sharp tool, not drilled; the surface should be prepared, and the
insulator should be glued in place with two-part epoxy.

The ground connection is made via the shortest available path,
using the heaviest, widest possible SMOOTH conductor, to a
dedicated RF ground constructed specifically for Tesla work. This
ground is referred to as the "system RF ground" or simply the
"system ground". The system ground is usually constructed, not
happened upon. I advise constructing a system ground from scratch
unless you can verify that any available grounds are electrically
isolated. Do not use a water pipe. Do not use the house ground.
Tesla rated grounds need to be extremely heavy, usually
comprising of several eight to ten foot copper pipes hammered
into the ground. The pipes should be separated in the ground by
their lengths (eight foot pipes are set eight feet apart) and
connected with one inch ground strap buried below sod level.

It should be noted that these instructions are designed to
produce a highly efficient RF resonator with exceptional
electrical strength at the lowest possible cost. Coils built to
these specifications are capable of producing, and withstanding,
discharge lengths that exceed the physical length of the coil by
a factor of 3.5 or more. These instructions are the product of
years of experimentation winding dozens and dozens of coils and
with the collaboration of others in the field of high powered
Tesla systems. This design method has been repeatedly tested and
reproduced by beginners with excellent results.

This completes the COILBLD series on construction of high
performance Tesla resonators.

COILBLD4.GIF      6/9/95           Graphics and text prepared by:

Richard T. Quick II                   <richard.quick-at-slug-dot-org>
10028 Manchester Rd 
Suite 253
Glendale  MO  63122  USA

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