Strickfaden’s practice of searching out ready-made items
that might be applied to its construction. The supporting
framework used here appears to have previously served as
a Lazy Susan food tray. The entire assembly is mounted on
a mobile cabinet originally designed for audio equipment.
Both the Lazy Susan and equipment cabinet were garage
sale purchases. Any craftsman skilled in woodworking
will have the tools and expertise to design and fashion
their own supporting structures. Plus, we’ve seen what
marvelous structures can be fashioned from PVC pipe.
The metal rod or tube [MT] extending from the small
central disc can either be soldered, welded, or bolted in
place. I chose the latter by pressing a threaded shaft
coupler into one end of the tube and secured it to the
disc with a flathead bolt. It was necessary to form a small
depression around the disc’s center hole so the head of
the bolt would be in the same plane with its bottom
surface. The small central disc is attached to the glass with
double-sided tape. It must be mounted at the exact center
of the glass disc. An electrical connection was made using
a toggle bolt. Once forced into the tube, the toggle stays
fixed by friction. It can be easily removed. The entire
screen assembly is held in place with simple retainers of
non-conducting materials such as plastic, bakelite, wood,
etc. [Figure 6].
I found that discharges emanating from the flat center
disc show a tendency for hugging to the surface of the
glass. This can create enough heat to eventually crack the
glass. By substituting a sturdy metal pie, pizza, or dinner
plate, the chance of overheating the glass is greatly
reduced. The raised “wings” of the plate position the edge
or discharge surfaces above the glass.
Heat resistant (tempered) glass is a better choice of
material when it comes to lightning screens. Round
tempered glass intended for protecting table surfaces can
be obtained from your local big box store (Target, etc.).
However, you will have to use it in the size at which it
comes as tempered glass cannot be cut down to size.
If you are thinking of ordering a custom-sized tempered
glass product from a local glass firm, brace yourself when
the clerk quotes the price. I used 3/16” common glass for
the dielectric. Avoid plain windowpane glass.
Discharges between the center disc and the copper
ring are not only impressive but also very loud (ear
protectors recommended). By again taking a tip from
Strickfaden, the effect is further enhanced when coating
the large metal disc with a special luminous paint or
paper. The sparks will temporarily leave their signature on
the luminous material. A self-stick luminous plastic product
can be obtained from Extreme Glow, P.O. Box 3037,
Tupelo, MS 38803. The USA phone is 1-888-748-4755.
Luminous paints are available from any craft or department store. I did not try paints so I am unable to tell you
just how well they work in this situation.
The best way to demonstrate the full effect of the
discharges is to operate the screen in total or near-total
darkness. Short runs not only create the best after-glow
■ FIGURE 3. The 65 kV (oil immersed) x-ray transformer used
to power the lightning screen. An inductive reactance is
hooked in series to limit the current draw.
effect but reduce the chance of overheating the glass.
Long exposures tend to blur the individual lightning trails
on the glow product. Interestingly, there is a simple sketch
of a lightning screen on page 180 of Kenneth Strickfaden,
Dr. Frankenstein’s Electrician (McFarland, 2005) suggesting
the use of a mirror as the dielectric.
To prevent electrical currents from running wild and
tripping circuit breakers, an inductive reactance [IR] or
choke must be inserted in series with the 120 volt input
line of the high voltage transformer [HVT]. I applied a
multi-tapped, iron-cored inductor from an old medical
machine [Figure 7]. The tap measuring 20 mH provided
the best results. A simple reactance can be made by
packing a one-inch by seven-inch plastic or phenolic tube
with soft iron (coat hanger) wire cut to 6” lengths and
winding it with no less than two layers of #14 or #16
copper conductor. Give each layer a wrapping of tape
before continuing winding. Tapping the ends and
center turn of the second layer will provide a choice of
reactances [Figure 8]. In place of the core of wires, ferrite
FIGURE 4. The lightning screen’s discharges are not only
impressive but very loud.
August 2009 39