Flat Spiral Tesla Coils
From: Richard Wayne Wall[SMTP:rwall-at-ix-dot-netcom-dot-com]
Sent: Monday, June 30, 1997 5:46 PM
To: Tesla List
Subject: Flat Spiral Tesla Coils
Nikola Tesla in the June issue of the 1919 Electrical Experimenter
wrote the fifth article in a series called "My Inventions". In this
article he states that his laboratory was destroyed by fire in 1995.
NT wrote, " . . . . This calamity set me back in many ways and
most of that year had to be devoted to planning and reconstruction.
However, as soon as circumstances permitted, I returned to the task.
Although I knew that higher electro-motive forces were attainable with
apparatus of larger dimensions, I had an instinctive perception that
the object could be accomplished by the proper design of a
comparatively small and compact transformer. In carrying on the tests
with a secondary in the form of a flat spiral, as illustrated in my
patents, the absence of streamers surprised me and it was not long
before I discovered that this was due to the position of the turns and
their mutual action. Profiting from this observation I resorted to the
use of a high tension conductor with turns of considerable diameter
sufficiently separate to keep down the distributed capacity, while at
the same time preventing undue accumulation of the charge at any point
The application of this principle enabled me to produce pressures of
4,000,000 volts which was about the limit obtainable in my new lab
oratory at Houston Street as the discharges extended through a distance
of 16 feet. A photograph of this transmitter was published in the
Electrical Review of November, 1998. . . . "
Tesla goes on to say that he had to go out in the open and this
ultimately was why he went to Colorado Spring in 1999 where he remained
for more than one year.
Recently, others on this list have had NT's same experience of very
unimpressive flat spiral discharges. Tesla nailed the problem of high
interturn distributed capacitance and seems to have corrected it with
spaced windings and high tension conductors. I'm not sure he could
accurately measure a 4,000,000 volt discharge, but he could probably
quite accurately measure a 16 foot discharge. To wit, our TC
measurement technologies have not changed that much in a century.
None the less, Tesla was quite successful in design and function of his
flat spiral geometries which were far more compact than his helical
coils. To that end, perhaps we should investigate the various
parameters of flat spiral secondaries such as distributed capacities
and inductances as we do in the helical varieties. After
"conventional" flat spiral secondaries are re-researched, a logical
extension would advance to "magnifier" spiral secondaries. And,
ultimately flat spirals in liquid N2.