Tesla ? coil - Griffith Observatory

From:  Bill Wysock [SMTP:wysock-at-ttr-dot-com]
Sent:  Monday, June 08, 1998 12:31 PM
To:  Tesla List
Cc:  Wysock, William C.
Subject:  Re: Tesla ? coil - Griffith Observatory

To Bill Noble an all who have written on this thread:

I do have personal knowledge of this coil, going all the way back
to 1956.  It was the *first* Tesla Coil I ever saw in my life; and
it changed my "life" from that day forward!  I have written to the
List in the past, that the coil at the Griffith Observatory, was my
"leaping off" point, when it comes to "coiling" (a phrase that must
be 'trade-marked' by R. Hull and the TCBOR group.)  I also wrote
about posting to the List, my *first* experience, of trying to
emulate the Griffith Observatory coil, on a smaller scale.  I still
don't have time to do that, but after reading all the responses RE:
the Griffith Coil, I felt it was appropriate to post this message.

The coil at the Griffith observatory is indeed only one part of a
two part system.  Originally, both secondary coils were identical
(but wound in opposite directions.)  These two coils were built by
Mr. Earl L. Ovington, (who worked for Dr. Frederick Finch Strong.)
Dr. Strong was a practicing medical doctor (AMA certified) and also
delivered a number of lectures/demonstrations on the possibilities
of using high frequency Tesla currents, for electro-medical
treatments of some types of maladies in human patients.  His work
(and lectures,) were featured in Hugo Gernsback's "The Electrical
Experimenter" magazines in the late 20's.  The exact illustration of
these two secondary coils shows them as being placed side-by-side,
with arcs (maybe up to 10 feet long,) passing between the two 
identical top-mounted 12" diameter copper spheres, with only one
corona point on each, facing each other.  To my knowledge, this
"double" 1/4 Lambda arangement had their primary coils connected
in parallel; not series, as in my Model 12 double coil system.  Note:
it is much harder to get both sides "balanced" and in resonance, when
the primary coils are series connected (which is the only true 1/2
Lambda case for seperated secondary coils.)  Also, to my knowledge,
the Griffith coils were *never* connected (physically) back-to-back,
or mounted opposite each other, in a horizontal manner.  Rather, they
were two separate secondary coils, that stood vertically and apart
from each other at all times.

Dr. Strong donated these two secondary coil assemblies, to the (then)
new Griffith Observatory, sometime in 1931.  At that time, Dr. Robert
Clemenshaw, was the Director of the Observatory.  As head exhibits
manager under him, a Mr. Leon Hall, was responsible for implementing
all public exhibits on the main floor of the Observatory.  Dr. 
Clemenshaw was Professor of Astronomy at USC, and my mother took
his courses there, when she was in college in the 1930's.  I first 
met Dr. Clemenshaw and Mr. Hall, in 1961.  My mother had taken me
back to the Observatory, for my birthday, that year (that was my only
birthday wish!)  I met both Dr. Clemenshaw and Mr. Hall in June, 
1961.  Mr. Hall and I spent several hours, discussing the coil and 
how it had managed to be installed at the Observatory.  

Mr. Hall explained to me, that when the Observatory first took 
receipt of the twin secondary coils, there were no associated primary
coil assemblies (or anything else....just the two secondary coils, 
and a group of about 24 original wireless telegraphy type flint glass
Layden Jar capacitors.)
So,  Mr. Hall and his work associates, set about devising two 
make-shift primary coils, a suitable rotary spark gap, and a 2 Kva
plate transformer (it is an Amertran unit with multiple low voltage
input taps, which translates to output voltages between 20-30 KV.)
All this was originally set up in the basement workshop of the
Observatory.  The two coils were placed about 15 feet apart.  An
arc would easily jump between the two coils.  However, due to the
limited amount of space on the main exhibit floor, it was decided
to only use one single secondary coil, and build a proper primary 
coil for that purpose.

One coil was kept in a storage room (under the back side of the 
Observatory building facing the down-hill side, where it shared
space with all the gardening equipment used to keep the grounds
in prestine shape,) and the other was pressed into service in the
famous alcove in the north-west wing of the "Hall of Science."
I (personally) saw the delapidated and shorted first secondary
winding in the storage room (along with all the litter that typically
is found in a gardening shed.)  Note: There's a Dick Aurandt story
attached to this part of the coil, that I will post in the future.  
It has to do with why in 1959, the first secondary coil on display
and in operation, had to be changed for the other part.  The first
part secondary coil, had a 12" diameter hollow copper sphere on
top, with two identical smaller copper spheres on either side; (not
the corona points that have been used ever since.)  I was given the
(last) copy of the "Griffith Observer," dated 1948, which carried the
original picture of the first secondary coil on its cover, as 
originally installed by L. Hall and his crew, in 1933, the first year
the coil was put on display in the Hall of Science.

When that coil finally had a turn-to-turn short (the coilforms are
actually made of wood,) it was changed for the other coilform, that
had been kept in reserve, and now the new apperance of a 12"
copper ball, with only two short corona pointed rods on each side,
took "center stage."  Also, the technical staff had been having 
problems with the Ladyen Jars puncturing, and were (finally) 
exhausted of any spares.  At this point, some 1/4" thick sheet glass
was constructed (the capacitor stack was about 18" thick, with
copper sheeting, and was the capacitor I saw in operation in 1959.)

The two identical coilforms were constructed much in the same way
as wine vats are constructed; tongue and groove panels of 3/16" or
so vertical "slats" with a circular bottom, middle, and top disc, to
support the assembly.  The two coilforms were 36" diameter at their
bases, 18" diameter at their tops, and 48" high.  The primary coil,
(as installed in the Hall of Science, is copper rectangular bar 
stock, about 2" high by 1/4" thick.)  Various tap positions have
been used over the years, (depending on what type and capacity
tank capacitor was available at the time,) and this continues today.

The next article (written for the "Griffith  Observer," was in June,
1965, and the last article I know of, by the Griffith Observer,) was
writtne in 1975.  The ony article to appear after that, was in Harry
Goldman's TCBA (Tesla Coil Builder's Association,) newsletter.  That
article as authored by Dick Aurandt, et. al.  I worked on diagnosing
the (obvious) ills of the coil with Dick, who was a close friend of 
mine for many years.

When time is available, I will scan the articles published in the 
Griffith Observer, along with letters of personal correspondance with
Dr. Clemenshaw and Leon Hall, if if possible, also the article that
appeared years ago, in the TCBA newsletter, (assuming Harry gives
me permission to do so!)

Best regards,

Bill Wysock.

> To:            "'Tesla List'" <tesla-at-pupman-dot-com>
> Subject:       Tesla ? coil - Griffith Observatory
> Date:          Fri, 5 Jun 1998 22:45:13 -0500
> From:          Tesla List <tesla-at-pupman-dot-com>

> ----------
> From:  Bill Noble [SMTP:william_b_noble-at-email.msn-dot-com]
> Sent:  Thursday, June 04, 1998 11:45 PM
> To:  Tesla List
> Subject:  Re: Tesla ? coil - Griffith Observatory
> the coil at the Griffith Observatory (in griffith park, in the Hollywood
> hills) is half of an older coil - it is run daily for visitors.  There is a
> data sheet available on the coil - perhaps the observatory has a web site??
> I haven't checked for that.  The original coil had two tapered secondaries
> and the primary in the middle, if I remember the brochure correctly.
> And,yes, the coil is still there.
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