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Re: "lightning machine" at Chicago's Museum of Science & Industry? (fwd)
Original poster: Steven Roys <sroys@xxxxxxxxxx>
---------- Forwarded message ----------
Date: Mon, 05 Jun 2006 14:16:03 -0500
From: Bert Hickman <bert.hickman@xxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: "lightning machine" at Chicago's Museum of Science & Industry?
(fwd)
High Voltage list wrote:
> Original poster: Steven Roys <sroys@xxxxxxxxxx>
>
>
>
> ---------- Forwarded message ----------
> Date: Fri, 02 Jun 2006 16:37:44 -0400
> From: David Speck <Dave@xxxxxxxxxxxxxxxx>
> To: High Voltage list <hvlist@xxxxxxxxxx>
> Subject: Re: "lightning machine" at Chicago's Museum of Science & Industry?
> (fwd)
>
> Doc,
>
> By any chance was this the machine that had been featured at the GE
> Pavilion of the 1939 NY World's Fair? The vintage and capabilities of
> the machine sound similar to what I've heard about the NYWF display.
>
> GE had both a Marx Generator and a multiple megavolt 3 phase flaming arc
> display at that fair. The transformers of the continuous display were
> dispersed, some being used for test stands in Pittsfield, MA. I never
> heard what happened to the Marx display.
>
> Dave
Hi Dave and all,
The Chicago and GE Marx generators were completely different. The
Chicago Museum of Science and Industry facility was a single Marx
generator that used ten relatively small 100 kV stages to develop 1 MV
discharges, while the GE facility (in 1939) consisted of twin 5 MV
bipolar Marx generators.
I was fortunate to see the Chicago Marx generator in operation when I
was in grade school (mid-1950's). It created a deafening discharge about
3 feet long. One of the demonstrations was to explode a block of wood
with the discharge. The blast when the Marx fired reverberated through
the entire building, echoing for a number of seconds. They would ring an
alarm before firing it so that you could cover your ears... I really
miss that display! :^)
For the 1939 World's Fair, GE used twin 5 MV bipolar Marx generators to
develop 10 MV discharges that spanned 30 feet. This really must have
been an incredible sight to see (and hear!). Following is some
information from the October, 1939 issue of GE Review about the twin
Marx generator, the 3-phase arc, and some subsequent history. I've also
included some links to some B&W pictures.
Each 5,000,000 volt Marx generator used 51 0.33 uF 100,000 volt Pyranol
capacitors, and each stage consisted of three capacitors connected
in series. Each generator was charged from a bipolar 300,000 volt DC
source (+/- 150 kV on either side of ground) which used high voltage
vacuum tube rectifiers ("Kenotrons"). The effective series capacitance
of each 5 MV unit was 0.00653 uF, for a stored energy of 81.6
kJ/generator or ~163 kJ during a 10 MV discharge. Following are some
images of the facility (you can get a feel for the scale in the first
picture):
http://205.243.100.155/photos/GE_Lab/10Mev2.jpg
http://205.243.100.155/photos/GE_Lab/10Mev1.jpg
http://205.243.100.155/photos/GE_Lab/Steinmtz.jpg
http://205.243.100.155/photos/GE_Lab/impulse.jpg
http://205.243.100.155/photos/GE_Lab/ltning.jpg
The million volt 3-phase arc was powered from a 1500 hp motor-generator
set, and used reactive current limiting. Open circuit voltage across
phases ranged from 850 kV to 1 MV. Six 350,000 volt cascade transformers
were used, each with a rating of 1,000 KVA, with pairs connected in
series-cascade to generate 700,000 volts to ground or about 1.2 MV
phase-to-phase. The grounded (bottom-most) transformers each had a
tertiary 2300 volt winding which drove the LV side of the floating
transformer.
Each floating transformer sat on a 5 foot high insulating pedestal and
operated at 350,000 volts above ground. The diameter of each transformer
was 85.5" and overall transformer height including insulator was 14 feet
10.5". The transformers were designed to harmlessly arc over the output
bushing at 450,000 volts and to safely withstand transient impulses of
over 1.3 MV. Images of one of these transformers undergoing 450 kV
dielectric and 1.3 MV impulse testing follow, and I've also included an
image of a single-phase million volt arc:
http://205.243.100.155/photos/GE_Lab/XfrmrArc.jpg
http://205.243.100.155/photos/GE_Lab/1mevarc.jpg
Electrodes for the three phase arc were mounted on 18 foot insulating
masts, and the masts were arranged to form an equilateral triangle 14
feet on a side. Each electrode consisted of a spinner electrode (a bar
mounted on ball bearings and tipped with 5" balls on the end. Tangential
to each ball was a sharp pointed half tube that held a colored fusee
which served to color the arc as well as increase its length. Corona
drove the spinners like giant pinwheels at 50-100 RPM depending upon the
length of the spinner. Two interchangeable length spinners (3 foot and 5
foot) were used. The minimum distance between spinners was between 9 and
11 feet depending upon the length of the spinner that was used. Once
ignited, the arc rises 20 feet above the gap in a tortuous path
estimated to be between 100-150 feet long.
Unfortunately, I haven't had any success in locating good pictures of
the spinning 3-phase arc. One picture (unfortunately very small) of a
static arc can be seen here:
http://205.243.100.155/photos/GE_Lab/3-Phase_Arc.jpeg
At the conclusion of the World's Fair in 1940, the HV transformers and
Marx generators were transported back to GE's HV Lab in Pittsfield,
MA. These were then used to build two larger impulse generators in a
new High Voltage Laboratory in 1949. The rebuilt Marx generators could
develop up to 15 MV (+7.5 and -7.5 MV versus ground), and could flash
across a 50 foot gap (the previous generator could "only" do 30 feet). A
picture of the newer 15 MV system (and a good view of the last two
stages of a a triple cascade transformer setup) can be seen at from this
article in National Geographic, June 1950, "Lightning in Action":
http://205.243.100.155/photos/GE-Lab/15MV_Discharge.pdf
The complete article can be found here:
http://www.usfcam.usf.edu/McCollumPDF/14.Colton.pdf
The Pittsfield facility finally closed its doors in 1995. GE's
Pittsfield manufacturing facilities are undergoing cleanup due to
PCB contamination from earlier electrical and chemical manufacturing
operations. Some of the equipment that was in the Pittsfield HV lab was
ultimately transferred to a smaller HV lab in Fort Edward, New York. I
don't know if this included the 350,000 volt transformers, since they
would have been over 55 years old by then...
BTW, those of us who are old enough to remember the "General Electric
Theater" on TV in the '50's and early 60's (hosted by Ronald Reagan!)
may also remember that GE began the show with about a 2 second video
clip of the million volt arc... :^)
Best wishes,
Bert
--
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***************************************************
>
> High Voltage list wrote:
>
>>Original poster: Steven Roys <sroys@xxxxxxxxxx>
>>
>>
>>
>>---------- Forwarded message ----------
>>Date: Fri, 2 Jun 2006 11:03:35 -0600
>>From: Dr. Resonance <resonance@xxxxxxxxxx>
>>To: High Voltage list <hvlist@xxxxxxxxxx>
>>Subject: Re: "lightning machine" at Chicago's Museum of Science & Industry?
>> (fwd)
>>
>>
>>
>>It was not a Cockroft-Walton circuit. It was a classic Marx impulse
>>generator. I repaired it for them several times. The original design used
>>HV resistors that were too small and they kept frying. The generator was
>>quickly and quitely removed from service when someone discovered the caps
>>were filled with PCBs. It was a 1,000,000 Volt Marx generator.
>>
>>Dr. Resonance
>>
>>
>>
>>
>>>Date: Thu, 1 Jun 2006 13:24:14 -0600
>>>From: Gomez Addams <gomez@xxxxxxxxxxxx>
>>>To: High Voltage list <hvlist@xxxxxxxxxx>, Tesla list <tesla@xxxxxxxxxx>
>>>Subject: "lightning machine" at Chicago's Museum of Science & Industry?
>>>
>>>This may have been asked on one of these lists before. I may have
>>>even asked it myself a few years ago, because it's something I've
>>>been interested in for a long time, but if I ever did get an answer
>>>here, I didn't put it where I could find it again. If I'm repeating
>>>myself, I apologize for my absent-mindedness.
>>>
>>>By the way, this isn't really Tesla coil related, but it's close
>>>enough it ought to interest many on the TC list, and I figure someone
>>>else my age or older may know about it.
>>>
>>>So: in the 1970s, the Chicago Museum of Science and Industry had
>>>something which my high school science teacher called a "Lightning
>>>Machine". We took a field trip there (from Peoria) but to my dismay,
>>>they had shut it down only a few months before our visit. According
>>>to the guide I talked to, they had found a hole in the ground cable
>>>which lead down from the second floor and into an elaborate ground
>>>system in the basement, and for that and other reasons (perhaps it
>>>had other problems) the powers that be had elected to not resume
>>>operating it.
>>>