High Voltage Photography at a Quarter Million Volts

 

 

copyright Gordon C. Kirkwood 2014
A fig leaf from my garden, experiencing 180 kV pulses from a homemade Marx high voltage generator. This was recorded on a large format view camera with 4×5″ film. Copyright 2014 Gordon C. Kirkwood.

A Marx Generator is a spectacularly impressive electrical machine for storing up energy,  and releasing it in brilliant bursts.   Using only spark gap switches, capacitors,  and either resistors or inductors,   one can multiply an intermediate high voltage (say, 30 kV) by many times- the multiple depends on the number of capacitor stages built.

In 2012 I made a very simple marx generator which had 6 stages and a maximum theoretical output of 180kV.  I used it to create images like these, of the veins of leaves conducting the arc through a leaf.

Copyright Gordon C. Kirkwood 2014.
Strawberry leaves at 180kV. A close crop of a 16×20″ print made from 4×5″ film negatives. Copyright Gordon C. Kirkwood 2014.

 

Copyright Gordon C. Kirkwood 2014
Strawberry Bouquet at 180kV, Copyright 2014 Gordon C. Kirkwood
Copyright 2014 Gordon C. Kirkwood
Fig Leaf at 180kV with ambient illumination. Copyright 2014 Gordon C. Kirkwood
Copyright 2014 Gordon C. Kirkwood
Lindsey Peck Scherloum’s Hand at 200kV, Copyright 2014 Gordon C. Kirkwood

Recently I found a few additional Sprague 30kV 3600pF capacitors,  and so decided to increase the number of stages in the system,  and thus bump the maximum attainable voltage from 180kV to 240kV.  It was also an opportunity to clean up the design  with laser cut acrylic and better fluid resistors (the blue tubing is actually blue copper sulfate solution inside of clear tubing).   These “Liquid Resistors” compare very favorably with the alternative,  commercially sourced, high voltage resistors.  Commercially available high voltage resistors are expensive, and there can be long lead times too.   By contrast, I made this in an afternoon, for about $20 in materials (I had the acrylic and capacitors already).    Plus,  Liquid resistors are tunable-  just change the electrolyte concentration!

The downside of liquid resistors is that periodically you must purge air bubbles,   and scrupulously check for leaks before any use.  (I’ve never found one,  and let this system sit for over a year at a time).  I have also noticed that after a year,  the old cheap vinyl tubing (bought at home depot for about $3) appeared to have lead precipitation at spots due to reactions between the copper sulfate and the lead plasticizers in the tubing wall.   However,  because of the long path length of the tubing between each copper “tap” on the tubing helix,   such localized presumably metallic deposits hardly perturb the nominal 10kOhm resistance between rungs.

Copyright Gordon C. Kirkwood 2014
The new 240kV Marx Generator is a tidy, laser cut acrylic and PVC tubing deal. After tuning the spark gaps to all trigger at the same voltage, It worked like a charm. Copyright Gordon C. Kirkwood 2014.
Copyright Gordon C. Kirkwood 2014.
Test discharge of new 240kV Marx Generator

A Bully-Buster for Jia

My friend Jia is an actor (amongst other things) in Pittsburgh.  He was playing “Data” in a rendition of the canonical 1980′s movie, Goonies,  and asked us to help build some of the gadgetry accompanying this character’s uber-inventive persona.

The Bully Buster is a spring-loaded scissor-type linkage that rapidly projects a boxing glove from within Data’s trench coat.

GCK_0153

GCK_0143

Total project time:  1.5 hours.

 

Robotic Smoke Ring Cannon

vortex ring cannon Whimsy engineering
A group of high school students from the Sarah Heinz House high school Robotics program visited Whimsy Engineering and was treated to a demonstration of a robotically aimed vortex-ring cannon.

Smoke rings are nifty phenomena.   Having previously made huge, ridiculously powerful ones (the sort to knock your cap off at 30 feet),  I decided to make something nuanced,  precise,  and also a bit of a tour-de-force of our craftsmanship.     I present to you the Robotic,  Azimuth/Elevation aimed,  motorized Iris,  laser illuminated,  smoke ring cannon!

 

Details:

  •    TIG welded 16 gauge steel exponential horn couples an 18″ subwoofer to a 4″ maximum aperture iris.
  • DC servo motors control azimuth and elevation via 55:1 Mectrol Gearboxes we had laying around.
  • Motorized Stainless Steel Iris Aperture, 4″ max opening.
  • Integrated Propylene Glycol Fog Boiler charges cannon with fog before each shot
  • 200 milliwatt (very very bright) green laser bounces off of rotating polygon mirror from a laser printer to produce a thin bright plane of light which reveals cross sectional detail of vortices.
    This is the Iris I designed for the smoke ring cannon.  It can change from 4" to 0.5" in about 0.5 seconds.  Since I made the blades out of stainless steel with thin (sharp) edges, it is a little scary...
    This is the Iris I designed for the smoke ring cannon. It can change from 4″ to 0.5″ in about 0.5 seconds. Since I made the blades out of stainless steel with thin (sharp) edges, it is a little scary…

    Why make one when you can make two?  The collision of vortices is where the fascinating beautiful fluid dynamics and symmetry breaking occur.
    Why make one when you can make two? The collision of vortices is where the fascinating beautiful fluid dynamics and symmetry breaking occur.

ridiculously competent engineers at work and play.