1. Five foot tall Jacobs Ladder (2010)

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I wanted to build one of these the first time I saw one in a horror movie from the distant past. Basically it consists of two long metal wires in parallel perpendicular to the ground, closer at the bottom and further apart at the top. When a sufficiently high ac voltage to ionise the air between them is applied, an electrical arc appears at the bottom, then slowly moves upward and ceases at the top.

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Mine uses an 8kVac neon transformer; this voltage is a little lower than most setups, but still lethal. People typically use straightened metal coat hangers with wider arcs but I wanted to build a larger one, and the lower voltage meant I had to keep the conductors quite close together. Ideally I'd have used metal rods but I didn't have any. I did have 3 foot long aluminium tubes, so I used those instead.

 

At first I got an arc at the bottom that just burned. I isolated the two tubes at the bottom with a ceramic tile off-cut and bent the tubes into a )( shape above it, and the arc began to rise, but again stopped. Eventually I discovered this was due to the tubes being too smooth. I roughened the inner opposing edges with a hand file and through trial and error, eventually got the famous rising arc.

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Smearing the tubes with a saltwater solution produced a nice yellow arc. I plan to experiment with carmine powder for red, and boric acid for green.

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Despite keeping the Jacobs Ladder in a far corner of my lounge and staying well away when it was running, I was always very wary of the dangerous voltage present but electrocution isn't the only hazard - the high voltage causes ozone to be produced, and the arc produces X-rays and RF which affect every piece of radio equipment for some appreciable distance, so I rarely ran it - the aim had simply been to see if I could build one. However I set about looking for a suitable protective cover.

 

Eventually I found a seller on eBay UK offering 1.5m (~5') long 65mm (~2.6") diameter quartz solar heater tubes for a mere $10 and bought one. Due to the size and delicate nature of the tube, shipping was out of the question. Instead the seller, who lived some considerable distance away, agreed to meet in a local cinema car park en-route to one of his businesses. At the time it felt a bit like we were secret agents conducting clandestine business!

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The quartz tube fitted well, but looked a bit silly towering over the two 3 foot long, but significantly shorter aluminium tubes. I had more aluminium tubes, and some smaller diameter that would fit snugly inside the existing tubes so I cut a couple of short lengths of the smaller tubes and screwed them into the ends of the bottom tubes to act as guide ferrules for the top tubes that I then added, cut Just shorter than the inside top of the quartz tube. I found the quartz tube adds an eerie hollow echo to the sound of the arc as it rises.

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With a bit of fiddling I managed to get a huge 5' arc that takes some 5 seconds to rise, but the aluminium tubes easily moved out of place, so I added a couple of outer screws to the top rods to align them using the inner surface of the quartz tube. The setup is still problematic, but generally works, see video below, which shows a yellowish arc from salted water (sodium) rubbed along the tubes.
 

Note - This video appears thin because it was filmed horizontally (the only way I could get it all in view), and then digitally rotated. For this reason the video is best viewed in full screen mode:

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501v01 P1160624 five foot tall Jacobs ladder.MP4    - 5750MB

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