I sat down one evening at Unit 15 in the old Rainier Brewery Building with Rob Flickenger. His projects have always been amazing – the can-tenna, shrunken quarters, building wireless networks for the UN in Africa, and writing the books (literally) on wireless networks. His most recent project pushes him even further into the mad scientist realm. He’s built a Tesla Gun.
NOTE TO READERS: This is a dangerous idea. An operator holds this device as it operates. Tesla coils and other high voltage devices can stop your heart. The operator must be ABSOLUTELY SURE that the case has a solid ground to shunt the electricity to earth, and not through you. And while I’m all about taking informed and calculated risks, this is me informing you. Ok. Read on.
When I asked him why he had started on this project, he cited Steven Sanders and Matt Fraction’s Five Fists of Science, a graphic novel in which Tesla and Twain battle the evil forces of Edison and Marconi. “How much more epically awesome can you get than a young Tesla fighting evil with a TESLA GUN?”
While Rob is undoubtedly brilliant, he had to learn a lot to make this project happen. If you made something like this out of duct tape and plastic, it would kill you. But if he wanted that Tesla Gun, he’d have to make a lot of the parts himself. Luckily for Rob, he lives in Seattle, where we have an outstanding group of hacker/makerspaces and incredible people doing crazy things in them. He went and talked to a lot of people. He learned about aluminum casting, 3D printing, working with ceramic slip, and machining — all things he had never had first-hand experience with. He learned even more about high voltage electronics. The end result is a hand-held (if you are very, very certain it is grounded) spark-gap Tesla Gun that puts out around 100k volts with sparks leaping a meter to DAGGAR*.
How and where it was made:
The casing needed to aluminum to withstand the high voltage and look cool. Rob headed over to Hazard Factory to talk with Rusty. They used the foundry there and green casted a NERF gun mold.
The resulting case was machined down with the Hackerbot mill so it would line up correctly and look pretty. He also machined some HDPE stand offs to house the primary coil, so it would be sturdy and resistant to HV. Then he needed a different switch – “no one in their right mind would manufacture what I needed for the consumer market.”
Off to Metrix Create:Space to 3D powder print a mold. They then poured porcelain slip into it, and fired the resulting piece in the kiln. The custom-made porcelain and tungsten switch can withstand 20kv at several hundred amps.
Most of the work was done at Rob’s resident hackerspace, Unit 15 (private). There, he put together his Hockey Puck of Doom. HPoD is a zero voltage sense flyback driver found on Instructables that lets you turn an 18 volt drill battery into 20k volts (the reason this device is more portable than other coils of the same effect). He hand-wound the 1100 turns of #30 copper wire, and laser etched some of the fiddly bits for a more mad-scientist feeling. And my personal favorite: the transformer is from an old TV, which is the best possible use I can think of for old TVs.
Finally, he did a talk at Ada’s Technical Books and at Jigsaw Renaissance to share the joy. The talk at Ada’s was video’d and can be viewed here.
“Telsa Coils are at the intersection of science and magic. It’s impossible to describe the visceral experience of the luminous discharge of a secondary terminal, from a machine that creates ion streams using 100 year old technology. They make a room smell like a thunderstorm.”
As a closing story, Rob told me about the most exciting thing he had ever electrified – himself. One evening, three Tesla coils were running in the same room at Hackerbot at the same time. He powered his down and noticed it was self-resonating – throwing sparks from secondary without being powered, presumably from being in-tune with the two others. He thought, the current coming off must be small, and wondered if he could draw it out with his finger. Rob was then surprised to pull a 4 foot spark — one of the the others was striking it from another angle. “It was awesome. But not the kind of awesome I like to promote. You want the controlled kind of high voltage project.”
You can read a whole lot more about the project over on his blog, Hacker Friendly. He’ll be showing it off at the Seattle Mini Maker Faire.
*DAGGAR is a staple of HV projects in Seattle. There is nothing more epic than catching lightning on this cheesily ornate blade.
images by yours truly and Rob Flickenger.