The Tesla Gun

The year was 1889. The War of the Currents was well underway. At stake: the future of electrical power distribution on planet Earth. With the financial backing of George Westinghouse, Tesla’s AC polyphase system competed for market dominance with Edison’s established (but less efficient) DC system, in one of the ugliest and most epic tales of technological competition of the modern age.

More than a hundred years after the dust settled, Matt Fraction and Steven Sanders published The Five Fists of Science: a rollicking graphical retelling of what really happened at the turn of the last century. (Get yourself a copy and read it immediately, unless you’re allergic to AWESOME). On the right is the cover to this fantastic tale of electrical fury.

See that dapper fellow in front? That’s a young Mr. Tesla. See what he’s packin’?

Yep. Tesla Guns. Akimbo.

As I read this fantastic story, gentle reader, certain irrevocable processes were set in motion. The result is my answer to The Problem of Increasing Human Energy: The Tesla Gun. For reals.

The Tesla Gun is a hand-held, battery powered lightning machine. It is a spark gap Tesla coil powered by an 18V drill battery. You pull the trigger, and lightning comes out the front.

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Aim away from face.

It is functionally inferior to that of Tesla’s design in the Five Fists in a few important respects. Notably, it is a bit longer and heavier than Tesla’s own. It also cannot (yet) create an ion wind strong enough to cushion the user when leaping from a four story building.

On the other hand, my design is an improvement in two important respects: 1) It is battery powered, and 2) It actually exists.

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Real sparks!

I’ve given a few talks about how this project came to be, and it’s a bit of a long story. I could not possibly have built it without the help and expertise of Seattle’s many hackerspaces. Take a look at the basic components, and you’ll see what I mean.

The Housing

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Save your soda cans.

The housing is made from a nerf gun cast in aluminum. I had never made a metal casting before, so I went to the expert: Rusty from Hazard Factory. With his expert metal working skills and my limited ability to gather scrap aluminum, follow directions, and stay the hell out of the way, we had a pretty good aluminum housing in a couple of evenings.

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Hot hot hot!

Sand casts inevitably have a few rough edges. Since I needed both halves of the housing to fit together perfectly, the next stop was Hackerbot Labs to put in some time on the Fadal 3-axis mill.

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Big robot is big and wants to kill you.

The milling process took a couple of days, but in the end I was able to remove a lot of the bulk of the interior aluminum, and the two halves lined up perfectly. With the housing finished, I set off on the next engineering challenge.

The HV switch

The heart of any spark gap Tesla coil is the high voltage switch. It needs to be able to withstand repeated switching events of many thousands of volts at an instantaneous current of a couple of thousand ampere, generating more than a little bit of heat along the way. This meant finding a material that was a good electrical insulator that was tough enough to withstand high temperatures. With the help of the fine folks at Metrix Create:Space, I decided to make my switch housing out of porcelain.

The first step required the use of a 3d powder printer. This kind of printer is perfect for printing molds for slip casting.

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Switch mold fresh off the printer.

Once the mold was printed, I made a couple of castings using porcelain slip. After air drying for a couple of days, I fired them in the kiln at Metrix, let them cool for another day, and… Ta da! A custom sized HV switch housing, complete with little lightning bolts.

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Radio Shack does not carry this switch.

Then it was just a matter of inserting a couple of tungsten welding electrodes, and I had a fully functional high power switch. The shape was chosen to fit inside the aluminum housing while still providing room for a cooling turbine fan: a CPU cooler reclaimed from a discarded 1U server. This draws hot ions out of the switch, making for bigger and more rapid lightning.

The power supply

Power is provided by an 18V lithium ion drill battery. That powers a  ZVS driver circuit which drives a flyback transformer, stepping up that 18V to around 20,000V. This stage is affectionately known as the HOCKEY PUCK OF DOOM.

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Looks harmless enough, right?

 The circuit is small enough that it fits neatly in a 2.5″ PVC plumbing end cap. It is potted with household-grade silicone (yes, Home Depot was an important supplier for this component). The output goes to a center tapped coil wrapped around the ferrite core of a flyback transformer salvaged from a TV.

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Little transformer. Big spark.

That leads us to…

The capacitor bank

No, I didn’t roll my own capacitors for this project. But I did make a nifty laser cut housing for them. Also, bleeder resistors are important for preventing unexpected surprises. Like waking up dead after touching this crazy toy.

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Stand well clear.

The caps are 942C20P15K-F by Cornell Dubilier (the cap of choice when your current absolutely, positively needs to get there ON TIME). Since the housing is made of highly conductive aluminum, electrical connections are made with 40kV high voltage wire.

The coils

All of that circuitry strobes the primary coil, protected by a couple of chunks of black HDPE (also milled on the Fadal).

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HV wire. Red means DANGER.

The HDPE sandwich makes a great electrical insulator, helping to prevent arcs between the primary and secondary coils. The bottom of the secondary is also wound with PTFE tape (another great insulator, commonly found at Home Depot). The coil form is a piece of 2.5″ ABS pipe (Home Depot again FTW!) wrapped in 30 gauge enameled wire, then sprayed with polyurethane finish (can you tell that the Home Depot is just a few minutes drive from my lair?)

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~1100 turns of #30.

The top load is an aluminum toroid purchased from Information Unlimited (sadly I don’t have access to a lathe big enough to turn one myself.) Put it all together and there you have it: instant lightning at your trigger-happy fingertips.

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Really, officer, it’s just a movie prop! It couldn’t possibly be as dangerous as it looks.

Of course, the devil is in the details. How do you tune this beast? What about eddy currents in the housing? What do you use for an earth ground? Why is it so LOUD? How do you not die while operating it?

I’m afraid that this post has already gone on far too long. I’ll explain a bit about those topics in future posts. Until then, stay safe and make AWESOME.

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155 thoughts on “The Tesla Gun

    1. My fiancée made it for me. Along with the gun, it was supposed to be my halloween costume last year. The coat was ready. The gun… took a little more effort. ~_^

      1. she really out to market this design…it is beautiful.

        been in the manufacturing industry for 30 years, wearing those uglies…i would pay to have one that nice…she is very talented :)

    1. A bit of both. When no earth is nearby, it makes a very even fringe of tiny sparks around the toroid, plus a very pretty corona field that is damn near impossible to photograph. This sort of shows it: http://www.flickr.com/photos/hackerfriendly/7005406212/

      If I add a spike to the top of the toroid, it pretty much goes straight forward. It’s a lot of fun to interact with grounded metal objects; the corona changes shape like a fluid. I’ll try to capture some on video, but I’m not too hopeful as it’s very dim.

      1. Would you even half-consider firing the thing off while holding it? The vid/pics I’ve seen are fired while on a bench (as I’d think, I’d be scared witless of trying to use it just holding it).

    1. Depends on the environment. Anywhere from 8″ to 24″ depending on what you’re shooting at. I’ll try to get some shots with better lighting for scale.

  1. That is the most awesome thing I’ve seen today. You remind me of the Mad Scientist from our iPhone game, Plan X: Global Domination.

    How much to build one for us?

    Any chance that you could make a Liquid Nitrogen powered Freeze Ray next? Perhaps a heat ray?

    Keep up the awesome work!!!

    1. Well, if you hit somebody over the head with it I’m sure it would hurt.

      You’re a lot more likely to hurt yourself if you’re foolish enough to fire the thing.

      This is sculpture. Art inspired by art. Not a weapon, any more than any object is a weapon if wielded with intent to harm.

  2. If you plan to make a mark II, what are your thoughts about carving the stock out of wood rather than aluminum?

    Not being a man of science I don’t know if there is a requirement for aluminum, however it might add a bit of weight, that you could offset perhaps with a brace or shoulder strap.

    It is very awesome just was trying to think of ways to pretty it up a little.

    1. Thinking about the next rev, any number of materials could work as a housing if a good faraday cage is made inside of it. The aluminum is actually a safety feature for the user. It is earth grounded, and any errant strikes from dangerous components (eg. the cap bank) are far more likely to find ground through the housing.

      Consider this the first working prototype. The three major features of the next rev will be:

      1. Solid state modulation (so it can make PEW PEW PEW noises with lightning)
      2. Moar power!
      3. Prettier housing

      The major feature of this proto being: IT FINALLY SHIPPED. ~_^

  3. Sorry my opinion, do not wanna die because of it, but geito that the world is today, do not need guns, something that we need these people aware of the respect and peace. I am Brazilian and I am tired of seeing violence on television news and bad things. You are very smart, use your intelligence to do good things for humanity :/

    1. Agreed, Mauricio. I think you misunderstand my intent.

      This is a toy, not a weapon. It is extremely impractical to use it to hurt people. A baseball bat is more dangerous than this device.

  4. I really like your work. some time back i built a stempunk raygun with a horizontal Jacobs ladder in it.

    I have fired you a FB friends request under my evilgenius name Boris van Galvin just so you know who it is.

    we may have to induct you in to the evilgenius group :)

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  7. Rob! You are an amazing person. I have to admit to kind of half-assing the engineering on the guns, (like you noticed, I left out the primary windings) The circular thing coming out of the box housing in the comic version is supposed to be a rotary spark-gap, but I just kind of black-boxed the rest of it.

    It’s hard to see because I didn’t know what I was doing at the time and the book came out darker than I meant, but there’s wiring coming down from the handles, that was supposed to go to the control box on Tesla’s chest and to a battery/power supply backpack that was never shown. So, if you end up making a v2, moving things to a backpack would be well within comic accuracy and maybe save you some hassle cramming everything into one unit. I’d be happy to send you some design drawings for the backpack if you’d like. (or not, as this turned out awesome. :D ) Just shoot me an email.

    Thanks for making this thing real, sir! Fantastic to see it in real life.

    regards,

    steven

    1. Ah, that makes more sense. I thought it was an extension cord, so I had always pictured him plugging it in somewhere (like in the elevator??!? Must have been through a light socket Edison adapter, oh the IRONY…)

      I’d love to see some sketches of the original backpack design. This is my first prototype; this thread is far from over. ;)

      Glad you like it! Thanks for making the inspired awesomeness in the first place.

      1. The backpack, although it sounds cool (and I admit, looks cool as well – I subscribe to Heavy Metal magazine)…would be a very bad idea. Safetywise. Discharging about 500kV through the umbilicus into your spinal cord could be a mind blowing experience.

        For coolness factor, you can probably do away with the torus. It is just a capacitor, and you can get the same value by running a rod down the center of the coil interior. The PVC could be capped with an evil looking discharge ball. This is a slow wave harmonic oscillator, and it uses distributed capacitance and inductance to transform the primary pulse. A bitch to model. Fun to bench.

        Replace the center capacitor rod with a tube and mount a 5W UV laser inside that. Pulsed in time with the primary. The discharge will follow the ionized air instead of arcing all over the place. Closet thing to a cheap beamed power weapon I can think of.

        Kudos for the make! And the cool outfit!

  8. Great work man! I really wanted to make something like this a couple of years back, but lacked the time/motivation (was right in the middle of engineering school) to go through with the build. I did however do a lot of brainstorming and research on transmitting the energy over a decent distance with minimal loss of effectiveness, as well as making targeting more… well… possible. I’m pretty certain the concepts would be valid for your gun. If you’re interested I could send you an e-mail with the details. Again, awesome work!

  9. You simply must come to Steamcon this year with this. check it out if you don’t already know about it Steamcon.org. This year its close to Holloween so your “Costume” would be approiate.

  10. Rob, Nice Job! Now, how about adding a tube using compressed air and iron filings to direct the sparks to ground? The air-driven stream should give you control over where the spark hits as it rides along this conductive channel. An option would be using Argon as a shielding gas to propel the iron filings.

  11. Awesome toy….where’s the ray gun!!??…..that things looks like a real life wonder waffle!! Very cool…is this yur job?making grown up toys? If so,I should beat up my h.s. guidance councler! I’ve been jipped!

  12. Word of warning. If you’re running this critter at 20,000 volts, then when the sparks hit anything, they’re going to be giving off 20,000 eV x-rays. You might want to get a radiation meter and check out what kind of dose you’re getting. But it does look awfully cool!

    1. Nice catch, Duane. The Geiger tube and meter could be cool additions to the look of the gun. The x-rays are a possible problem, but the tubes running at 20kV are finicky, and need a close to vacuum condition to produce much. If they run for a long time, they need to be tweaked since the heat from the electron beam changes the internal pressure. Original Roentgen tubes had an extra glass bulb added that had something to do with pressure balance. The kicker here is, this coil is NOT running at 20kV. It’s running at more like 200kV. A rule of thumb is 10kV every .25 inches of air gap. The corona alone is zapping out nearly 40 to 80 under no-load conditions – but that is distributed around the circumference. The flyback transformer which runs at 20kV is only powering the discharge gap and the capacitor bank. That stored energy powers the primary coil (the black torus), which in turn provides the big charge of magnetic field that powers the secondary winding.

      1. Thanks for posting the clarification so I didn’t have to, Dennis! :D

        I’m not sure who picked up the “20,000 Volts of Electricity” nonsense first, but it got parroted quite a bit.

        The PRIMARY runs at 20kV, people. The discharge is much, much higher than that. Probably around a couple of hundred kV, but I’ve had a tough time measuring exactly how high.

        I was worried about X-ray emission early on in my Tesla projects, but I’ve never been able to detect anything at all. To produce X-rays, you need accelerated electrons hitting a hard surface, preferably in a vacuum. The streamers you see are actually evidence of electrons dumping energy as they collide with air, making pretty ion trails (but not x-rays).

        There is quite a lot of UV, heat, and noise generated by the spark gap, but it is kept turbine cooled and slightly muffled inside the aluminum case. The flashing orange light in the video is the spark gap light leaking out through the mounting holes in the capacitor cover on top.

  13. Next step I would make a directed arcs! Air blow would work, also microwave radio concentrated energy, like mobile phone transmitter and directional antenna

  14. excellent. I’m a big fan of Tesla and what he did. One correction: the plastic pipe that you used looks like white PVC, and I’ll bet that it was “2″, not “2.5″. It measured 2.5″ OD, but it is called out (and purchased as) 2″, schedule 40 (wall thickness). I know, picky, picky, picky, but if someone is going to try to make this, the devil it in the details (I just read that somewhere). I’m also a big fan of Home Depot and do a lot of plumbing, as well as an electrical engineer.

    1. I used black ABS pipe. http://j.mp/JreFOW

      You are correct on the size: it is listed as 2″ (ID) but I care more about the size of the coil wrapped around it (2.5″ OD). I’m not a very good plumber. ;)

      The white you see is PTFE tape wrapped around the outside of the base of the secondary for extra insulation.

  15. Rob! Bloody hell! An actual working Tesla Rifle! I was completely chuffed by the video on How To Geek which led me here. Simple incredible! I also with the comments regarding a steampunk look for a future version. As for the video, the choice of lab coat and the music are nothing short of inspiring.

    I’d love to write this up in my blog using some of the pictures you have here, with complete credit and links for you, of course. Would this be alright with you?

    Poppy

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  17. Get to a pneumatic surplus place or order (skycraft in orlando/winter park good cheap helpful source) and a small 20lb bottle of argon or some other readily available noble gas.

    Rig a little trigger valve to jet a stream of gas out of the front of the thing, and you can have a directed stream of lightning instead of random even emissions from the head.

    Thumbs up.

  18. if you could hook up a streem of preasurised argon gas to jet out as it is fired, it should not only follow the path of the argon, increasing accuracy and posobly range, but instead os lightning, it would shoot a stream of plasma for even greater awesomeness.

  19. I have a full machine shop and I know people…lol. We could scan a housing and assign a thickness and machine it complete. Email me and we can talk. I can help you build a much “gun”.

  20. hey im an engineering student at my trade school and i have been working on a tesla concert with 4-5 tesla coils playing a song hopefully makeing something awsome. i love the gun you made, it reminds me of the coil gun we made in lab here. im new to tesla coils any good tips i should know before messing with them?

  21. What kind of Flyback transformer did you use on the hockey puck if doom. And can you put up blue prints and instructions on how to make the puck of doom?

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