DIY hacking has given us some great things -- a Raspberry Pi turned mini Super Nintendo, a Kinect sensor turned 3D archaeological scanner. But now, US basement hacker Rob Flickenger has given us something utterly awe-inspiring. A 20,000-volt Tesla coil lightning-blasting Nerf gun.
The finished article took Flickenger nine months to build and was made using cheap everyday objects like old cans, an old TV and a lithium-ion battery from a drill. The total cost came to around $800 (£500) and, after nine long months tinkering away at it, Flickenger debuted the lightening bolt gun at his wedding reception.
"When it's running, it makes the whole room smell like a thunderstorm," he told Popsci.com.
First up, Nerf guns, or "foam-based weaponry" as toy developers Hasbro refers to them, presented the perfect aspirational gun model for Flickenger. Inspired by The Five Fists of Science graphic novel, in which inventor Nikola Tesla fights crime with a few of his Tesla coils, part of the project's attraction for Flickenger was capturing this kitsch, fun, comic book-style design ethos.
An original Nerf gun would not make for a great current conductor though -- the plastic probably wouldn't last long -- so Flickenger developed a copy made out of aluminium. He gathered scrap metal, melted it down and poured it into a sand cast of the original motorised toy, made using a 3D powder printer. Once the moulded weapon was milled and finished, the hard part began.
After brushing up on his physics using online MIT courses, Flickenger, through trial and error, setup the interior circuits.
"I'd switch it on, and nothing would happen, so I'd switch it off. Then I'd switch it on again and set something on fire," he told Popsci.com. In the end he used the transformer from an old television -- the current from an 18-volt lithium-ion battery flows through a circuit series over and over again, doubling the power each time. It then flows into a Cornell Dubilier capacitor bank, which stores it until it reaches 20,000 volts -- at this point, the current can jump between two tungsten wires, creating a spark (this part is housed in porcelain and a computer fan is fixed nearby to make sure it doesn't get too hot). The current jumps from one wire to the next, then feeds through to one coil (insulated high-voltage wire), then the next (plumbing pipe wrapped in copper wire). This process induces a magnetic field, which in turn creates an electrical field at the gun's nose and finally, the bursts of electric blue lightening.
Though Flickenger explains the mod in detail at his "the best science is mad science" website, hackerfriendly.com, he's also careful to explain every safety procedure, from how he earth's it to the build itself. For instance, porcelain is used to house the switch, as he explains: "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."
Elsewhere, he tries a different tact to hit the point home that this cartoonish invention is ultimately a pretty dangerous bit of kit, saying, "bleeder resistors are important for preventing unexpected surprises. Like waking up dead after touching this crazy toy".
Flickenger concedes that he's not quite managed to mirror the fantastical Tesla coil handgun of the comic book.
"Notably, it is a bit longer and heavier than Tesla's own," he says. "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."
