Shrinking Quarters

Before I started hanging out with the folks at Hackerbot, they had built a coin shrinker and brought it down to Makerfaire, where they took some amazing high speed video (more details over at Intellectual Ventures Lab's website).

Apparently my dear friend, and high voltage mentor Rob had a great deal to do with it, but he's quite humble speaks only to the contributions of the rest of the Hackerbot folks who helped like Chris and Chicken and Dan many others... I'm not even sure who, It was all before my time.

When I started hanging out regularly at lab nights, I showed curiosity and aptitude and I became a competent operator of the coin shrinker. Sometimes I feel like someone must have made some terrible mistake to let me (of all people) play with such an incomprehensibly potent and dangerous device... then I feel every stranger when everyone in the room is asking me to explain how it works.

The coin shrinker is quite simple. Its a gigantic capacitor we charge up, then discharge into a coil: 12 windings of 12 gauge, with a coin in the middle. All the energy we just dumped into the coil creates a tremendously powerful magnetic field, which in turn causes another (opposing) magnetic field in the coin. The magnetic forces cause the material of the coin rush to the center of the field at something like 400 miles per hour, for 40 micro-seconds. Then the coil explodes/vaporizes inside the blast chamber.

Very simple. Could kill you to death if you touch it wrong when its charged. Good stuff. Crazy dangerous.

At some point the TV show Time Warp tried to take high speed video of quarter shrinking. They missed the shrinking event.

From the 100,000 fps video taken by Intellectual Ventures and Hackerbot at Makerfaire you can see at 1:03 the shrinking event occurs, and is done. Then the explosion happens:



In the Time Warp episode, the first frame they show (about 1:10) is explosion. They missed the event. They were shooting at 100,000 fps same as the original Makerfaire Hackerbot shoot were using.

This inspired us to shoot again, and try for a higher frame rate. Nathan showed up with a sweet light ring he'd built. High speed photography requires very very bright light. We got some amazing video that night at increasingly high frame rates. The prizes of the night were the euro and quarter at 180,000 frames per second.

These videos are really boring after the white flash in the 6th or 7th second. Its all about rewatching those first few seconds, and pausing judiciously.





We gave the shrunken euro to some hackers visiting from Europe. I still have that quarter.