Our Shrinking Economy

Posted by rob on 30 March 2009


Coin Shrinking from Jeremy Ruhland on Vimeo.

Turn half dollars into quarters! Turn quarters into dimes! Turn dimes into little semi-molten balls of metal! All this is possible with the proper application of insanely high electrical current at very high voltage.

"God made the quarters. It's up to us to make them shrink."  --anon.

The coins don't just shrink; they keep their identity and fine details. But do they keep their value?

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Hackerbot Labs is proud to contribute to America's economic downsizing.

How does it work?

A high voltage DC supply charges the big 300 µF capacitor to 10 kV, or about 15,000 J of stored energy.

The rig.

This energy is released as quickly as possible into a small copper coil wrapped around a coin.

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The fast changing current creates a very powerful magnetic field in the coil, which creates a very powerful magnetic field in the coin itself. The strong opposition between the two fields causes the material of the coin to contract, while at the same time the copper coil expands. A few dozens of microseconds later, the coil has violently exploded inside a specially built blast chamber. And the coin itself is much smaller!

spark gap trigger

Where does the coin go?

No material is lost from the original coin: the weight and volume are the same as the original. But the coin now has a smaller diameter and is thicker, while retaining much of its surface detail. It's also extremely hot just after firing!

Isn't this dangerous?

Oh yes. An average automated defibrillator (AED) provides a jolt of about 150 joules. The energy stored in the big cap is about 100 times that much.

shrapnel

There's also the tremendously loud noise, a very bright flash of UV when the spark gap switch closes,  the possibility of fire and toxic gas when stuff in the chamber burns or pyrolyzes, and bits of copper shrapnel moving with enough energy to blast clean through six-ply blocks of plywood. And somebody always burns themselves when they try to pick up the newly shrunken quarter.

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To contain and prevent much of that danger, we have designed a custom-built blast chamber out of very thick high density plastic. It contains the shrapnel and covers most of the electrodes, and provides a solid platform to hold the mechanical spark gap trigger. The trigger is engaged by yanking a very long rope: simple but effective.

ready to fire

Who invented this thing?

It wasn't us. We just built one. It's an actual industrial process called electromagnetic forming. See some of these links for more coin shrinking madness:

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