Microwatt wrote ...

There is not a single reason why you can't crush a can with only 100 or less joules of power. why not consider machining a single turn coil from copper or aluminum. a coil such as this could stand up to 100KJ and crush rolls of quarters at a time.

Patrick wrote ...

What if his copper cylinder billet is 3 inches tall, with the plan form he shows above? Would roll shrinking be possible, given a few megajoules?

Xray wrote ...


The real trick would be to mechanically hold the roll of quarters together so that they don't explosively fly out of the shrinker coil assembly before they had time to get shrunk.

Klugesmith wrote ...

Interesting thought, but there's nothing magic about 1 turn. Electromagnet coils can be rewound to trade off voltage for current, to match the power source. For example, suppose your coil were replaced with a 10-turn Bitter coil in the same volume:

With 10 times the voltage and 1/10 of the current, it would produce the same magnetic effects with the same input energy and power. Actually better, because the field distortion at the gazin and gazout connections is limited to the ends of the solenoid. The new V and I values would be more practical for making the pulse-discharge capacitor, switch, and connecting wires.

At lower energy levels, a 1-turn coil might be a good match in a can crusher using electrolytic capacitors (relatively low voltage and high capacitance). To get the most out of 1 turn, the interconnection loop between capacitors, switch, and coil should be geometrically compact and arranged to minimize its inductance.

As for being obviously strong enough to crush a roll of quarters without being damaged, I don't think so (whether 1 turn or 10). The radial pressure on work coil is no less than on the workpiece. Quarters are made with hard steel dies, and are work-hardened in the process.

>>a coil such as this could stand up to 100KJ and crush rolls of quarters at a time.
Show us the numbers. 100 kJ can [edit] heat about 270 grams of copper to its melting point.

[edit again] As xray said, coin shrinking doesn't reduce the volume of the workpiece. To reduce the diameter of a stacked roll of quarters, its length must increase by the square of the diameter ratio. You're putting huge demands on the strength of the coil material. And since the work is done in microseconds, I guess the inertial resistance will be significant even with strong materials. Hypothetically, if the electromagnetic forces were much stronger than the yield strength of coil and work bar, conservation of momentum and minimization of kinetic energy suggest a solution where thick coil expands radially at low velocity while work bar extrudes axially at high velocity.