I also consider pneumatics/hydraulics but they would be complicated and a little expensive. Electic actuators would be great but they're too pricey for the capcity needed.

I'm thinking of adapting the guts of one two electric scissor jacks as this seems to be the cheapest way to get a decent power screw with motor and trans. to twist. They're cheap and if they can lift a ton or two they should be able to crush some cans.

Any suggestions?

The type 30 means that the diaphragm has 30 square inches of area, and with 30 PSI at the faucet, you'll generate 900 pounds of crush.

You can make a neato electric control valve by stripping the water solenoids out of an automatic washing machine. You will need two snap switches (like for a wall box to turn on your dining room light) Put one solenoid valve in the supply line to fill the brake chamber, and tee the other one to drain water out of the chamber.

If you're crazy enough to tackle this thing, I'm enough of an enabler to give you a specific plumbing and electrical schematic diagram. Just email me with the request.