Jem Stansfield from BBC's Bang Goes the Theory has "put scientific theory to the test" with his Vortex Cannon. Filmed at 1300-fps, you can see the cannon knock down three different houses made of straw, stick, and brick with an explosive vortex ring.
The vortex ring that comes out is not smoke, however. After detonating the explosive gas mixture of acetylene and oxygen, "one of the most dangerous gas mixes in the world," the ring forms from the pressure drop inside the vortex. It condenses the lake's damp air and shoots a cloud out at 200-mph, knocking down anything in its path.
Stansfield's cannon is probably too big for the average do-it-yourselfer, but Edwin Wise from Make Magazine has a few garage-friendly vortex cannons - the Tub Thumper, Barking Tube, and Big Bad Boom Cannon.
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