What it Shows
With an air pressure of 105 Nm-2 at sea level, even a heavy duty oil drum will be crushed if it has nothing inside to balance the pressure.
How it Works
The screw cap on the drum is fitted with a vacuum pump connector. Simply turn on the Varian SD-200 pump and wait—it usually takes a few minutes to pump down, so you can carry on with what you were doing interrupted by various creaks and bangs as the drum's side walls begin to give. Because drums of this size are ribbed for strength, they can hold up under the strain, but when it finally goes it collapses with a mighty implosion! 35 gallon drums are more robust, but a sharp thump with a mallet on the ribbing is enough to remove any last resistance and a loud instant implosion follows.
Setting it Up
Make sure to adequately tighten both screw caps. As a test, turn on the pump for about 5-10 seconds and then listen for leaks. Use a plug strip as an on/off switch for the pump. Provide ear protection and a rubber mallet.
We use refurbished 55 gallon drums, which have a closed top and a bung. The top and bottom of each drum has a radius of about 0.3m, and the side is about 1m tall. This means the atmosphere pushes down on the top of the drum with about 3.25 US tons, and pushes in on the sides with a total of about 20 US tons.
Can be done with any size drum you lay your hands on; obviously it is important to check the previous contents, to avoid toxic or corrosive residues. A smaller version can be done with a one gallon oil can and a Bunsen burner replacing the vacuum pump. Boil quarter of a can-full of water so that the steam replaces air in the can. After you're sure it's purged, take it off the heat and screw the cap on tightly. As the steam condenses, a vacuum is formed and the can will crumple. Here you haven't got the possible misconception of the can being 'sucked in' by the pump.