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Potato Bazookas
Zog The Undeniable writes "The latest craze in Germany is "Kartoffelkanone" or potato bazookas. These use hairspray ignited by a spark to fire potatoes at colossal speeds. The authorities are not amused." Everyone needs a hobby I guess.
My friends and I built a potato canon and regularly fired it over the skies over Tucson. It was fun to a potato hang in the air for up to 10 seconds at a time, and a bit of basic math estimated it to travel over 1/3 a mile. Beware though that the potato emerges at about 100 miles per hour (but slows down alomost immediately due to air resistance).
We stopped fiting it after we stuck a 1/4 inch thick board of plywood about 3 feet in front of the canon and fired away.
Damned if that potato didn't punch a perfect 4 inch hole through that board. As the potato emerged on the far side though, it almost completely stripped off the last ply layer from the board.
We gained a new respect for tuber-based weaponry that day....
Dr Fish
We have done this for physics often... no explosives or flammables involved. (I know... where's the fun then :} )
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All you need is a length of pipe that just barely fits a pingpong (table tennis whatever) ball through it. Fit a connector into one end of it that can hook to a vacuum pump.
Ok.. now here is the operation.
*WARNING do not have anything in line with EITHER end of this device!!! It is VERY unlikely but either end can give way and it fire either direction!*
Place the pingpong ball in the pipe. Place a single piece of plastic packing tape over each end. (Clear or brown... not filament!)
Use your pump and lower the pressure as far as you can. (You will have to expirement to make sure you can get it that low without imploding the tape on the ends)
When ready to fire.. put end with fitting slightly lower. Wait for pingpong ball to settle at that end of the tube. Aim. Using something sharp or pointed pierce the tape on that end of the pipe.
Bye-bye pingpong ball
Basically the inrush of air propels the ball through the tube and straight through the tape on the other end. We have clocked these pingpong balls in excess of 150mph
Please only do this under carefully controlled circumstances... It makes a great science expirement and is relatively safe. But as always be careful, wear protection and DON'T BE STUPID.
BTW You can pick up used vacuum pumps for cheap on Ebay... cheaper than 20 or 30 cans of hairspray so...
Telcos have alot of dark fibre in the States. Most people assume that's optical fibre...but it's actually moral fibre.
Another option is harnessing years of aerodynamics research and firing golf balls.
For added fun, take your cannon to the course!
-S