Slashdot Mirror
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.
We made one in our Physics class in high school. I'm due to go to my 10 year high school reunion in a little more than a year.
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
The most "impressive" one was a 6ft long black barreled cannon known as "black beauty". It had an ignition switch from a grill, eliminating more clumsy homemade solutions for ignition and could put a potato through a wooden fence from about 20 yards. It could fire them @150 yards on a good day. It was tremendously dangerous, with a 3 foot flame shooting out of the barrel each time you fired it. The heat and pressure on the piping caused it to crack and need replacement, a function often ignored by my more idiotic friends. Here in texas some younger kids at my church got caught firing one in a golf course not too long ago and recieved some fines from the local police. These things are not safe...
My last memory of that cannon involved modification to shoot sprays of water. Ignition, upon filling the barrel with water after placing a "separator" in the piping caused a huge spray of water and steam to eject in every direction. Took the bark right off of trees...
STUPID
Slashdot needs to interview Natalie Portman.
We have done this for physics often... no explosives or flammables involved. (I know... where's the fun then :} )
:}
:}
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
Building the things was pretty simple -- all you need is a strong tube, a projectile, propellant, and an ignition system. As others in this thread have mentioned, my friends' ignition of choice was the ignitor from old BBG grills. This worked fairly well -- you actually get a trigger to work with -- but they always seemed to break down after a while, so the design had to be built such that you could swap out the ignitition every now and then.
That is how Jeff burned his damn face off :-)
See, like I say, everyone would just sit around in their dorm, building these guns and preparing their next shots. Jeff was about to shoot his when, wouldn't you know it, the ignition jammed. Bummer. So as usual, he unscrewed the back to get at the ignition to check on it. Unwisely, this involved taking a look into the ignition chamber to see -- well, the back end of a potato & some invisible ether.
Did I mention that? I guess not -- their propellant of choice was ether. I have no idea where they got the stuff, but damn it was good for making a nice little controlled explosion. Or in this case, uncontrolled explosion.
So anyway, there Jeff was staring into the back end of the gun, when somehow he bumped the trigger.
And it went off.
And the ether exploded.
Remember how when you were a little kid, and you liked playing with the garden hose in the summer, but your evil older brother (that would be me :-) would hide around the corner pinching off the flow, and you'd get confused and look into the hose trying to find the water -- and just at that very moment that bastard of an older brother would uncrimp the hose and blast you in the face?
This was a lot like that, but with fire instead of water.
So anyway, there Jeff sits, with a ball of fire around his head, and well you get the idea. I wasn't actually there when this happened -- I was back at my dorm, probably cowering under the bed from my psycho buddies (or reading email more likely...). But Jeff was my roommate and, about five minutes after the incident, Jeff comes staggering back to the room. He has no eyebrows -- just white molten lumps where they used to be. He has no eyelashes. Or rather, he does have some remnants of eyelashes, but they are half an inch long each and there is is a six inch line across the front of his hairless brow. And exactly in the middle of his (now apparently sunburned) forehead is a bright red circle -- as if someone had thrown a tennis ball, dripping with paint, really hard at the middle of his forehead.
Jeff took a little nap at that point. He woke up a day or two later, ordered some pizza, ate, and went back to sleep. He slept for most of the next several days, it took a couple of weeks for the tennis ball spot to fade away, and it took a month or more for the hair to grow back. He wore a hat a lot those days, IIRC :-)
So, let this be a lesson to you spud projectionists -- the back end of the gun is just as dangerous as the front!
DO NOT LEAVE IT IS NOT REAL