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50 Comments
- iMactel, on 10/12/2007, -1/+32I made one of these in my physics department in undergrad. I wasn't able to get this video to work, but I can explain how we did it. We had the tube with very tight fitting caps on the ends and the center of the caps cut out. We used them to hold mylar tight over the openings. We had a very low pressure, lab quality, vacuum hooked up to a coupling in the side and a ping pong ball in the tube. When you turn on the vacuum, the mylar sucks in to look like the bottom of a coke can. Stand back and poke a hole in the mylar of the end you want the ball to go away from. Air rushes in and shoots the ball out the other end. I've persnonally shot a ping pong ball cleanly through a large cardboard box. I also used it as a development platform for indoor testing of a sabot round designed to shoot a dart. It got 50 yards range before hitting the end of the hall and sticking in the concrete wall at the end. It was definitely NOT lame. I miss that part of undergrad.
- jgreath, on 10/12/2007, -1/+22Too bad it's not a cannon that shoots vacuums...
- NumberFour, on 10/12/2007, -2/+9Am I the only one who doesn't see it shoot? All I see is the guy move his hand, then nothing comes out. I hear a noise but thats it.
- adamlazz, on 10/12/2007, -3/+9I don't see how this is lame...
It is just a simple how to. "How to"s arent supposed to tell you how to do something extraordinary. They show you how to do something easy, with ordinary household items that prodouces a mediocre effect.
This is really no differient than other "How to" featured on digg.
I honestly don't know what you were expecting. This is not lame at all. - ssj6goku161, on 10/12/2007, -1/+7gimme an hour and I'm sure I can work something out ;)
- card2570, on 10/12/2007, -2/+7"It got 50 yards range before hitting the end of the hall and sticking in the concrete wall at the end. It was definitely NOT lame."
FWIW... From my perspective, that's the polar opposite of lame. That's freaking AWESOME.
Besides, harnessing the laws of physics to do really cool things always rocks, that should be like geek law or something. - MuffinMan, on 10/12/2007, -1/+6Just call (800)-MAC-GYVR
- Cerberus047, on 10/12/2007, -1/+6or it shoots super fast
- Tiabin, on 10/12/2007, -2/+7or they have an AMAZING sound effects editor. :-)
- dclowd9901, on 10/12/2007, -1/+6you have to do a frame by frame, but it does definitely shoot.
- redzombi2k, on 10/12/2007, -1/+5I couldn't see it do anything a first either, but after watching it several times you can see the ball shoot out of the opposite end into (or mabey all the way through) a cardboard box. It happens quick so dont blink or you will miss it. ;)
- kaytrem, on 10/12/2007, -0/+2Chuck Norris can do this with his nostrils
- itsmekirby, on 10/12/2007, -1/+3It's not comparable to a railgun. It's more comparable to a coil gun (aka gauss rifle I believe).
It seems the idea behind this is that the vacuum must be placed at the end of the tube. This way, the vacuum barely affects the ball as it leaves because once it's out of the tube the vacuum no longer pulls on it. This is similar to how a coil gun works (both end up pulling back on the projectile to some extent, but negligibly).
A railgun applies a continuous force by creating a magnetic field with two rails with opposite currents and flowing those currents through a projectile which connects them. The magnetic field is able to propel this projectile with no possibility of pulling back on it since the projectile has a current flowing through it.
But I guess you could compare the vacuum cannon and a railgun by virtue of the fact that they shoot things? - Toloran, on 10/12/2007, -1/+3The difference between this and a potato gun is that this is less likely to explode on you.
- n0ah, on 10/12/2007, -0/+2How about a Wooden Cannon that shoots Vacuums?
(I love that Myth Busters ep..) - MrManFitz, on 10/12/2007, -1/+3Dry ice bombs are way cooler.
- ssj6goku161, on 10/12/2007, -0/+2ever try a liquid nitrogen bomb? that's where its at man
- noahhoward, on 10/12/2007, -3/+5That sounds like something I need to arm my sailboat with. :D Diagrams?
- Otto, on 10/12/2007, -0/+2"How about just hooking up the vacuum's exhaust to one end of the tube?"
Because that doesn't work as well. Hey, why not hook a fan to a tube and blow air in? Same thing.
Sea level pressure is approximately 15 pounds per square inch. In order for your method to work, the vacuum would have to output 30 PSI and a surprisingly large amount of air (depends on the surface area of the tube's opening) just to get the same pressure difference. But if you suck the air out of the tube then suddenly let pressure in, you can get that 15 PSI for free. - kmarchiori, on 10/12/2007, -0/+2Not the same, I guess the concept is escaping you completely.
EDIT: Heh, beat me to the punch, Otto. - iMactel, on 10/12/2007, -0/+1Take a two liter bottle and tape it into a concrete block of some sort. Ours was the broken concrete from around a dug up firehydrant, though pouring your own would be better. Take the bottle/block combo to a shallow lake with a pier. Fill the bottle with liquid nitrogen, cap it, and toss it in the water at the end. The depth-charge effect is awesome. 20 ft of spray into the air and feeling the shockwave travel through the pier... very cool. The only thing my professor was upset with us about, after stealing the liquid nitrogen, was the fact that we didn't record the explosion on video.
- iMactel, on 10/12/2007, -0/+1It shouldn't really need a diagram, as the simplicity cannot be overstated. Long pipe/pvc... drill & tap for a nozzle on the side, preferably near the end you load the projectile. Find a snug fitting to cap the ends of the pipe but still leaving the hole open. Insert projectile that closely approximates the diameter of the pipe into the end but is still small enough to travel down the pipe easily. It should not make a seal in the pipe. Cut 2 pieces of mylar out of one of those ultra thin emergency blankets and use the fittings to cover the ends of the pipe with mylar, makeing an air tight fit. Hook a vacuum hose up to the nozzle; the higher powered the vacuum the better. Ours could get to a near complete vacuum. Turn on the vacuum pump and watch the mylar get sucked in and pulled tight. Affix a nail to the end of a long stick for safety purposes and, stading off to the side, use said stick to puncture the mylar closest to the projectile.
The dart sabot was made on a lathe out of a block of plastic I had laying around. Shave it down to the right diameter and then cut it in half lenght wise. Core out a tunnel in both halves for the dart. I used those really cheap plastic darts that used to come with a dart board. You could probably buy them in bulk. I also cored out a cone shaped hole in the end of the sabot around where the point of the dart would be. It needs to catch air for the plastic to split away from the dart in air, allowing the dart to fly forward on its own. In reality, all three projectiles fly down range.
Using a much more powerful potatoe gun fueled by an air compressor, I managed to launch darts all the way through high density foam archery targets. The plastic sabot shell was a pain because it would always get stuck halfway through the target and need to be dug out again for the 2nd shot. - wolver1ne, on 10/12/2007, -1/+2Or just take a bicycle pump, a thin pipe, some rubber and transform into an airgun. Shoots anything from clay to small metal balls... and hard.
- card2570, on 10/12/2007, -0/+1"Thank You, Chuck Norris."
"Thank *You*, Peter."
:-) - Djerrid, on 10/12/2007, -0/+1For real fun, fill it with shaving cream. The fast rate of expansion will have everything covered in foam.
- zerovertex, on 10/12/2007, -2/+3mmm...marshmallows...
- Kamino, on 10/12/2007, -1/+2This is so A-Team...
- Otto, on 10/12/2007, -1/+2Simple concept, I've seen it before. Works like this: Use a tube and a shot that almost fills the tube. Can't have too much air flowing around your projectile. Suck most of the air out of the tube. Open the end of the tube, the air rushes in, pushing your shot out the other end.
It's important to seal the tube *before* sucking the air out of it. You want your shot to be at the far end of the tube, not up close and blocking the vacuum. This gives it the most velocity from the air travelling down the tube.
If you put the vacuum pump at the very end of your tube, then you don't need a ball valve, as the reverse suction when the ball exits the tube is not enough to make a difference, but that means that the vacuum must be attached to the firing end, which is problematic. The more usual approach is to attach the vacuum in a more convienent location, and then use a ball valve to shut off the vacuum just before you fire the thing. Works just as well, really. Another approach is to put the vacuum at the end of the tube away from the shot, insert projectile, seal the end, and suck it back towards the vacuum. Then you can use a two way ball valve to both shut off the vacuum and let in air at the same time. This gives you a more gun like approach, with a single "trigger" and also putting the vacuum source at the end of the tube away from the firing end. - plnegative1, on 10/12/2007, -0/+1double lame
- hppyfngy, on 10/12/2007, -1/+2it shoots fast all right, but I wouldn't be the guy with my fingers over the other end...
- iknezek, on 10/12/2007, -1/+2You are almost correct, but the momentum isn't created by the vacuum.
What happens is that they stick a ball in and put caps on both ends of the tube, then turn the vacuum on, sucking most of the air out. This leaves the pressure inside the tube much less then outside. When the guy takes the cap off the end of the tube, the air pressure outside rushes in and shoots the ball forward.
So really, it's the atmosphere/air pressure that is the propellant.
You could actually stick the vacuum anywhere in the tube and have the same effect, but it might slow the ball down slightly as it travels away from it when you shoot it. - Gullop, on 10/12/2007, -0/+1Make a how to then.
- thewayne, on 10/12/2007, -1/+1Some kid did this as a science project on David Letterman a few months ago. It shoots hard enough to hurt you.
- enoughrope, on 10/12/2007, -0/+0I saw the "kid scientists" demonstrating this experiment on the Letterman's show.
- finalmillenium, on 10/12/2007, -1/+1$5 in parts at Lowe's or Home Depot and a cheap can of hairspray is all you need to make a descent potato cannon. I'm sure all of us can think of a better cannon design. And this was just what I was doing in the hall to my dorm room. I wonder what would have happened if I was allowed back in the labs.
- matthewaaron, on 10/12/2007, -0/+0Somebody needs to find a way to do this with a Dust Buster
- RowlandPhysics, on 10/12/2007, -0/+0Who would have imagined that something that "sucks" could be this cool!
- WhiskerTheMad, on 10/12/2007, -0/+0ARG! I meant to digg your last comment but hit the wrong button! Isn't there an "un-un-digg" feature anywhere around here!?
BTW That sound like it kicks total ass. I WANT ONE. - inactive, on 10/12/2007, -1/+1Thats what she said.
- Urusai, on 10/12/2007, -2/+1How about just hooking up the vacuum's exhaust to one end of the tube? It's not rocket science, people! I guess the obvious is just too easy for some people.
- mbthompson, on 10/12/2007, -3/+2"Dodge this!"
- Verisimilitude, on 10/12/2007, -2/+1Ok, looks like he uses a golf ball, cover both ends, open the long end, away from the vacuum source, it travels towards the source, picking up speed, enough to bypass the vacuum and blow out the other end. Poor footage, good concept. It's a vacuum rail gun, pretty simple.
- wolver1ne, on 10/12/2007, -2/+1Bah, it's not even mobile. Useless!
- Xinareiaz, on 10/12/2007, -2/+1That could be remidied easly
just hook it to a wagon :P - Uthman, on 10/12/2007, -4/+3if you're go through the trouble of making a homemade cannon then post it online, at least learn how to encode video. that clip looks like some uber LQ footage not uncommon some 13 years ago.
- ikickass, on 10/12/2007, -6/+2ya doesnt seem very effective
- Alphateam, on 10/12/2007, -7/+1So did I
- justice7, on 10/12/2007, -10/+3look at this
a story on digg on how to use your vacuum cleaner for more than sucking you off
(obviously none of you retreds ever used one for cleaning, short of cleaning your own hose out)
oh and..
yes guys this is a joke ;) - datastorageguy, on 10/12/2007, -10/+1reported as lame..
- plnegative1, on 10/12/2007, -23/+6lame
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