sending a potato into the house at super-spud speed
So be for a look out for super-villans with potato guns.

If you froze it, you would have to keep it 99% frozen...so just bring a cooler with a bunch of ice and all your projectiles.

As an added bonus (or negative, depending on what you want), a frozen watermelon probably won't bust open when you hit your target. Instead of a huge watermelon explosion when it hits the brick wall, you end up with a big hole in the wall...

Ice expands when frozen, so a perfect fit when frozen may be too small when thawed.

i'm an engineer, but unfortunately i'm doing the whole compsci/econ thing. i'd love to help though, a watermelon gun sounds awesome ;)

Doctechnical - But of course! You could make a wooden seal perfectly fitting the barrel!

Thanks Vrax, that was great.

Alright, where do all the people working on this live. We need a watermelon gun design/construction/testing fark party some weekend in the summer.

Doing a bit of reading, some guys managed to fashion a potential watermelon barrel using a 12 inch PVC sail pipe... I figure though that if one were to make one out of metal you would have to worry far less about potential explosions (of course portability would be affected if that were the case, as well as aiming)

Exactly OBB, give it a wadding of sorts to seal it at the bottom. Fark that pieces integrity, I see what you mean about the slice not working, if its only the slice. I meant slice, pack it down, watermelon/cantelope. It would be like the wadding in a shotgun, goes out behind the projectile without nearly the same force. This is how you can fire paintballs from an Air-Cannon.

OBB: But of course! You could make a wooden seal perfectly fitting the barrel!

And after firing you'd have some material left over for a nice pair of shoes. It's always good to recycle.

You could use liquid hydrogen as the fuel. Now THAT would be awesome. PVC would wilt in the heat of such and explosion. We need good ole 4140 or A2 steel.

heheh. Freedom gun.

My main objection to the slice idea is aesthetic. Which would look more frightening, a 20 pound whole watermelon flying at you, or a 5 pound slice that's ready to be eaten?

please let my lack of html skills work

[url]http://www.corin.com/bill/paintball/aircannon/[url]

What about one of those spiny orange melons?

Fark, oh well lack of skills it is. Url goes to air cannon how-to

Slice is not whats being fired, you still have the whole thing. The slice is just to create the seal.

i knocked a sizeable (about 1' diameter) hole in my neighbors fence with my spud gun (using just hairspray).

when i loaded it with starting fluid and did a nice parabolic shot, i lost sight of it LONG before it touched down...

heheh...i should go build myself another one...

WittyLogonName: type this next time:

<a href="http://www.corin.com/bill/paintball/aircannon/">Insert Witty Link Comment Here</a>

/reading "HTML for Dummies"

WittyLogonName:

Yeah, nothing like creating anti-aircraft artillery in your spare time. 700 METERS per second and 10km range!! hahaha I love that one.

I have a old spud gun lying around here somewhere. It will throw a potato about 150 yards, uses starter fluid for propulsion. However, I wanted to post regarding a story I heard from New Hampshire. Apparently, a hunter up there shot a deer with a spud gun loaded with a quince (a really hard, small, apple like fruit). Quince blew right through the deer, killed it. He got arrested. He had a hunting licence, but did not own a firearms licence, nor did he own any conventional guns. Went to court over it, and won his case, so in NH at least, spud guns are perfectly legal. Just don't do anything stupid with them to ruin it for the rest of us.

Thanks Micah476

I was in a hurry and have no real html skills.
Please don't stone me!!

Hmm...maybe pineapple instead. Much more structurally solid than the watermelon, great aerodynamic shape (if leaves are removed)...

I used to have a spud gun in my college days...but we used to fill them with tennis balls soaked in WD40. The ignition lit a fiery sphere skyward and would constantly freak out our RA's. Good times...

What if you made a teflon coated barrel that was tapered a bit so the frozen watermellon snugged its self down in there to create the airtight seal?


On a second note if this thing can launch a spud that far that fast, what could it do with a carrot? or even better a lot of carrots?

WittyLogonName: Stoning is such a primitive act for someone amidst so much how-to knowledge on spud guns.

The sharpened barrel thing works really well, even for potatoes. That way you could get a potato that was too big and get an airtight seal. Plus you then had the juicy insides contacting the barrel, rather than the dry outside, and it had a lot less friction.

Micah476 - Thank you for your compassion

Sidi - your right...file down the edges of the pipe so they cut the spud into the barrel. Thats why we keep breaking them in half while shoving them, they have no cutting surface. Thanks

Stereosaurus:

As with many things, that is a great idea, but really expensive to manufacture.

You'd need to EDM or ream a taper in the barrel. That would be really expensive! Like 5 figures expensive! The only other alternative is to cast a barrel with a taper already inside of it, but cast parts tend to have voids and fissures inside of the lattice structure, and ulitimately fail when pressurized.

Don't file the edge too far away from the inside of the barrel though. It's better to file it down mostly from the outside. If it cuts a piece of potato that's too big, it's nearly impossible to shove it down the barrel because it's so compressed.

o.o

Good point, I was already formulating to file the inside, you may have saved our cannon.

There's some sort of perfect medium though. Some compression leads to a better seal and allows for more pressure to build up before it starts moving (good for propellants with low expansion rates). Too much and you end up slamming your loading rod into the ground as hard as you can to move the projectile.

Save yourselves the trouble of slicing anything... if you really want a clean seal, separate the firing chamber form the barrel entirely. The last spud gun I made used compressed air (1000 cc's in radially arrayed 100 cc pressure vessels) to fill a chamber in the center of the gun. The end of that chamber was a sliding wall that was free to run down the entire length of the barrel, pushing the spud as it went. Worked out pretty well, but we just about killed ourselves the first time we fired it, since we forgot to put in a vent valve and blew off one of our feeder lines trying to reload. After that, we waited for it to bleed off on its own.

Well naturally that was just a perfect case idea. For some reason I doubt any of us actually have the means to make a teflon coated tapered barrel. What about just a tapered barrel, Im sure not fusing teflon onto metal at a molecular level would cut costs.
And could you configure a spud gun to launch carrots? that would be like an arrow right?

Is there a preferred length for the spud gun?

I have a few lengths of 2" id, 1/4" wall thickness Aluminum tubing, in 30 inch lengths.

cartridge

for anyone still here who cares

This is downright funny. I guess they're bored in Iowa.

One word: PROPANE

Yes, I have a spud cannon and I use propane for that puppy to launch potato chunks into orbit. (Or damn near close to it).

We used hair-spray for the fuel source in my first cannon, and while it worked well, I found that the hair-spray leaves this nasty, gummy residue all over the place. Eventually, the igintion system got gummed out and wouldn't work properly.

The second cannon uses clean-burning propane. It takes about 1 second's worth to launch a potato about 300 yards. (This is only using PVC pipe too!)

I don't recommend compressed air for a PVC spud cannon, it'll shatter and leave pieces of PVC stuck into you. Not pretty. (Friend tried that once).

If anyone needs any potato cannon tricks, I can be e-mailed at t­w­i­ztid_vim­ap­son­ho­t­m­ai­lcom (Ya know the trick). I've built a dozen of the things for friends and haven't had one bad one yet.

Wanna know the best part? I'm from Prince Edward Island - Potato Capital of Canada.

/Bud the spud from the bright red might

Hornwrecker, the longer the barrel, the better distance and accuracy you're going to get.

These aren't going to be 100% accurate, the barrels aren't bored out like a gun. But, you want a barrel about 4-6 feet in length, plus a chamber for the fuel that runs about a foot long.

Overall, you want your spud cannon to be somewhere between 5-7 feet.

Airguns are commonplace. I've been to many sporting events where they shoot foil wrapped hot dogs at people in an arena. I've slo seen the same concept used for shooting compressed t-shirts.

I'd LOVE to see a watermelon cannon though!

/Paintball playa

Hmmm, if your carefully regulate teh pressure of the air in the chamber, its not going to explode. Plus you have to know how many psi the pipe can take. Yes, overfill is very dangerous, but can be avoided by not being an asshat. I dont understand why an explosion can not rupture the PVC too, If you ask me its all dangerous, but hell if it isnt fun.

It's much easier to regulate air pressure to stay within safety tolerances too. But the firing/reload mechanisms are significantly more complicated with air powered.

WLN - PVC piping has to be able to handle (at least someone) sewer gas, and possible explosions caused by it.

PVC weakens over time. It can easily blow up with propane and hair-spray as a fuel source too.

100 PSI of air is hardly worth building a spud cannon for. It's usless. A GOOD cannon will need about 200-300 PSI of compressed air per shot. PVC pipe won't hold up to that kind of pressue. It may work once or twice, but it'll eventually give out.

The risks of these things are very minimal if you don't be a total asshat about it. But if you fark up, the injuries can be maximum.

Either there are a lot of other somewhat bored Iowans (with noteworthy knowledge of physics) here armed to the teeth with potential projectile pototoes or the governor of Idaho is the new ruler of North America.

/takes another hit of burning corn silk

100 psi not enough my ass
GCD - there was a link much earlier in this thread. In it were videos of a guy shooting a cannon (not sure if it was air or gas) before he shot the thing he would tell the cameraman how much pressure he was using. He notably said 100psi and 97psi in two different vids. I have one that shoots at 100psi...it is quite worth building.