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Mythbusters and Their Cannons

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: miskaman » Tue Oct 09, 2007 4:18 pm

Redcoat wrote:I agree with wiliamfeldmann, You should use juts one barrel with the nets and balls in it.
Did you notice how the net Jamie fire in the Episode went?
It wasn't all that far probably 50ft at max. Putting it all in the one barrel would work alot better.

Though if you gave each barrel it's own individual valve it might work better as well.Though you would still have to tackle the problem of synchronising them all at once, otherwise you'd run the risk of one valve opening before the others and releasing half of the air too soon.

Happy Spuddin'


But if I put it all in one barrel, would the tennis balls even spread out enough to catch something with a net? Or would centrifigal force do something to spread them out?
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Unread postAuthor: Redcoat » Tue Oct 09, 2007 4:48 pm

I thin at 50ft it would spread out enough to catch about 5 birds, though if you remember to the episode the initial noise of the launcher and the fact that it is a relatively low velocity projectile, the birds had time to escape.

How many did you want to catch? One would do me. If you put Four balls on each corner of the net I'd put my money on it spreading out.
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Unread postAuthor: miskaman » Tue Oct 09, 2007 5:17 pm

Redcoat wrote:I thin at 50ft it would spread out enough to catch about 5 birds, though if you remember to the episode the initial noise of the launcher and the fact that it is a relatively low velocity projectile, the birds had time to escape.

How many did you want to catch? One would do me. If you put Four balls on each corner of the net I'd put my money on it spreading out.


I'm actually thinking of doing clay pigeons or some other random objects thrown in the air. Maybe a football or something. Or birds.
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Unread postAuthor: DYI » Tue Oct 09, 2007 7:10 pm

If you could get the net going supersonic, it would hit them before the sound reached them. On the other hand, if it was going supersonic it would probably rip right through the target, or destroy the net.

I think that Redcoat is right. One barrel would probably work the best, and be the most simple.
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Unread postAuthor: Lentamentalisk » Tue Oct 09, 2007 7:35 pm

the drag of the net behind the balls will force it to collapse back in to its non-spread-out shape. this means that either you need to shoot them out at an angle, or there needs to be some continual force pushing them out... just shooting and hoping that they spread will result in a dead bird, hit by your tennis ball, but not netted...
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Unread postAuthor: ammosmoke » Tue Oct 09, 2007 9:15 pm

LOL :D Are those crazy pvc pieces pressure rated??? If they are, those are awesome!
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Unread postAuthor: Redcoat » Tue Oct 09, 2007 10:33 pm

@Lentamentalisk, I think you are right, but
Putting another ball in the middle of the net might help as well.

I'm not to good in the physics department, so me a break.

@Ammosmoke, which Pipes of PVC?
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Unread postAuthor: Tsukiten » Wed Oct 10, 2007 3:10 pm

You should see their chicken cannon o.0 Or their typhoon simulateo (cannon which shoots stuff at typhoon vilocities)
It can pierce through a palm tree with a piano snare :shock: :shock:
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Unread postAuthor: ALIHISGREAT » Wed Oct 10, 2007 3:19 pm

the chicken cannon was pretty cool
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Unread postAuthor: williamfeldmann » Wed Oct 10, 2007 3:29 pm

I tested a homemade jobber with golfballs and simple rope net last night out of my single barrel. The net does slow the system down significantly and as such also greatly limits the range. I tried a couple of shots at 150 psi and could only get a usuable range of around 75 to 100 feet.

Every shot, the golfballs spread out perfectly by around a third of the range (20 feet or so) and then at the very end, due to speed, they collapsed in on themselves and landed. I was able to hit a red dodgeball I set out on a post and it "caught" it, but with the speed of the net being so slow and the noise of the cannon at high pressures, I am thinking birds are going to be awful hard to catch.

I would post pics but they didn't turn out because the F#@*ing sun goes down too early. I will try and get some pics Friday or Saturday for posting.
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Unread postAuthor: Redcoat » Wed Oct 10, 2007 4:12 pm

WilliamFeldmann, Try putting a fifth golf ball in the dead centre of the net.
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Unread postAuthor: miskaman » Wed Oct 10, 2007 5:26 pm

williamfeldmann wrote:I tested a homemade jobber with golfballs and simple rope net last night out of my single barrel. The net does slow the system down significantly and as such also greatly limits the range. I tried a couple of shots at 150 psi and could only get a usuable range of around 75 to 100 feet.

Every shot, the golfballs spread out perfectly by around a third of the range (20 feet or so) and then at the very end, due to speed, they collapsed in on themselves and landed. I was able to hit a red dodgeball I set out on a post and it "caught" it, but with the speed of the net being so slow and the noise of the cannon at high pressures, I am thinking birds are going to be awful hard to catch.

I would post pics but they didn't turn out because the F#@*ing sun goes down too early. I will try and get some pics Friday or Saturday for posting.


Thanks to you and all who gave comments. But you especially because you tested. I think I might go start buying parts tonight.

Edit: Went to Menards, but didn't make a list and my dad said "make a list or your not buying anything". So I didn't buy anything.
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Unread postAuthor: Lentamentalisk » Fri Oct 12, 2007 11:11 pm

@william: did you just use a sabot to shoot the net and balls, or did you make separate barrels?
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Unread postAuthor: williamfeldmann » Mon Oct 15, 2007 10:16 am

So I took apart the net I made and attached another golf ball in the middle of the net. Also tied in a lot more rope almost 40 foot of 3/16 nylon in the net now. There are a lot more cross ropes in the net than shown, squares around 1 inch square. Total size is about 16 inches square.
Image

I used a sabot to keep the net together until out of the gun. The true net performed only marginally better than the quick job I was able to do last week. I am able to hit and catch the dodge ball when flying away or towards me but the gun and net perform so slowly that a taget moving perpendicular to me is impossible, I can't even get close. The sabot is set up like this. Load the center ball first, then rope and a corner, rope and adjacent corner, rope and opposite corner, rope and last corner. The numbers correspond to pic above.
Image

The increased weight of the net forced me to move up to my tennis ball gun and I dropped some extra golfball barrel down the barrel and duct taped it in. The increased air capacity definitely increased speed. Still under 150 fps (rough guess, net is way to big for a chrono) Range is not too bad. The golf ball in the middle of net actually increased range about 100% when fired out of a bigger gun (100 cu in in sniper to ~550 cu in in tennis ball gun) and I can get around 150 feet if I shoot at an upward angle. However the net didn't close in on itself in 10 shots and I was finally able to hit the stationary dodgeball at around 80 feet (with maybe a 10-15 degree elevation for the lobbing effect).

Birds still horribly out of the question. Tanks or opposing players in scenario games however are excellent targets, though not with golfballs. That would hurt like sum bit@h, tennis balls would make an awesome large net, probably fired out of three inch sabots.

If I can convice the wife that a new digital camera is a must have (mine got soaked :( )I will try to get some pics up. Unfortunatly vet school is draining our finances quickly this time of year (her tuition just came due, boooooo).
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Unread postAuthor: ammosmoke » Tue Oct 16, 2007 10:11 pm

PVC Arsenal 17 wrote:Would this help?

http://www.flexpvc.com/cart/picserve.cg ... spigot.png


These pvc pieces. Maybe try using those dense foam golfballs?
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