Semi-automatic snowball cannon

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b-29er
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Semi-automatic snowball cannon

Post by b-29er » Thu Mar 18, 2010 1:21 am

I am looking at making a pneumatic snowball cannon that loads from a clip for rapid firing. My design would use a pair of paintball tanks for propulsion, and use a pneumatic piston to move a clip, thus, loading the next round. MY question is- What can I use for a quick trigger mechanism?
Last edited by b-29er on Thu Mar 18, 2010 1:38 am, edited 1 time in total.

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martianshark
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Re: Semi-automatic snowball cannon

Post by martianshark » Thu Mar 18, 2010 3:52 am

First of all, you have to make this out of metal - plastic will shatter under pressure when chilled. Second, nobody has ever made a multi-shot laucher, let alone a semi-automatic launcher. Sorry. :(

There's an FAQ question for this. You might also want to check out the rest of the WBL FAQ because it probably contains information that you need.

b-29er
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Re: Semi-automatic snowball cannon

Post by b-29er » Thu Mar 18, 2010 6:50 am

Just because it hasn't been done doesn't mean it is impossible!

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C-A_99
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Re: Semi-automatic snowball cannon

Post by C-A_99 » Thu Mar 18, 2010 4:04 pm

You will need some well packed snowballs so they don't break easily since any semi-automatic system will put stress on the rounds to load. The entire system will have to be mostly metal not just due to cold air but also because of the complexity of the parts needed.

That said, I also haven't a clue on how to go about this. Your trigger has to make a brief release of regulated air (put the air source to a regulator and then to a pressure chamber) and that air not only has to launch the snowball, but also drive the loading action. Not all snowballs can be made to the same size so you may need sabots. (you'd probably need them anyway because air could shatter them apart) Then to design sabots, you need tough materials that can withstand the stress of the loading system.

I'm not sure how you'd use a clip. You could use a magazine but that would be difficult, or you could use a hopper. With a clip, you need a way to detatch each shell/load from the clip to feed into the chamber.

This project makes an automatic water balloon launcher look easy. Good luck; you'll need it.

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cantab
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Re: Semi-automatic snowball cannon

Post by cantab » Thu Mar 18, 2010 5:04 pm

Not all plastics become brittle at low temperatures. But you definitely need to check.

Instead of using air pressure to drive the reloading, there's always hand cranked or motorised. How about a piece of PVC that fits snugly around the breech. You cut a hole in the top of the breech, and a matching hole in the sleeve - when the holes line up, a projectile drops into the breech. In another position, the breech is sealed, and the firing valve is opened (lugs, gears, electronics, whatever). By rotating the sleeve you can fire as fast as the feed system allows. A reciprocating action, instead of the full 360 rotation, would work also.
Challenge is probably sealing the gap well.
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C-A_99
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Re: Semi-automatic snowball cannon

Post by C-A_99 » Thu Mar 18, 2010 7:25 pm

The point of using pressure to drive the reloading is that it's more efficient; instead of having to worry about a motor and battery, you only have to manage the air pressure. Loading by hand (bolt action or breech loading regardless) is not semi-auto.

For the rotary breech Cantab mentioned, I highly doubt you can simply just drop the projectile in and close the breech without pushing the projectile forward. Air will be lost because it will go past the part of the projectile where the breech closes; an area that cannot be sealed well by the sabot.

A non-rotary breech will be needed; a bolt system. I'm not sure exactly how to drive a bolt with air since I haven't looked at paintball guns extensively enough, but for the bolt, you basically have one similar to a real gun; a piston that closes up against a barrel and pushes a round in as it closes. There needs to be O-rings to seal out the air that will blast it. The next issue is keeping the bolt locked while the projectile is blasted out; perhaps the bolt is supposed to be locked, then the air/pressurized source simultaneously feeds into another tube that drives the bolt by unlocking it first, then pushing it backwards to let another round load in. The bolt is spring loaded so it closes by itself. I'm not sure how the air pushing on the piston works, or if it works that way; I'm assuming the bolt is locked by rotation (like in bolt action rifles where the bolt must be rotated before pulling back) but that may not be the case for auto and semi auto systems.

It may also be possible to combine the systems; using the rotary breech Cantab mentioned and adding a piston to push the load forwards. The two systems should be synchronized, perhaps via gears, or it maybe possible to manage them seperately if whatever controls them can do so in a synchronized manner. The timing of the air blast to shoot the projectile must also match.

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martianshark
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Re: Semi-automatic snowball cannon

Post by martianshark » Thu Mar 18, 2010 7:44 pm

b-29er wrote:Just because it hasn't been done doesn't mean it is impossible!
True, but it would be very hard. Nobody as far as I know on water fight, nerf, or spudgun sites has made a semi-automatic cannon. This will require hard-to-find parts, and lots of prototypes, money, planning, testing, and more.

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zeda.beta
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Re: Semi-automatic snowball cannon

Post by zeda.beta » Thu Mar 18, 2010 9:46 pm

There was one semi-automatic nerf gun, which ended up being an underpowered water balloon launcher. Other than that I think you will have to design this entire thing by yourself.
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Specter
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Re: Semi-automatic snowball cannon

Post by Specter » Thu Mar 18, 2010 9:54 pm

C-A_99 wrote: I'm not sure exactly how to drive a bolt with air since I haven't looked at paintball guns extensively enough,
http://www.howstuffworks.com/paintball-3d-gun.htm
this is basically a diagram of a semi-auto mechanical marker. full auto markers operate slightly differently. I wish i could but I don't have the resources to take video of my full-auto Spyder Mr-1 marker to show how it operates

paintball markers are typically a "stacked tube" design, i don't recall the whole process the air goes thru to shoot the paintball. but when i go home this weekend i can take apart my marker to try an explain how it works... the air is what recocks the bolt when it shoots as well..
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C-A_99
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Re: Semi-automatic snowball cannon

Post by C-A_99 » Fri Mar 19, 2010 8:41 pm

If you have a digital camera you could take a video and upload it to youtube.

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Specter
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Re: Semi-automatic snowball cannon

Post by Specter » Fri Mar 19, 2010 10:19 pm

I do have a camera, however, I didn't bring it home this weekend. and no matter how i record it, i don't think you'd be able to see how the system in the marker actually works.
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SSCBen
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Re: Semi-automatic snowball cannon

Post by SSCBen » Mon Mar 22, 2010 10:15 pm

A number of people have made homemade semi-automatic pneumatic guns. I'd suggest scaling this up with metal parts and an air cylinder to actuate something: http://nerfhaven.com/forums/index.php?showtopic=12468

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