paintball grenade air mortar

[roxcreek]

I have heard a lot about home made "potato cannons" where someone sprays some butane propelled aerosol into a tube then stuffs a potato in and lights the fuel. I also saw a video of a couple guys in their backyard using a PVC barrel/valve/tank design that worked really well for firing wet towels accross a pool.

With the two cannons in mind I sat sown and drew up a first draft of an air powered towel or potato cannon that used a PVC ball valve and a fill nipple for an air pressurizer. After stopping by Lowes and realizing how difficult it was to quickly turn the big ball valves, I incorporated a large lever to the top of the valve. At this stage of the design, I had restricted all of my building materials to PVC pieces.

A few days later, I was showing the potential design to my friends when a friend of a friend walked up and showed some interest. Apparently, he had fired off some potato cannons before and expressed some possible design flaws. He suggested that I use metal or copper piping instead of PVC, because the seals would be tighter. I had been looking for a faster way to release the pressurized air too, and asked him about it. He said that there were quick release valves that, at the press of a button, would open quicly and easily.

My second draft took the basics of the first design and added the quick release, threaded metal piping, an ASA, regulator and a portable air source (paintball tank). I also re-thought it's purpose from a potato air cannon to a paintball grenade launcher. Basically a paintball mortar.

And so, I come to you guys to see what you think and discuss any improvements I could make.

I'll get some pictures of the design up soon

[TeamBob]

have seen alot of these, they are cool. not too hard to make. not to expensive either. What we use them for, is at scenario games, to shoot nerf rockets and paintball tanks. Nerf rockets stop tanks. But u can easily drop a handfull of paintballs down the tube instead of the nerf rocket. They shoot just as well. And instead of butane and all. Just make it run off CO2. And thats easy to come by when ur at a paintball field

[roxcreek]

has anyone in this forum ever made one of these and might be able tro lend me a hand with the dimensioning and parts?

[Papa Smoke]

I built my first Anti tank launcher using pressure rated PVC and a modified sprinkler valve. I found the site http://www.spudfiles.com/ to be of tremendous help for the beginner launcher builder. Tutorials, lots of information and knowledgeable people. Good luck with your project.

[om3n]

I built one that uses a co2 or HPA tank, and operates at a much higher pressure than PVC air guns. The valve I use is rated at 100 psi, but it fires at up to 230 psi. It cost about 50 bucks to build- this video is the older version of it, but if your interested in how I built this one I'll show you. It now uses a regulator that only allows the expansion chamber to fill to 200 psi, and also it is filled by remote line. I can just disconnect my remote from my mag and connect it to this gun, fill it up, and then reconnect my mag. I plan on getting some pvc that will work well for smoke grenades and foam rockets.

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Also, what I'm shooting in this video is a glass marble- obviously not for paintball. Once I find some smoke grenades or foam rockets or whatever I'm going to be shooting for paintball, I am going to obviously decrease the pressure to something more sane than what this is shooting at in this video.

[chafnerjr]

Holy Batman!

Well that would have a negative moral effect on the playing field now wouldn't it!

[Looper]

Go here http://www.automags.org/forums/showthread.php?t=241744
Buy the Launcher (really good price, normally twice that)
Done

And in the long rung you have a better product that probable cost less than if you try to clobber something together. You will also run into issues at paintball fields if you try to bring and use home made launchers. You will need them to go through "Tech Inspection" by the field owners and that can be a pain in the ***.

[om3n]

Go here http://www.automags.org/forums/showthread.php?t=241744
Buy the Launcher (really good price, normally twice that)
Done

And in the long rung you have a better product that probable cost less than if you try to clobber something together. You will also run into issues at paintball fields if you try to bring and use home made launchers. You will need them to go through "Tech Inspection" by the field owners and that can be a pain in the ***.

While that may be true, this will only cost around 50 or 60 dollars depending on how much of the hardware he already has, and it's fun to make your own I usually play with my friends on our own field, so I don't have to worry about an inspection, but I can understand how that could be a pain.

Ok this is how my launcher works:

I have a co2 tank attached to a regulator which is set to output 220 psi. On the other side of the regulator is a ball valve, which holds gas back from a 2.5 foot 1" diameter galvanized pipe, which is the main expansion chamber of the gun. Between the ball valve and the pipe I have a large air pressure gauge mounted. On the other side of the galvanized pipe is a modified sprinkler valve. I will post a link to a video on how to modify it- It's a Rainbird cp-100. They sell for about 15 dollars at Lowes. They are rated for around 100 psi, but they can shoot at up to 230 psi from my experimenting [note that after 230 psi the valve will not open, and you have to find some other way to release gas from the gun. I strongly recommend you do not even fill it to 230, and in fact I just want to say build this gun at your own risk- I am not responsible for any damage from building or firing this gun or one like it]

The valve is held closed by a rubber diaphragm, and when pressure is released from the diaphragm the valve opens- what I did was close all the holes in the valve and drilled and tapped a hole right below it and mounted a blow gun on the tapped hole, allowing me to pull the blowgun like a trigger to release pressure on the diaphragm to open the valve, dumping all the gas from the galvanized pipe very quickly, and in turn shooting the gun. Here are some pictures and a link on how to modify the sprinkler valve.










Video to modify sprinkler valve:

http://www.youtube.com/watch?v=A3EOdNP6Iag

[om3n]

Ok guys I'm going to further modify this rocket launcher to look like an actual rocket launcher. I'm going to remove the air tank, I bought some 2" pvc that i'm going to enclose the whole back half of the gun in, and then I'm going to spray paint it black. I'm going to buy a few of THESE rockets to shoot out of it, and then I'm going to get a pvc barrel that will shoot these well and also paint it black. I'm going to paint in white letters something awesome on the side of the launcher and it will be complete. I'll post pics as things go along

(sorry to jack the thread by the way)

[roxcreek]

I am not even considering buying an air cannon made by someone else, this is going to be a project that I will design from the ground up with assistance in fields that I don't yet understand. Plus, the purpose and projectiles that I'm going to be using are completely different than that of the other pre-made cannon.

Om3n, it's alright that you if you've got your own project on here too.... The same thing happened in my Devil Mag thread, and look how awesome P8nt's frame has come out.

I'll be starting on my mortar launcher soon because I think I've almost gotten my design final draft done. And just so I don't have to go register on spudgun files (which I will later) I wanted to ask those of you who have already made a spudgun with a sprinkler valve...
-What psi are you using?
-how do you mount your gauges?
-which brand of sprinkler valve do you buy and from where? (I'm pretty much looking for the cheapest one that will work and can be found at Home Depot or Lowe's)


These are some of the assumptions and conclusions I've come to and I would love if you could check them for correctness...
-the larger the dump chamber is... the less psi you have to use to achieve a similar launch with a smaller dump chamber
-the sprinkler valve does not need to be pressurized separately from the dump chambers, it does so while you are pressurizing the dump chambers
-the best barrel length is approximately 3 to 4 feet
-using packing increases the amount of force transferred to the projectile from the air pressure (if the projectile isn't already tight in the barrel already)

[om3n]

-What psi are you using? The valve is rated at 100 psi: it operates at 200 psi: it won't shoot past 230 psi, so you have to let the gas bleed out of the blow gun at 230+ psi

-how do you mount your gauges? Check the picture; I used a T fitting after the ball valve which fills the tank, and it works perfectly like that. I bought a 600 psi gauge not knowing what exaclty I would have to buy, so you could use a 300 psi gauge and be fine.

-which brand of sprinkler valve do you buy and from where? I bought a Rainbird CP-100. It is 15 dollars at lowes.


-the larger the dump chamber is... the less psi you have to use to achieve a similar launch with a smaller dump chamberNot necessarily. If you have a 3000000 cubic inch expansion chamber,, but only 2 psi, you probably won't shoot very far. I think a balance would be best, but I'm not totally sure on this. I was thinking about doing some math to figure out what would be best, but I haven't done it yet.

-the sprinkler valve does not need to be pressurized separately from the dump chambers, it does so while you are pressurizing the dump chambersNope. The pressure already in the expansion chamber forces the valve closed and it pressurizes the diaphragm.

-the best barrel length is approximately 3 to 4 feetthe BEST barrel lenght depends on the acceleration of your projectile and the volume/pressure of gas behind it. If you have a 2 in barrel but 40000 pounds of gas behind it going through a 1" diameter hole, not all of the gas is going to be used to push the projectile down the barrel. I haven't done the math yet but I will figure out the perfect length for the rockets I'm going to be shooting.

-using packing increases the amount of force transferred to the projectile from the air pressure (if the projectile isn't already tight in the barrel already)generally, yes. However, it is best if you don't have to use packing; try to get your projectile to fit perfectly in the barrel. This works the best.

Check the quoted portion for my answers to your questions


ALSO check here to see how to modify the sprinkler valve: this is exactly the one I'm using and this is how I did mine.

http://www.youtube.com/watch?v=A3EOdNP6Iag

[roxcreek]

yeah, I know how to modify the sprinkler valve, I just didn't know why the valve shuts, I had assumed that the air pressure would just push the piston out of it's way...

now, when you said that if I had a large area that was two psi greater than the area outside, there would still be a burst of air when the air inside equalizes with the air outside. The air will always seek to create an equilibrium, no matter how small the difference. Look at the weather for example, wind is caused by the air moving from an area of HP to an area of LP. The main cause of pressure change in that situation is by temperature and I can only assume that the temperature cannot increase the air pressure but so quick, but since there is a lot of air being moved, the change is more drastic. I wouldn't want to even imagine if two air systems had a sudden difference of 80psi!

[om3n]

yeah, I know how to modify the sprinkler valve, I just didn't know why the valve shuts, I had assumed that the air pressure would just push the piston out of it's way...

now, when you said that if I had a large area that was two psi greater than the area outside, there would still be a burst of air when the air inside equalizes with the air outside. The air will always seek to create an equilibrium, no matter how small the difference. Look at the weather for example, wind is caused by the air moving from an area of HP to an area of LP. The main cause of pressure change in that situation is by temperature and I can only assume that the temperature cannot increase the air pressure but so quick, but since there is a lot of air being moved, the change is more drastic. I wouldn't want to even imagine if two air systems had a sudden difference of 80psi!

sure, but it would be a slow steady stream of gas, and not a fast hard stream. A high concentration of gas in a small area should fire a projectile alot better than a low concentration of gas in a large volume.

[roxcreek]

Does anyone know how to create a model for a situation like this... I would love to find out how the graph looks when showing the relationship between pressure & volume and how different combination of the two factors modify the velocity of the projectile.

Another interesting graph for spudfiles might be the relationship between velocity and barrel length on several different projectiles...