Pneumatic tater gun

[AcemanPB]

I was planning on building a pneumatic potato gun as a summer project. I really don't know exactly how to do it though and figured atleast one person on these boards will know something....

I'll be running the gun off of my 68/4500 850psi crossfire nitrogen tank. I was thinking the gun would just be a very simple dump chamber design. But I have a few questions

Do I need to reg down the incoming 850psi?

If I don't reg down the 850psi about how large should my chamber be (I want this thing to kick butt)

What type of valve should I use inbetween the chamber and barrel? I was thinking some type of ball valve, where would I get one of these?

Here is a pic of the general Idea I was going for, nothing is proportional, it's just a concept to show what I'm thinking.

[Will Wood]

850 PSI.. that thing will be deadly.

Here's how we did it


-[1]====[2]===============[3]



1. Is fill nipple. We hook up our air compressor to this, and fill it up. There is a valve here, with a lever.

Between 1 and 2, is the air chamber.

2. Is the firing trigger. It is a simple twist lever that opens up the air chamber.

2 to 3 is the barrel. Shove a tato down with a hockey stick. BOOM. It goes far with 200 psi, I can't imagine what 850 is going to do.


.. Since your going to be using 850 I can't stress how much you should make sure you use steel pipes and seal them very well.

[Thordic]

You won't find a ball valve that will handle 850 PSI. They piss air at 600 PSI, even though the big ones are rated for it.

Your best bet is a larger dumb chamber at 300 - 400 PSI for a ball valve.


1- 2" Black Steel Cap ($2.25)
2- 2" x 6" Black Steel Nipple ($2.80)
3- 2" to 1.5" Reduction Coupling ($2.94)
4- 1.5" Close Nipple ($1.28)
5- 1.5" Brass Full Release Ball Valve ($35.00 on sale from $41.00)
6- 1.5" Male PVC Fitting (Less than $2)
7- 5' SCH 40 330PSI WP PVC (Less than $5)



This post for more info:

http://www.automags.org/forums/showthread.php?s=&threadid=22668&highlight=potato+gun

[AcemanPB]

Wow thanks! I did figure 850psi would be a little much, could I use just a normal pball regulator to reg down the pressure?

[Thordic]

Yep, I used an adjutable tank but a reg would work.

The steel pipe will hold like 5000 PSI so thats not a problem really. Just don't make anything that is gonna be holding pressure out of PVC, the strongest PVC only holds 300 PSI.

Use locite when you put the pipe together or it'll leak quite a bit.

[AcemanPB]

Would there be any problems with using PVC for the barrel? I can't see the barrel getting 300+psi in it..

[Thordic]

Nope, because the air will take the path of least resistance to relieve the pressure.

Pushing a slimy potato down the barrel is easier than breaching the wall of the barrel.

[magnj]

I am so doing this

[einhander619]

As a seasoned spudgunner, I can tell you that what you want to do is extremely dangerous, and will not work correctly. First of all, 850 is rediculous. Schedule 40 PVC pipe and fittings are only rated for around 280 psi at room temperature. When air at that pressure expands, it could chill the pvc to below zero, drastically increasing the chances of it fracturing. Second, there is no valve commercially available that would be able to utilize that much pressure. The potato would be out the barrel before it saw even half the force that much pressure has to offer, if indeed the spud cuold stand that kind of acceleration in the first place. Please don't do this!!!

[AcemanPB]

Yeah I was already planning on regging it down, whats a good psi to work with 200-300psi?

[PurePower]

100 Psi.

[magnj]

I heard 200-300 is good, And Im thinking tennis balls or something

[Thordic]

einhander, sorry to break it to you, but you are wrong.

If you use steel plumbing pipe, its good to 5000 psi. A stainless steel ball valve is rated at 400 psi to 600 psi depending on what size you get. The 1.5" ball valve in my gun is rated at 600 psi, although it leaks a little at around 550.

The potato makes it out of the gun just fine. the barrel on my spudgun is around 5 feet long, leaving plenty of room for gas expansion to propel the potato.

It's perfectly safe if you make the pressure-withstanding areas out of steel.

If you actually READ the post, you'd see that I told him not to use PVC for anything holding back pressure.

I've been messing with my potato gun for about a year now, and it has had NO problems, and it operates around 525 psi. Many members of AO saw my potato gun in action at NJ AO Day 1, and they can tell you it worked fine.

[BlackVCG]

Already been done...

http://www.automags.org/forums/showthread.php?s=&threadid=22668

[Thordic]

I already posted that link, Black