SpudFiles

Yesterday, I posted a comment on a topic that alluded to using unregulated helium in a golfball gun, and it got me thinking:

How hard would it really be to use unregulated helium? All you would need is a CGA 580 - NPT adapter (found on any helium or nitrogen regulator), a high pressure ball valve (spring loaded of course), and some high pressure steel pipe for the chamber.

I fiddled around with it on GGDT today, and found that, with a 28ci chamber and a 24' long, 3/4" barrel, I could launch a 10 gram projectile at about Mach 2, or, more usefully, a 100 gram projectile (think sharpened steel dart), at around 1200fps. Projectiles much heavier than that could cause the barrel (type L copper) to rupture.

From what I can tell, the entire design could be built for a little over $300.

I also have a question: Would 1.5" SCH 80 seamless steel be OK for 2200 psi, or would I need SCH 160?

Please post any ideas or comments that you have in relation to this idea, and how it could be made cheaper or more effective. Please do not tell me to build a 2200 psi piston valve, because I can't.

I would go with sch 160 just to be on the safe side, but then again, I'm notsure wha the pressure rating for sch 80 steel is. If it's actuall high grade steel, then you should be fine with sch 80 or maybe even sch 40, but high grade steel pipe is expensive. You could also use a steel barrel if you want to fire heavier projectiles. If you can build it, I look forward to seeing it. Oh, btw, GGDT tends to be a little screwy at higher velocities, so your estimation my be a tad optimisitic.

Haha, that was a response to my post. I hope you don't get blown up because of it. Why would you want to go unregulated?

Have I ever told you about my DOBA (dead on balls accurate) super-duper pneumatic launcher or my 20x steel hybrid launcher?

DYI wrote:Yesterday, I posted a comment on a topic that alluded to using unregulated helium in a golfball gun, and it got me thinking:

How hard would it really be to use unregulated helium? All you would need is a CGA 580 - NPT adapter (found on any helium or nitrogen regulator), a high pressure ball valve (spring loaded of course), and some high pressure steel pipe for the chamber.

I fiddled around with it on GGDT today, and found that, with a 28ci chamber and a 24' long, 3/4" barrel, I could launch a 10 gram projectile at about Mach 2, or, more usefully, a 100 gram projectile (think sharpened steel dart), at around 1200fps. Projectiles much heavier than that could cause the barrel (type L copper) to rupture.

From what I can tell, the entire design could be built for a little over $300.

I also have a question: Would 1.5" SCH 80 seamless steel be OK for 2200 psi, or would I need SCH 160?

Please post any ideas or comments that you have in relation to this idea, and how it could be made cheaper or more effective. Please do not tell me to build a 2200 psi piston valve, because I can't.

Someone linked me to this thread, and I have no idea what to say. I get worried enough when I am using 100 PSI in my 1" diameter copper piston rifle.

For this to work safely, you would need it welded, end of story. Threaded fittings won't cut it safely. Sure, I could build a launcher that could theoretically handle 2200 PSI (I have one in my basement actually). But its threaded

Threads = bad

If threads=bad, why are there threaded steel fittings available rated for up to 6000 psi? There are threads on the gate valve on top of my nitrogen tank (2400 psi), and there are also threads on the high pressure side of my regulator, and the gauge for the high pressure side. The gate valve on the tank is just teflon taped and tightened into the fitting, and it holds 2400 psi continually with no problem, and no appreciable leakage, so I fail to see the problem.

Benstern, could you give me links to those, or at least explain them?

Will it really reach mach 2? What I'm getting at is will the helium be able to expand fast enough to reach like 460m/s? A golf ball will have alot of drag so it will be even harder.

But none the less it will be very cool. i hope you make it lol.

If you are concerned about the chamber, why not use a helium tank as the chamber, it may be a little expensive, but you will be able to have full confidence in it holding.

Well i think i said this b4 but if you surpass the speed of sound, im pre,tty sure it will make a sonicboom and you may have to wear protective earmuffs for that. Im sorry but i cant help you with steel since i have never worked with it but maybe you could use a burst disk rather than a ball valve, but idk if there is any material that could last 2200 psi. Make sure your ball valve is pressure rated though. That'll be one hell of an accident if something went wrong 8)

Good luck

Yeah, a burst disk would tremendously increase power, but then there is the problem of it rupturing before maximum pressure is reached.

For one thing, I would never hold this, especially with a

24' long, 3/4" barrel

.

And it also wouldn't shoot golf balls, which you would know if you had read my entire post. This whole thing is hypothetical at the moment, since it would require parts that I can't purchase locally.

The ball valve that I would be using is rated for 4500 psi, and would cost more than 1/3 of the projected budget for this project.

The speed of sound in helium is about 3 times the speed of sound in air, so I don't see it being too much of a problem at Mach2. The only potential problem that I can see so far is the air in front of the projectile being compressed, slowing it down. GGDT can't account for that kind of situation, which is one of the reasons that it is inaccurate for high velocities.

I have trouble enough sealing a triggered burst disk system at 350 psi, hence the delay in the burst disk gun project, so I wouldn't even attempt it at 2200 psi. That is an insanely high pressure, and ghetto sealing solutions just won't cut it.

Ahh ok i just wasnt sure if there would be a differnce in the sonicboom because you are using helium. I was just makin sure. And when you say

The speed of sound in helium is about 3 times the speed of sound in air

do you mean that 3 times the speed of sound in heluim is equal to the speed of sound in air? If i interpreted this, or you wrote it wrong (idk) it would mean that you need 3 times the speed of sound in air?

Ohhh nvm. Over analyzed
Dont wanna bother erasing (and i want the spudbux to get a quote )
(most of my spudbux are in the bank )

The ball valve that I would be using is rated for 4500 psi, and would cost more than 1/3 of the projected budget for this project.

Where are you getting that ball valve? I bought a ball valve rated to 7500 psi for 25 bucks from mcmaster. I'm kind of suprised a ball valve would cost a hundred bucks, but if your buying stuff locally I could see how.

And 1.5" sch 80 seamless steel pipe should be fine. With a safety factor of 4 it has a working pressure of 2700 psi, and a burst pressure of 10000 psi. Threaded or unthreaded shouldn't matter. The majority of high pressure setups (cannons, filling stations, stuff at factories) I've seen all use threaded parts, and they're perfectly safe. If you want that extra safety factor, get the parts welded. But if your not really good at welding or don't know anyone who is, then threads will be fine.

And you could seal the front of the barrel with tape and a union, and use a vacuum pump to remove as much air as you can. A decent vacuum pump will run you a hundred bucks though, and you'll probably hae to order it. But then you wouldn't have to worry about the ari infront of the projectile compressing...

Oh yeah, good luck

Here is something simple you should consider:

Put a union a few inches in front of your ball valve.

The small amount of dead space filling up will allow the valve to open farther before the burst disk breaks. This will increase the power you can get very noticeably.

You would really want a valve that can open completely before much gas reaches the projectile. With helium this is difficult since it travels so fast, so a burst disk is the best option.

You'll probably want to use a few layers of aluminum cans for a disk.

whats the benifit of helium over any other commpessed gas? is it the low density creating a faster flow or somthing else?

is it the low density creating a faster flow or somthing else?

A projectile can only travel as fast as the air that's pushing it, that's pretty much it.