Air Cannon

[Dick Linn]

You can get a one inch solenoid-operated lawn sprinkler valve for under $15. They can be retrofit with a pneumatic release for manual operation or if you wanted to use a 12 volt valve from the KOP to operate the larger valve. I believe the standard lawn sprinkler valves are nominally 24 volt.

[Rob2713g]

Originally Posted by Otaku

Definately change the air tank to ABS.

What kind of ABS? The kind at our local Lowe's and Home Depot don't have pressure ratings? Is it just the generic one they have, or do we need a special type? Thanks!

[Otaku]

Originally Posted by Rob2713g

What kind of ABS? The kind at our local Lowe's and Home Depot don't have pressure ratings? Is it just the generic one they have, or do we need a special type? Thanks!

Schedule 40, should say "SCH40" on it. Schedule 80 if you want to, as well.

[Pat Arnold]

An interesting article entitled "Kids, Do Try This at Home...We built a backyard cannon, and you can, too" appeared in the September 2007 issue of the Electrical Engineering magazine: Spectrum. Since so many of us enjoy this stuff, here's a link to the article online: http://www.spectrum.ieee.org/sep07/5483 Who wouldn't like to try some of the projects in the book cited. (Do pay careful attention to the safety issues it discusses before trying projects).

[Josh Fox]

Originally Posted by Schnabel

that was so classic

[Dark element]

OK a air cannon how to make one quick and easy for about 50-75 USD you need

1. PVC pipe
2. Sprinkler valve
3. pneumatics tube
4. pneumatics fittings

take the sprinkler valve top off and drill a hole in the top of it in all the other holes plug up air tight. then let it dry for at lease 10 to 20 min. Make your cannon as big as you want but make sure you can fit it on the sprinkler valve. make sure one end has a cap on it and leave one end open for your barrel. drill a small hole in the end of the end cap and put a pneumatic hose fitting on it and connect you hose to the end of your gun. then screw you barrel and the end that you put the hose on to the valve then put a air trigger on the hose comming from the top of your valve and pump it up and you are good to go have fun and be safe my buddys put a hole in there wall

[Daniel_LaFleur]

Originally Posted by Dark element

OK a air cannon how to make one quick and easy for about 50-75 USD you need

1. PVC pipe
2. Sprinkler valve
3. pneumatics tube
4. pneumatics fittings

take the sprinkler valve top off and drill a hole in the top of it in all the other holes plug up air tight. then let it dry for at lease 10 to 20 min. Make your cannon as big as you want but make sure you can fit it on the sprinkler valve. make sure one end has a cap on it and leave one end open for your barrel. drill a small hole in the end of the end cap and put a pneumatic hose fitting on it and connect you hose to the end of your gun. then screw you barrel and the end that you put the hose on to the valve then put a air trigger on the hose comming from the top of your valve and pump it up and you are good to go have fun and be safe my buddys put a hole in there wall

Please, for safeties sake. Do not use PVC for compressed gasses, it is not safe.

[Matt Howard]

Before this thread goes badly downhill like the other one, take a look at this:

http://www.chiefdelphi.com/forums/sh...ht=Matt+Howard

Pay attention to the last page.

[Cody Carey]

Hey all... I just wan to clear some stuff up about PVC, and there really isn't a better way to do that then to borrow Some words from a physics prof on a forum I frequent.

I can understand why Fred and others here feel a strong twinge of concern when someone in school suggests using PVC for an air tank. We've all seen explosions from pressurized tanks and pipe, and students don't typically have the experience to know how to design and test pressurized systems. Sure, we've all seen potato guns, but we don't know what it is you're really planning to build, it sounds a bit more sophisticated. And besides, potato guns have been known to explode.

The piping codes in the US apply to these systems. This would fall under ASME B31.3, Appendix A. Note appendix A refers you to the main body of the piping code for most calculations. I'll be using this as a guide to make suggestions.

Regarding materials, PVC pipe falls under ASTM D 1785 or D 2241. The fittings fall under a variety of ASTM standards including ASTM D 2464, D 2467 and D 2468. There are others. If you decide to use PVC, one thing that would help ensure safety would be to verify one of these numbers is printed directly on all the pipe and fittings you use. If they don't have these ASTM numbers printed on them, they probably don't meet the minimum standards and shouldn't be used.

Cements used for PVC pipe should meet ASTM D 2564. Verify the stuff you purchase meets this code. Follow the directions on the can.

None of the pipe should be threaded except for purchased fittings. Everything should be glued using the appropriate cement. If you cut any threads, you're doing something dangerous.

At 70 psi, you have a roughly 3 to 1 safety factor on top of the standard safety factors. The "stress allowable" for PVC at 100 F is 1.6 ksi which says the pipe is good for roughly 210 psi operating pressure. If temperature exceeds this, the pressure rating drops off very quickly, I'd not recommend it above this temperature. The code also prohibits its use below 0 F. If the plastic gets cold, which it could because of the expanding gasses doing work on whatever, wait till it is warm again before pressurizing. Cold plastic is more likely to break.

Consider what external stresses you are imposing such as bending of the pipe between supports. The pipe should be reasonably well supported over long sections.

Once you've manufactured the piping, do a pressure test on it using water. Fill with water, make sure there is no air in the system, and then pressurize to at least 200 psi, preferably 300 psi. Hold this pressure for 5 minutes, then release the pressure and verify there are no leaks or distortion of any part. If it holds this pressure, I'd feel a lot better about using it.

I'd also suggest repeating this pressure test every 100 cycles or whenever you suspect damage or leave it sitting for extended periods of time. Cyclic pressure and other uncontrolled factors could damage the piping, regular testing will help prevent catastrophic explosions.

Verify all valves you use are rated for the given pressure.

You really should have a relief device, set at about 100 psi, immediately downstream of your regulator, just in case the regulator fails.

For a pressure source, do not use any source of pressure above 150 psi. High pressure cylinders are extremely dangerous.

Off hand, I can't think of anything else to warn you about. Maybe the others here could suggest specific considerations.

In short, as long as everything is set up correctly, and safety checked multiple times, there is very little that can go wrong, especially while operating at 100psi and under... a 2 to 1 safety factor on top of standard is really good.

I'm not saying this is a good Idea, but people in my local offroading club have been using PVC as air tanks for portable systems for years. They mount these on bottoms of bumpers, roll cages, and other places where they are almost sure to get hit, and HARD. When I went to my first meeting and saw that, I remembered threads like this from when I frequented CD and asked if they'd ever had any blowouts or problems associated with this, and I was surprised to find that there had only been one... And it had happened when the guy forgot to put PVC cement on an end cap.

Hows that for working in the real world?

As a side note, the reason he says to test the system with liquid is because at pressure, the main difference between water and air is that air will explosively expand, and water won't. This means that if you have a leak and fill it with water, you won't have any sort of explosion, and if it holds up for five minutes at 200 psi, you know you won't have any problems below 100.


Then again, It's pretty easy just to weld up a steel tank.

[Brandon Holley]

One of my good friends built a potato gun using PVC pipe as the air storage tank.

He was outside, with the tank pressurized and loaded, getting ready to launch one. He accidentally dropped it from a height of <3 feet...the tank exploded sending shards of PVC everywhere. One of those shards lodged itself into my friends forehead.

He's ok, but he still has a harry potter like scar on his head. I'm not advocating the use or non-use of PVC as a tank here...but a story like this is definitely something to consider. Safety is always imporant, especially when working with pressurized vessels...

[dpeterson3]

How far are you planning on shooting. If you don't have to shoot far, a PVC tank is fine because you don't need a lot of pressure. I attached some data I took from out air gun in the hopes it will ease some minds. Sorry it is in a documents. I couldn't make it fit any other way.