Step 6: Troubleshooting

Okay, so you're losing air pressure in the pressure chamber. This is because you've got a leak somewhere. No matter how much PVC cement you used, leaks are usually inevitable. But there is only one part of the air cannon that they're found at-the pressure chamber. To seal them, you have to find where you're losing pressure. There are methods to finding air leaks that range from simply listening for a fizzing noise and trying to find it that way, by coating the pipe with a film of soapy water and looking for the formation of bubbles due to escaping air, or even submerging the unit under water and looking for streams of bubbles traveling upwards. All of these methods work with different results. It's how you seal the leak that matters. Any other weird problems, please leave a comment southward on this instructable, and I'll see what I can do.
What are the fittings used to go from the 1/4" on the solenoid valve to the 2"pvc?
<p>where did you get your schrader valve? </p><p>and is this one good enough </p><p><a href="http://www.ebay.com/itm/1-4-Schrader-Valve-/370090183980?pt=LH_DefaultDomain_0&hash=item562b180d2c" rel="nofollow">http://www.ebay.com/itm/1-4-Schrader-Valve-/370090...</a></p>
<p>to late ive bought it</p>
<p>does the barrel have to be a specific length? or can I make the pressure tank larger to compensate for a shorter barrel?</p>
<p>the barrel dos not have to be a specific length. 1-2' works best I think.</p>
<p>So I've assembled and attached everything except the end cap for the pressurised chamber.</p><p>My question: Where the hell do I find a schroeder (schrader?) valve? I've got all the relevant tapping equipment and have a pressure gauge ready to screw in. It seems as is I have looked goddamn everywhere. If anyone has a link it would be incredibly helpful.</p>
<p>How big of a compartment of compressed air would you need? Or does it just matter how much it is pressurized?</p>
<p>The liquid of your choice. I am building an air gun with a 1/2 inch barrel and a 1 1/2 inch chamber. The barrel is 3 feet.</p><p>Specs:</p><p>Main valve:</p><p>QEV valve</p><p>Minimum operating pressure: 3 psi</p><p>Maximum operating pressure: 150 psi</p><p>Ensure pressure resistance: 200 psi </p><p>Valve warranty: 1 year!</p><p>Piliot Valve:</p><p>Blowgun valve</p><p>Minimum pressure: 30 mmHg Vacuum</p><p>Maximum pressure: 150 psi:</p>
<p>The liquid of your choice. I am building an air gun with a 1/2 inch barrel and a 1 1/2 inch chamber. The barrel is 3 feet.</p><p>Specs:</p><p>Main valve:</p><p>QEV valve</p><p>Minimum operating pressure: 3 psi</p><p>Maximum operating pressure: 150 psi</p><p>Ensure pressure resistance: 200 psi </p><p>Valve warranty: 1 year!</p><p>Piliot Valve:</p><p>Blowgun valve</p><p>Minimum pressure: 30 mmHg Vacuum</p><p>Maximum pressure: 150 psi:</p>
<p>Masher007 is very smart. For my friend's air gun, I talked him out of PVC.</p>
<p>Danger: See link: This is not spam, but a warning. PVC will fail suddenly after a while. This was band member that hurt badly by a T-Shirt launcher explosion.</p><p>See the pictures and never use PVC to hold air, Please.</p><p><a href="https://fundrazr.com/campaigns/1Zs3c" rel="nofollow">https://fundrazr.com/campaigns/1Zs3c</a><br>..</p>
<p>seal leaks with epoxy</p>
<p>bell reducers are not pressure rated</p>
I pump my air cannon up to 110 psi and I can't seem to get it to shoot very far at all, the leaks are sealed, but it doesn't want to fire far at all, any suggestions?
Try using more wadding behind the projectile. It will create a better seal for the air pressure to push against getting more power out of the shot.
also check out my air cannon im gonna post a new one in a week or 2
dont use as much psi because if the seal on the projectile isnt right then maybe 40 - 50 psi would be better
Would a longer pressure chamber somehow be better? Perhaps allow for multiple shots on each charge?
Is the ball valve easy to turn? I want to make an air cannon that is stationary on the ground like a mortar that is set at a 45 degree angle for max distance, but I also want to be able to trigger the firing mechanism (turn the valve) from a distance. Do you think it would be possible to attach a thin rope to the trigger and pull that to fire, or is the valve handle too hard to turn from a rope?
It is difficult to open and close. Even if lubricated, it takes a little bit of force to break the valve and release the pressure for the shot. However slow the opening may be, the airflow couldn't be much straighter. A solenoid valve, which requires an electrical current to open is an alternative option that is used in most air cannons nowadays. Used in sprinkler irrigation systems for lawns, this type of valve opens MUCH faster from the push of a button, however the airflow is not very direct and may affect the shot.
Oh and by the way, 5 stars buddy this is an awesome instructable!
I would like to hear the commentariat's point-of-view on the pros and cons of PVC and or metal pressure chambers.<br> <br> <a href="http://www.instructables.com/id/NASH-Air-Gun/" rel="nofollow">http://www.instructables.com/id/NASH-Air-Gun/</a>&nbsp;<br> <br> Also, how many of you guys have an air cannon yourselves? I'm always curious ;-) And what have you used for ammo? I'm thinking about making an 'ible for paper rockets, as they're pretty fun to shoot and work great for airsoft wars...
Nice!!!<br>Few questions: <br>Will a 1/2&quot; ball valve work properly (lever ball valve)?<br>Isnt the valve too hard to open when firing?
Yes and no. You can use whatever size valve you wish. I lubricated my valve so that it would be easier to open, so no it's not hard to open/close at all.
What do you use/recommend for ball-valve lubrication?
WD-40 for a metal ball valve, silicone for PVC. :)
Got one that shoots 250 yards
Your &quot;disclaimer&quot; needs beefing up.&nbsp;&nbsp; I would like to suggest that all high pressure air cannon instructables should include a warning such as:<br> <br> &quot;These air weapons can shoot things fast enough to cause severe injuries or death. Never use them to shoot things at people.&quot;<br>
Yes that's pretty self explanatory unless your an incompetent idiot. Therefore it's not entirely necessary.
love the commentary, pretty hilarious :P
Couldn't you wrap the pressure chamber in duct tape so that 1. air doesn't escape as easily and 2. even if the chamber does explode, the duct tape would take most of the force.
Of course. However I'm not positive that will prevent the air from escaping. Unfortunately, duct tape will not take most of the force from a rupturing pressure chamber. For one, the chamber would have to be under immense pressure for it to rupture to begin with (we're talking 200 psi-ish, but it depends on the size of the pressure chamber), which should it explode-the duct tape may only help prevent a certain amount of shrapnel from peppering your body. The pressure chamber would still explode nonetheless.<br>I have seen people wrap their pressure chambers in chicken wire/wire mesh for the sole purpose of containing shrapnel, but again-pressure chambers are DANGEROUS!!!!<br><br>That being said- NEVER over-pressurize your pressure chamber, ALWAYS treat the pressure chamber with extreme care (as you would any firearm) when under pressure, and ALWAYS use schedule-40 Pressure-rated PVC pipe when building PVC pressure chambers. It's also never a good idea to leave it under pressure when not it use as this can weaken the chamber as does cold temperatures.<br><br>However, the tape always gives things a nice look anyways and there's no harm in wrapping your pressure chamber in duct tape.
Would there be someway of making the ballvalve assembly able to screw on and off to change between types of &quot;combustion&quot; chambers?
Sure. Just use threaded adapters. That's what I used here! Basically, the pressure chamber, the ball valve, and the barrel can all be separated and interchanged with other parts.
do you use a bike pump or air compressor
Air compressor. Bike pump would also work I suppose... Have fun pumping it once the PSI in the chamber hits 80 though.
Wowzers! this is exactly what i was looking for! I have been looking for a plan for building one of these things, but all of them ( except this one and a couple of other ones) require money, and i dont feel like paying anyone money. I intend to use your design, just with the pressure chamber larger and bent underneath the barrel so that it is more compact. I'll probably post it on instructables, so keep an eye out!
Sounds good. Remember:over-under cannons are compact, and still very good, but when you curve pipe you lose a little power due to weaker airflow. But to compensate, just pump it up more!<br />
Say...If you packed it right so it was sealed, could you shoot water out of it? I mean pure water, not in a balloon or a bottle or anything.<br />
Sure. Any liquid, actually. Salt water, urine, blood, vanilla extract, olive oil, crude oil, paint, you name it. Just aim the cannon at an inclination so that the liquid completely covers the ball valve. This will push the liquid out better.<br />
How many PSI can you fit in?
I can only get to 90 psi right now, but after I seal the leak (between my bushing and my ball valve), I'll be able to hold more. My target pressure is 100-110 psi.<br />
how much does it cost<br />
Some of the stuff was given to me by a buddy, but the fittings cost me under $30. The barrel could probably be purchased for $10-$20, and the valve will cost probably $20-$30. The smaller the valve, the cheaper they are.<br />
I dont have anything to say just no-one had commented on this before so i felt sorry for you :) <br />
Very Nice!
&nbsp;i was thinking of making one of these only using a 2'' barrel, how long was your barrel and how long was the total cannon?
The whole thing was approximately 5 feet long, and the barrel length was about 3 of those feet.<br />

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