Air Cannon V3

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Introduction: Air Cannon V3

About: Engineer making renewable energy products for African entrepreneurs.

A pneumatic cannon for launching plastic soda bottles.... or ketchup packets. Almost all parts can be obtained from home depot and probably any local hardware store with a plumbing section.

Bigger is cool looking... But not always better. I have found smaller more robust designs to be far more fun that the gigantic heavy cannons. I can recharge (with a foot pump) and reload in less than 30 seconds and hold this thing much easier than its heavy breathing counterparts. Other than this design, I no longer build using PVC as it does fail catastrophically.

I made this particular cannon to be used for physic's demos for middle and high school physics students. 2l bottle fail at surprisingly high pressures (relatively) and have served as a reservoir very well.

Step 1: Parts List

All parts are 0.5" unless specified

1 2l bottle of soda - minus the soda and washed out
1 .75" sprinkler valve with manual switch
1 45 elbow
2 female/male 90 elbow
1 female/threaded adapter
1 end cap
1 .5" thread-> .25" threaded bushing (mine is galvanized)
3 1.5" long pieces of pipe
2 2-2.5" long pieces of pipe
2 .5" female - .75" threaded adapter
1 4 wayfitting
1 Tire Stem with schrader valve (walmart or autoparts store) - home depot did not have this item
PVC cement
Teflon Tape
1 male threaded cap OR 1 gauge (might be listed as manometer)

Optional Add on (for bypass and a later project)
3 more 1.5" tubes
1 ball valve
1 45 elbow
1 3 way Tee

Step 2: Prepping Components

Disassemble your valve. I am not going to be modding it as it is really unnecessary for this project. Taking it apart simply makes it easier to paint.

While the paint is drying (if you choose to paint), now is a good time to cut your tubes if you have not done so already. PVC saws (looks like a metal string) are cheap and effective. I personally use a band saw to zip though everything. Guitar strings also work, just be very careful - it will eventually snap and the filament will be extremely hot (I've had burns from this). Guitar strings also have a tendancy to wrap themselves around when they snap.

Now is also a good time to sand off any burrs and lightly sand the mating edges of the fittings and tubes.

Step 3: Make a Filler Valve Fitting

Using a dremel (or even a regular drill) -- cut a hole in the center of your cap. Chamfering the inner edge will help greatly in getting the stem on.

Tire stems are a press (or pull :P) fit. So make the hole as small as you possibly can. .5" caps are a tight fit, but it fits nontheless.

When you think you're ready -- push the stem through the back of the cap. Then pull it through as hard as you can. Pull one way and then another direction until you notice an edge pop out and set itself on the outside of the cap.

Step 4: Fitting It All Together

Hopefully you get the general idea from the picture of the end goal.

The longer lengths of tube are for the reservoir (2l bottle) and for the filler stem post. Ideally, everything should be in the same plane except for the gauge post. Therefore, I recommend you make attaching the reservoir the last thing you cement together. I find an angle of about 45 degrees is ideal for the gauge post - this allows your hand to naturally hold it and allows easy viewing of the gauge while refilling.

If a part has threads, do not cement. Instead - wait until after you paint (if you choose to do so) and use the Teflon tape to seal everything.

The last picture is with the optional add on. Everything AFTER the ball valve was not cemented in place. It will not be holding pressure and allows me to change my mind on what should go there (ie another 2l bottle). If anyone needs a better description, let me know and I'll take the time to go more in detail.

Step 5: Final Assembly, Safety and Firing

When the cement has cured for a few hour you can not attach the sprinkler valve. Be sure to use teflon on the pressurized side.

Keep tightening and make sure you stop when the solenoid is facing downward. This makes a nice little point to grab on and puts the manual bypass switch at your fingertip.

I currently use a 3' barrel. Honestly, this is too short for loaded projectiles, but it is almost too big for water bottle rockets.

SAFETY
I always pressure test my guns above what their normal operating pressure is. I tend to stay around 60psi and I tested at 90psi. I attach my air line to the filler valve and place the whole thing in a wooden box. I then slowly bring the pressure up to 90psi and I stay here for about an hour.

FIRING
I purposely leave the teflon tape off of adapter on the barrel side. This allows me to unscrew and make the whole thing easier to transport and load projectiles. I find that ketchup packets will fit if coaxed in there slowly while twisting. But, don't fire at higher pressures - otherwise the packet rips open inside the barrel and a rectangular foil wrapper shoots falls about 3 feet away.

Firing water bottle rockets: Fill a 2L (or even a smaller 20oz bottle) a third to halfway full and set it on the ground. Charge the reservoir to your firing pressure. When you are ready to fire, make sure your firing range is clear and push the barrel into the full length of the bottle.. Pick up the whole cannon/rocket and point upwards. Let everyone know you are about to fire and pull the trigger.

You will get wet -- I tend to hold it out the side a little bit.

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106 Discussions

Only use galvanized, black iron or copper pipe for air cannons. Also, only use air tank valves, not homemade systems. NEVER use drink bottles for storing compressed air, they will rupture very easily.

2 replies

I would caution against using very high pressures as well. You really don't need high pressure as much as air volume. My project (above) uses only 30 lbs of pressure and sends a 3" rubber ball at least 50'. I built mine for my dog though and he just loves to chase that ball! LOL

Oh, and by the way, use a used fire extinguisher, small air tank or other strong metal tank designed for high pressure gasses.

Is there an adapter from the PVC screw to the 2L bottle screw? Also if you wanted to make this a paintball gun, put a 3 way connector on the part right after the sprinkler valve, the extra connection facing up, fill a 2L bottle with paintballs and screw in! the paintballs will fall into the chamber to be shot out like a real paintball gun!

2 replies

I struggled with that as well. I tried 3D printing an adapter but it didn't hold air very well and I didn't know a garden hose adapter would work so I substituted the 2l bottle with a length of PVC pipe instead. That way you can use PVC for the entire project. See my pics above.

2-liter bottles use garden hose threads. Just buy a female garden hose to pipe adapter.

mod an EMPTY coleman campstove propane bottle, and i bet you could run 200-300 psi easy :-)

2 replies

I would like to suggest that all high pressure air cannon instructables should include a warning such as:

"These high pressure air weapons can shoot things fast enough to cause severe injuries or death. Never use them to shoot things at people."

I built a cannon sort of like this one for launching tennis balls and t-shirts i used an inner tube bike pump adapter attached to my air compressor and i can shoot them well over 150 yards i wonder if you hooked yours up to an air compressor it might go farther.

The model I bought looks EXACTLY like this exept for the flush trigger, it doesnt have one, its made by the same manufacturer and its the same model, did they remove it from the design?

do you have to use an orbit valve? I have a rainbird that isn't in a cannon yet. will that work too?

1 reply

There's this "plastic fusion" paint that might stick really well depending on what kind of plastic the valve is made of. There's something that works even better than a band saw or friction saw/guitar strings. They make special PVC "scissors" that have extra leverage and a ratcheting mechanism. They're the best thing to use on smaller diameter pipe. They cut clean and leave no shavings.

2 replies

     I've seen those "PVC scissors" before, maybe on TV. They're incredibly, but not as much, huge. Should be easy to spot when you need it. Unless you were in a warehouse it would be lost for sure.