How to Build a 150 PSI Compressed Air Cannon!

This is an air cannon that I designed. It is made completely of very simple PVC parts, a sprinkler valve, and a blow gun nozzle. It can also make really cool noises!

To make this air cannon, first you must need some basic tools:

• Drill
• Drill Bit - Ranging from very small(to drill pilot holes) to 7/16" drill bit
• A 1/4" NPT Tap (This link is good -- it has both the 7/16" drill bit AND the 1/4" tap on amazon.)
• Teflon Tape
• Sandpaper
• Saw
• JB Weld

Next, this air cannon consists of the air chamber(s) and the barrel. They are essentially the same to make but the chamber requires a few more steps.

I bought all of the PVC pipe parts at Home Depot and Lowes, and I will link the other parts to Amazon or wherever I bought them.

To make the barrel, you need:

• A section of 2" diameter SCH40 PVC pipe (length is up to you to decide -- I used 25")
• 2.5" section of 1" diameter SCH40 PVC pipe
• 1" threaded male PVC adapter
• 2" to 1" PVC Reducer
• 2" PVC Coupling

If you would like to make a single-chamber air cannon, you need these (If you want multiple chambers just skip to the next material list):

• A section of 2" diameter SCH40 PVC pipe (length is up to you to decide -- I used 30" for my single-chamber prototype)
• 2.5" section of 1" diameter SCH40 PVC pipe
• 1" threaded male PVC adapter
• 2" to 1" PVC Reducer
• 2" PVC Coupling
• 2" diameter PVC end cap
• 1/4" NPT Pressure Gauge (This I got from here on amazon)
• 1/4" NPT Schrader Valve (Amazon. I bought the one that came in a box of ten.)
• 1/4" NPT Drain Valve (Amazon)

For a double-chambered cannon:

• 2x 2" diameter SCH40 PVC pipe (length is up to you to decide -- I used 20" for my double-chamber prototype)
• 7x of 2.5" section of 1" diameter SCH40 PVC pipe
• 1x 1" threaded male PVC adapter
• 2x 2" to 1" PVC Reducer
• 2x 2" PVC Coupling
• 2x 2" diameter PVC end cap
• 2x 1/4" NPT Pressure Gauge (This I got from here on amazon)
• 2x 1/4" NPT Schrader Valve (Amazon. I bought the one that came in a box of ten.)
• 1x 1/4" NPT Drain Valve (Amazon)
• 1x 1" T-Joint PVC connector
• 2x 1" 90-Degree PVC Pipe Joint
• 2x 1" diameter PVC NON THREADED Ball Valve

Finally, the firing mechanism:

• 1" threaded Sprinkler Valve (Amazon)
• 1/4" Blowgun nozzle (Home depot)
• 1/4" NPT Male to Male adapter (You only need one but it comes in 4 on amazon)

Besides that, you also need some miscellaneous things such as:

• PVC Glue and Cement (home depot)
• Wrench
• Towels
• A surface to build on that you are not afraid of getting ruined
• Well-ventilated area
• Paint (if you want to make it look good)
• Acetone (optional for painting)
• A HIGH pressure bike pump (I bought a manual one that can reach 160psi from target and this electric one that also hits 160 psi on amazon)

Now you are ready to build! :)

The picture on the right shows the general layout of the pieces you must glue.

The order does not matter, by I started sprinkler side first.

1. First, take the 1" male adapter and the 2.5" section of 1" diameter PVC pipe. Prime and cement both mating surfaces and insert the 1" pipe into the adapter. Make sure to read gluing instructions to follow the manufacturer's steps.
2. Next, take the 2" to 1" reducer. Prime and cement the inside mating surface and glue it to the other end of the 1" PVC pipe.
3. Glue the coupler to the outside surface of the reducer and then finally attach that to one end of the 2" diameter pipe.

Now you have your barrel!

IF YOU WANT TO BUILD A DUAL AIR CHAMBER CANNON, SKIP THIS STEP AND GO TO STEP 3

Now, onto the air chamber!

The single-chamber one is quite easy to make, just follow the steps listed in the previous step exactly and then glue on a 2" diameter PVC end cap.

Now you have the completed chamber without any pressure gauges or valves. Those will be added in the future after we put it all together.

The picture on the right is actually my 4-chamber prototype except I chopped off one on each side since it was very heavy. The steps are still correct for the double-chamber cannon, just know that your final product won't look like the picture in the right.

1. To start, take two pieces of 2.5" 1" diameter PVC and glue them to both ends of the ball valve.
2. Then, take one end with the protruding 1" pipe and glue that to the 2" to 1" reducer.
3. Glue the coupler onto the reducer and then the 2" PVC chamber section.
4. Finally, glue the 2" diameter endcap on at the other end of the 2" diameter PVC chamber.

Now you have one of your valve chambers! Repeat those steps once to build the other one.

1. Now you have to build the adapter for the sprinkler. Start with the T-joint. Glue three 2.5" sections of 1" diameter PVC into all three holes, forming a larger T shape.
2. Then, take the straight section with both 1" PVC pipes and glue one 90-degree elbow to each end. This should form a shape that looks similar to a two-pronged fork. See the diagram.
3. Finally, take the two air chambers and glue them to each elbow. Orientation does not matter but just make sure that the valve handles are facing the same side.

1. Take the sprinkler valve and remove the solenoid valve and plug.
2. Unscrew the top half of the sprinkler valve from the body. Be careful not to damage the spring inside or lose the membrane.
3. Next, you must use a saw and cut out the lip that the solenoid valve was attached to that is protruding out of the sprinkler valve. This way the surface sits flush with each other.
4. Start from smaller bits and slowly work your way up to the 7/16" drill and drill the hole in the middle of the sprinkler valve.
5. Take JB weld and seal the hole for the plug as well as the spot where the solenoid once was. It should look like the picture on the right.
6. Finally, take your 1/4" NPT tap and tap the hole. Make sure you do not over-tap the hole which could cause leaking.

At this point, make sure to let your JB-Weld completely dry overnight. Take your 1/4" NPT male to male bit and add five wraps of Teflon tape to one end and then screw it into the valve. It should look similar to the second picture.

Add five more wraps of Teflon tape to the exposed end and then screw in the blowgun. Make sure that the trigger-pulling direction is opposite of the flow of the air as labeled on the sprinkler.

Now you have completed your sprinkler valve. it should look like the last picture.

IF YOU HAVE A DUAL-CHAMBER SKIP THIS STEP

1. Apply five wraps of Teflon tape to both male adapters on the barrel and the chamber.
2. Screw it into the sprinkler valve. Make sure that the barrel is on the side where the flow arrow is pointing away from the valve. Look at the picture all the way on the right and see the flow arrows starting from the bottom and pointing to the top.
3. Next, mark three points on the end of the air chamber approximately 90-degrees from each other. Drill these holes starting from smaller bits all the way up to the 7/16" bit. Tap all three holes and shake out any shavings to make sure it is clear.
4. Now, figure out where you want to put each valve. Make sure that the pressure gauge is not in the way of the blowgun protruding out of the sprinkler valve but you can orient the valves and gauge in any way you want.
5. Apply five wraps Teflon tape to each valve/gauge and then screw them into the hole. Make sure they are seated properly and that they are perfectly perpendicular.

Now you have your fully completed cannon!

Apply five wraps of Teflon tape to both the adapter/air chamber and the barrel.

Note the flow direction of the sprinkler valve and make sure the barrel is on the side that where the flow arrow is pointing away from the valve.

1. Screw the entire adapter/air chamber setup and barrel into the sprinkler valve.
2. Make sure that the air chamber setup is completely horizontal and not tilted when screwed into the valve. Also note that when you set the cannon onto the table, the blowgun faces directly upwards like the picture on the left. This will affect your drill hole placement.
3. First, drill a 7/16" hole into the end of each air chamber that you have. Orientation does not really matter but I like to keep it all facing the bottom so it is the easiest to fill.
4. Tap each hole with the 1/4" NPT tap and then apply Teflon tape to each Schrader valve and screw into the chamber. make sure it is seated properly.
5. Look at pictures 3-5 and see the valve placement. You only need one gauge even for the double chamber as you can just pressurize all of it at the same time.
6. Drill 7/16" holes directly down the middle of the T-joint and then one on the top of it. The one on the top is for the pressure gauge, which gives you easy readings when it faces up.
7. Tap both holes and apply Teflon tape to the drain valve and pressure gauge and then screw them in.

Now you have completed your air cannon!

Mix up some soapy water and fill a spray bottle with it.

1. Slowly pressurize the air chamber and DO NOT TOUCH the blowgun trigger.
2. First, check the pressure gauge to see if it works and reports a pressure reading.
3. Then, listen closely to the air cannon and see if you hear any obvious hissing noises which indicate a leak.
4. If you do not hear anything, spray each valve seating point or any other connection point with the soapy water. Look to make sure that there are no bubbles being made on any of the connection points.

If you hear leaking/see bubbles, immediately open the drain valve and let the air out. Unscrew whichever section is leaking and then clean off the Teflon tape. Reapply more Teflon tape and screw it in again. Repeat this step and make sure it no longer leaks.

IF IT STILL LEAKS:

You most likely have a threading problem when you tapped the holes so get a small file like in the picture and lightly file the hole to remove the threading. YOU CANNOT DO THIS MULTIPLE TIMES.

Once you remove a very small layer of PVC, tap the hole again as well as possible to make sure it is seated properly. Screw in the valve again and then repeat this step.

Once you have completed this step and you know for a fact there are no leaks, you are ready to shoot! Just pressurize the cannon and then squeeze the trigger to fire. Make sure you do not point it at any person or animal!

IMPORTANT!!!

Please note that the sprinkler valve that I linked to on amazon can only be pressurized to 150 PSI. Still, make sure to check your valve ratings yourself.

DO NOT go over 150 psi and if you do, it has a high risk of exploding. Also, although schedule 40 2" PVC is rated for up to 280 PSI, the valve connections and PVC joints DRASTICALLY lower the pressure rating. I have fired it at 150 PSI multiple times but just make sure you take proper safety precautions and use at YOUR OWN RISK!

To paint PVC, you must first sand all surfaces to make sure the paint can grip onto it.

Then, make sure to wash and clean the cannon with acetone to clean off any markings and to prep it for painting.

Finally wrap any sections you don't want to paint in tape.

Now you are ready to paint!

Make sure to paint in a well ventilated area and let it dry fully between coats.

Enjoy! :)