Intro: PVC Backpack Air Cannon
Be prepared, for you are about to build the greatest Double Barrel Backpack Portable PVC T-Shirt Launcher this side of the galaxy! When I was younger, a friend and I built potato launching devices using pressurized air and sprinkler valves, which has served as an inspiration for this design.
The cannon uses a pressurized air tank and two valves to control firing the two barrels which can pivot to match the operator's arm positions. The initial intention was for this device to launch t-shirts into a crowd during a high school football game, but its uses extend far beyond that :) (Launching Jello out of it might be my favorite). This is my first instructable, so enjoy, and happy building!
Step 1: Get Materials!
I was able to find a lot of the parts for this project around the house since it is mainly made up of PVC and ABS piping, but I am sure a local hardware store has all the materials we will need.
- (2) sprinkler control valves (one-inch female connections for both input and output, and you want the one that is straight) The ones i used can be found here.
- (4ft) 3 in. diameter ABS pipe
- (38in) 1 in. diameter PVC pipe
- (4ft) 2 in. diameter PVC pipe
- (2) 3 in. diameter ABS 90 degree corner connectors
- (2) caps for 3 in. diameter ABS
- (1) T for 3 in. ABS with a 1 1/2 in output on the center of the T
- (3) 1 1/2 in. to 1 in. PVC reducer
- (2) 1 in. PVC 90 degree corners
- (1) 1 in. PVC T fitting
- (2) 2 in. to 1 1/2 in PVC reducer
- (2) 2 in. PVC Coupling
- (4) 1 in. to male 1 in. PVC fitting (to go from 1 in. PVC to the sprinkler valves)
- (1) old bike tube (I use the valve off of it to fill the tanks)
- (4ft) of thin wiring
- (1) electronic switch (anything that will complete a circuit when pressed)
- (1) 9v battery
- (1) 9v battery connector (It should look like this)
- (1) pair of backpack straps (I used straps I fond at an Army surplus store)
- Bottles of PVC primer and cement
- Bottle of ABS Cement
- A roll of Teflon tape
Tools you will need:
- PVC pipe cutter
- Soldering Iron
- Heat Gun
Step 2: Making the Tank
The first step is to use scissors to cut a small circle of material around the valve of the bike tire tube. This will provide a surface for us to later epoxy to the inside of one of the caps for the 3 in. diameter ABS.
Then drill a hole in the center of One of the caps for the 3 in. ABS caps just big enough for the trunk of the bike valve to slide through. Then epoxy the top of the cut surface of the bike valve to the inside of the cap. The valve should be sticking out the end of the cap through the whole drilled in the cap.
Now, cut the 3 in diameter ABS pipe into (2) 18 in. lengths and (2) 2 in. lengths.
Using the ABS Cement, connect a cap and a 90 degree corner onto each end of the 18 in. lengths (one should be the cap with the bike valve sticking out of it) and cement the (2) 2 in. lengths to either end of the T connector. Once these connections are dry, cement the corner pieces of the longer lengths to the shorter piping coming out of the T connection as shown in the picture. BE SURE TO LAY/HOLD THE TANK FLAT WHILE IT IS DRYING WITH THE SMALL OUTPUT OF THE T CONNECTOR FACING PARALLEL TO THE LONG LENGTHS OF THE TANK this what forms the backpack shape of the device.
Step 3: GOING FROM THE TANK TO THE BARRELS
Now to go from the tank to the barrels.
Cut the 1 in. PVC into the following lengths:
- (1) 21 in. length
- (6) 3 in. length
We will be making one overall T shaped connection and two corner connections that can be reversible so don't worry about mirroring anything.
For the T shaped connection:
Using the PVC primer and cement connect two of the 3 in lengths to the upper parts of the 1 in PVC t connector such that they are opposite each other. Then cement the 1 in pipe to 1 in male fittings onto either end of the connections coming out of the T such that it looks like the part labeled "X1" in the picture above.
For the corner connection:
Use the primer and cement to connect a 3 in length to either end of a 90 degree connector piece. Then cement a male connector onto one of the lengths and a 1 1/2 in. to 1 in. reducer on the other. Once those are dry, cement the 2 in. to 1 1/2 in. reducer onto the end of the 1 1/2 in. to 1 in. reducer such that it looks like the part labels "X2" in the picture. Repeat this process so that you end with (2) corner assemblies.
Next, cement the remaining 1 1/2 in. to 1 in. reducer into the small hole of the ABS T. Once that is dry, prime and cement the 21 in. length of 1 in. diameter PVC into this reducer. If you cemented the ABS correctly, this length should extend parallel to the long portions of the tank.
Once this is done, prime and cement the 21 in. length to attach to the bottom opening of the T assembly from earlier.
After that, I used a thin layer Teflon tape around the male connector pieces so that when they are screwed into the sprinkle valves, they will for a tight seal.
Finally screw the sprinkler valves to the ends of the T assembly and then screw the corners into the output ports of the sprinkler valves and we are almost there! (it should look like the final assembly in the picture above)
Step 4: ADDING THE BARRELS
Now for the barrels.
The first thing to do is to cut the 2 in. diameter PVC pipe into (2) lengths of 2 ft.
Once this is done, prime and cement one end of the length to connect to one of the 2 in. couplings. Repeat this such that you have two barrels each with a coupling on one end.
Once the previous connection is dry, prime and cement the pipe so that you can connect the coupling attached to the barrel to the output of the corner assembly. The picture shows one barrel finished and the other in preparation for this step.
Step 5: WIRING IT UP!
Congratulations! Your well on you way to firing things out of an air powered cannon!
Making this project was actually the first time I've soldered something of my own creation so don't be afraid of this section. If this is your first time soldering, I suggest you take a moment and google "how to solder two wires together".
The sprinkler valves can be actuated electronically or manually. In order to make this project wearable, I had to create a switch that I could hold in my hand in order to open the valve and fire the cannon.
The picture included is a wiring schematic of what should connect to what.
First, cut the wire into two lengths of 3 ft (it could be shorter, but I have long arms so this is what worked for me).
The sprinkler valves should already have wires coming out of them. neither is noted as positive or negative, so don't get too worried whether you have the right wire.
Make a solder connection with a wire from each of the sprinkler valves and one of the lengths of 3 ft wire. This can be a little tricky so an extra pair of helping hands what of great use to me. Make sure to use shrink wrap or another method to protect your connections! Repeat this three way connection for the remaining wires from the sprinkler valves and length of 3 ft wire.
Once this is complete, solder the open ends of the 3 ft wire to your electrical switch. THE CIRCUIT SHOULD REMAIN OPEN AT REST, sending any electricity through the valves will cause them to open and release any pressure that might be stored in the tanks.
Cut one of the 3 ft lengths of wire about an inch from where it was soldered in the three-way connection. Solder one of the cut ends to the positive (red) wire of the 9v battery connector and the other end of the cut wire to the negative(black) wire of the battery connector.
Once your wiring is complete and protected, the only thing left to do is to attach the backpack straps to it!
Step 6: MAKING IT a BACKPACK
You might have to get a little creative with this part, depending on what you are using as straps.
The Army surplus strap that i used had some useful clips that i attached around the T assembly and I used some paracord to make loops around the bottom parts of the tank which I could attache my clips to.
Getting the straps to fit right and stay on will take some tweaking and it will be different from person to person so adjust until you feel comfortable.
Step 7: FIRE!!!!!!!!!!!!
Only one thing left to do and that is FIRE!!!!!!!!!!!
WARNING: DO NOT EXCEED THE CAPABILITY OF YOUR SYSTEM, OVER PRESSURIZING THE TANK COULD CAUSE IT TO RUPTURE!
(The highest that I have filled my tank is to 60 psi and it can fire t-shirts a good 20 yards)
Use a bike pump or air compressor to fill the tanks at the bike valve build into the tank and then walk around, get in position, and fire at will!!!!!!
As a safety precaution, objects are propelled at high velocity when exiting the cannon so DO NOT aim the cannon directly at another person!
(if you're firing t-shirts into a crowd like I am, aim high so it can arc and land on them rather that hit them, and don't worry about folding/rolling the shirts, just shoving them into the barrel will provide enough of a seal to launch them)
I hope you enjoyed this build and happy firing!
Step 8: IMPROVE
You can never stop improving. This is a CAD model I've made of a potential firing tank to allow control of pressure from shot to shot. This project can serve as a base so feel free to improve and modify!