Well my friends and I bought some fireworks and set them off for fun but we thought that they didn't go high enough. So we decided to build something to make them go higher. What we came up with is an air cannon. We codenamed the project
Firework Automatic Intelligent Launcher (F.A.I.L)

The air cannon is operated by using pressurized air and a sprinkler valve as control. The purpose of the cannon is to give the firework and extra boost of height before it ignites and shoots itself.Here is a picture of the final air cannon.

Step 1: Planning

Here is a plan of the air cannon. However due to the unavailability of some parts , we didn't use the exact same pieces shown here. The actual materials used are shown in the next step.

The cannon is composed of mainly 2 parts : The barrel and the air tanks. The barrel is made from and 5 feet long 2 inch abs plastic tube and some adapters to reduce one of it's end to 3/4 inch to be able to connect to the valve

The air tanks is made of 4 inch pvc tube and a t-connector. The t-connected is also connected to some adapters to reduce it to 3/4 inch. In our cannon we added an air gauge. However you don't really need it as most pumps have internal air gauge. Additionally, the extra air gauge in the cannon leads to more chances of air leaking. The less parts you have,the better.

The 2 parts are connected together by a sprinkler valve, which acts as the controller

Step 2: Materials

1st image:

1 x 8 feet of 4 inch pvc pipe (air tank)
1 x 6 feet of 2 inch abs or pvc pipe (barrel)
1 x Sprinkler valve
1 x pvc t connector (4inch)
2 x pvc end cap (4 inch)
1 x 4inch to 2 inch pvc reducer
Duct Tape

3rd image:

1 x abs 90 degree elbow (2inch)
2 x abs 2 inch to 2 inch adapter
1 x abs 2 inch to 3/4 inch reducer
3 x 3/4 inch threaded metal tube (1 or 2 inches long)
1 x 3/4 inch metal t connector

5th image:

1 x pvc cement
1 x abs cement
1 x pvc to abs cement
1 x pvc primer
1 x teflon tape

Not shown

1 x 9v battery for controlling the valve
1 x bike valve for pumping air into the tank
10m of wires to connect the battery to the valve
A switch for turning on the valve
Air pump
Spray-paint
90 degree elbow (4 inch PVC)

Tools

Hacksaw for cutting the pvc
Hot glue or epoxy for sealing edges
Newspaper for pvc glueing
Mask-gloves
Drill

Step 3: Building

For the building just assemble the pieces in the same way as shown in the images from the previous step except for 3 things.

1.We decided to cut the 4 inch pvc pipe in half and put 1 piece on each side of the t-connector. Furthermore, we added a 90 degree elbow to one of the pieces so that the 2 pieces together would form an L and can be places on the ground for support. That way the cannon can support itself.(see last image)

2. You need to cut a 2inch long abs pipe from the barrel tube to be able to connect the 90 abs elbow to the 4inch PVC t-connector ( see images 7-9)

3. We need to make a sort of valve to be able to pump air into the tank. All we did was to drill a hole in the end cap. We then inserted a bike valve into the whole (it has to fit snugly) and sealed off everything with epoxy. We left alot of rubber on the other side to provide more contact surface with the PVC. ( see images 11-12)

Tips

Wrap all the treads in with Teflon tape to prevent leaks.

Be careful working with PVC cement. They smell a lot and you should only do it in a open space. Keep a rag to wipe off the excess cement.

After you are done, use epoxy to seal all the threads. EDIT: actually it's better to use silicone since it's more waterproof than epoxy. I've found that epoxy doesn't resist the rain very well

The valve has 2 wires leading out. Just extend those wires and connect them to a switch and the 9v battery. It should make a click sound when it turns on. If not, read the manual.

Step 4: Paiting

For painting we used 2 colors of spray paint : White and red. The white provides a base paint while the red is the final color. We also cut out some paper letters and glued them on the cannon AFTER the canon was painted white. Then we paint the red over and removed the papers, thus giving us the letters in white.

Step 5: Testing

The firework we used were slightly modified. We put a paper cone on top of it to make it more aerodynamic and we also put some rocks on the bottom to increase stability .** To launch the firework, we set up everything and pump the air cannon to about 40 psi. Then one person lights the fuse of the firework while the other control the valve. One the fuse is lit, the firework is dropped into the barrel. Depending on the length of the fuse, there is a 1-2 seconds delay before we launch it (or else the firework will fall on the ground before it fires). If everything goes correctly, the firework should fire while it's at maximum altitude.

In our test however, we've found that the firework doesn't always stay up during its flight and sometimes fires horizontally, as shown here:

Other times, the cannon's valve opens a bit late and releases the firework after it's been fired. Therefore it doesn't not provide much boost to the height of the firework.

In the end, it all comes down to the timing. We've found that it's better for the firework to fire while it's falling down because that way, the firework will be pointing up. But it's hard to time it right.

**EDIT: As suggest by doctormerlin

Regarding improving the stabily of the firework:

- dispense with the rock at the bottom. The rock creates a new center of gravity that is off center and probably contribbutes to the spin problem.

- fins would prob work, but an easier solution to to attach a long streamer or streamers (cut from a garbage bag?) to the bottom end. This will have the same effect as fins, but much easier to do, and not as complicated at trying to get the fins matched in size and truly in line with the long axis of the firework.

Let us know if you do modifications."

Here is a video with the modifications(we didn't light the fuse) :

As you can see, it didn't really work...maybe it was too windy

Just for fun, we aimed the cannon at 45 degree.

Step 6: Final Thoughts

From here, there are 2 ways to solve the problem.

1. Build somekind of fins on the firework to increase it's stability and preventing it from spinning during launch.
2. Use different fireworks. Instead of using the cylinder ones, we could use the sphere ones which would fit in the barrel. This way there wouldn't be any risk of it firing sideways (since it's a sphere and has no direction duh). The air cannon would provide all the height it needs

If anyone has any other ideas, plz tell us.

In short, it was a fun project.