I have made many different rocket launchers but most didn't hold air pressure for a long period of time. This rocket design can hold high air pressure for a very long time.The way it works is by building up air pressure in the tank and when ready you release the pressure into bottle and releasing it to launch the rocket.
You will need:
Two 20 ounce Pepsi bottles
6" of 1/2" pvc
3" of 2" pvc
Some thick gauge wire ( I used the wire from a campaign sign frame )
at least a 3" square of a 2x4
One gallon propane tank
Two threaded 1/2" connectors
1/2" three way "T"
Pressure valve with 1/4" threads (optional)
1/2" ball valve
three way "T" with two 1/2" and one 3/4"
Valve Stem with threads
at least 2" of 2x4
Step 1: making the rocket
You will need two Bottles, one to hold the tank and the other to make a nose cone. There are two ways of making the nose. One is a sharp, pointy tip that is made using the flat middle part of the bottle.
Step 1: cutting the bottle
1. Cut the bottle at the the top part were the cap goes. ( Cut the hardened part with a hack saw.
2. Were the bottles goes smooth cut about and inch below. Look at the picture for a better understanding
Step 2: Balancing
1. Use a quarter in the big hole in the front.
2. Put two pennies on the bottle where the cap you cut off covers
4. Take five pennies and place them evenly
5. Glue all them on (epoxy would also work)
Step 3: Attaching the tip
1. Attach the tip with ether hot glue or epoxy.
Step 2: Making the launcher
The launcher works by slipping the bottle rocket over the 1/2" pvc and is held in place by a pin made with that wire while it is being pressurized.
Step 1: Cutting the pvc
1. Use a hand saw to cut the 1/2" pvc 6" long
2. Cut the 2 pvc down to 3".
Step 2: Making the support holes
1. Take a piece of paper and trace the 2" pvc all the way around
2. Fold it in half
3. measure 5/8" from the center at the top and bottom of the circle on both sides. If you connect both sides they will be parallel to the center line. Make sure it is not perpendicular.
4. Place the 2" pvc on the paper and mark on the pvc were they are on the paper.
5. Measure 5/8" on the pvc from the top part on the line
Step 3: Drill
1. Use a 1/4" drill bit or any bit that is a little bigger than the wire you are using. Drill through the pvc on the X were the two lines meet.
2. I used a dremal to make the holes parallel to the center. Make sure that they are straight because that's were the pin goes through to hold the rocket.
Step 4: putting it together
1. Take your 2x4 and bore it out with a hole saw bit the same size as the inside of the 2" pvc
2. Drill a 7/8" hole with an spade bit on the center of the 2x4. This makes it wide enough for the 1/2" pvc to fit snug.
3. Drill a pilot hole in four places around the outside. (make shire that you have the 2x4 inside it so that they line up correctly and don't split the wood.
4. Put some screws in the pilot holes you drilled THIS IS THE IMPORTANT PART don't screw in the screws all the way otherwise it will break the pressure seal. So once you feel it bite into the pvc STOP. you can grind them off it you don't like them.
Step 3: The pin
I used the wire from the Frame of a campaign poster. You can also use any other wire that can hold its shape.
Step 1: Bending wire
1. Take the wire you choose and cut 9" off of it, bolt cutters work best
2. Mark 3" from both sides, do not bend beyond those lines, they have to be strait because those two ends go in the holes you drilled
3. Bend the wire into a U shape
Step 4: Air tank
I used a portable propane tank. The kind that are used for torches and lanterns. The way it works is by letting the pressure being stored in the tank and not the rocket. The rocket will not hold 80 psi for a couple of seconds but a propane air tank will hold an air tank at that pressure for years.
Step 1: Putting it together
You could choose different ways to put it together I used a pressure gauge, and a valve stem for the air compressor to hook up to.
A propane tank has something that needs to be compressed to allow air flow in and out. Well you don't need that so drill the inside of the propane tank out. Just enough so that the air can flow into it.
Use teflon tape on all the fittings
1. Use a tap and di to make some threads on the 1/2" pvc that is connected to the launcher
2. Screw that into the ball valve.
3. Attach the ball valve to a 1/2" to 3/4" T with male connectors
4. Screw on the propane tank that is the 3/4" female end
5.Drill into the the metal plug that is the same size as the valve stem. then tap some treads that are the same thread as the valve stem
6. On the end that doesn't have a connector put a metal plug that has the treads to screw into the T
7. screw the valve stem into the metal plug.
Step 5: Have Fun
The best working pressure is around 80 psi
If it is not holding any pressure, then fill the pressure up and put soapy water on the fittings.
The bubbles will show wear the pressure is leaking.
Dry off the water and put some JB weld on it. It will hold fine.
I'm not liable for anything you do.