Building your own water bottle rocket launcher is a hands on way to learn the scientific principles of volume, air pressure and propulsion while having fun. An overhead launcher is safer than one launched at ground level as misfires are less likely to hit nearby spectators. Materials required for the project are available at your local hardware store and some of them you may already have around your home. Adult supervision is required to safely assemble and launch your water bottle high above the rooftops in a cleared space.
- Skill level:
- Moderately Challenging
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Things you need
- 10-foot-long piece of PVC 1/2-inch pipe
- Measuring tape
- 1/2-inch PVC tee
- Two 1/2-inch PVC end caps
- 2-inch long scrap of PVC 1 1/2-inch pipe
- Electric drill
- 1/2-inch bit
- Small piece of scrap wood
- Valve for a tubeless tire
- PVC pipe cleaner
- PVC pipe cement
- Duct tape
- Nine 8-inch cable ties
- Clamp for 1 1/2-inch hose
- Two empty 2-liter soda bottles
- Exacto knife
- Bicycle pump with air pressure indicator
Measure and mark three lengths on the 10-foot-long piece of 1/2-inch PVC pipe. The pieces should be 2 inches, 18 inches and 78 inches. Cut the three lengths of PVC 1/2-inch pipe using a hacksaw.
Fit your electric drill with a 1/2-inch bit. Hold one of the PVC end caps steady over a scrap piece of wood using your pliers. Drill a hole through the end cap and into the scrap of wood. Reverse the drill and pull the bit back through the end cap.
Remove the screw cap from your tire valve. Slide the valve through the hole you just drilled in the end cap. Screw the valve top back on. Grip the valve with your pliers and pull it until it sticks through the end of the PVC end cap and rests firmly there.
Clean the outside of the pipe and the inside of the fittings with PVC pipe cleaner. Glue the connections together using PVC pipe cement. Assemble in the following order: solid end cap, 18-inch pipe, tee, 78-inch pipe and the 2-inch piece connected to the tee leg. Hold the parts together as you go to allow the cement to set.
Mark your assembled pipe 11 inches from the long open end. Light your candle and hold the flame at the marked spot until the pipe softens. Push the pipe from both sides until a slight bump or bulge forms. Hold the pipe straight until the bump rehardens.
Slide a 2-liter soda bottle over the end of the pipe and pull it tightly over the bulge. Wrap the nine 8-inch cable ties around the pipe so that the tie heads hold the bottle tight to the bulge. Tape the cable ties together with duct tape. Keep the cable ties in place by tightening your hose clamp around the duct tape.
Cut the top and bottom off a second 2-liter soda bottle using scissors to create a pliable tube. Cut a 1 1/4-inch hole through two opposing sides of the tube with the exacto knife. The tube will act as a spring to hold the trigger.
Drill a small hole in the side of the 2-inch scrap piece of 1 1/2-inch PVC pipe. Measure and cut a 4-foot piece of twine. Thread the twine through the small hole and secure the end with a knot.
Slide the plastic tube spring onto the pipe, over the cable ties and up to the pipe clamp. Slide the 2-inch piece of 1 1/2-inch PVC scrap over the pipe and cable ties. Thread the twine through the 1 1/4-inch holes in the tube spring. Tape the other end of the twine to the pipe using duct tape.
Rocket Launcher Assembly
Fill a 2-liter bottle 1/3 full of water and slide the bottle on to the end of the pipe.
Pull the twine so the bottle rests against the bulge and the cable ties catch the lip of the bottle.
Release the twine so the trigger slides back over the cable ties and holds the bottle ready for launch.
Attach a bicycle pump to the valve jutting out of the tee. Pump until the pressure indicator reaches 70 psi.
Point the launcher straight up. Pull the string to achieve blast off.
Tips and warnings
- You can make your rocket more aerodynamic with the addition of hot-glued plastic side fins and a styrofoam nose cone.
- Pump no more than 31.8 Kilogram per square inch into the launcher. Too much pressure can break your launcher or cause a dangerous misfire.
- Launch your rocket only when a responsible adult is present.
- Use PVC pipe cement in a well ventilated area to avoid over exposure to harmful fumes.
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