2 Liter Bottle Rocket Launcher

 

Materials

Note: Many measurements are approximate and can be varied. Materials were purchased from Wal-Mart and Lowes at a total cost of approximately $25 - $30 (tools were not purchased).

Set-Up

  1. Use a hacksaw to cut the steel bar into two 1-foot pieces and one three-inch piece.
  2. Mark the drill holes in the steel and wood as shown in the diagrams above. Note that the diagram is for a piece of wood that is 1 foot by 2 feet. You may need to adjust the intervals if your piece is a different size, but keep the spacing between the center holes the same.
  3. Drill the holes with the following bit sizes: pivot holes (4) - 1/4", compression spring holes (2) - 1/4", string attachment holes (2) - 1/8" (note that these are slightly off-center), anchor holes (4) - 3/8" or other depending on your spikes, wood screw holes (4) - 1/8" or other depending on your screws, air inlet hole (1) - 1-1/8". It will probably be difficult to find a drill or bit big enough to make the air inlet hole. To make the hole without a large drill bit, trace around the large end of the PVC elbow to make a circle where the air inlet hole should be. Then drill several holes within this circle so that most of the wood is removed. Finally, use the file or sandpaper to make the hole smooth and big enough for the PVC elbow to fit through.

Assembly
Release System

  1. Use the wood screws to attach the two 2"x2" wood supports to the bottom of the bookshelf piece as shown in the diagram.
  2. Place two of the 1/4" bolts into the pivot holes in the wood such that the threaded ends stick out the top. On top of these threaded ends place the following items in order: metal pipe piece, steel bars (through the pivot holes on the bars and with the string attachment holes toward the outside), washer, and wing nut.
  3. Place the other 1/4" bolt through the spring compression hole in the wood so that the threaded end sticks out the top. Place the following items in order on top of the bolt: compression spring, washer, 3" steel bar, and wing nut.
  4. Place the eyebolts near the edge of the wood piece so that when the steel bar is swung outward the string attachment holes are next to the eyebolts. You may need to use a nail or drill to start the holes.
  5. Tie one end of the string through the string attachment hole in one of the steel bars. Thread the string through the closest eyebolt, then the other eyebolt, then attach the string to the other steel bar through the string attachment hole, as shown in the picture.

Pressure Hose

  1. Put the small end of the PVC elbow into one end of the flexible hose. You may need to use soap to lubricate the hose or heat to expand it. Secure the hose with a hose clamp.
  2. Place the large end of the tire stem valve into the other end of the hose. Place a hose clamp slightly ahead of the tire valve bulge and tighten it.
  3. Put the small piece of PVC into the large end of the PVC elbow and push it in as tightly as possible.
  4. Place the PVC elbow through the air inlet hole so that the hose is on the underside of the launcher. Secure the hose to the bottom using the hose strap and small wood screws. It may be necessary to secure the hose with a second hose strap directly under the male PVC elbow to prevent high-pressure blowout. When constructed, the 1/2" PVC pipe that the bottle will fit over should NOT be able to be pressed downward under the air inlet hole of the main board.

Air inlet hole

  1. If you do not have a pre-made neoprene washer, cut the piece of neoprene into a washer with an outer diameter of 2-1/2", and an inner diameter of 5/8". Do the same with the piece of rubber.
  2. Check to make sure that washer(s) fit snugly over the PVC piece sticking out above the air inlet hole. You should have to stretch the washers to get them around the pipe. Remove the washers.
  3. Apply contact cement to an area about 2-1/2" around the air inlet hole. Place the neoprene washer around the PVC pipe and onto the bookshelf piece. If you have two washers, first put down the neoprene piece, then apply a lot of contact cement to the neoprene piece and put the rubber washer on top. Make sure that the washer(s) lie flat and are secure. Let the glue set overnight.

Launch

  1. Put a spike in each of the anchor holes and use the hammer to secure them into the ground. Attach the bicycle pump to the tire valve stem.
  2. Check to make sure that the opening of your empty 2-liter soda bottle will fit over the PVC pipe. It should be a close fit, but some bottles are irregular and may not work.
  3. Add varying amounts of water to the bottle (0% to 100% full). Quickly turn the bottle upside down so that the neck is over the air inlet hole.
  4. Pivot the 1' steel bars inward so that they go over the bottle lip and under the 3" steel bar.
  5. Tighten the wing nut above the compression spring to secure the bottle and make a tight seal.
  6. Using the air pump, increase the pressure in the bottle to about 40 psi. Be sure that nobody is above the bottle, then pull the string to remove the steel bars and thus launch the rocket.
  7. Observe the motion and record your results.

Note: The industrial specifications for the pop bottles maintain that the bottles can withstand 180 psi. For maximum safety, do not exceed 90 psi.