Introduction: Cheap and Easy Pneumatic Rockets
Here's a way to make a launcher for a few dollars and rockets for about two cents each. The launcher is made from 1/2" copper pipe. It is powered by an air compressor. We used shop air at The MakerBarn, but a small pancake compressor would be a good source of power. The rockets are made from a sheet of printer paper. Used print outs and sheets from loose-leaf binders would work well. Kids can make the rockets in just a few minutes, and experiment with different designs to see how well they fly. The rockets are lawnmower friendly.
Step 1: You Need to Scrounge Up Some 1/2 Copper Pipe and a Few Fittings
The key parts are shown above. Copper pipe that is trade size 1/2" is actually 5/8" outside diameter. You'll need about 3 feet of pipe, a 45 degree fitting and a couple of supports. Make sure the pipe in free of dents.
You will also need a block of wood to mount it to, some sort of air valve, and a copper fitting to connect to the valve through a few feet of rubber air hose. You will need a source of compressed air. Air at 80 to 100 PSI would be ideal. Lower pressure would work, but don't go over 100 PSI for safety reasons.
Step 2: Assemble the Copper Components
This is really a scrap box project. So much of the way you build it will depend on your scrap box. The 45 degree fitting elevates the launching tube to a nice angle. You could shoot them straight up using a 90 degree fitting. but it's harder to judge how far they go.
The hose barb was something I found in my scrap box. I think it's off some sort of old carburetor. I turned and tapped a bushing to solder in the tube and screw the hose barb into. The plumbing department at the hardware store should be able to come up with a solution that can be soldered together.
Step 3: Tubing and Valve
I used a four foot length of 1/4" air hose to a foot valve. The foot valve came off an old planishing hammer, but you can find foot valves on eBay and surplus suppliers. A ball valve would work if you could get it loose enough to operate quickly. The kids loved jumping on the foot valve.
Step 4: Now We Make the Rockets
CPVC pipe is the same outside dimension as copper pipe. Copper pipe is used in the launcher because of its strength. As a form to roll the rockets on, CPVC is a bit better because it is light and won't dent when dropped on the floor. Its also a bunch cheaper. You need some sticks of 1/2" CPVC about 14" long.
The body of the rocket is printer paper held together with scotch tape. Blue painter's tape it excellent for making the fins.
The nose of the rocket is plugged with a short piece of 5/8" dowel. Cut the dowels plugs about 3/4" long. The plugs add a little weight to the nose and prevent the compressed air from blowing out the nose.
Step 5: Roll for Rocket Body
Use the CPVC as a form to roll the rocket. Put the dowel nose plug in place and snugly roll the paper. Leave about 1" of paper above the nose plug. Roll the long edge of the paper, so the the rocket is long (11" for letter size). After rolling, secure the body with a few pieces of scotch tape.
Step 6: Shape the Rocket Nose
Crimp the nose and give it a little twist. Secure to nose with some tape. The nose needs to be strong enough to hold the nose plug while under pressure.
Step 7: Make the Guidance Control System (fins)
Take a piece of blue tape about 5 inches long and place the rocket 1/4 of the way from one end of the tape. Fold the tape over and press it against the body so it is close to center on each side. Then trim the fins with scissors to give them the proper shape.
Step 8: Load the Launcher
Carefully slide the rocket on the launch tube. The kids may need help until they learn how to do it. Denting the end of the rocket may make it impossible to slide on the launcher.
Stand back and open the valve. The rockets come off at a very high velocity, so make sure everyone is out of the way before launching.
Step 9: Now There's a Proud Rockteer
Once they get the hang of it, the kids will be able to build new rockets and experiment with various fin and nose designs with a very quick turn around. Some rockets will steak through the air and go over 100 feet. Some will go 10 feet and fall like a dead bird. It's all part of the fun and learning.