This project has been one of the most popular on Make, but no one, so far, has had the thought of making the compressed air launcher remotely controlled.
Anyway, this is the last module I've built, in order to use all the possible ways to launch nearly anything: rockets (water, solid fuel) and compressed air projectiles, using the same launch pad.
Thanks to the different modules previously built, I can launch a water rocket, a pyro rocket and a compressed air projectile (sorry, technically It's not a rocket).
BE safe!!! Do not inflate the compressed air chamber at more than 40psi. This pressure is more than enough to launch foam made projectiles.
Do not point the projectile toward people, animals or properties.
Step 1: Shopping List
1x Male Gardena connector
1 Soap Dispenser Top (which has the same thread of the sPET oda bottle)
2x PET soda bottle 500ml (the surface of the cyclindrical part of it, has to be smooth)
1x water bottle thread to 1/2 inches adapter
1x 1/2 inch DC 12V 250mA Electric Solenoid Valve Flow Switch
1 relay 1 channel
1x adapter 1/2 inches Female to 3/4 inches Male
1 Speedfit PVC connector 3/4 inches Female to 22mm pipe
1x PVC pipe (approx 25 cm long) - Diameter 22mm
8 zip ties
3x3grams Loctite Powerflex
1x PP3 9V battery, or a Lipo Battery 11.1V (it works even with 7.4V)
1 Female connector for the PP3 9V battery, or a Female JST connector
Electrical wire (20 cm)
4 3x15mm screws for wood
White Painting (water based)
wrench for plumbing
utility knife (Please use it very carefully!!!)
Step 2: Make the Compressed Air Chamber
Basically you have to build a sort "water rocket", using the splicing technique perfectly described by the video of Air Command Rockets.
Cut the bottom of 2 PET 500ml bottles and glue them together, using a Loctite Powerflex Superglue.
Insert one part inside of the other one. Before gluing the parts, you should sand the internal part of one and the external part of the other one, to obtain a better grip.
Once you have finished this operation, clean all the dust created by the sand paper, using a paper towel. Try the fit first, and if it's snug enough, glue the 2 halves together, overlapping the surfaces of the bottles by (at least) 5/6 cm.
Wait 24 hours and wrap the joint using the duct tape.
Attach the Gardena connector to one of the side of the compression chamber.
There are plenty of tutorials on Youtube about how to make a Gardena connector for Water Rockes and you can even download the 3D drawing for free, from US Water Rockets to print it by yourself.
The Male Gardena connector will allow you to slot this module into the previously made PVC launch pad for water rockets.
In this way you can use the same launch pad for water rockets, pyro rockets...
and last, but not least compressed air projectiles.
Once you have made the compression chamber, you can paint it.
Step 3: Connect All the Adapters
Start to screw the connector attached to the thread of the PET soda bottle and to the solenoid valve.
Use a wrench to tighten all the connectors.
I'm very sensible to the health & safety, therefore I've decided to create 2 eyelets using 4 zip ties to keep the compression chamber, attached to the solenoid valve, even in the unfortunate even the thread of both will fail. Attach one zip tie to the collar of the soda bottle and another one to the solenoid valve.
Do not tighten the zip tie too much (especially the one you put around the collar of the PET bottle).
Now slide 2 zip ties securing the collar of the bottle to the solenoid valve.
You can wrap PTFE tape around the thread to seal the thread properly.
Now you have to connect the adapter 1/2 inches Female to 3/4 inches Male, in order to attach the Speedfit PVC connector 3/4 inches Female to 22mm pipe.
Again, use the PTFE tape to wrap the thread.
Slot a piece (25cm long) of PVC pipe 22mm inside the Speedfit connector (this is going to be your launch tube).
The launch pad must be secured to the compressed air launcher at all time, therefore you must create 2 eyelets using 4 zip ties, in order to secure a carabiner that keeps the launch pad and the compressed air launcher safely attached. You should never inflate the compressed air launcher at more than 40psi/2atm.
Using this safety feature, even if the unfortunate event the Female Gardena connector will fail, the compressed air launcher will stay in place.
Step 4: Wiring the 1 Channel Relay to the Solenoid Valve
Please follow the schematic to connect the remote controlled relay, the solenoid valve and the Lipo battery.
There are 4 screw female thread on the solenoid valve, therefore using 4x 3mm wood screws you can attach easily the relay to the the valve.
Use 2 zip ties to attach the battery to the case of the relay.
Connect also the Female pp3/jst connector to the relay.
In this way you can plug and unplug the battery, when you need to change/recharge it.
Step 5: Make/Buy Your Foam Projectile
The foam projectiles are so inexpensive, you can even avoid to build your own one.
The diameter of the launch tube is (more or less) the same, therefore you can fit foam projectiles made by different Companies...
If you'd like to make yours, using a water bottle, you should sand the interior part of the collar (1mm), otherwise the 22mm PVC pipe will not fit.
Step 6: Confused? Take a Look at My Previous Instructables
For the launch pad, please take a look at my Instructables competition finalist
"PVC Water Rocket Modular Launch Pad With Gardena Connector"
If you'd like to use my PVC Water Rocket Launch Pad to launch Pyro Rockets, please take a look at my Instructable:
Again, using the different modules, you can launch nearly everything... just slot into the launch pad your favourite one and have fun!