Introduction: Straw Rocket Launcher - V 1.1
Build a remote controlled, straw rocket launcher with just a sprinkler valve, some PVC pipe and a little electronics.
This little straw rocket launcher specifically launches McDonalds straws. I went with McDonald straws because:
1. They have a larger diameter than most straws which should mean more force when launching.
2. They're free!
A straw rocket can be as simple as adding blue-tack and a couple of paper fins, to going all out with foam fins and weighted heads.
The rockets are launched with a remote but you could also just use a switch on a long length of wire to set them off. The remote however isn't hard to do and I have documented how to use one in this ‘ible.
This is really just a proof on concept. It's too big still and I don't really like how you can see the box with the electronics. I'm already working on the next one which will be more compact and look a lot sleeker.
I also had to change a couple of things as I went along so you might see a few inconsistencies in the images. Overall though I'm really happy how this works, the little straw rockets really get some height!
Check out the video below to see it in action. If the below doesn't work for you, try this link
Step 1: Parts and Tools
1. 1 x 40mm PVC pipe. 220mm length
2. 1 x 40mm cap
3. 1 x 40mm to 20mm reducer
4. 2 x 20mm female threaded couplings
5. 1 x tyre valve - eBay
Air valve and launcher section.
Note: I made a change about half way through the build when I realized the design wasn't going to work. I introduced a 90 degree piece of PVC and couple of female couplings
6. 1 x 90 degree bend 20mm
7. 1 x 20mm male to 20mm coupling
8. 1 x 20mm female to 20mm coupling
9. 1 x sprinkler valve - eBay
10. 1 x length of copper or aluminium tube. Should be able to fit inside a straw.
11. Fuel Air Hose 8.2mm Barb 3/4" Female Threaded Brass Adapter. eBay
Stand and remote
12. 2 x plastic clamps. These are used to hold rain pipes to walls.
13. 1 x Piece of wood to attach the launcher to.
14. 1 x Remote control module
15. 2 x 9v batteries
16. 2 x 9v battery clips
17. 1 x project box
18. 1 x foot or hand pump
19. Various lengths of wire
1. Soldering iron
3. Various screwdrivers, phillips heads etc
4. PVC glue
6. Plumbers tape
7. Hot glue
Step 2: Getting Started - Adding the Valve
Once you’re ready to start sticking the entire lot of pipe pieces together, make sure you lay them out first in the order they go. It will help to make sure that you don’t glue something incorrectly. I did a small change near the end of the build and introduced a 90 degree bend. The reason being the energy of the compressed air wasn't being directed properly and I wasn't getting much lift. The bend allowed the air to flow better and it seemed to do the trick.
1. Drill a hole in the end of the 40mm cap. The hole will need to be big enough to add the tyre valve into. It should be a very tight fit
2. Once you gave the valve in, add some hot glue to the inside section. This will ensure that you have no air leaks
3. Lastly, glue the cap to one of the ends of the 40mm pipe
Step 3: Making the Air Chamber
1. On the other end of the air chamber, glue on the 40mm to 20mm reducer
2. Next glue into place the 20mm coupler to 20mm female piece
3. Lastly glue into place the 40mm cap with the valve on the end
Step 4: Attaching the Chamber to the Mount
It’s up to you how you want to mount the air chamber. I found some drain pipe plastic clamps which worked really well. When mounting the chamber remember that you will need to leave room for the electronics. Ignore the sprinkler valve in the end of the air chamber - I had to change this.
1. Mark out on the wood where you want to mount the chamber.
2. Drill out some pilot holes and measure again to make sure everything’s straight.
3. Place one of the plastic clamps around the 40mm cap and the other around the 40mm reducer. You might find that the one around the cap is a little loose. I just added a small length of foam to the inside of the clamp to make it a tighter fit.
4. Screw into place
Step 5: Adding the Launcher
1. To complete the “neck” of the launcher, glue together the 2 couplings to the 90 degree elbow. Once dry screw into the female end of the air chamber
2. Screw the sprinkler valve to the top of the neck section.
Step 6: Adding the Sprinkler Valve
You might notice that the images above don't all match. That's because I initially had the valve coming straight out of the air chamber. I decided to change this and add a 90 degree elbow to help with air flow
1. Screw the sprinkler valve into the end of the chamber. make sure you use plumbers tape any time you have to screw something in place. This will ensure an airtight fit. If you are using the sprinkler valve that I used and are in Australia then you’ll find that they are a very tight fit. This is because the thread is imperial whist the pipe is metric. They do fit, you just have to use a wrench to turn it once it is half on.
2. The wires on the valve come out to the side. If you want to fix this all you need to do is to unscrew the 4 screws and turn the bottom section 90 degrees. Be careful as there is a small spring inside and it can easily pop out. If it does, don't stress as it's simple to put back in.
3. Next add the section that the actual rocket will launch from. First make sure that the tube is the right size for the straw. You want to have the straw slide easily but at the same time have no slop. The better the fit the better the height you'll get.
4. Attach the piece of copper tubing (I used a piece of aluminium tubing in the end) to the barb on the brass coupling. If the hole is too small in the barb, then you can just drill it out. If you find that the piece of tubing is slipping out, then you can solder into place.
5. Screw the brass coupling to the end of the sprinkler valve.
5. Fill the chamber with air and test everything works
Step 7: Adding the Electronics
This is probably the most difficult section. If however you want to go down a simpler route, then I have included instructions for this as well. If you want to add a remote triggering system, then I’d suggest you visit my “add a remote to just about anything” Instructable and read through that. It has step by step instructions and schematics on how to do it. Actually it isn’t that difficult
Adding a remote
1. Once you have done all of the wiring (see this ‘ible on how to do this) and added all of the bits into a project box, test and make sure you can hear the relay opening. Easiest way to do this is to just hit the button on the controller and listening out for the “click”.
2. Decide where to locate the project box and add some Velcro to stick it down.
3. Next thing is to attach the wires from the valve to the remote wires. I used a terminal so I could easily remove either the project box or valve. You could just solder these together as well.
4. Once attached test again. This time you should be able to hear 2 clicks, one from the valve and one from the relay. Fill the chamber up with some air and make sure that when you push the button, the value opens to release the air. You should also fill the chamber up with air and check for leaks. If you can feel any air coming out or the PSI gauge on the pump goes slowly down, then you’ve got a problem.
Adding a Wired Button
1. Wire-up a couple of 9v battery clips so that they are in series.
2. Grab a small project box and drill 2 holes on either side. Thread the wire from the valve through one of the holes and solder to one of the battery wires.
3. thread a long length of speaker wire through the other hole and solder one end to the other battery clip and the other to the other valve wire
4. Add a push button switch to the end of the speaker wire. Add the batteries and test. If everything works ok then you can add the switch to a small piece of PVC pipe with a cap on the end.
Step 8: Making the Straw Rockets
Straw rockets can be as simple or complicated as you want to make them. The most simplest can just be a straw with a couple of sinkers pushed into the end for weight. Below are a few ideas that I have tied.
1. First you should think about adding some weights to the end of the straw. This will help give you some distance and balance. I used some size 1 sinkers and pushed 3 or 4 down the end. Add some masking tape to the end so its airtight.
2. Next add some fins. I used some fast drying super glue but you could use hot glue or tape. experiment on the sizes of the fins. My fins were quite large and I reckon a smaller fin would work even better.
3. Go crazy with the designs!
Step 9: What Next...
Overall I'm happy with the final product, but I do have a few ideas for improvements! Below are a few ideas I have for version 1.2:
1. Smaller air chamber. The chamber on this version is a little too big. I think I could get away with something half the size and still get the same result.
2. More compact. I think I could easily make this half the size. There are smaller valves available and I would put the electronics into a wooden box that the launcher would be attached to.
3. Wooden box base. Next one I make I'll have all the electronics hidden inside a ply wood box.
4. Little repair kit. I think I'll also include a small repair kit for when your out in the field which would be stored inside the base.
5. LED indicator to tell when when the launcher is turned on
6. Lastly, I'm thinking of making a pistol sized launcher next. Maybe something that can shoot paper airplanes with a straw attached...