Introduction: Semi-Recycled Cardboard Tube Launcher

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About: I am a high schooler who really wants to be a mechanical engineer. In school I tryhard my school's FTC team in my free time and at home I spend my free time building my random ideas.

I have always loved finding things that are broken and saving the parts of them that still work to use in building my ideas. Because of this I have accumulated quite a few electronic parts that work great but that no one had a use for. I decided a fun way to start with electronics would be to build a simple device to run a flywheel to launch something harmless and plentiful. The cardboard tubes left from toilet paper rolls looked to me like a fun item to launch.

When coming up with this project I wanted my launcher to:

  1. Be super cheap,
  2. Use as many reused parts as possible,
  3. Hold multiple tubes and launch them at a decently fast rate,
  4. Have the circuitry be simple, straightforward, and most importantly, safe.

I designed the whole project in the free version of Autodesk Fusion and it took quite a bit of tweaking to get everything to fit together in the way I imagined it.

Step 1: Gathering Tools & Materials

While most of the launcher is made of salvaged and reused pieces, I used a Lego wheel and Lego shaft for the flywheel and three 3D printed parts to make the whole design work better. Here is the list of the tools and materials I used in the build.

Tools:

  1. Hot glue gun
  2. Screwdriver
  3. Boxcutter
  4. Soldering kit

Materials:

  1. Small DC motor, probably with 600+RPM
  2. Battery with an output that matches the voltage of the motor
  3. A little bit of solder
  4. A few small wires
  5. Small power switch
  6. Access to a 3D printer with PLA filament
  7. Pencil for a shaft (Must be a hexagonal pencil and not round)
  8. Plastic container big enough to hold the barrel WITH the cardboard tubes loaded.
  9. Small box to house the electronics

Step 2: Printing Out Parts

I 3D printed the barrel, my motor mount, and a small adapter to make my motor compatible with a Lego shaft for the flywheel. All these parts are modeled specifically to fit on the salvaged parts I had, so you might have to edit the parts a bit to have them work on different containers and motors.

Attachments

Step 3: Assemble and Test Electronics

The motor needs to be safely secured to the battery with a good way to turn it off and on. This can be done with a simple circuit with a switch that blocks or allows power to flow from the battery into the motor. In order to get the motor to spin the right direction to launch the tubes, you must have it spin counterclockwise if mounted to the left side of the launcher and clockwise if mounted to the right. Test your motor before soldering connections on to make sure you have it spinning in the correct direction. If it is spinning in the wrong direction, swap the connections of the ground and neutral wires on the inputs to the motor. Once everything is arranged, solder on the connections to the motor and power switch. Rechargeable batteries should not be soldered into the circuit so that they can be unplugged and recharged.

Once everything is soldered, connect the motor to a Lego shaft so that it spins with the motor. I used hot glue and the little adapter to secure the shaft to the motor's output gear. Now secure the motor into the motor holder and use a small box to tidy up the wiring and hold the power switch in place. All the electronics should now be ready to go!

Step 4: Assemble the Launcher

Soon you shall have a completed launcher!

  1. Drill a hole in the center of the lid and bottom of the container to fit the size of a pencil loosely enough to let it rotate.
  2. Put a pencil through the hexagonal hole in the 3D printed barrel and put it into the container with the lid on so that the pencil holds the barrel in the middle and rotates it when the pencil is spun.
  3. Using a boxcutter, cut holes in the container so that the Lego wheel can spin freely and come in contact with the carboard tubes as they are rotated up into it. There should be one larger hole to let the wheel not touch the outside of the container and a smaller hole to let the shaft from the motor come in and hold the wheel.
  4. Push the wheel onto the Lego shaft and hot glue the mount so that it stays securely in place, holding the motor in a spot where it can launch the tubes. Be careful not to sever any of the connections.
  5. Cut a hole in the lid of the container where the tubes will come out from, being careful not to cut into the drilled hole for the pencil shaft. The hole must be quite a bit bigger than the tubes to accommodate for rotation of the barrel during launch and inconsistencies in the tubes.
  6. Hot glue the electronics box onto the outside of the container and make sure the lid is secured with everything inside.

Step 5: Test and Use!

With everything assembled and a charged battery, load cardboard tubes in through the shooting hole, flip the switch on, and rotate the pencil shaft. It should rotate the barrel and launch the tubes out of the front. A video of the launcher being operated optimally is attached. If this all works, you now have a fun launcher to confuse your friends and family with!

Step 6: CAD

When originally doing the CAD, I modeled everything around a much smaller container. When I finished printing the parts, I realized that I had forgotten to measure whether the barrel with the tubes in it would fit, and the barrel did not fit in the container with the tubes loaded. While this changed a lot about my final design, this model still helped me a lot because it is what I used to make the parts that I printed for my final design.