Triangle Slinger




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Intro: Triangle Slinger

Inspired by the various Viking Catapult designs, I endeavored to create my own version that is more portable, durable, and easy to build. This design also allows for more adjustable trajectories. Although many of my projects are projectile launchers, this one definitely feels and behaves much differently than a typical catapult.

Like this project? Check out my book: The STEAM Handbook, which has 18 innovative project ideas!

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Step 1: Materials

Per student:

9 skewers
1 milkshake straw
3 rubber bands
1 plastic cup
Projectiles, either corks or balls of tape

Step 2: Make the Frame

Use tape to bundle the 9 skewers into three bundles, each made up of three skewers.
Cut the straw into three equal pieces. Use the pieces of straw to connect the skewer bundles together. Secure it in place with tape.
Form a large triangle and tape it together.

Students are encouraged to try other frame designs! How can it be made stronger? Can it be larger or smaller? Will a square frame also work? What if it's square, but also uses trusses in the corner to support it?

Step 3: Add the Sling

Show students how to make a hitch knot to tie a rubberband to the center of each side of the triangle. Be sure to tighten the knot or else it will come loose.
Use tape to secure the rubberband to the sides of a cup. You may want to put two layers of tape on to prevent the tape from ripping during use.
Finally, use one long piece of tape that attaches to the sides of the cup and accross the bottom of the cup. Tape the tape to itself near the bottom center of the cup to create a simple tab which can be used to easily grasp the cup.

Step 4: Fire!

Launching is fun and easy!
  1. Use one hand to hold the apex of slinger in an upright position.
  2. Load the projectile with your free hand, then use that hand to firmly pinch the tape tab.
  3. Adjust the trajectory by tilting the slinger backward or forward.
  4. Pull back on the cup to store energy in the rubberbands, then release it!

Step 5: Advanced Ideas: Pyramid Slinger and Four-Point Slinger

The pyramid slinger is made of three triangles.

The Four-Point Slinger is made from a square frame rather than a triangular one. The square transforms into a 3D, four-pointed shape by pinching opposite corners together. Two craft sticks support the frame.

Step 6: Safety, Tips and Troubleshooting

Caution! This project can be dangerous! Be sure to reiterate that no one should ever aim the slinger at another student or something breakable. If a student intentionally or accidentally aims or fires the slinger at someone, give that student a warning with a consequence of having the slinger revoked until end of class.
  • This design is very simple with a lot of room for modifications. Can it be made smaller? More rubberbands? What about a pyramid frame rather than just a triangle? Can something sticky be added to the bottom to prevent the slinger from sliding around? What is the best projectile? Encourage your students to experiement and¬†think of improvements!
  • If you are confined to an indoor area, set up a designated launching zone. Have students take turns firing, or have everyone fire at once and retrieve their projectiles at the same time. Setup safe targets to encourage students to aim at a designated area.
  • This design is largely untested, so please report any design flaws that I may have overlooked



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