Introduction: Pyramid Catapult
This project is born from the idea of making a mini catapult that doesn't require any glue, but is just as sturdy and high-performing as other designs.
You can find the lesson plan, 1-page project sheet, and more project ideas at STEM-Inventions.com
Step 1: Materials
The Engineering Creation Kit has everything you need for this project and many more from STEM Inventions.
3 milkshake straws (2.5 cut into quarters)
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Step 2: Pyramid Frame
Cut 2.5 milkshake straws into quarters. Pinch the straw piece and insert a craft stick. Repeat until there are 3 straw pieces and 3 sticks connected end-to-end.
Fold the shape into a triangle and connect the ends together.
Peel off a length of tape from the roll without severing it. Wrap the entire perimeter triangle in tape as you peel it off of the roll.
Repeat 2 more times to create a total of three triangles. Arrange them in a trapezoid pattern and tape the edges together in at least two places.
Fold the outer two triangles upwards to form the pyramid. Tape the edge together to keep the pyramid shape intact.
Step 3: Catapult Arm
Lay 5 skewers flat and neatly lined up. Keeping the skewers flat, wrap tape around the skewers in at least two places. Tape a craft stick to the center of the skewer bundle to reinforce it.
Insert the pointed end of the three middle skewers into the remaining 1/2 straw piece. Tape it on.
Lay the skewer bundle inside the catapult and align the straw with the front of the pyramid. Tape the straw to the front edge of the pyramid. This will create a flexible joint which will allow the catapult arm to move up and down.
Attaching the arm to the catapult frame requires a lot of dexterity. Encourage your students to take turns helping each other with this step: one person holds the pieces in place while the other tapes it.
Step 4: Rubberband
Loop a rubberband around the catapult arm, then pull it through the pyramid frame. Stretch the rubberband and pull it over the catapult arm again.
Step 5: Attach the Cup
Place a piece of tape at a perpendicular angle on the back of the catapult arm. Hold a cup near the top of the arm and wrap the ends of the tape to the sides of the cup. Be sure to leave some of the skewers exposed at the top of the catapult arm. Use more tape to secure the cup to the catapult arm.
Step 6: Fire!
Place one hand inside the pyramid frame and firmly press on it. Use the fingertips on the other hand to press down on the end of the catapult arm. Pull back, then release by allowing your fingertips to slide off of the skewers.
Step 7: Advanced Ideas: Collapsible Catapult
Click on the images to read the design notes.
Step 8: Safety, Tips, and Troubleshooting
- If students are having trouble launching their catapult, be sure that they have a little bit of skewer exposed at the top of the arm and that they are launching according to the technique displayed in step 6. It is difficult to launch by grasping the cup or pushing on the middle of the catapult arm.
- Some students may have difficulty forming the pyramid shape. Encourage students to work together: one person holds the shape in place while another person tapes it together.
- Attaching the rubber band can be tricky for some students. You may offer to do this part yourself.
- If the catapult arm is wobbly, check to make sure that the end is securely taped to the bottom front of the catapult
- If the cup is wobbly, encourage the student to apply more tape around all sides and around the catapult arm.
4 People Made This Project!
anandrajchristopher789 made it!- jabacrack made it!
- shaffer74 made it!
- PierceP1 made it!
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13 Comments
Tip 5 years ago on Step 8
The straws in the Amazon link are too wide, the popsicle stick will fall out. McDonalds straws are the right size. Try those
6 years ago
i love this
project!
7 years ago
People seemed to have issues finding straws. Mcdonald's straws were large enough to use.
7 years ago on Introduction
Love this
7 years ago on Introduction
Took me forever to find the straws. I found them at Smart and Final, they have a variety of straws.
8 years ago on Introduction
my final product :)
8 years ago on Introduction
8 years ago on Introduction
I am preparing to do these activities with a group of homeschooled boys ranging from 5-12 years old. The projects look so great and I am very excited! Do you have any suggestions for keeping things moving smoothly? We have an hour to work with the boys and thought we would rotate them through a couple of activities (one being an activity from your site). How do you logistically manage all of the taping and glueing for the younger children? And does it matter what size the craft sticks are? Thanks for your hard work!
Reply 8 years ago on Introduction
Greetings!
One hour is just about the right amount of time for most of these projects. For simpler ones, like the pyramid catapult, I follow this formula: 1. Build the project ahead of time. 2. At the start of the rotation, show how the project works. 3. Explain how it works 4. Explain how to use it. 5. Build a model in front of your students - this is how they will learn how to make it.
For younger students (under 7 years old) you may need to walk them through step-by-step how to build it.
Lastly, the straws I use are milkshake straws. I purchase them from a small business-oriented store, but I imagine that many supermarkets and superstores also sell them.
Have fun!
Reply 8 years ago on Introduction
Thank you so much! Is it okay to use an image from your website on our registration page for our club - provided we cite The Workshop for Young Engineers and include a link to your site?
Reply 8 years ago on Introduction
Yes, that's fine - thanks for asking :)
Reply 8 years ago on Introduction
I also have the question from the previous poster - where do you find straws big enough to fit the craft sticks?
8 years ago on Introduction
I love your projects and am putting together a kit for my son to build some of your projects. But I am wondering where I might find the larger straws? I has never seen them before.