Building Lab, Part VI: Geodesic Domes:Triangles, Toothpick Structures and Dowel Designs

Have kids form domes by bending a few sheets of newspaper into a bowl shape. They will quickly note that the domes cannot support much of a live load. 

Which shape is more stable, a triangle or a square?

What shapes do you think would make the domes that are the most sturdy and support the most load? Guide your students into discovering that triangles are the most stable shape by building them. Help them to understand that this is so because compression acting at one joint is balanced by tension along the opposite side.

Making Structures out of Toothpicks and Gumdrops.

Have your students begin building a bridge (without trusses) by constructed a rectangular box of toothpicks and gumdrops. Test the bridge's stability by pressing down on it and wiggling it, Is it stable?

If not, challenge them to add more materials to strengthen the box with trusses. A truss is a rigid frame composed of short, straight pieces joined to form a series of triangles or other stable shapes. They can add cross-pieces and triangular braces.  Next, have your students extended their trusses to see how wide a gap they could make that still could be stable. 

Finally, have your students build miniature geodesic domes using the gumdrops and toothpicks. 

After the lesson, I let them go whichever way they wanted to with the materials and they had a wonderful time being creative and their structures just kept on growing!

What's the strongest dome you can build out of newspaper?

The Power of Buttresses

A dome is a curved roof enclosing a circular space. It is a three-dimensional arch. How can  you strengthen a dome?

Have five students stand in a circle around a ball, placing their fingertips on t he ball and lifting it towards the center of the circle, sliding back their feet. Reach into the center and push down gently on the ball. Ask your students where the dome could use more support. They may come up with the idea themselves, but if they don't, have a student sit at the feet of each student in the dome, around the outside edge, forming a buttress. As in an arch, the buttresses exert an inward force on the sides of the dome that balances the outward force created by the load pressing down on the top of the arch.) 

Making a Paper Geodesic Dome

A geodesic dome is a dome formed by joining triangles together. You can build a giant geodesic dome out of newspaper. First, gather some friends or family members to help you.

What You Will Need

• many newspapers

• masking tape

• measuring tape

Have your students predict how many magazines you think your newspaper dome will be able to support.

A dome must support its own dead load as well as the live load of wind, rain, snow, or ice. The geodesic dome's strength is due to the fact that triangles, as we have seen, are very stable shapes. The geodesic dome's design distributes loads over all of the different triangles within its design.

The task of this week was to build a structure that would stand out of newspaper and tape only. The dowels are just made from newspapers rolled up and taped together.

How strong is your dome? Did the results surprise you? Why or why not? What was the hardest part about creating the dome?

How could you make your dome stronger without interrupting the space underneath it? Make a prediction and test it. 

Sources:

GEMS: Build It! Festival
Kindergarten-6
9 Activities
224 pages
A wide assortment of classroom learning station activities focus on mathematics relating to construction, geometric challenges, and spatial visualization. Activities connect to the real world and potential careers. Free exploration sets the stage for such mathematical challenges as Create-A-Shape, Dowel Designs, Polyhedra, Symmetry, Tangrams, and What Comes Next? Background on geometry is provided. Special materials required include pattern blocks and polyhedra. Template patterns for folding and constructing shapes and creating tangrams are provided.