TE Activity: Balsa Towers
Contributed by: Techtronics Program, Pratt School of Engineering, Duke University
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The Sears Tower, Chicago, IL |
Summary |
Engineering Connection |
| Students are placed in the role of civil engineers for balsa wood towers in this activity. |
Contents
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| Grade Level: 7 (6-8) | Group Size: 4 |
| Time Required: 2 hours |
Activity Dependency  :Skyscrapers: Engineering Up! |
Expendable Cost Per Group
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US$ 10 |
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| Keywords: Civil Engineering, Structures, Towers, Skyscrapers, Design | |
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Related Curriculum
:
| subject areas | Geometry Science and Technology |
| curricular units | Building Towards the Future |
| lessons | Skyscrapers: Engineering Up! |
Learning Objectives (Return to Contents)
- Students will be able to draw structurally sound 2D designs on paper
- Students will be able to construct 3D structures from 2D designs
Materials List (Return to Contents)
- Markers
- Large sheets of paper (Butcher paper will work)
- Quick drying Epoxy glue (90 second or 5 minute)
- 1/4 x 1/4 inch balsa wood strips
- 1/8 inch balsa wood sheets
- Dremel tool (optional)
- Rulers
- Utility Knives (for students, if possible, otherwise one for the teacher)
- Newspaper (to glue on)
- Scrapwood (to cut on)
Introduction/Motivation (Return to Contents)
The purpose of this activity is to build a structurally sound tower with a favorable strength-to-weight ratio. Students will have to experiment with various designs and come up with what they believe is the best one. One possible technique for building the tower would be to build each side (either 3 or 4) and then attach each side together. Students could also take a ground up approach and build all of the sides of the tower at the same time. Students should discover what shapes are the strongest in the design of a physical structure. A good way to excite the students and make the activity more fun is to introduce it as a contest to see who can build the tower with the highest strength-to-weight ratio. A special note regarding the epoxy glue, it actually has two components: resin, and hardener. A small amount of the resin should be applied to the area to be glued, and then the hardener, to make it dry practically instantly.
Vocabulary/Definitions (Return to Contents)
| Buckling: | When a column fails by bending at some point in the height of the column, usually towards the midpoint caused by a vertical force. |
| Lateral Force: | A force that impacts a structure horizontally (i.e. wind and earthquakes). |
| Deflection : | The amount a structure bends or moves from its "at rest" position. |
| Civil Engineering: | The field of engineering pertaining to non-moving structures such as roads, sewers, towers, buildings, and bridges. |
| Strength-to-Weight Ratio: | This is the ratio of the amount of weight a structure can hold to the mass of the structure itself. |
Procedure (Return to Contents)
- Divide students into groups of 3-4.
- Ask each group to sketch their tower design on butcher paper.
- Distribute supplies, and instruct students on safety techniques. (see Safety Issues)
- Instruct students on how to properly cut and glue two pieces of balsa wood together.
- Ask groups to build the towers on their own.
- If some groups finish early, they may decorate their towers.
- Test each tower to see how much it weighs, and how heavy a load it can handle. In order to test the load, place a flat board on the top of the tower. Then, use masses to carefully place a load on top. Books are useful as testing masses.
Safety Issues (Return to Contents)
Several safety Issues must be taken into account when building the towers. Safety goggles must be worn when students are using the dremel tool, cutting wood with the utility knives, or using the epoxy glue. Also, students or teachers will be using utility knives which are very sharp. They should be warned to cut down, and away from other people and themselves. They must be supervised at all times. The epoxy glue is very strong, and dries very fast. Students should be careful not to get any on their skin.
Note: If there is not enough supervision for students to use utility knives, 1/8 inch square balsa wood strips may be used. These can be cut with scissors.
Troubleshooting Tips (Return to Contents)
If students' towers are weak or not stable, have the students go over each region of their tower and think about how they can reinforce it. If Epoxy glue is not practical, or the students are having trouble with it, super glue would work as well.
Investigating Questions (Return to Contents)
- Which shapes/structures seem to be the strongest while using the least material?
- If you were going to tell someone how to build a strong and light tower, what would you tell them?
Assessment (Return to Contents)
- Did all students participate in the design/construction of the tower?
- How well did the towers perform, compared to expectations?
- What would students do differently next time (did they learn from their mistakes)?
Activity Extensions (Return to Contents)
Host a class brainstorming session in which you ask them what they would tell someone who wanted to build a strong tower and had no idea how.
Other Related Information (Return to Contents)
Site to buy balsa wood and glue: http://www.specializedbalsa.com/
Contributors
Kelly Devereaux and Benjamin Burnham, Primary Contributors, Duke University, Pratt School of EngineeringCopyright
© 2004 by Engineering K-Ph.D. Program, Pratt School of Engineering, Duke Universityincluding copyrighted works from other educational institutions and/or U.S. government agencies; all rights reserved.
Supporting Program (Return to Contents)
Techtronics Program, Pratt School of Engineering, Duke UniversityLast Modified: September 26, 2008