Engineering Challenge: Build a Chair for a Teddy Bear

Engineering Challenge: Build a Chair for a Teddy Bear: Design and build a functional chair using only paper and tape that is strong enough to support a teddy bear (or small stuffed animal). You’ll learn how engineers make things strong and stable with limited materials!

Materials:

• Construction Paper
• Tape
• A Teddy Bear (or small stuffed animal)
• Scissors
• Ruler (Optional)

Plan Your Chair

1. Meet Your Client: Look at your teddy bear. How big is it? How heavy does it feel? This will help you decide how big and strong your chair needs to be.
2. Chair Basics: All chairs need:
   • Legs: To hold the chair up.
   • A Seat: For the teddy bear to sit on.
   • Back Support (Optional but helpful): To keep the teddy bear from falling backward.
3. Sketch Your Ideas: On a scrap piece of paper, draw at least two different ways your chair could look. Consider:
   • How many legs will it have? (Usually 3 or 4, but maybe more for extra stability!)
   • How will the legs connect to the seat?
   • What shape will the seat be? (Square? Circle?)
   • How will you make each part strong? (We’ll learn some tricks for this soon!)
4. Predict: Look at your sketches. Which design do you think will be the strongest and why?
5. Select your design.

Making Paper Strong

Flat paper is floppy. Engineers use methods to make materials stronger.

• Method 1: The Power of the Tube!
  • Take one full sheet of construction paper.
  • How To: Starting from one long edge, roll the paper as tightly as you can into a tube. Imagine rolling a tight scroll.
  • How To: Once rolled, secure the end with a piece of tape so it doesn’t unroll.
  • Test It! Try to stand this tube up. Gently press down on it with your hand. How much weight can it hold? Now, try rolling a loose tube. What’s the difference in strength?
  • Why it works: Tightly rolled tubes are great at resisting “squishing” (compression). Think of bridge supports!
• Method 2: The Mighty Fold!
  • Take another sheet of construction paper.
  • How To: Fold the paper in half lengthwise. Now fold it in half again. Now fold it a third time. The more folds, the thicker and stiffer it gets.
  • Test It! How does this folded piece compare to a flat sheet?
  • How To: Try folding a piece of paper into a “V” shape or an “L” shape. Hold it upright. How much stiffer does it become?
  • Why it works: Folds create “beams” or “columns” that help distribute weight and prevent bending.
• Method 3: Layer Up!
  • Take two or three sheets of paper.
  • How To: Stack them perfectly on top of each other.
  • How To: Use several pieces of tape to stick them together securely all around the edges.
  • Test It! How does this multi-layered sheet feel compared to a single sheet?
  • Why it works: More material means more strength!

Build Your Chair

1. Build the Legs: 
   • Tube Legs: Roll at least 4 (or more if you want extra stability) pieces of construction paper into tight tubes. Make them all roughly the same height (you can trim them with scissors if needed). Secure each tube with tape so it holds its shape.
   • Folded Legs: Try folding a piece of paper in half, then half again, and tape it into a square or rectangular column. Make at least 4 of these.
   • Tip: The wider the base of your legs, the more stable your chair will be.
2. Create the Seat: Consider ways to make the construction paper sturdier.
   • Folded: Fold it in half, then half again to make it a thick rectangle. Or, fold the edges inward to create a sturdy “tray” shape.
   • Layered: Or, tape two or three sheets of paper together to create a thick, strong seat platform. This works well for a flatter seat.
   • Tip: Make sure your seat is large enough for your teddy bear to sit on comfortably.
3. Assemble Your Chair:

1. Place your seat platform flat on your workspace.
2. Take one leg and stand it upright. Carefully tape the top of the leg to the underside of your seat. Use generous amounts of tape, wrapping it around the leg and onto the seat, or folding pieces of tape to create strong “L” brackets.
3. Repeat this for all your legs. Try to space them evenly around the seat.
4. As you add legs, constantly check your chair’s balance. Does it wobble? Adjust the legs slightly until it stands upright and feels stable. Make sure the tape connections are very Loose tape means a wobbly chair!

1. Add Back Support (Optional, but Good for Stability):

1. Take a piece of paper. You can fold it in half for extra stiffness.
2. Tape one long edge of this folded paper to the back edge of your chair’s seat, making it stand upright.
3. For extra strength, you can tape the back support to the back legs of your chair, forming triangles, which are the strongest of shapes!

Part 4: Test, Observe, and Improve!

1. The Teddy Bear Test: Gently place your teddy bear on the seat of your chair.
2. Observe.
   • Success! If your chair holds your teddy bear without collapsing, congratulations! You’ve built a strong chair!
   • Collapse!?! If it wobbles, sags, or collapses, that’s okay! This is how engineers learn.
3. Fix It (Iterate!):
   • Where did it fail? Did a leg buckle? Did the seat sag? Did a piece of tape come loose?
   • How to improve?
     • If a leg buckled, make it a tighter roll or add more layers of paper.
     • If the seat sagged, add more layers of paper, or try folding it differently to make it stiffer.
     • If a connection came loose, use more tape and make sure it’s wrapped securely around both parts.
     • If it’s wobbly, try making the legs spread out a bit wider, or add more legs!
   • Repeat! Make your changes, then test your chair again with the teddy bear. Keep going until your chair holds the teddy bear safely!

Real-Life Correlations: How This Applies to the World Around Us

1. Structural Engineering:
   • Buildings and Bridges: The paper tubes you made for legs are analogous to columns in buildings or the vertical supports in bridges. The flat or folded seat is like a beam or slab. Learning how to make paper strong through rolling and folding directly relates to how engineers choose shapes (like I-beams, trusses, or hollow columns) to make large structures withstand heavy loads.
   • Load Bearing Walls vs. Frames: Your chair is a small-scale example of a load-bearing structure, where the walls/legs directly support the weight. In real buildings, some use load-bearing walls (common in older or smaller buildings), while others use framed structures (beams and columns, like skyscrapers) where the walls are often non-load-bearing partitions.
   • Foundation: Just as your chair needs a stable base, every building, bridge, and tower needs a strong foundation that distributes its weight evenly into the ground.
2. Materials Science:
   • Strength-to-Weight Ratio: You experienced how a lightweight material like paper can become surprisingly strong when manipulated correctly. Engineers constantly consider the strength-to-weight ratio of materials (e.g., aluminum in airplanes, carbon fiber in race cars) to optimize performance and efficiency.
   • Material Properties: You intuitively explored concepts like compression (pushing force, like on the legs) and tension (pulling force, like if the seat tried to rip apart at a joint). Different materials excel at resisting different types of forces. Steel is great in tension, concrete in compression.
3. Design and Iteration (The Engineering Design Process):
   • Planning and Sketching: Just like you sketched your chair ideas, engineers use blueprints, CAD (Computer-Aided Design) software, and models to plan structures before construction.
   • Prototyping and Testing: Your paper chair is a prototype. Engineers build prototypes of everything from cars to consumer products to test their designs and identify flaws before mass production.
   • Iteration and Improvement: When your chair collapsed, you didn’t give up; you iterated – you learned from the failure, identified the weak points, and made improvements. This is a core principle of engineering: designs are rarely perfect on the first try. Failures provide valuable data.
4. Stability and Balance:
   • Center of Gravity: You learned that a wider base generally makes a chair more stable. This relates to the center of gravity. For something to be stable, its center of gravity must stay within its base of support. Think about why a pyramid is incredibly stable, but a tall, narrow tower needs a very strong foundation.
   • Tipping Points: When you leaned your teddy bear on the chair, you were testing its “tipping point.” This is critical in designing everything from furniture to cranes to ensure they don’t topple over under various loads or movements.
5. Efficiency and Resource Management:
   • “How few pieces of paper/tape can I use?” This optional challenge introduces the idea of efficiency. Engineers don’t just want to build strong structures; they want to build strong structures using the least amount of material and energy possible to save costs and reduce environmental impact.

 Extensions:

1. Varying Materials:
   • Cardboard Challenge: Repeat the activity using only cardboard and glue/tape. How does the strength of cardboard compare to construction paper? What new challenges or opportunities does it present?
   • Straws and Connectors: Provide straws and pipe cleaners or clay for connectors. How does this change the design possibilities? This introduces the concept of joints and how they affect overall structural integrity.
2. Quantitative Testing and Measurement:
   • Measure Load Capacity: Instead of just a teddy bear, use small weights (washers, pennies, small books) and count how many your chair can hold before it collapses. Record the data for each design.
   • Measure Leg Strength: Build individual paper tubes/columns and measure how much weight one can hold before it buckles. Then, predict how much a chair with four such legs should hold. Does your prediction match the actual chair’s performance? (This introduces concepts of individual component strength vs. system strength).
   • Height vs. Stability: Build chairs of different heights but similar bases. Which one is more stable? Quantify this by gently pushing the chairs to see how much force it takes to tip them.
3. Specific Engineering Concepts:
   • Truss Structures: Challenge students to build a chair using only paper rolled into tubes, connected in triangles (like a bridge truss). Triangles are inherently strong shapes because they resist deformation.
   • Cantilevers: Design a chair with a seat that extends far out, like a diving board. How do you make the cantilever strong enough not to sag? This introduces the concept of bending moments.
   • Joint Design: Focus on how the pieces are connected. Experiment with different taping techniques to see which creates the strongest joints. How do engineers join different materials (welding, bolts, glue, rivets)?
4. Design Constraints and Optimization:
   • Limited Resources: Give students a fixed number of paper sheets or a limited length of tape. This forces them to be more creative and efficient with their material use.
   • Aesthetics: Add a challenge to make the chair not just strong, but also visually appealing. This brings in elements of industrial design and ergonomics.
5. Ergonomics and Human Factors (for older students):
• Research “ergonomics” and discuss how chairs are designed to support the human body. How would you modify your paper chair to be more “ergonomic” for the teddy bear? (e.g., adding armrests, a lumbar curve).