Teeter-Totter Test
Exercise: Teeter-Totter Test¶
Objective: Demonstrate how weight distribution and torque affect a robot's stability.
Materials Needed:¶
- Assembled B3D1 robot (or chassis-only if unpowered).
- LEGO weights (e.g., bricks, metal coins, or clay).
- Fulcrum base (e.g., wooden block, ruler, or 3D-printed pivot).
- Ruler/measuring tape.
Step-by-Step Instructions:¶
- Setup the Teeter-Totter (10 min)
- Place a ruler or flat plank over a fulcrum (e.g., wooden block).
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Position the robot horizontally on the plank.
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Baseline Balance Test (10 min)
- Observe where the robot balances naturally without added weights.
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Mark the center of gravity (CoG) with a sticker or pencil.
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Weight Adjustment Experiment (20 min)
- Attach LEGO weights to different robot parts (front/back/sides).
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Test how each modification shifts the CoG:
- Example: "Add 50g to the robot's head – does it tip forward?"
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Torque Calculation (Advanced, 10 min)
- Use formula: Torque = Weight × Distance from Fulcrum.
- Compare torque values for different weight placements.
Example Scenarios¶
| Weight Placement | Effect on Balance | Torque Calculation |
|---|---|---|
| Back legs | Tips backward | 50g × 5cm = 250 g·cm |
| Front legs | Tips forward | 50g × 8cm = 400 g·cm |
Key Learning Outcomes¶
- Balance: Understand how weight distribution impacts stability.
- Torque: Learn how force × distance creates rotational effects.
- Design Insight: Optimize payload placement for real-world robots.
Differentiation for Ages¶
- Ages 11–13: Focus on qualitative observations (e.g., "heavier side tips down").
- Ages 14–17: Calculate torque and graph results (torque vs. distance).
Discussion Questions¶
- "Where should you place a heavy sensor to keep the robot stable?"
- "Why do construction cranes have counterweights?"
Assessment¶
- Submit a diagram showing CoG shifts and explain findings.
Extension Activity¶
- Design a LEGO "backpack" to keep the robot balanced on a slope.