Tower O’ Power: Strength-to-Weight-Ratio Competition
Figure 1. Students ready to test their CAD tower
In this activity, students learn about creating a design directly from a CAD (computer-aided design) program. Teams design towers in CAD and manufacture the parts with a laser cutter. A competition determines the tower design with the best strength:weight ratio. Students also investigate basic structural truss concepts and stress concentrations. Partnership with a local college or manufacturing center is necessary for project completion (testing).
Engineers often revise a design in a computer modeling program many times before finalizing the project. Many CAD (computer-aided design) programs can be used in conjunction with other programs or equipment to mathematically replicate the effects of loads on structures or to machine prototype parts from a variety of materials. Engineers must balance many different constraints and parameters when designing parts and structures. A solid bar is almost always stronger than an I-beam of the same size, but is also heavier and more expensive. Often, engineers redesign to make it lighter and/or more cost effective without sacrificing too much strength .
After this activity, students should be able to:
- Define a stress concentration.
- Describe what geometrical shapes influence higher stress concentrations.
- Use calculations to determine a strength vs. weight ratio of a prototyped tower.
- Explain why engineers do not always use solid pieces of materials in design.