University of Southern California The USC Andrew and Erna Viterbi School of Engineering Pre-College Summer Programs - Student Portfolios

Balsawood Bridge

Dimensions of the bridge

  • Driving surface must be a distance of 4ft.
  • Bridge will have span two standard tables placed 3ft apart
  •  The clearance under the bridge will be a minimum of 1ft from the table over the entire open space between tables
  • The minimum width is 1ft
  • Bridge to be composed only of 144 balsawood strips (1/8” x 1/8” x 36”), 15 balsa wood planks (1/8” x 3” x 36”) and 15 hot glue sticks
  • Will support a Vex car carrying 3 standard red bricks


Vex Car

  • Will be driven by remote controller
  • Size to be determined by students
  • Must be able to drive the length of the bridge, turn around and return in the other lane
  • Must be capable of carrying 3 standard red bricks.


Essential Questions

  • How can geometry affect the distribution of force?
  • Why are safe, stable and strong not sufficient for designing structures?
  • How can the motion of an object change how forces are applied on a structure?


Students will be able to answer the following questions:

  1. When does a support structure actually add support or additional weight?
  2. Would I drive my family over this bridge in 25 years?
  3. Why must mechanical engineers consider outside factors in addition to design specifications in designing machines such as cars?


Students should be able to:

  • Distinguish between civil engineering and architecture.
  • Use calculations to determine tensile and compressive forces in order to construct stable structures
  • Optimize size and strength factors in designing the test ROV


Students will know:

  • How to represent forces with vectors
  • How to calculate forces acting on sections of the bridge
  • That trade-offs between distribution of weight on the ROV and size limitations of ROV will affect their bridge design.
  • How to build a bridge
  • How to relay their knowledge to architecture students in different contexts.
  • How to coordinate between ROV builders, bridge designers/builders and architects