Crossing the Gap

Crossing the Gap is a free-form robotics activity that requires a minimal amount of setup. It is an excellent choice for novices, but can also present a challenge to experienced students.

One of our after-school robotics classes recently completed this unit – check out the video to see the results!

Our basic lesson outline is as follows:


Build a robot that can safely cross the gap between two desks. The gap starts at 15 cm, and will increase by 5 cm each time your robot reaches the other side.


Two desks (or other movable raised surfaces) and a soft floor! A large ruler should be on hand to set tables to specific distances.

Warning: Robots WILL hit the ground during this activity. Take steps to minimise damage.

Challenge Rules

  • There are no instructions or examples provided.
  • No human assistance is allowed.
  • Students operate with limited parts (a single MINDSTORMS kit) and time (as defined by teacher).
  • All Robots must start ENTIRELY on one table.
  • Robots must cross the gap to reach the other table, then stop without falling off!
  • Robots can use any method to cross the gap.
  • Each student begins the exercise with a gap of 15 cm (approx. 6 inches).
  • After each success, the student expands their gap by 5 cm (approx 2 inches).
  • All students work on their own gap, making individual progress.

Design and Planning

Whilst students are not given instructions for this activity, a teacher can choose to pose the following questions to the help the design process:

  • Where is the robot’s tipping point?
  • Will the robot always need to support both ends during a crossing?
  • Will the robot always need at least one wheel in contact with a table?
  • How can the robot be designed to handle increasing gaps?
  • Will the robot be all-in-one unit, or will it use a tool?


After providing the information above, let the students begin. Teachers should display a countdown so students are aware of the remaining challenge time.

An enthusiastic class will race to see the largest gap that can be crossed!

I hope you find this useful.

Andrew Clark

“Project Bucephalus” Coach

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Coach of "Project Bucephalus", an FLL team from Wollongong Australia. We've been running after-school and school holiday robotics activities since 2010

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