Cantilever Beams with Spaghetti

Objectives

Upon completion of this activity, students will be able to:

• Describe examples of cantilever beams in the transportation engineering field.
• Have a better understanding of how cantilever beams function and are supported.
• Learn that engineers need to work within a budget.

Background

A cantilever beam is a projecting beam or member supported at only one end.  There are many different examples of cantilever beams.  In Transportation, examples include:

• Illumination light fixtures
• Mast-arms for traffic signal lights
• Cantilever traffic sign supports

Ask the students what other things are cantilever beams.  Possible Answers: flag pole, basketball hoop, tree limb, etc.

Materials Needed

Spaghetti, Scotch tape, Scissors, Measuring tape or yard stick

Procedure

Students work in groups of 2 to 4 (3 preferable) at a table or desk.

The goal is to build the longest/ least expense cantilever beam possible, as measured horizontally from the edge of a table/desk.

• Each group’s initial supply is 1 foot of tape and 15 pieces of spaghetti.
• “Initial Cost” $20 ($1 for each piece of spaghetti and $5/foot of tape). If the students want/need more than that, it will “cost” them that much for the extra supplies.
• If the students don’t use all of the supplies, they are “refunded” half of the amount of the initial cost (i.e. 50 cents for each piece of spaghetti).
• The beam cannot touch the end of the table. A support should be built to anchor the cantilever beam in order for the beam to be elevated over the top edge of the table. The support is allowed to be anchored to the end of the table.
• The beam cannot touch the ground.
• A TRAC member measures the horizontal distance to the end of the beam from the edge of the table.

• TRAC members award the best designed beam based on least expensive/longest beam.
• The TRAC team had a few examples of their own to compare with the students. The students did not see the examples until they were finished.