Bridges, Cranes, Robots

After some humble beginnings to the semester (Newton’s Laws, basic structural mechanics, and gear ratios), we have had a string of exciting projects in our middle school engineering elective. Within the last few weeks, students have built railway bridges, designed high-torque crane systems, and are now writing code for simple three-wheeled robots.

Mr Meadth stands watch over the first train journey of the day–all is well!
The Bridge Challenge had students demonstrate their understanding of structural rigidity. The students were told that triangular structures are inherently rigid, and can’t change shape without breaking. They also identified the bridge as being primarily subject to bending loads, in which case it is best to build a bridge that is tall.
(For all you engineers out there, they learned to use a cross-section with a high second moment of area!)

Another bridge with an underslung truss system

Asher and Christine carefully plan out their triangular structures
From here, we looked at the interplay between torque and rotational speed. Anyone who has ridden a bike with gears or driven a manual shift car understands that different gear arrangements really do produce a change in outcome–you shift down gears to pedal up a steep hill. Our middle school students calculated various gear ratios, and also felt the hands-on difference, thanks to Jake’s Educational Design project from last year.

Zach and Isaiah feel the increase/decrease in torque for a 3:1 ratio
The lessons in gears were put to the test in the Crane Challenge, where students used the EV3 Medium Motor to raise as much weight as possible. The structure had to be strong enough to hold the weight (think triangles and rigidity again), and the gear ratios had to be reduced down one or two or even three times. Bottom line: a slower crane is a stronger crane!

Zach and Sam added a few “characters” to their
impressive submission, and were able to
raise 800 grams (almost 2 lb)

Lily and Isabela and “The Giraffe”; they raised
a total of 300 grams

Currently, students are working with a basic robot called the “Robot Educator”. This three-wheeled design is built from instructions, and is for the purpose of learning basic programming skills. The students are learning to tell the robot to move forward/backward, turn around, raise and lower its front trap, and make noises. They are also finding out about loops and conditions and switches, which help make programs more sophisticated. All of this experience will be used later in the semester as the teams design, build, and program their own robot.

Seven Robot Educators, lined up and ready for action!

More to come, so stay tuned!

630 E Canon Perdido St, Santa Barbara, CA 93103, USA

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