Teaching by design

In the winter of 2010-2011, Geometry embarked on several design projects in an attempt to gain experience in applying concepts of Geometry to tangible, real world circumstances. The three projects included a paper airplane design contest, a model bridge building contest, and a planned model dream house design project. At this point in time, two of the three projects have been completed, and this blog will attempt to publicize some of the events that happened along the way. We will begin with the bridge project.

The aim of this project was to draft and build model bridges from limited materials. Students were asked to first produce drawings of the bridges they hoped to build in several views, including a side view, a roadbed view, and an end view. I also participated in the project, aiming to beat out my students in the efficiency category. (Two prizes were awarded- for Efficiency (Load held/Weight of bridge) and for Overall Load Held.)

Students first researched images of real bridges for inspiration, then began the process of drafting plans.

After three periods of drafting, and given approval of their design, students were ready to commence building bridges. Materials for the bridges included standard craft sticks, nylon string, wood glue, and hot glue. Bridge designs were limited to these materials, and the designs had to include a roadbed at least 5cm wide to allow for cars to pass through the bridge.

For my own design, I incorporated a double diamond frame with sparse cross-bridge supports in order to minimize the weight of the bridge. I was counting on the strength of the triangular shapes in the diamonds to form a sort of crystalline rigidity in the finished product. I used string supports on the bottom of the bridge in order to minimize weight and prevent downward bowing of the frame. Here are some images of my bridge, taken during the building process:

You can see the double diamond , composed of four triangles, taking shape in this image:




I used hot glue to assemble the bridge only in the very last steps. (Hot glue is weaker and heavier than wood glue) I hoped that the use of wood glue to bond the vertically oriented structures would pay off in the end.















My finalized bridge is bare bones, but feels very strong when given a quick test by hand.











The class was divided into three groups, so that students could work in a collaborative fashion. Each bridge design was remarkably unique, as you can see in these images taken during the building phase.

Hazaiah and Daisy's bridge included right-triangle trusses below and a decagonal arch above the roadbed.
















Another view of Daisy and Hazaiah's bridge taking shape. Note the string suspension supports hung from the arch.











Adam and Matteo envisioned a complex bridge that included towers on the ends of the wide roadbed, arches on either side, and triangle-reinforced trusses below. Needless to say, hot glue was liberally applied.











Matteo thinks over the placement of the roadbed.













Giselle, Epyana, and Angelica modeled theirs after a Brooklyn- style suspension bridge. Note the rectangular tower supports and the suspension "cables" being strung here.












After two weeks of building, the bridges were ready to go!














A '69 Chevy Camaro was our mascot for the testing phase of the project.
















In most cases, bridges very closely matched the designs drafted by the students.


Following their bridge's collapse, Giselle, Angelica, and Epyana contemplate possible design amendments.














Matteo and Adam's design was so elaborate, they required additional time to finish up. As you'll see in the videos shown below, being behind schedule didn't stop them from taking the prize for Overall Load Held!











The behemoth of all bridges is ready to test!















Please enjoy the youtube videos below that document the testing phase of the project. Don't forget your safety goggles!

http://www.youtube.com/watch?v=iSEAAf1r6rU

http://www.youtube.com/watch?v=j8R-wYwmTC8

http://www.youtube.com/watch?v=Av3ybz535Ww