STEM | Suspension Bridges and A Tour of SRAM

March 04, 2016

Designing models of suspension bridges The STEM ECS is underway. We learned today that we will be building models of suspension bridges that range from 4 to 8 feet long. If things go well, we will build a larger free-standing temporary bridge to cross the creek behind the Upper School. There are two forces at work with these bridges, compression and tension. We had a contest to see which group could build the strongest tower under compression, and we were allowed to only use 50 popsicle sticks, glue guns, and some wire for joints. The picture below shows us testing the towers with a drill press and a compression sensor. The winning group made the strongest structure with a square base and a pyramid top, which supported 243 Newtons of pressure, or 54 pounds. After this, we assembled back into our groups to plan what suspension bridge we would construct. We googled pictures of bridges and this helped each group create a different design. One group is using an arch for strength, another trusses, and many of us are using a catenary curve to run hangers.

On the second day we visited SRAM, a world leader in bike-part design. Mechanical engineers used custom-designed machines to test parts ranging from suspensions, to seat posts, to frames. We witnessed different prototypes, and also different tests on the Rock Shox. We then saw a design of a rear shock that had been worked on for two years. We learned how just one faulty piece in the shock can make the entire shock worthless. Engineers walked us through the process of computer model design, fabrication in their machine shop, testing and marketing. We were all amazed at the program they have developed to provided over 300,000 bicycles to people in need around the world.

Designing models of suspension bridges
Visiting SRAM in Colorado Springs