I used sheet metal and some lightweight 2'x4's to construct the wall, and have embedded small magnets into each marble run component so that it can be easily placed and moved around the wall. While these components would work fine with PVC, cardboard or other material, since we have access to 3D printers and design software, this seemed the more enjoyable option. I have experimented with a few models using 123D design and our Taz 6 printers, and in the fall will work with my 7th grade technology students to fabricate 3D components of their own design.
My challenge for next year's students will be to design their parts in such a way that as a team they must build a run that will last at least 10 seconds on the wall from top to bottom. Components will be assessed on the basis of creativity, marble run duration, and a minimal use of material.