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For my Senior Capstone project, I was assigned a team to complete development of a hands-on, STEM board game to provide experiential learning of bridge design for high school science classes. As a Phase-2 team, we were tasked with improving the prototype board game made by a previous capstone team, in which two competing players would build a physical bridge made out of 3D-printed blocks connected with embedded magnets. Players would perform load tests on their bridges to earn money and purchase upgraded pieces that could survive heavier load tests. However, the previous team's bridge design was comprised of large 3"x3" blocks, and each block had to be replaced every time it was upgraded, which meant the game materials barely fit into a 10-gallon, 25 lb. bin while providing only enough pieces for two possible players. The bridge was also very strong, at times holding up to 1.6kg before failing, creating a potential safety hazard from falling pieces.
Our team of Mechanical Engineers worked alongside an Industrial Engineering team that edited the ruleset of the board game, while our team focused on developing a new optimized design to replace the existing prototype bridge with a new modular bridge. As project manager, I oversaw all project elements, created a development plan, coordinated with the IE team, experts, and advisors, and created a schedule to meet deadlines. After months of fabrication, iteration, and analysis, we successfully reduced the size and weight of the game components while also reducing the strength of the components by 70%, eliminating the safety hazard during load testing. With our new design, all materials could fit into a normal-sized board game box, weighing only 8.4 lbs., and including enough bridge pieces to allow up to 4 teams of students to play, thus exceeding each of our goals.
Unselected Designs - Modular Bridge & Flexible Bridge Design Iterations:
Our team simultaneously developed three different potential bridge designs, constantly printing new iterations for each bridge to solve problems as they occurred. Below are two design solutions that we decided were not successful enough to be included in the final game.
The Modular Bridge simulated the appearance and function of real-world truss bridges, with magnets connecting the center of members rather than at the joints.
Pros:
Magnetic connections located at members, not joints
Single and double truss upgrades
Cons:
Trusses only strengthen middle of bridge - always fail at the edges
First Iteration
Fifth Iteration
The Flexible Bridge made gameplay more dynamic, as the flexible components would sag during load testing causing the entire bridge to collapse once it passed a critical angle dictated by the end-pillar geometry.
Pros:
Bridge sags under loading, providing visual feedback to the players
Cons:
Torsion on the platforms caused inconsistent failure loads
End-Pillar Iterations
Fourth Iteration
Final Design - Rotating Bridge Iterations:
While the Modular and Flexible Bridge designs had potential, they failed to meet the desired specs for the component upgrades. Instead, the best design was a Rotating Bridge design which used different magnet strengths within each face of a block, allowing blocks to be rotated 90° to a side where the magnets were stronger instead of having to entirely replace each block to upgrade. This allowed us to reduce the number of large components in the box and decrease the block size by 1/3 to only 2"x2" and successfully meet each goal to improve the previous prototype.
V1: Axially magnetized magnets, varying diameters
Issue: Inconsistent connection behavior
V2: Uniform diameter magnets, varying magnet grade
Issue: Strong connections, large strength increase between levels
V3: Details added for intuitive and accessible bridge assembly. Upgrade levels were dictated by introducing gaps between magnets of the same size and strength
Issue: 3D printed gaps had too much tolerance for effective differences in upgrade levels
V4: External gaps (Teflon shims), new end tower design
Issue: Shims fell off easily during play, resolved by using industrial grade adhesive intended for Teflon
Magnet interference tests were performed in Ansys to determine the radius of the magnetic field for each of the magnets in the rotating bridge design, and found to be around .25 in.
Spheres with this same radius were then superimposed onto the SolidWorks model to confirm that no magnets would interfere with each other at any point during gameplay.
Using K&J Magnetics pull force calculator helped us determine which shim thickness would provide the ideal pull strength for the bridge.
To ensure balanced gameplay, we identified the shim sizes which caused the pull strength between magnets to differ by ~50% between each upgrade tier. Also, adding shims between magnets reduced the overall strength of the bridge, improving user safety during bridge failure.
Configuration testing:
It was critical that each upgrade consistently provided the bridge with an increase in strength. Multiple load tests were done for each bridge configuration with the following results:
Level Total: Sum of all block "levels," or upgrades
Load Held: Linear regression with positive slope (18.52) shows bridge strength generally increases with each upgrade
Average Load Held: the mean load held at every level total is greater than the preceding level
Variability in average loads (R2 = 0.83) due to bridge's tendency to fail at the edge piece connections.
Overall, bridge upgrades were consistent on average and there were no cases where an upgrade led to a decrease in strength. It was also found that realistic bridge failure behaviors were replicated, as configurations where the edge pieces were upgraded held greater weight over configurations with upgrades in the center of the bridge.
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