Balsawood Bridge

 Here is another project that I completed for a course here at RIT. For this one, we were put into groups and had to try and design the most efficient bridge possible. What made this one fun was that we were only allowed a certain amount of materials which challenged us to use our resources wisely. We were provided with three different sized pieces of balsa wood, two were good for beams and the third was meant for gussets at critical joints. 

Bridge prior to testing

Simple concept sketch of bridge

To start with the design process, a concept sketch was made to present to group members to get everyone on the same page.

Bridge modeled in SolidWorks

I was tasked with modeling the bridge in CAD since I was the only one with CAD experience in my group, though very minimal at the time. This model looks very different from the concept sketch but that was to be expected since the concept sketch was to present the general idea of the design. The trusses are positioned the way they are because it allows for them to be in compression when a load is applied at the top which is when the wood and the joints are their strongest. The physical bridge was then built over the course of a few days and I am very happy with out turned out. 

Graph of load testing across the class, my bridge is the green line (#3)

Bridge after testing, failure spots circle in red

Everyone's bridges were tested on a compression testing machine that had a jig to hold the bridges. The bridge spanned a gap of 35 cm and a downward force was applied in the middle of that gap. I am very pleased with how my bridge performed, it ended up supporting a total weight of 503.5 lbf until some of the joints failed. I also found it surprising that the bridge had such small points of failure, for some reason I would have expected it to be more catastrophic. Since the bridge only weighed 116 g its structural efficiency was 895%. I was also proud of the fact that it outperformed any other bridge tested in my class. 

Overall this project helped me teamwork and communication skills, as well as helped me improve on utilizing the engineering design process to accomplish a task. It also allowed for me to get more familiarized with SolidWorks.