Document Type
Undergraduate Project
Date of Degree Completion
Spring 2023
Degree Name
Bachelor of Science
Department
Engineering Technology
Committee Chair
Charles Pringle, PE
Second Committee Member
Dr. John Choi
Abstract
For all of human history, people have been working to increase efficiency. This project followed in that pursuit by forcing engineers to create a 400 mm long bridge out of only balsa wood and glue that could withstand over 20 kgs of force with the bridge weighing a maximum of only 85 grams. The bridge also needed to have a lifting mechanism to raise it 140 mm above the starting position.
To accomplish this task, a strong truss needed to be built. Balsa wood is strong in compression so a truss with more beams in compression was used. Statics was used to determine the stress on each beam in the truss. The beams under more stress needed to be thicker to hold the weight placed on the bridge. Other beams were thinner to decrease the weight of the bridge. Balsa wood strips were purchased, cut down to size using a miter saw, and glued together. The lifting mechanism was created by fixing one end of a string to the bridge and the other to a reel, with a tower between them so that the string lifted the bridge upwards. The parts for the lifting mechanism were all purchased.
After testing, the bridge withstood over 20 kgs before collapsing. The top beams of the truss broke first. The lifting mechanism was also successful and the bridge rose above the required height of 140 mm and did so in less than 10 seconds.
Recommended Citation
Moe, Ryan, "Balsa Wood Bridge Senior Project" (2023). All Undergraduate Projects. 196.
https://digitalcommons.cwu.edu/undergradproj/196