Engineering intro class stages mini-pumpkin chuckin on the Bardeen Quad

To make their introductory engineering classes more interesting and “hands-on,” engineering instructors added an ancient weapon to their arsenal: The trebuchet.

Assistant Professor James Allison and his graduate students in the Department of Industrial and Enterprise Systems Engineering (ISE) developed table-top trebuchet kits using SimMechanics software and proposed implementing the project in the General Engineering 100 (GE 100) class taught by Lynnell Lacy.

When Lacy first took over the class three years ago, the freshman seminar course lacked active student participation.

“We wanted to make sure that we gave them an opportunity to do something that would excite them about engineering,” Lacy said. The trebuchets, built this summer by Allison and his students, were three feet long, one foot wide and two feet tall, with a three-foot-long throwing arm. The projectiles are made from orange modeling clay, weigh 30 grams, and are about the size of a golf ball. They were intended to resemble miniature pumpkins.

“If it weren’t for Professor Allison and his grad students, this particular project could not have come to fruition,” Lacy said. “They really did a great job building the kits and making them available so the students could work on the design component.”

For the trebuchet project, the GE 100 class was divided into 30 groups of about five students each. Over the last few weeks, the students tested the trebuchets in a preliminary launch, ran a simulation using MATLAB software to determine their optimal function and then modified the individual units — adjusting launch angle, fulcrum position, and sling length while also deciding whether to attach wheels on the bottom of the trebuchet — for the best results.

“They got some experience in how much faster it is using a model to tune a design versus a physical prototype,” Allison said. “Now the students have come out using the knowledge they’ve gained from using the model to adjust and update their designs,  and it looks like a lot of the groups are getting much better results than they did last time.”

The project offered students the opportunity to learn the value of using computational models in design projects while also allowing them to work on teammate work and communication skills.

“I think it’s fun,” said Kelsey Roberts, freshman in general engineering. “Just the concepts of designing and testing it and optimizing its results.”

After running the simulation with MATLAB, Roberts and her group members added wheels to the bottom of the trebuchet and adjusted the fulcrum position to make the arm longer and improved their results for the final launch.

“Ours went almost backwards last time,” she said. “This time it went 90 feet!”

With the class only being offered in the second half of the fall semester, they decided on the trebuchet project, modeled after "pumpkin chuckin'" competitions to fit the fall theme. While the weather for the inaugural launch was 45 degrees and sunny with minimal winds, that won’t always be the case for late November in Illinois, so Lacy is hoping they can secure an indoor location with the proper height and distance for future classes.

“I would love to continue it,” she said. “I don’t see any reason not to.”