Students get medieval with custom-built trebuchets

Nov 3, 2017

By the end of Samuel Brodsky’s engineering class, the baseball field at Dartmouth High School was littered with shattered pumpkins and craters created by bowling balls.

Both were fired by trebuchets – medieval catapult-like siege weapons historically used to fire projectiles over long distances in times before gunpowder and cannons were in use. Students in Brodsky’s class spent weeks perfecting the designs of three devices before taking them out to the baseball fields and testing them out.

Instead of projectiles used on the battlefield, students loaded pumpkins onto the sling and fired them into the air. Of the three teams of students, however, only a few had success with their creations.

Logan Bosworth, Charles Gamache, and Owen Sherman’s trebuchet did successfully fire a bowling ball, but the 83-foot distance was nowhere near the school record of 121 feet and the 97 feet the group achieved in a practice run the day before.

“Today we hoped to break the record, but our [trebuchet] didn’t survive,” Bosworth said.

After reviewing video footage of their semi-successful launch, Bosworth was able to diagnose the problem – the supports weren’t long enough, and the heavy weights used on the device struck and demolished half of the trebuchet upon swinging back. It ended the team’s plans to try again.

Oksana Pimentel, David Pimentel, and Ryan Taylor’s trebuchet failed mid-launch, sending a pumpkin flying backwards before shattering several feet behind the machine. During a test-fire the day before, David said the trebuchet collapsed under the weight of the launch, in part because their unit lacked wheels.

“Since we didn’t have wheels it flipped over [yesterday],” David said. Oskana added that there weren’t enough pre-fabricated wheels left for her team, and creating them manually would have been a time-consuming process.

Olivia Chesney and her team, however, managed to keep their trebuchet relatively intact after launching a large pumpkin 196 feet down the field. She said the design inspiration came from a film she watched in class. The team settled on a triangular structure owing to the ability to handle heavy weight evenly across the structure.

Students in Brodsky’s introductory-level engineering class start out by building smaller-scale models in class. By the third level of his class, he challenges his students to design and build working trebuchets capable of launching pumpkins, and dedicates a day of class time to testing them out. In the past, he’s had students build catapults, but they weren’t able to launch pumpkins that far and could be dangerous.

“There’s a lot more engineering involved in trebuchets,” Brodsky said. “There’s a reason they changed the battlefield.”