Professor William Campbell built a trebuchet in his basement workshop during stay-at-home orders, figuring, “Why should the mad scientists have all the fun?” (Aimee Obidzinski/University of Pittsburgh)
The trebuchet—a catapult with a counterweight—is four feet wide, six feet long and 13 feet high. (Aimee Obidzinski/University of Pittsburgh)
The Sept. 15 Clusterchuck event featured flying fruits and vegetables for fun and more official weights for the actual demonstration. (Aimee Obidzinski/University of Pittsburgh)
Up, up and away (for now). (Aimee Obidzinski/University of Pittsburgh)
Women’s soccer player, History Club president and senior Kiara DeVore helped measure the distance of the objects flung from the trebuchet, called Delapidator. (Aimee Obidzinski/University of Pittsburgh)
“This is fun,” said Alexis Martir, an information technology student, as she watched the heaviest weight soar through the air. (Aimee Obidzinski/University of Pittsburgh)
History Professor’s Far-Flung Fun Brings Students Together
Place your bets: Will a cantaloupe, cabbage or grapefruit launch farthest in a homemade trebuchet? Students at the University of Pittsburgh at Greensburg recently found out with the help of history instructor William Campbell.
“I was stuck in quarantine with nothing to do,” said Campbell of the event’s genesis. “I had the materials and thought, ‘Why should the mad scientists have all the fun?’” The result was a functional catapult with counterweights that he assembled in his backyard with parts he made in his basement workshop. “A lot of work went into building it, and for me, getting to set it up and play is the payback.”
Campbell, who is a visiting professor of history at Pitt-Greensburg, thought students might enjoy it too, so he mentioned the project to the president of the campus History Club, who was immediately on board. The Science Club and Academic Village leadership were just as enthusiastic.
“I want our students to see that even fields as different as physics and history can have a lot of points of contact. And because physical distancing is depriving our students of most of their normal ways of getting together, it was important to me to create an event now where we could gather safely and have a good time doing something out of the ordinary,” said Campbell.
On Sept. 15, a crowd of approximately 70 students, faculty and staff gathered outdoors for the first-ever Clusterchuck. Campbell warmed up the crowd by slinging a couple of cabbages across the soccer practice field. There was a festive atmosphere as the group “ooh’d,” “ahh’d” and applauded as the cabbages broke into chunks past midfield. An assortment of other cabbages, cantaloupes and grapefruit were piled nearby, waiting to be flung through the air—as well as weights of more formal measure for the demonstration.
Campbell invited attendees to guess which configuration would result in the longest throw by adding their names to a grid blocking out the choices between each weight—1 kilogram, 1.5 kilograms and 2 kilograms—and the length of the sling—longest length, medium length and shortest length. The objective was to compare the weight of the object to the distance thrown.
Women’s soccer player, senior and History Club president Kiara DeVore stood ready to jog across the field, flags in hand, to mark the landing point of each weight for official measurements.
Campbell said that building the trebuchet, which he named Delapidator, was a lot of trial and error. He tested and adjusted, then researched scientific test results, medieval manuscripts and videos. When at rest, Delapidator is four feet wide, six feet long and 13 feet high. “But because there’s a sling on the end of the arm, at the moment it releases the projectile, it’s almost 20 feet off the ground,” he said. The machine is made up of 18 wooden parts, two metal parts (the axle and the winding ratchet) and the sling, plus dozens of bolts—all of which have to go together in a particular sequence. Part of the design process was to make sure it would fit into his Honda hatchback, another interesting geometric challenge.
Then there is the material that is put into the counterweight bucket. Mirroring what his medieval counterparts would have done, Campbell initially used canvas bags filled with dirt. For Clusterchuck, he was able to use iron weights from campus, which gave him a more accurate measure of how much weight was used for each throw. “Most of today’s tests were done with 250 pounds,” he said. “But at the end, I put it up to 300 pounds and the only thing that broke was the cantaloupe I threw with it—we got some satisfying splatters!”
Like a late night talk show host, Campbell paused between tosses to share historical tidbits with the crowd. For instance, did you know that before the cannon was invented, the trebuchet was the greatest siege weapon? Campbell then went on to tell the story of how King Edward I attacked Scotland’s Stirling Castle using a trebuchet named Warwolf—the largest known at that time—and then refused to accept the Scots’ surrender because Edward I wanted to test the weapon.
As Campbell pumped the ratchet to set the sling, he explained to the crowd that, in the past, large trebuchets used manpower—that is, groups of men walking on circular wooden wheels—to ratchet the weapons. Nearby, someone commented, “Could you imagine having to do that during a battle?” Campbell also explained that the trebuchet was a double pendulum and encouraged the audience to watch how the counterweight moved and shifted as the object was thrown.
“I think it’s pretty amazing,” said Lewis Colabine, a first-year history major. “Dr. Campbell constructed a pretty mean instrument of war.” He continued, “It’s cool to see it and learn about history. If you’re a science major, you can learn about physics, and if you’re not a history, math or science major, you get the fun of launching produce.”
Another freshman history major Matthew Hiller came prepared to enjoy the show. Sitting in a folding chair at a small table, he heated water on a small camp stove for his coffee press. “I’ve always loved history,” said Hiller, who’s taking Campbell’s Christians, Muslims, and Jews in the Middle Ages class this term.
“This is fun,” said Alexis Martir, a commuting student majoring in information technology, as she watched the heaviest weight soar through the air.
By the end of the demonstration, the longest throw recorded was 233 feet achieved by lobbing the one-kilogram weight on the shortest sling. Three students guessed correctly.
“I thought it was something that we needed to get the students out of the residence halls,” said Barbara Barnhart, a biology instructor, who was encouraging students to add their guesses to the results grid. “The students needed an opportunity to be outside and do something. This just has the added benefit of physics, math and engineering.”