By Nate Jones

Staff Writer 

The semi-annual live fire testing of the Terminal Response Ballistic Unit, Combat (Heavy), Tactical System commenced outside Hilldreth Hall on the Southern Maine Community College (SMCC) campus on April 22. Assistant Physics Professor and U.S. Navy retiree Kevin Kimball invited all hands to witness the firing of the “Intimidator,” a 6-year-old weapon with medieval roots. 

Kimball said trebuchets were originally designed as siege weapons during medieval times. Medieval trebuchets, similar in function to Roman designed catapults, could be up to five times as large as the “Intimidator” and were capable of launching several thousand pound sandstone blocks to knock down castle walls, he said. 

“These were designed as a weapon, it’s very dangerous,” Kimball reminded students before allowing them to operate the machine. 

The “Intimidator” is the second trebuchet Kimball and his physics students have constructed. Inspired by a NOVA special, Kimball and his students took a “hands-on” approach to physics and spent the fall of 2000 building a similarly sized device. Unfortunately, the original “Intimidator” only fired a few rounds before being decommissioned.

“It was constructed along the same dimensions of the one we now have, but with much lighter materials,” Kimball said. “We assumed, incorrectly as it turns out, that since our model was so much smaller than the original siege weapon that we could use a simpler design.”

Kimball said the weight-rated axle designed to support the 500-pound counterweights was insufficient to withstand the momentum the trebuchet created.

“To say that we were shocked by the violent forces displayed in the machine’s first launch would be an understatement - we simply had no idea,” he said. 

Kimball said the trebuchet lifted off the ground each time it was fired and before long the axle was severely bent.

“Even if the axle had lasted, the structure had already begun to come apart, and I believe that another dozen throws would have shaken the thing to pieces,” he said. “Nevertheless, the prototype succeeded to the extent that it showed us the Achilles Heel in trebuchet design.”

Two years later a determined Kimball challenged his students to construct a trebuchet that could withstand years of abuse. 

The 9-foot high, 15-foot long “Intimidator” features forged steel axles, bearings and gussets and four Ford LTD wheel bearings. Incorporating wheels into the design not only allows the “Intimidator” to be moved easily, but also absorbs the momentum of the swinging arm by rolling slightly back and forth with each shot.

By combing weight, leverage and resistance, the “Intimidator” is capable of exerting 250 pounds of pressure on whatever ammunition will fit in the small satchel tied to the end of the swinging arm. The physics of the device and its projectiles are the basis for lessons Kimball and his students have been working with for some time.

“Before this we had little table launchers,” SMCC senior Joe Bell said. “This is way different; It’s awesome!”

Students carefully loaded water jugs into the “Intimidator” all afternoon as campus pedestrians and traffic stopped to witness the aerial display. Some of the jugs were tossed nearly 200 feet before exploding upon impact with the pavement.

“Try to tear a milk jug apart with your bare hands,” Kimball said. “That’s the kind of force we’re talking about here.”

In the eight years the “Intimidator” has been hurling water jugs and other projectiles Kimball said the SMCC staff have learned to equate the trebuchet with the changing of the season. 

“The faculty love to see it come out because they know the end is near,” he said. 

Students will spend the next several classes studying the physics behind the “Intimidator” before moving onto the second phase of the project: launching melons onto nearby Willard Beach. 

“It’s nice to finally get outside,” Bell said.