SILER CITY — Leah Riggsbee has always wanted to get thrown down a hill.
She’s about to get her chance.
Riggsbee is part of the Chatham School of Science & Engineering Gravity Games team. The team designed, and will soon drive, a gravity-powered car to compete in the N.C. Gravity Games.
The five-student Chatham County team is among the more than 50 teams from throughout the state slated to compete on Saturday, April 29, in downtown Lenoir as part of the 10th running of the N.C. Gravity Games, a STEM-education racing event sponsored by Google, Appalachian State University and the N.C. Science Festival.
Riggsbee, a CSSE sophomore, will be the driver behind the unique contraption the CSSE team devised. They call it “The Mouse Trap.” The triangular prism-shaped vehicle is meant to cut through the air and propel Riggsbee down the hills of Lenoir, hopefully on her way to victory.
”I’m really excited for that hill,” she said. “I wanted to try something different, this is definitely different.”
Driven designers
CSSE will be competing in the engineering division, which means their car must be built from scratch, with their own sourced materials. While there are no specific requirements on used materials, the blueprints and final cars are subject to safety inspections. It also means the assembled car, weights, wheels, safety equipment and driver cannot exceed 300 pounds.
The team of five — Riggsbee, sophomore Caden Bailey, sophomore Nickleus Castevens, sophomore Blake Green and freshman Dominick Pietryga — was gifted $1,000 to build the car courtesy of the Morehead Planetarium and Science Center in Chapel Hill. The funds have covered all necessary expenses for the construction of the car; leftover funds will go toward lodging, transportation and other Gravity Games expenses.
Thus far, the team has purchased 3D printer filament for the car’s gears, ball bearings, plexiglass and wooden panels.
Castevens said the design for The Mouse Trap came from throwing ideas at the wall and seeing what stuck.
“The design isn’t quite a right triangle because that would create too much drag,” he said. “We wanted to go for something that could reduce that air resistance as much as possible.”
They determined designing a vehicle with a rounded front cone, like many of the ones pictured prominently on the Gravity Games website, would be difficult because it would require bending wood and plexiglass and keeping it in place.
The group also decided it wanted Riggsbee to be fully inside the vehicle, so they’ll build a door on the outside for her to climb into. Their hypothesis is that the human body has too many different angles, which if exposed would make the car less aerodynamic.
By putting her inside the car, the team can also make the floor lower to the ground, which lowers the center of gravity and allows less air to flow under the bottom of the vehicle.
The hardest part of the design, Castevens said, was the braking system. The final blueprint, which was approved by professors at Appalachian State University for safety, included a lever inside for Riggsbee to pull with her hand.
The brake lever will stop the movement of the back axle because the pressure from the lever forces a brake pad against it, eventually slowing the car.
Off-roading
“There was a lot of back-and-forth discussions,” said Kevin McDaniel, CSSE math teacher and the group’s supervisor. “They ran into a lot of problems initially asking things like, ‘How does a car move? How do you steer an axle?’”
Eventually, the team figured out how to make the vehicle steer and brake, at least on paper. Without all the material in hand, construction is still yet to begin on The Mouse Trap. In fact, one of the pieces needed for the steering mechanisms won’t arrive until about a week before the competition.
“It’s been difficult because we can’t practice on the exact hill,” Bailey said. “It could be a flier on whatever we test on, but totally different in Lenoir because of the conditions.”
But rest assured, team members remains confident they’ll be ready to go on race day.
Take it to the streets
Because the design of the gravity racer has been entirely student-driven, any problems the small group encounters they’ve had to work through themselves.
“I’ve really tried to step back and let them troubleshoot this,” McDaniel said. “These students, being at CSSE, wanted something more than just sitting in the classroom and learning from the textbook, and that’s what this is.”
Many of the problems the group has had to troubleshoot in the design stage revolve around the mathematics and physics of the car. For example, the original concept had to be significantly altered once they determined Riggsbee would be the person driving because the vehicle needed to fit her exact measurements.
“We had to make it comfortable enough for her body,” Bailey said. “But not so comfortable that it loses its efficiency.”
The 2023 Gravity Games marks the first time a Chatham County team has competed in the event. It’s also the first time the event has been held since 2019, since the Covid-19 pandemic.
McDaniel said his goal for the group is to have a car that makes it to Lenoir and across the finish line. For their first attempt, he said that would be a major accomplishment and something students could build on in future years. He said he hopes other schools in the county get involved in the contest in the years to come.
So as Riggsbee lives out her dreams, rolling The Mouse Trap down the hills of Ashe Avenue in downtown Lenoir, she’ll be driving with the spirit of her school, and the county behind her.
For more information about N.C. Gravity Games visit www.ncgravitygames.com.
Reporter Ben Rappaport can be reached at brappaport@chathamnr.com or on Twitter @b_rappaport