But here’s the
trouble: They had to be engineered well enough to hold 200 pounds – lovingly
cradle every ounce – but without the bough breaking and, unlike the famous
children’s rhyme about the one in London, without falling down.
Teams of mechanical engineering whizzes, with
that spark of well-studied know-how and construction savvy in their eyes, had
this challenge: Build a suspension bridge from kid-friendly K’Nex sets, keep
the cost within a slim-and-trim $200 materials budget (each K’Nex piece was
assigned a price), and — oh yeah — make sure your awesome K’Nex set bridge is
able to hold 200 pounds of weight.
Challenge on.
The assignment –
lovingly dubbed the Suspension Bridge Project — was a gauntlet thrown down
by College of Science, Engineering and Technologyprofessor Li
Tan and one accepted by the students in his MEE 352 class. The students
presented their bridges, suspended with the help of fishing lines, paracord and
the like, as their lab project while, across the hallway, fellow engineering
students raced battery-operated cars.
“This class is
all about static and solid mechanics,” Tan said. “The goal here is to try to
assess students’ understanding of the topic.”
The project
spurred them on to understanding concepts such as force, stress and weight
distribution – the big players in a bridge-building project – and how they interact
together in a structure.
Students built
3D, virtual models of their bridges on a computer, where the structures
underwent redesigns if they needed it. Once their conceptual bridge looked as
if they met the challenge, they then broke out their GCU-supplied K’Nex sets
and started the toy-sized, real-life builds.
Tan said the
project also included Christian worldview concepts, such as the ethical
questions surrounding the project: Is it ethical to stretch a job out longer
than it needs to last just to make more money, or should you always aim to get
the job done under time and under budget? What about the environmental impact
of your construction project? Or cost vs. safety?
Haydon Hinson, Hunter
Hoyt and Tobin Morse dressed in dapper fashion for their presentation,
complete with solid-colored shirts, bow ties and suspenders.
Their bridge,
dappled with yellow, dark blue, orange and white K’Nex pieces, didn’t come
without some issues. The team saw connector pieces start to bend during the
pre-presentation testing phase, so it reduced the bending by including
additional spacers.
The bridge was
able to support 74 pounds before breaking.
he time
involved?
18 hours.
The cost?
$61 for
materials, “so we’re the value bridge,” Hoyt said with a smile, assuring the class
that the structure would not collapse because of the wind and that the team
“provides quality assurance and quality products.”
But, with labor
included – that’s 4.25 hours multiplied by $50 an hour for four engineers –
customers were looking at some definite labor costs.
Things the team
members learned: Next time, they would use paracord instead of fishing line,
would include more metal, would employ a trapezoidal tower design and would
consider using better cable attachments.
“The kryptonite
was the way we assembled the bridge. There were too many breaking points,” Hoyt
said after the presentation. “So it’s a matter of putting the right material in
the right position” to avoid bridge failure at specific points.
He added that communication
is, by far, the most important thing when working on a team. Team members all
had ideas they wanted to include in the design and had to decide which ideas to
use.
Junior
engineering student Cooper Davis said his team spent two to three
weeks designing and four days building its suspension bridge, which was
book-ended by trapezoidal cable towers incorporating line upon line of paracord
diving down from the tops of those towers to the deck below.
Davis said what
he learned from the project is to “know your materials before you start. … We
didn’t know the angles that could be made.”
The team
members, he added, quickly realized that fishing line was only going to get the
bridge to hold 100 or so pounds, so they switched to paracord. They also
learned to be mindful of how weight is distributed through the ropes.
What Guskey most
enjoyed most about the project was seeing the team’s bridge stand up to heavier
and heavier weights.
“It’s still not
failing,” he said with some wonder in his voice.
But when it was
over he added, “It was just fun to build, mostly.”
The team’s
bridge held 216 pounds, though that total didn’t come close to Graham
Guskey’s team.
“Ours was one
tower, but we had the strongest deck built,” he said of the bridge – a
completely suspended bridge whose deck swayed when carried. It was able to hold
866 pounds of weight. He credited the strength of the deck to the team weaving
paracord through the base to make it “more compressive.” The force goes into
the cords themselves, he said.
Hoyt said he
played with K’Nex as a kid, building roller-coasters, but never had used them
to engineer something as complex as a suspension bridge able to support 200
pounds.
https://news.gcu.edu/2018/01/student-project-bridges-engineering-concepts/
