Matt Sherburne (left)
and Tom Devine
PEG SKORPINSKI PHOTOS
Getting to know your
bike atom by atom
Pedaling 16 hilly miles from Moraga to the Berkeley
campus and back — a daily journey Professor Tom Devine made
rain or shine for a year — gave the materials science and
engineering professor ample opportunity to plan a class using
his bike to teach basic engineering concepts.
The result: MSE 24, a popular freshman seminar Devine has taught
on and off for the past nine years. "Biking is a good way
to teach the fundamentals of engineering systems and engineering
design," says Devine. "No one is intimidated when you
talk about bikes."
Last fall a relaxed group of 18 students met weekly with Professor
Devine, to tear down and reassemble bikes, peer at parts under
a microscope, then analyze the materials for hardness, strength,
impact loading, resistance, and metal fatigue. Their analyses
led to their final project: select resilient materials, then design
a "perfect" bike.
"How many parts does your bike have?" Devine asks.
"Would you believe more than a thousand?
The closer you look at the bike, the more you realize
how many parts there are and how they function," he tells
the students, who will soon be afloat in hundreds of parts, from
rims, spokes, bushings, and tierods, to brake levers, steering
tubes, and aluminum lugs.
Matt Sherburne, MSE graduate student, former bike
racer, and Devine’s graduate assistant, says, "In this
class we talk about why the components work the way they do. When
we talk about spokes, we talk about ‘Euler’ buckling
and why a bicycle wheel is built with the spokes in tension, unlike
the old wagon wheels built with the spokes in compression. Now
the students understand the engineering principles that go into
making a wheel, and why and where steel or aluminum frames sometimes
"I’m interested in the molecular level
of materials," says Julie Chao, having just completed a set
of metal impurities tests. Sometimes, she says, impurities can
strengthen a metal. "At the molecular level, all the atoms
are next to each other. To make a dent, the atoms have to break
the bond and form another bond with the atom right next to it.
When an impurity gets into a metal, the atoms around it can’t
move as easily as if it was a pure metal. So the bond of the atoms
around the impurities can be harder to break."
Mountain biker and ChemE freshman Vincent Chan sawed quarter-inch
lengths of metal tubing, sampling carbon and low-alloy steel,
aluminum, and titanium — the metals used in bike frames
— testing them using the Rockwell hardness tests.
After heating the steel samples to 800°C, and
the titanium tubes to 1,000°C, Chan quenched some of the red
hot samples in oil, to cool them slowly. He quenched others in
water, to cool them rapidly, before testing both batches. "Freshman
seminars are different from other courses," says Chan. "They
are low pressure classes that encourage students to interact more
BioE major Stephan Zmugg took his turn smashing
a piece of low-alloy steel tubing that had been heated, then plunged
into a vat of liquid nitrogen at a frigid –196°C for
15 minutes. Smash tests help assess whether or not a frame has
core resistance to impact.
"We want to know if the metals behave like glass or taffy,"
says Devine explaining the test. "What we want is taffy,
for a ductile, tough material. It’s a simple binary test.
You grab the sample, drop it, smack it, and either it breaks or