Human-Powered Vehicles
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Barrie Royce (r) with Ben Wukasch '03 (back), Brent Bollman '03 (l) and Robert Wuertz '02 (Photo by Denise Applewhite) |
By Steven Schultz
By the time students left the second session of MAE 199 this fall, they were sweating.
That wasn't because they had spent the last couple hours steeped in problems of physics, fluid dynamics and materials science. It had more to do with sitting on a stationary bicycle and pedaling madly while talking about physics, fluid dynamics and materials science.
That's the way it is in Barrie Royce's Human-Powered Vehicles, a class in which the bicycle is as much a teaching tool as the blackboard. The course explores the machines humans have devised to leverage their own strength and propel themselves faster and farther than their own two feet could carry them. It ranges from dugout canoes to human-powered airplanes but focuses on the bicycle.
"The idea is to get students to think about science and engineering as something that's part of real life," says Royce, who is professor of mechanical and aerospace engineering.
The class has no prerequisites and welcomes students who are not concentrating in the sciences. Yet it also aims to fully engage students who do have a strong science aptitude, in an effort to cement their interest in a BSE degree. So, with two classroom sessions and a Friday afternoon lab, Royce weaves together elements of history, hands-on experimentation and pure physics.
Take, for example, the sweaty stationary biking session. Royce wanted to give the students a physical sense of how little power they have available to propel any kind of vehicle. He hooked a bicycle to a computer that displayed the rider's power output in watts, a measurement of how much energy is produced per second. Each of the seven students took a 10-minute turn. Some created spikes of more than 500 watts, but most could produce a sustained output of only 200 watts, which is equivalent to the power consumed by two 100-watt light bulbs.
"You really can't generate a lot of power, so you have to be tricky in how you use it," observed freshman Brent Bollman, who is considering a major in engineering.
After the initial demonstration, Royce leads the students through a series of discussions and experiments about wind resistance, aerodynamics, friction, gears, chains, materials and anything else that goes into engineering an effective form of human-powered transport.
To help sustain a general level of interest, he also has an extensive course website that walks viewers through an illustrated history of human-powered vehicles, from the ancient Egyptian use of logs as roller bearings to a NASA-sponsored project to build bicycle-powered airplanes (www.princeton.edu/~maelabs/bike/cover_1.htm).
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Royce's class is itself a vehicle that leads students beyond the particular subject and into the broader concepts of experimental methods, problemsolving and scientific reasoning.
"Many people misunderstand the relationship between theory and experimentation, because they believe that experiments are always done to prove theories," Royce says. "Often experiments are done before one knows what the theory is. There's a lot of symbiotic interplay between the two. I try to help people to get a gut feeling for a problem through experiments and then get them to ask 'What are the issues at play here?'"
Students seem to appreciate that approach. "It's pretty neat," says Bollman. "In the experiments, he tells us how to do it, but not exactly how to do it. He says 'You figure it out.'"
"This is one of the labs that is actually very fun," says junior Chris Nam, an economics major. "It's not something tedious like titrations in chemistry. You learn a lot in this lab."
In a recent lab, Royce divided the class into two groups, one measuring the resistance of wheel bearings, another measuring the friction of objects sliding down a glass ramp. The group with the ramp soon had problems. Not only did the glass sag, the little metal and wooden blocks refused to slide in a consistent way. No matter how diligently the students wiped the ramp with glass cleaner, the objects stopped and started at random, skidding to a halt, then racing inexplicably ahead.
Royce stopped by to look at the problem. His style is a mix of seriousness and enthusiasm. Even in one-on-one conversation, he speaks with the booming voice of a lecturer, but any intimidation is checked by the sparkle in his eyes. When he is particularly intrigued, his face breaks into a smile above the tuft of snow-white beard that juts from his chin.
"What we're finding here is that we can't do the experiment," said freshman Ben Wukasch.
Royce disagreed. "The observation you're making--that the friction is not constant--is a good one," he said. "It's very nice to write down m = F/N, but it's not right, really. You can do the experiment; it's what you make of the observations that matters. If you think about why it's not going the way you expect, then you're learning something. Your observations are really good."
40 years at Princeton
Royce has been shepherding Princeton students through experiments for nearly 40 years. He came to the University in 1960 as a research associate after three years at the Carnegie Institute of Technology in Pittsburgh. He received his undergraduate and graduate degrees from University of London King's College, earning his PhD in 1957. Although he has taught a human-powered vehicles course for several years, the official "research interests" entry on his home page contains no reference to bicycles. The focus of his research is materials and the way that their atomic structures dictate their overall characteristics. He is associated with the Princeton Materials Institute.
Cycling is not even on Royce's list of favorite pastimes. Despite his demonstrations, students are not likely to see him barreling over to the E-quad on two wheels. He started using bicycles in his teaching, however, when he noticed that fewer and fewer students had a strong feeling for mechanical things. For many years at Princeton he could count on new crops of engineering students who either grew up around farm machinery or spent their high school years tinkering with cars. But lately, cars have become dependent on electronics and harder to fiddle with, and technically minded high school students spend their time playing around with computers.
Zipp 3001
So Royce turned to the bicycle. "For $4,000 I can buy a bike that really impresses students," Royce says. And indeed he has. In one of the course's first classes students ride a bike called the Zipp 3001, a bizarre-looking affair made from a carbon fiber composite material. Instead of the conventional diamond and triangles, the Zipp frame is nothing more than a single sideways V with the seat perched high on one end, the pedals at the other and the handlebars at the point.
Students seem to think it goes faster than a regular bike, Royce says. But behind the flashy red paint, Royce sees a question worthy of investigation.
"Would you pay $1,000 extra for that?" he asks. "I think it's a good question to ask engineering students, or anyone for that matter. What do you need to know to make a decision?"
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