Over the past year and a half, in a narrow, equipment-jammed lab in Bucknell University's engineering building, a riderless bike has been balanced atop a computer-controlled test rig designed and built by Bucknell engineering students.
The bike is outfitted with a prototype of an innovative new gearing system developed by a Pittsburgh-area inventor, who says it could end up having a major impact on bicycle manufacturing and bike usage worldwide. In testing that began in February 2001, the test rig's computer has been directing the transmission to make shift after shift, now in sequence from gears one through 24, now in other patterns that simulate the shifts a human rider would make, over and over and over again.
During one day of testing, the rig had been driving the bike for hours, and the new gearing system was running smoothly. In the traditional sprocket and derailleur (S&D) system, where shifting involves lifting the chain from one toothed gear to a toothed gear of a different size, you would expect to see some missed shifts over an extended period of time.
But that day, with the new system, there hadn't been any dropped shifts. "In a few hours we can put a tremendous amount of shifting on the system," said Steve Shooter, an associate professor of mechanical engineering at Bucknell who is in charge of the project. "In this test there has not been a single missed shift."
The bike transmission testing project is supported by and has received funding from Bucknell's Small Business Development Center (SBDC). In fact, the project came to Shooter's engineering class via a recommendation from SBDC director Jon Vernam. The developer of the new gearing system had spoken to Vernam in the project's earlier stages and in turn Vernam had referred the developer to Shooter.
"This project is an excellent example of how the SBDC links our clients with faculty and students at the university," said Vernam. "The strength of Bucknell's center is that it's located in the College of Engineering -- and that we do product development -- so we can tap into the expertise of the faculty and the students here to serve the needs of our clients."
After the referral from Vernam, Shooter became involved and incorporated the multi-year project into a senior design course he teaches in mechanical engineering. It began in fall 2000, with the students designing and building the test rig in the 2000-01 academic year and starting to test the transmission system in February 2001.
"My approach to teaching is to involve students on projects throughout their years here at Bucknell, so that they can develop their skills over time," said Shooter. To accomplish that, he assembled a team that included four seniors, two juniors, and a sophomore, as well as a graduate student to help lead the team.
For the students, the process has been an invaluable real-world opportunity to work with a real client involved in an entrepreneurial enterprise, and design and build a sophisticated, working rig to test a product that could actually end up in the marketplace.
For the entrepreneur developing the new system, the Bucknell testing process is helping to determine whether the system is reliable and durable enough for commercial development. That isn't known at this point, but the entrepreneur says the system has "huge potential" and could end up having a major impact on the bike manufacturing industry worldwide.
After about a year and a half of testing, the bike has recently been returned to the developer, who is now working on a second prototype of the transmission system.
When it's in operation, the test rig's computer moves the system through each of its 24 gears in a sequence that mimics the shifting choices a human rider would make. At the same time, it gathers and stores data on the "cleanness" and accuracy of the shifts and the system's durability.
The bike's pedals are connected to a one-horsepower motor that simulates the cranking of a rider. The rear wheel drives a drum that is connected to another motor that provides resistance to simulate varied terrain. And a bank of oversized, 200-watt bulbs lights up brightly, dissipating the energy generated by the rear wheel.
Like the traditional sprocket and derailleur (S&D) system, this new gearing system uses a chain. But instead of the chain moving from sprocket to sprocket, as in the traditional system, here the gears are shifted by circular arrays of small plastic pins that retract and extend as different gears are selected.
Advantages of the new system include:
-- The ability to shift "under power" - for example, while you're pedaling up a steep hill - which you can't do with the traditional system.
-- Its reliability, lightness, and efficiency. "It can take a good beating" and keep on shifting, says Shooter.
-- The ability to shift when you're not pedaling at all -- a move that would disengage the chain in the traditional system.
-- Elimination of "cross-chaining" -- a situation in the traditional S&D system where certain gears bend the chain at varying angles, putting additional stress on the chain. "Chains don't like to bend," says Shooter. "Since the new system moves the pins and not the chain, the chain always stays in-line."
Tim Hoffman of Lewisberry, the graduate student who helped lead the team last year, said the value of the project for the students lies in its many aspects: exposure to the design/build/test process, entrepreneurship, product development, working with microelectronics, and writing computer code. Seeing the test rig become operational was a big payoff, he said: "It was really great for us to see it in action."
-The overall project has also involved the University of Pitttsburgh's SBDC and Manufacturing Assistance Center, which helped develop the prototype.
The developer of the new gearing system, Joe Lane, credits his progress to date to his "very nice collaboration" with both Pitt and Bucknell. Of the Bucknell students' work, he said: "The Bucknell team designed a test rig that was well conceived, well built and extremely efficient. Very impressive and well done."
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