In the nearly 150 years since the bicycle debuted, its operation has remained remarkably consistent. That is, until this year, when a group of mechanical engineering students at Yale created what might be the first spokeless bicycle.
Redesigning something so fundamental was bound to be difficult. So Vern Van Fleet, a Sikorsky test engineer who taught the course, broke his students into three groups (frame, drivetrain and wheel) to tackle the challenge.
The result? An 8-pound frame, made from sheet aluminum, which holds the spokeless rear wheel in place. Inside the wheel housing, rollers fit into grooves carved into the wheel rim to prevent wobbling and to provide support. In place of the normal rear hub, the team added teeth along the inner rim of the wheel to spin a small gear behind the pedals. That gear ratio, however, is lower than first gear on most 10-speeds. So the team improved performance by connecting an 18-tooth rear cog to two 53-tooth chain rings. An outside vendor who was supposed to machine the bike's wheels fell through, forcing the students to focus solely on the rear wheel to get things done quickly and inexpensively. "That was a good lesson," Van Fleet says. "You've got to have contingency plans."