UW-Madison engineers design new disabled-access bike

Top: Craig Conner, a 1994 master’s degree graduate of mechanical engineering, sits on a hand-powered prototype bicycle for people who have lost the use of their legs. His professor, Frank Fronczak, right, continues to advise students who are fine-tuning the project. Bottom: Connor’s power train design allows the rider to get more power with less fatigue.

What started as a challenge to improve disabled access for a local outdoor recreation club put a team of UW–Madison engineers on the road to a better bike.

Since 1993, a succession of graduate students in the mechanical engineering department have developed a new style of hand-powered cycle designed for people who use wheelchairs. The three-wheeled bike’s power train, unlike anything else on the market, employs a downward arm motion that gives the rider more power and control over the bicycle.

Craig Conner, a 1994 master’s degree graduate of mechanical engineering, built the first prototype and has a patent pending on the power-train invention. And three graduate students since Conner have perfected a second prototype of the bike that is road-tested and ready for the next step of commercial development.

“We’re at a really good time to start working with bike companies,” says Conner, who plans to contact industry leaders such as TREK Bicycles of Waterloo and Cannondale Inc. of Connecticut. “Making these bikes available to people has always been a big hope, especially if we can prove all the benefits we intended.”

The major benefit is giving people with disabilities a more natural way to ride. Conner says the current bikes on the market are cumbersome and difficult to ride. Most hand-powered bikes use either a chest-level hand crank — a variation on traditional bikes — or require a horizontal rowing motion.

Conner says these bikes make arms replicate the pedaling motion of feet, rather than allowing for a more natural motion. Conner developed a four-bar linkage under the bike seat, which moves the bike forward when the rider pushes down and pulls up on the handlebars.

This motion uses much stronger arm and upper-body muscles, Conner says, which allows the rider to get more power with less fatigue. The design also combines the braking, shifting and steering mechanisms on the handle bar, giving the rider more control.

Conner, a bike enthusiast himself, got the idea in 1993 from Hoofers, an outdoor recreation club. The club was looking for university-based ideas to make their recreational pursuits more accessible to the disabled.

Conner spent an entire year researching the concept. He worked with staff from the University Hospital’s Rehabilitation Unit, the kinesiology department and several disabled local athletes to identify physical needs and limitations of people who use wheelchairs. “The more you understand the problem, the more self-evident the solution becomes,” he says.

More than 350,000 Americans have lost the use of their legs through either spinal cord injury or amputations. But there is a growing core of people dedicated to staying active through adaptive sports such as wheelchair basketball and biking.

The bike project has had amazing staying power in the mechanical engineering department, with new graduate students keeping it alive. David Pringle, a 1995 master’s graduate, developed the steering and controls for the first bike. Kurt Ramsey, a master’s graduate in May 1998, built the second prototype, which made a number of improvements on the original.

Now a fourth mechanical engineering graduate student, Chris Egle, is “debugging and fine-tuning” the prototype to make the bike ride more smoothly.

Frank Fronczak, a mechanical engineering professor and advisor for the project, says the multi-year aspect of the project is not unique with his students. Fronczak teaches an upper-level course called Product Design, and many students from that course — this group included — end up building those products as part of independent study or graduate work.

“A lot of my projects work this way, because we design and build stuff here,” Fronczak says, noting that combination of skills is becoming a lost art. “The work here is essentially never finished.”

Fronczak says the goal of this project “is doing good for the sake of doing good, rather than trying to make money.” But he is excited by the prospect of seeing a student design developed by a bicycle company.