Students Revamp Tractor for Use by Workers with Disabilities
By installing a seat-lifting device and hand-operated driving controls, undergraduate engineers at Johns Hopkins have transformed a tractor to allow people with disabilities to help maintain the grounds of a southern Maryland state park.
The project resulted from a request from Donnie Hammett, ranger and manager of the 596-acre Greenwell State Park in St. Mary s County. In keeping with the wishes of the Greenwell family, which donated part of the property, the park has a special emphasis on outdoor recreation for people with disabilities. When some of these users offered to help with trail maintenance, hay rides and other chores, Hammett obtained a federal grant to purchase a tractor, then adapt it for use by people with disabilities.
After buying the tractor more than a year ago, Hammett could not find a business willing to make the alterations, so he sought help from the Baltimore-based Volunteers for Medical Engineering. Because of successful collaborations with Johns Hopkins in the past, the VME referred the tractor challenge to students in the two-semester Engineering Design Project course offered by the Department of Mechanical Engineering. A team of four undergraduates was assigned to confer with the VME and people with disabilities in devising and constructing modifications for the tractor.
The students needed to adapt the tractor so that people who are paraplegic and others who use wheelchairs could access and operate it. To address the first challenge, they installed a folding chair and hydraulic lift system, powered by the tractor’s diesel engine, onto the side of the tractor. The user can start the engine with a remote control, transfer to the lift and raise the seat via a hand control. At cab level, the operator can fold down a ramp, grab onto handholds and slide into the driver’s seat. To enable a person who is paraplegic to operate the tractor, the students modified an electronic video game controller to serve as a hand-controlled throttle. They also built a mechanical device that allows the driver to depress the brake pedal with a hand. In addition, the controls were set up so that a person without disabilities can disengage or by-pass the hand controls and drive the tractor in a conventional manner.
The student inventors, all seniors majoring in mechanical engineering, were Alex Forman, 22, of Denver, Colo.; Jon Haslanger, 22, of Chapel Hill, N.C.; Emily Nalven, 21, of Potomac, Md.; and Brian Wolcott, 22, of Harding, Pa. Their modifications cost about $10,000.
A few days before their graduation, the students gave the customized tractor to Hammett, the park ranger who commissioned the project. “This is going to offer some unique opportunities for people in wheelchairs to work as interns, volunteers or even employees on the park’s trails,” he said. “You don’t know what an esteem-builder it’s going to be.”
Hammett added, “We couldn’t find anyone in the commercial sector to take on this tractor project. I think it was a great learning experience for the students.”
The project is not completely finished. The ranger said he plans to replace the hydraulic system that powers the lift with an electric motor that will not require the tractor’s engine to be started before the lift can be activated. He also wants to install sturdier, more permanent grips in place of the rope handholds placed by the students. Overall, he was pleased with their work. “I think it’s 85 percent of the way there,” Hammett said. “I’m going to have someone with disabilities riding on that tractor before the end of the summer.”
The students enjoyed applying their engineering education to a real-world project. “It was rewarding because you could see everything you’d studied and worked on coming together,” Haslanger said.
Added Forman, “A project like this makes everything else worthwhile. You get to apply everything you’ve learned and find out if this is what you really want to do. It’s a great exercise.”
Forman, Haslanger and Nalven plan to continue their studies in graduate school. Wolcott has lined up a job with a private consulting firm.
The modified tractor was one of nine Johns Hopkins projects completed this year by undergraduates in the engineering design course. The class is taught by Andrew F. Conn, a Johns Hopkins graduate with more than 30 years of experience in public and private research and development. Each team of three or four students, working within budgets of up to $10,000, had to design a device, purchase or fabricate the parts, and assemble the final product. Corporations, government agencies and nonprofit groups provided the assignments and funding. The course is traditionally a well-received, hands-on engineering experience for Johns Hopkins undergraduates.
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