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-
Contact: Phil Sneiderman
Johns Hopkins University