Getting Handicapped Kids 
Onto the Playground

edited by Stephanie Gooch

For children who wear leg braces or use walkers or wheelchairs, the elevated activity platforms on many playgrounds remain sadly out of reach. To solve this problem, an assignment proposed by the Baltimore-based Volunteers for Medical Engineering, Inc., was put before area schools to ask how the group could help make playgrounds more accessible to children with limited mobility. Ramps are often impractical because of space limitations. 

In response, three Johns Hopkins undergraduate engineering students invented a portable, air-powered device that can lift a disabled child and a caregiver more than 3 feet above the ground, giving them easy access to play structures. Designed and built by seniors Christian Callaghan, Denice Koh and Nate Kruis, the aluminum lifting device features a 3-ft square passenger compartment capable of supporting 500 lbs. Their biggest challenge, however, was figuring out the safest and most efficient power source for raising and lowering the enclosure. Because the lifter was to be used outside on a busy playground, an electric motor requiring a long extension cord was ruled out. The engineering students considered water power, a weight and pulley system and other options before settling on a scuba tank. “It turned out that compressed air was the cheapest and cleanest power supply,” Callaghan says.

Air pressure from the tank activates a pneumatic piston and pulley system that gently moves the passenger compartment up and down. The students estimate the device can be used for 100 lifts and descents before the air tank requires a $5 refill. To help prevent accidents, the students added several safety features. A brake holds the passenger compartment in place even if air pressure is lost, and a lock box restricts access to the controls. The students also installed two pairs of wheels on one end so that the lifter can be tilted back like an appliance dolly and rolled from one place to another.

“I was impressed by how smoothly it worked and how easy it was to wheel the lifter from one place to another,” said Jan Hoffberger, the VME executive director. “We’re hoping this is a design that can be replicated and used wherever it’s needed.”

The assignment was completed during a two-semester Senior Design Project course in which students tackle real-world engineering assignments. Each team of two or three students, working within a budget of no more than $8,000, has to design a device, purchase or fabricate the parts, and assemble the final product. Corporations, government agencies and nonprofit groups provide the assignments and funding. For the lifter project, the three students prepared a budget of $6,100, which they exceeded by only $400.

Kruis said the practical engineering experience was invaluable. “It’s a big jump from working something out on paper to making the real thing,” he said. Added Koh: “It was exciting to be able to do a real hands-on project that will help children.”