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Special bike for a spunky tyke

Special bike for a spunky tyke


Amber pedals DARMA down the hall, with some help from Ogle.

Evansville, IN-"Watch your feet, watch your feet! Thank you."

Students and professors jump out of the way as four-year-old Amber steers her tricycle down a hall at the University of Evansville.

It's a fairly normal scene for most rambunctious little girls, but this one has a few extra challenges: cerebral palsy has left her legally blind and deaf, undersized, and prone to seizures. So the achievement of building her a specialized vehicle was impressive-especially when you hear it was done by four undergraduate engineering students.

For their work, they have won Design News' first annual College Design Engineering Award. Courtesy of contest sponsor ANSYS, they win a $10,000 prize and a $10,000 grant to their school's scholarship fund, as well as a commemorative plaque awarded at the Design News Engineering Awards Banquet in Chicago.

The process began when Prof. Douglas Stamps invited Monica Duff to visit his senior mechanical design course and describe her daughter's disabilities. A former dialysis nurse and EMT, Monica lives in Cynthiana, IN with her children Ashleigh, 10, and Amber.

She flooded the students with medical and anecdotal details, and with the help of a physical therapy professor, the students translated the tales into design requirements. The vehicle had to be: stable, mobile, safe, inexpensive, transportable, and adjustable to a child's growth in size, strength, and coordination.

Then the class broke into four teams, and created competing solutions. The winning design, chosen by Stamps and Duff, was an "inverted tricycle with front steering axle," created by Dalen Zuehsow, Andy Nicholson, Ryan Ogle, and Mike Strange.

Officially, the vehicle is called DARMA, an acronym for the students' first names (the final "A" is for Amber). But in the words of the squirming four-year-old in the driver's seat, it's a Darmasicle (rhymes with "popsicle").

The four students used Pro/ENGINEER 2000i solid modeling software in the design, and ran a finite element analysis. Since their goal is for Amber to use the bike at any age from 4-10, they had to make the aluminum frame strong enough to hold Amber as she grows from her current 31 lbs to as large as 80 lbs.


FEA testing on teh CAD model showed that DARMA needed a stronger front axle.

They then created a wooden prototype of DARMA, and asked Amber to visit the class again so they could double-check their measurements, says Nicholson. In this stage, they discovered that Amber needed some foot straps to hold her feet on the pedals. And they designed a telescoping pedal arm, so Amber can reach the pedals as her legs grow longer.

The students also had to steer a course between design requirements from Duff-who wanted a fun, mobile trike-and the physical therapist-who wanted an exercise machine.

So they built both at once. DARMA has a small, fourth wheel in the back that lifts the rear-wheel drive off the ground, changing DARMA into an indoor exercise bike. It even has adjustable resistance (leather brake pads taken off a junked exercise machine in Zuehsow's father's garage) so she can pedal inside all winter long.

"Any physical development helps simulate the mind's growth, too," says Stamps. "Especially for the blind and deaf, since they have no input to describe their world."

Like most tricycles, DARMA has fixed gears, so its brakes are its pedals. But hampered in exercise by her disabilities, Amber's muscles are so weak that she is not able to pedal a traditional tricycle. So the students fitted DARMA with a series of six high-ratio gears. The lowest is about equal to the hill-climbing gear on an 18-speed mountain bike. This approach had the added safety benefit of limiting the bike's top speed to about 3 mph, says Strange.

"For us it's not fast, but for her it feels like she's really getting somewhere," says Zuehsow.

Since she's nearly blind, Amber tends to explore her world through touch. Around people, this means she gives frequent hugs and high-fives to students and family. But around a moving bicycle, the mechanical parts could be dangerous. So DARMA has wheel and spoke covers, to protect her inquisitive fingers.

Amber's arms are also weak, so DARMA is simple to steer, with the two front wheels pivoting around a single pin. For safety, the team gave it a low center of gravity and a tipping angle of 38 degrees , so it won't capsize on sidewalk curbs. And Amber sits in a cushioned, safety-belted, recumbent chair, taken from an automotive child's safety seat.

"We tried to get the wheel base as wide as possible, but still fit through a standard doorway," says Ogle. "She just starts playing and steering, and it's great when she realizes she's doing the action."

Along with quick-release wheels, its simple assembly was one of Duff's favorite details: "I'm a single mom, on the go constantly. If I can't pop it apart, throw it in the van, and take it to school, it won't get used."

Cruising down the hallway, Amber calls out, "Mommy, you feel that wheel please," and breaks into giggles. "She's a ham," her mother admits. "But the best part of this is that she comes out on top. She gets the benefit of all these great minds."

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Timeline for creating DARMA

Aug. 28, 2000 Duff visits Stamps' class, and students draft conceptual designs

Sept. 1 Students begin technical design

Sept. 12 Create first prototype

Sept. 15 Finish technical design and CAD model

Sept. 26 Make presentation of design to class

Oct. 9 Acquire materials

Oct. 26 Construction complete

Nov. 1 Testing complete

TAGS: Medical
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