1 of 8
Jeffrey D. Allred, Deseret News
Andrew Mills, 9, rides his new bike donated and adapted by a group of student engineers at BYU in Provo on Friday, April 14, 2017. Andrew has limb length discrepancy, where his right leg is far longer than his left, and BYU engineering students made a modification that will allow him and other kids who have leg problems to ride bikes more naturally.

PROVO — Since he first learned to ride a bike several years ago, Andrew Mills, 9, has used a work-around for the fact that his right leg has very limited range of motion and is several inches longer than his left leg. The fourth-grader always let his right foot slide off the pedal partway through the revolution, while he pedaled like crazy with his left leg.

Not anymore, thanks to a team of BYU seniors studying engineering. As a project for their Capstone program, they designed a drop-arm — a contraption that drops lower and supports his leg to change the circle it has to make. It goes between the bike pedal and crank and makes the circle smaller so he can do it without strain.

The inexpensive, simple-to-build device could help any family where someone has a range-of-motion issue — an estimated 4.5 million Americans — from knee surgery recovery to osteoarthritis. So the team will put the design and detailed instructions online for free, making it possible for even people with limited mechanical skills to build their own.

The bike project was one of two humanitarian, family-friendly projects the students tackled this year. Another student team designed and built an inexpensive silicone socket that helps amputees by connecting a limb stump to a basic prosthesis. It was targeted specifically for people in Sierra Leone, where as many as 27,000 people lost an arm or a leg in a brutal civil war in which rebel forces chopped off people's limbs at random to scare them from joining the other side.

Both projects join a long list of student-designed engineering efforts to solve basic human challenges. Last year, for example, students built a light, portable bike trailer that allows an adult with a disability to go along for the ride. The year before, students designed small, lightweight, inexpensive wheelchairs.

The wheelchairs were built specifically for Skyler and Tanner Jensen, a pair of toddler siblings who have spinal muscular atrophy and can't get around on their own. The trailer was for McKay Mitton, then 19, who has cerebral palsy.

Andrew Mills, 9, checks out his new bike donated and adapted by a group of BYU student engineers, including Trent Porter and Jordan McGregor in Provo on April 13, 2017. Andrew has limb length discrepancy, where his right leg is far longer than his left, and BYU engineering students made a modification that will allow him and other kids who have leg problems to ride bikes more naturally.| Jeffrey D. Allred, Deseret News

The projects each create bigger ripples, helping not just the people who inspired them and their families, but others with similar challenges who could benefit from the designs that are made publicly available.

"Open sourcing is so important for us," says BYU's Kelly Marcum, the external relationship manager for the Mechanical Engineering Department, who lines up the projects.

"Beyond McKay Mitton or Andrew Mills, we can affect hundreds of people."

One child becomes many

In addition to being longer, the bone in Andrew's right leg is also thinner than his left leg, increasing the risk he could be injured. It makes running hard, too, but he doesn't let it slow him down, says his mom, Rachel Smith Mills.

At birth, Andrew had a distinctive birthmark the length of his leg. "It was interesting," she says now, but when the doctor examined it, "everything seemed to be OK."

Andrew Mills, 9, checks out his new bike donated and adapted by a group of student engineers at BYU in Provo on Friday, April 14, 2017. Andrew has limb length discrepancy, where his right leg is far longer than his left, and BYU engineering students made a modification that will allow him and other kids who have leg problems to ride bikes more naturally.| Jeffrey D. Allred, Deseret News

As he grew, the length difference became noticeable and pesky. So did his limited range of motion and poor muscle tone. Hardware was screwed into the leg to slow down its growth, and the hope is it will slow down enough that when he stops growing, his leg lengths will be similar.

"One of his talents is that he's really adaptable, so he has a lot of good physical abilities," says his mom. But she and her husband Michael appreciate anything that helps him with his challenges.

Enter the engineering project.

All mechanical, electrical and manufacturing engineering seniors at Brigham Young University take the Capstone class — two hours every day, four days a week, all year, focusing on one project. This year, they had 32 projects, most for institutions or corporations. The list always includes a couple of projects targeted at helping an individual or group of people directly.

Students indicate which project they'd like to work on before the fall semester starts, says Marcum; they almost always get their first or second choice as he assigns teams of five or six students. The first semester they research and toss around ideas, then narrow it to what they will build and test the next semester.

Andrew Mills, 9, checks out his new bike donated and adapted by a group of student engineers at BYU in Provo on Friday, April 14, 2017. Andrew has limb length discrepancy, where his right leg is far longer than his left, and BYU engineering students made a modification that will allow him and other kids who have leg problems to ride bikes more naturally.| Jeffrey D. Allred, Deseret News

Powerful reach

"We thought of a couple of other designs that could have worked that were pretty good designs," says student team leader Trent Porter, who described making and testing different prototypes. Because they were building it specifically for Andrew, they went to his house and invited him into the lab. They took pictures and measurements of his leg and made a computer model so their design would fit.

But perhaps the most important thing Porter and team members Hunter Erickson, Chris Reynolds, Jordan McGregor and Michael Brough did is provide detailed instructions so that anyone can make the simple device. Porter says they wanted it to be easy to reproduce. People can put in their own measurements to see what they need.

The students' market analysis showed few children have Andrew's exact challenge, but lots of people have limited range of motion. Porter believes the biggest group of potential beneficiaries is older people who have arthritis. Smith Mills said it would have helped her recovery when she had an ACL repair on her knee a few years ago.

Andrew Mills, 9, rides his new bike donated and adapted by a group of student engineers at BYU in Provo on Friday, April 14, 2017. Andrew has limb length discrepancy, where his right leg is far longer than his left, and BYU engineering students made a modification that will allow him and other kids who have leg problems to ride bikes more naturally.| Jeffrey D. Allred, Deseret News

Most of the funding for the humanitarian projects came from donors: Martin Frey, Goodfellow Crushers and Michelle Burnham funded the drop-pedal project, while Martin Shipp and the Shipp Family Fund made the prosthetic project possible.

Marcum knows that the student designs are changing lives, and he offers specific examples. In May, for instance, teams at Edwards Lifesciences in South Salt Lake are going to build four of the light, toddler-sized wheelchairs for some local kids who need them. And recently, Marcum received a video from an older couple in Rhode Island with no BYU connection which saw the design online and built one for a granddaughter.

"That's probably the best part of the job, when you get to see people positively influenced because of the work these students do and the donations from these people. It makes it all worthwhile," Marcum says.

Andrew may be the first kid ever to be thrilled that his leg hurt from using his muscle so much to pedal his bike.

It was a good hurt.