Tech Briefs Magazine - April 2022 - 12

Reinventing Mobility
A pull to push wheelchair continues to roll forward.
L
ong-term use of a manual wheelchair is a disaster for the
shoulders. Impingement, rotator cuff issues, degenerative
joint disease, and pinched nerves are just some of the problems
that crop up and debilitate after years of pushing a wheelchair.
It's the pushing that's the problem, as Salim Nasser realized
when he was a mechanical engineering student at Florida International
University. " I wanted to do something that I was
personally interested in, " he said. " I'm in a wheelchair and
knew some of the problems. " So, for his senior design project
he created a chair that would go forward when pulled.
To make it move in this seemingly paradoxical way, Nasser
quickly settled on a design that used a hub with planetary gears.
" It was the obvious solution for me, the simplest way to reverse
that motion, " he said. " I didn't have to think about it more than
once. " It was this design - its simplicity, viability, and extraordinary
effectiveness at minimizing shoulder problems for those
in wheelchairs - that won Nasser SAE's Create the Future Design
Contest in 2010.
The award helped Nasser fi nd a fi nancial partner and go
from prototype to product in a matter of fi ve years. Now wheelchair
bound people all over the country are pulling on their
wheels to go forward and saving their shoulders from a world of
pain in the process.
The Rowheel has come a long way since its fi rst inception. " I
had to completely redesign it, so that it was manufacturable,
and cost-effective, " said Nasser. " It had to be reliable, lightweight
enough to transfer to cars, and it had to look good. "
To lighten the hub, Nasser tried a variety of materials and
manufacturing methods before settling on thixomolding (essentially
an injection molding process done with magnesium in
a semisolid state). The result was a more rugged hub, pounds
2010 GRAND PRIZE WINNER
INNOVATOR: Salim Nasser,
Founder, Rowheel
INNOVATION: The Rowheel
Wheelchair Propulsion System helps
manual wheelchair users increase
their mobility while decreasing
upper body, repetitive stress
injuries.
IMPACT: Easier wheelchair usage for those who suffer
from muscle pain, torn rotator cuffs, joint degeneration,
and carpal tunnel syndrome.
Enter the 20th Anniversary Contest:
www.createthefuturecontest.com
12
lighter, and a good 80 dollars cheaper than machining from
aluminum. To keep the gears themselves light and low maintenance,
they are now self-lubricating and made of nylon and
Delrin. To further lower the weight and increase reliability
Nasser switched to wire race bearings that are made in house.
The initial fi rst commercial version of a Rowheel had a high
gear ratio which made it fast and responsive but better suited to
those with good upper body strength. A second version, which
uses a low gear ratio makes it easier to propel than standard
wheelchairs and is the more popular and simpler of the two.
Using Rowheels actually builds shoulder strength. On a traditional
chair, the harder you push the greater the risk of injury
to the shoulders. But Rowheel users can go as fast as they want.
" The harder you pull, the better it is - the motion is completely
benign to those issues, " said Nasser. A study published in the
Journal of Spinal Cord Medicine confi rmed the benefi ts to the
shoulders of anyone switching from a forward-push wheelchair
to a Rowheel.
Despite the successes, though, Rowheels are still far from
commonplace. " Muscle memory works against us, " said Nasser.
" Physical therapists, when they see it, a light bulb goes off in
their heads - they know. But for longtime users, we're asking
them to do exactly the opposite of what they've been doing for
years. It's like asking you to walk backward to go forward. A lot
of people freak out. "
There is one group of people that don't need any convincing:
anyone who's already experienced shoulder pain or injury
from wheelchair usage. " The moment they sit in it they notice
the difference, " said Nasser. " It's instantaneous. "
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Tech Briefs Magazine - April 2022

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