Published 1/03, Copyright 2003, WheelchairJunkie.com
A Helping Hand:|
Power-Assist Manual Wheelchair Technology
by Mark E. Smith
During my early undergraduate days in college, I prided myself to a fault on struggling to use a
lightweight manual wheelchair at school. As a result, the first year of college was horrendous -- fighting
with my poor muscle control to push myself and 25lbs. of text books around a sprawling hillside campus,
traveling all of 1.5mph from class to class, relying on strangers to assist me up hills. My second year,
however, I wised up - at least a little - and scheduled my classes so that my days began at the top of
the hill, where the morning bus dropped me off, and ended the day at the bottom of the hill, where the
afternoon bus picked me up. How awesome it would be, I always thought, that if no matter where I went
in my manual chair, the Earth tilted on its axis so that I always traveled down hill?|
years, several companies have developed "power-assist" systems for manual wheelchair users, offering
the helpful hand they need toward pushing distances and up hills - not exactly tilting the Earth on its
axis, but taking much of the effort out of pushing a manual wheelchair.
The means by which power-assist
systems operate is both simple and complex at once. On the simple side, when you exert a push stroke
on the push rims, it activates the wheels' hub-type motors, giving you a boost that multiplies your original
force by up to three times. Put in everyday terms, it's like getting the rolling distance of three push
strokes for the price of one on the flats, and having three times the strength for climbing hills.
On the complex side, each motor has its own internal electronic controller, to which the push rim is
linked. As the push rim senses movement, it accelerates or stops the motor accordingly. The electronics
are fairly sophisticated, but as you may suppose, translating the biomechanical subtleties of pushing
and steering into precise motor movements is exceptionally difficult. The systems respond well to deliberate
linier movement, but become a tad sporadic when it comes to sudden directional movements (forget naturally
swinging a fluent 360-turn in the grocery store when you realize you just rolled past the Cheerios!).
Similarly, sudden spasms in your push stroke - ones that may only slow a regular manual chair - can
cause the power-assist system to come to a sudden halt (to the controller, a rearward jerk on the push
rim means stop). Nevertheless, for linier, fluent push strokes - those by paras and C6/C7 quads -- the
motors are amazingly graceful, seemingly allowing the wind to carry you at an all but effortless 4mph
Being power-assist, the power is in the form of batteries. Designs vary from the Alber
E-Motion system that has a battery in each rear wheel, to the Quickie Xtender that features a single
battery mounted on the rear of the chair. The optimal range on these systems averages around 9-miles
(with "optimal" underlined for the very small-capacity batteries used, and don't forget, you're still
pushing during that mileage, too!). Much like using a conventional powerchair, it's important to monitor
the battery level, as once the battery is dead, not only are you back to pushing without assistance,
you are also hauling 35lbs. to 50lbs. of power-assist equipment on top of the weight of your chair, making
it far less efficient to push than a stock lightweight manual wheelchair.
Among the advantages
of power-assist systems is portability. Where a complete powerchair system typically weighs 150lbs.
or more (and transportable powerchairs may require five or more components removed for stowage), a complete
power-assist package, including the chair may weigh as little a 70lbs., and require little disassembly
for stowage (I say "little disassembly" because systems like Quickie's require battery removal, and the
disconnection of plugs if you wish to remove the rear wheels). Additionally, caution must be used not
to damage the push rims during stowage, as the push rims are the link to operation (you may not want
a careless cousin merely tossing your power-assist rig on its side in a car trunk as you do on your present
folding manual chair).
With complete power-assist packages at around $8,000 ($6,000 for the
system, and $2,000 for the manual wheelchair), they cost more than most powerchairs. As government funding
regulations define us into manual or powerchair users, and with common powerchair funding limits under
$6,000, there isn't presently funding protocol to purchase the costly, "in-between" mobility solution
of power-assist technology. Some manufacturers suggest that U.S. providers submit for funding under
a "miscellaneous" funding code - not typical K0011 for a powerchair or K0005 for a manual rehab chair
- but, again, based on user classifications and the high price, it's a tough bill to fund. Still, private
insurers, vocational rehab programs, and self-funding provide alternative means to obtaining the technology.
Indeed, for the right user, with the right funding, power-assist technology can improve one's life,
decreasing fatigue and increasing mobility, adding that helping hand when needed.
As for me,
getting back to my collegiate days, by my third year in college, I began using my powerchair at school,
just as I had the previous 15 years of my life - and was a better man for it, with less stress, dramatically
improved mobility, and far more energy to focus on studies. What all this proves is not that I could
have benefited from today's power-assist technology (it hates my tight-grip and spastic push stroke).
Rather, my experience proves that college made me a wiser man toward maximizing my mobility according
to my abilities, and taught me that no matter how much I close my eyes and concentrate, I can't cause
the Earth to tilt on its axis.