Published 6/03, Copyright 2003, WheelchairJunkie.com
A Master's Definitive Guide to Ultra-Lightweight Manual Wheelchair Order Forms|
By Mark E. Smith
If I had a dollar for every fellow user I've helped define specifications and options when ordering
an ultra-lightweight manual wheelchair, I wouldn't have to work any more. . . . OK, I'd still have to
work, but at least I'd have a couple hundred bucks in my pocket. |
As much as I enjoy panicked,
last-minute cell-phone calls from users wondering "what in the heck is 'frame offset,'" as they sit in
their providers' offices, or the occasional powerchair provider whom, at the end of our conversation,
asks such questions as, "What's a 'grade aide' on a manual chair?" I thought it was time to share the
knowledge, providing you with A Master's Definitive Guide to Ultra-Lightweight Manual Wheelchair Order
The frame length is measured from the center of the backrest tube,
to the center of the front down tube where the footrest extension tubes enter the frame - put simply,
it's the overall length of the side frame. This specification dictates your body position -- specifically
your leg angle - and relates to the anatomical distance from your back to your heal on a horizontal plane.
A short frame pulls your legs in, and a long frame may stretch your legs out. Of course, the objective
of this measurement is to fit the frame length to your positioning and comfort requirements. Comparing
two users of a 16" seat depth, one of normal stature whom wishes a tight, tucked leg position might go
with a short, 20" frame length; on the other side, a user whom has longer legs, or wishes greater leg
extension, may best fit a long, 24" frame. It is important to note that most order forms share the terms
"Short," "Medium," and "Long," but each manufacturer has its own measurements, so check the order form
footnotes or contact the manufacturer for specifications.
FRAME/FRONT FRAME TYPE:
are three front frame types - fixed, swing-away, and tapered. A fixed frame has legrests that are permanently
fixed in place (a Quickie GPV is a fixed frame). A swing-away frame allows the legrests to pivot to
the side for removal (as is the standard on most folding chairs, like the Quickie 2). A tapered frame
- which nowadays is found on both fixed and swing-away frames - features a front-end section that is
wider at the seat than the footplate, following the natural narrowing from your knees to your feet -
a V-shape - which permits a more compact front end, and gives a more tailored aesthetic.
Unfortunately, manufacturers haven't set up standards to define the front taper. Some
define taper as the overall narrowing of the front of the chair - if the seat width is 18", with a 4"
taper, the front of the chair tapers from 18" at the knees to 14" at the feet. Other manufacturers label
taper as "offset," which only takes into account the vertical plane on one side of the chair, meaning
that if the footplate is offset 2" inward of the edge of the seat, you have an 18" to 14" taper once
again. And, still other manufacturers specify taper in relation to the overall footplate width, as in
14" on an 18"-wide chair. Therefore, understand how the manufacturer defines taper, so you don't order
a 2" offset thinking it's a 2" taper, or visa versa.
FRONT FRAME ANGLE:
The front frame angle
is the bend where seat tube flows down to the footplate (that is, the steepness of the front of the chair).
On order forms, this bend is categorized from 60- to 85-degrees. Depending on your positioning, this
angle may dictate your leg angle, as well as footplate location. The study of anatomy and ergonomics
dictates that the most natural seated position is with an outside knee angle of 70-degrees; however,
wheelchair positioning and performance demands often require as little as 60-degrees or as much as 85-degrees
on everyday chairs. As a general guide, every 10-degrees equals plus or minus 1" in length, so if a
70-degree bend offers a 23.5" frame length, an 80-degree bend will shorten the chair to 22.5" (again,
this varies among manufactures based on down tube length, so refer to individual specifications).
Seat width seems like the most simple measurement, but in the manual chair genre,
where each manufacturer has set its own measurement standard, it can get complicated. Some manufacturers
measure outside edge to outside edge of the side frames; others measure from center tube to center tube
on the side frames; and yet others measure the upholstery (which can provide a measurement in-between
the outsides and centers of the tubes). The consequence is, of two leading chairs ordered with an 18"-wide
seat selected, one will arrive with 19" of seating surface, and the other, 17.5". Always confirm from
which points the manufacturer measures seat width.
The seat depth
is typically measured via the seat sling, itself, from the rear edge to the front edge of the fabric.
An additional ˝" of seat depth usually exists between the rear edge of the upholstery to the backrest,
which is accounted for with a cushion.
FRONT/REAR SEAT HEIGHT:
Seat height is measured from
the ground plane to the seat plane (also called seat-to-floor height). On manual chairs, the front and
rear seat heights are most often independent, providing seat angle. On ultra-lightweight everyday chairs,
the industry range for seat-to-floor height options is approximately 12" to 21", depending on the model
and specifications. In practical, use most adult chairs are configured in the 14" to 19" range for such
reasons as transfer heights and the most comfortable push stroke. Remember, your cushion adds height,
so take into account the thickness of your seat cushion when considering seat heights.
There are three general types of footplates: Flip-up, rigid/platform, and flip-up platform.
Flip-up footplates are the most traditional, where the left and right footplates flip-up so that your
feet can reach the floor for transfers. Rigid/platform footplates are found on rigid chairs where flip-up
and swing-away legrests aren't needed. A flip-up platform provide the strength and rigidity of a footplate,
but flips up in the center or to one side to allow foot clearance or folding of the chair. An "angle-adjustable"
footplate allows you to change the footplates angle to best accommodate calf and ankle positioning.
"Extension tubes" are the mounting tubes that telescope from the footplate into the mounting frame
(this is the tube section that adjusts the overall legrest length, and must be selected in a range appropriate
to your stature.).
Most chairs offer back heights in adjustable packages,
such as 12.5"-15.5", in 1" increments. This measurement is from the top of the seat sling tube to the
top of the backrest upholstery, so it's important to remember to also consider the height of your seat
cushion. Among the best tactics is to order a height package where your back height is mid-range - as
in ordering 12.5"-15.5" for a 14" back height - permitting adjustment in either direction as needed.
The three styles of backrests are fixed, angle-adjustable, and folding. Fixed
backrests don't offer folding or angle adjustment, but may offer height adjustment depending on the chair.
Angle-adjustable backrests allow you to adjust the angle in relation to the seat (this is especially
important if you wish a "squeeze frame," where there's a lot of frame and seat angle, but you need the
backrest to retain a 90-degree position to the ground. Additionally, an angle-adjustable back is especially
useful in tailoring the seat's positioning and comfort to your exact needs. Folding backrests, which
are most often combined with angle-adjustability, increase transportability, namely on rigid chairs.
Camber is the "angle" of the rear wheels, where the top of the wheel is pulled in
toward your body. The purpose of camber is to both increase pushing efficiency and enhance a chair's
performance, as a chair with camber is more stable and responds truer in quick turns. For the everyday
user, camber is a Bell curve - some camber is good, but too much camber may be bad. Because camber flairs
the overall width of the chair where the rear wheels contact the ground, every increased degree of camber
widens the chair. Everyday chairs run 0- to 8-degrees of camber, with 3- to 6-degrees best reflecting
the marketplace. Camber beyond 8-degrees widens a chair significantly, and restricts access through
tight doorways. If you're in doubt as to how camber affects a particular chair's overall width, contact
AXLE PLATE/CAMBER TUBE:
An axle plate is a bolt-on, adjustable plate the
receives the rear wheels and allows for vertical and horizontal adjustment of the chair's center-of-gravity,
as well as adjustments of camber and toe (the parallel tracking adjustment of rear wheels). An optional
configuration is an "amputee axle plate," which offsets the axle behind the backrest for enhanced rearward
stability. A camber tube, similarly, connects the axle to the chair, and may be fully adjustable, but
acts as a rigid member that spans the width of the chair for enhanced performance. In everyday use,
axle plates and camber tubes serve users well, so the choice is often merely defined by which version
a manufacturer builds into a given product.
The industry standard is a stainless-steel
quick release axle - push a button in the center of a wheel, and the wheel comes off. A variation of
this is a "quad-release axle," which requires little dexterity to remove the wheel - just flip a lever
to release the wheel. Titanium axles save weight and enhance strength, but $135 is a lot of money for
such a small component upgrade.
20", 22", 24", 25" (559), and 26" rear wheels
are the typical wheel selections, with 24" as the most common. Rear wheel size dictates roll rate, push
stroke, and seat to floor height. Spoke wheels are typically light and responsive, whereas molded "composite"
wheels are a bit weighty but very durable. A hub term to note is "high-flange," which means that the
hub is larger in diameter, requiring shorter spokes, which results in a stiffer spoke wheel. "X-Core"
and "Spynergy" are high-end brand-name wheels, and "Primo" and "Kik" are tire brands.
Handrims, AKA "pushrims" are either tubular metal or composite, with aluminum the most common. Finishes
are anodized, which creates a smooth, durable finish on aluminum; powder-coated, which is a paint process
that doesn't hold up as well as anodizing; and, vinyl coated, which provides a friction surface, but
can chip over time. Projection handrims feature nubs, so that those with limited grip can palm the projections.
Projection handrims come in "vertical," extending straight up from the pushrim, or "oblique," which
positions them at approximately 45-degrees to the side.
There are three variations
of wheel locks (brakes): push-to-lock, pull-to-lock, and scissor lock. Push- and pull-to-lock are your
typical brake, usually mounted on the top side-frame tube, and the designation merely defines the direction
used to lock the brake (this can be vital to some with limited strength in particular muscle groups).
Scissor lock brakes retract out of the way when not in use, but may not be as easily operated as conventional
brakes. A "grade aide" is a cam device that prevents the chair from rolling backward during uphill travel.
Casters are available in 3", 4", 5", 6", 7", and 8" sizes, with 5" and 6" the most common.
"Low-profile polyurethane" refers to a hard, solid tire typically found on 4" and 5" casters. "Semi-pneumatic"
is a rubber tire with a foam or rubber insert, as on most 6" casters. "Pneumatic" is a tire with a tube,
prone to puncture. "Caster pins" are a device that locks the front caster fork in place, preventing
it from pivoting during transfers.
The two armrest variations are "tubular" and
"removable." Tubular arms are single, formed tubes that reside in sockets behind the backrest. Tubular
arms are lightweight, and provide arm support, but do not provide hip coverage. Removable arms are traditional
in function, with height adjustability and hip coverage.
are panels - either fabric or solid - that keep your hips, clothes, and cushion from protruding beyond
the sides of the seat. If you wish to keep all tucked in nicely, but don't need armrests, side guards
are a meaningful alternative.
"Anti-tips" are wheelie wheels. "Impact guards"
protect the front frame from… well… impacts. "Spoke guards" are plastic overlays that cover the rear
wheel spokes to prevent damage during sport impacts. "Travel aides" are small wheels that replace the
rear wheels, allowing the chair to fit in confined spaces like airplane aisles.
There you have
it, the mysteries of ultra-lightweight wheelchair order forms divulged, from grade aides to offsets.
Is this ultra-lightweight wheelchair dissertation complete? Of course not - everyday new components
are designed, and evil-but-creative industry wordsmiths like me spin terms to distinguish one manufactures
multi-adjustable widget from another manufacturer's multi-adjustable widget on competing order forms.
However, with this base reference source, you'll be ahead of the game toward checking order form specification
boxes with confidence - and think of all the extra time you'll have to ponder frame colors like Candy
Turquoise versus Toxic Green.