TABLE 1: INDOOR PERFORMANCE CHARACTERISTIC
BAD
BETTER
Overall turning circumference
BEST
Smaller
TABLE 2: OUTDOOR PERFORMANCE PLATFORM
MWD
Distance between pivot (rotating) point and furthest point on base
Shortest
MWD
Length located in front of driver
Shortest
FWD
Length located in front of driver
Longest
RWD
CHARACTERISTIC
BEST
PLATFORM
Driving wheel
BAD
BETTER
In front
FWD
Larger leading wheel
In front
FWD
Caster and wheel size
Larger
All*
Ground clearance
Higher
Power/torque
All* More
All*
Sensitivity to “ideal” weight distribution and centre of gravity
Lower
MWD/FWD
Tire width
Greater
All*
* Most brands offer solutions. TABLE 3: STABILITY CHARACTERISTIC
TABLE 4: DRIVER & SEAT PLACEMENT BAD
BAD
BETTER
BEST
MWD
Unencumbered space, including at 90 degrees
RWD
MWD
FWD
RWD
FWD
MWD
FWD
MWD
Ability to position powered seating without compromising stability
RWD
FWD
MWD
Maintaining stability during tilt and recline
RWD
FWD
MWD
RWD
FWD
MWD
The ability to maintain ideal weight distribution and centre of gravity, regardless of seating and lower extremity needs.
Maintaining stability up and down ramps, etc.
RWD
FWD
MWD
BETTER
BEST
CHARACTERISTIC
BETTER
BEST
Absorbs/ reduces bumps, jolts, vibrations
MWD
FWD RWD
Pivot point at or close to drivers head
FWD
MWD RWD
Provides stable seat (reduced rocking and bouncing)
MWD
FWD RWD
FWD
MWD
Platform with the least sensitivity to ideal distribution of weight and balance and centre of gravity
RWD
Weight-distribution friendly architecture
RWD
Anti-tip characteristics
BETTER
FWD
BEST
TABLE 5: RIDE SMOOTHNESS CHARACTERISTIC
BAD
CHARACTERISTIC
TABLE 6: INTUITIVE FEEL
tight corners due to the position of the turning pivot point and short front protrusion. However, FWD chairs do have significantly larger 360-degree turning circumference than those operating on an MWD platform. You may more easily negotiate a tight turn with an FWD chair, but if you need to rotate in that space, make certain there is enough space. If not, MWD will be the answer (Table 1).
Outdoor Performance When operating on sidewalks, parking lots and rougher surfaces, larger wheels and casters and a wider tire/caster profile (footprint) provide flotation against sinking and ploughing. Weight distribution that unloads casters and places more of the weight over the larger drive wheels is also positive. Ground clearance of three or four inches – enough to clear typical obstacles – is industry standard. It is also important to prevent
Maneuverability in confined areas
BAD
RWD
stalling, so adequate power/torque is a must (Table 2). Simply put, FWD offers superior performance during outdoor use for these reasons: 1. The larger front drive wheels are significantly more capable of transitioning over obstacles of all types (monster trucks prove it). 2. The typical weight distribution on the FWD platform tends to be over the drive wheels, which supports good traction. 3. It is easier to “pull” then to “push” casters over obstacles or soft surfaces (pushing is an RWD characteristic). Casters loaded down due to poor weight distribution are a significant impediment to traversing rough, soft surfaces. Again, this is a typical RWD characteristic. 4. FWD platforms do NOT “high centre.” High centering may be present as an MWD weakness outdoors.
Spinal Columns
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