Page 294 - Handbook of Electronic Assistive Technology

Chapter 9 • Powered Mobility 283

wheel centre, effectively making the chair rear wheel drive with a long, unnecessary and
unhelpful extension at the rear, in which case a compact rear wheel drive chair might be
more suitable.
Some mid-wheel drive chairs offer a very narrow overall width, which is really helpful
for access to a small environment; this will be highly appropriate in many cases but there
are two considerations:

• Maximal lateral stability (as opposed to that defined by the testing standards) will
be reduced due to the reduced track width (the distance across the chair between
the drive wheels). This will only cause a problem if the chair is used over very rough
ground and/or if the person has a wide seat width and/or high body weight, and/or is
positioned with an increased seat height.
• The batteries may be smaller than those fitted to wider chairs, which will reduce the
available driving distance. Again, this will not cause a problem in many cases but
where the person drives a considerable distance every day, such as for commuting to
work, battery capacity will be more critical.

Kerb climbing is achieved by articulation of the front pair of castor wheel arms. The
height which can be climbed may be limited in some mid-wheel drive chairs compared to
most rear drive chairs with a kerb climber. Therefore there is a need to decide on the impor-
tance of the feature, study the manufacturers’ specifications and, most importantly, have the
person try the chair for themselves in the environment in which it will be used most often.

Front Wheel Drive
Front wheel drive chairs (Fig. 9-5) are still very popular with some users but lost some
popularity when mid-wheel drive chairs became more available and affordable.
They can offer a very good drive option for outdoors on more challenging terrain but
are more difficult to drive up a kerb, which must be approached with careful judgement as
to its height because the chair can ‘bounce’ off the face of the kerb if it is too high, which
may throw the occupant forward or even out of the chair. If the kerb is to be tackled, it
must be done so with commitment and a moderate amount of speed with which to carry
the chair up the obstruction with its momentum.

FIGURE 9-5 Front wheel drive�