SPECIAL SEATS AND WHEELCHAIRS 597
FEATURE
Wood wheels—big or small
CASTERS AND WHEELS
(Caster means that the
wheel can swing in
different directions for
making turns.)
DESIGN DETAILS
• Use boards or plywood.
• To avoid splitting,
screw and glue 2 layers
together with grain
running in opposite tire
directions.
• Cut notch
in rim to
hold solid
tire.
edge
of
wheel
• Casters come with
hard or balloon
tires in many sizes,
weights, styles, and
prices.
Standard
wheelchair
caster wheels
If possible, get
(or make) casters
with ball bearings.
Casters from other
(non-wheelchair) equipment
(used or new) for mounting
into metal
tube frame
for mounting
on wood frame
caster welded
to metal plate
for screwing to
wood
• Use 3 inch to 6 inch
wheels.
• larger, wider wheels for
rough ground
• Be sure bearings are
strong enough and in
good condition.
• Drill holes in
rubber wheels
to make them
weigh less.
Bent and welded steel
caster forks
30°
angle
bolt
strong
bronze weld
holes to make
fork weigh less
• Choose bolt width to
fit bearings.
• A bent steel tube can
be used instead of a
metal band.
hole sized to fit axle
ADVANTAGES
• relatively cheap
• little skill required—
mostly carpentry
• works with wood
axles
• heavy-duty bearing
can be added
• little work to attach—
especially if standard
mount and bearings
are used
• less costly
(especially if not
new)
• often full wheel
and caster bearings
come with them
• less costly than
factory-made casters
• strong (if well made)
HUBS, BEARINGS, AND AXLES
Standard wheelchair
bearings ball
bearings
ball bearings at
each end of hub
• A standard wheelchair
uses 12 bearings: 2 for
each wheel axle and 2
for each upright caster
bearing.
• How a ball bearing
works:
axle does
not move
turning
wheel
• These bearings come
as part of standard
wheelchair hubs and
wheels.
• Most factory-built
wheelchairs have
unusual sized axles
and therefore must
be fit with special
wheelchair bearings.
DISADVANTAGES
• often heavy
• may not hold up
long—especially in
wet climate or mud
(Keeping wood
oil-soaked helps them
last. Use old engine
oil.)
• usually very costly
• may not be locally
available
• Poor quality casters
make wheelchair
much harder and more
awkward to use.
• Hard-rubber casters
make a bumpy ride.
• Some used casters are
too weak.
• needs special
equipment
(bending jig) and
welding skills
• Bearings on most
factory-built chairs are
costly, of poor quality,
and wear out quickly.
• Unusual hub size
makes it hard to
replace commercial
wheelchair bearings
with other standard
machine bearings.
axle hub
Bicycle bearings and axles
front wheel axle
hub axle
For mounting alternatives,
see wheelchair designs
p. 598 and 615. Also, see
the Healthlink Worldwide
Manual (see p. 604).
• cheap—especially if
old bicycles are used
• easy to get
• can be used with
complete bicycle
wheels
• Axle is too weak
to be supported
by one end only
(except in a small
child’s wheelchair).
disabled village children