A basic manual wheelchair incorporates a seat, foot rests and four wheels: two, caster wheels at the front and two large wheels at the back. The two larger wheels in the back usually have handrims; two metal or plastic circles approximately 3/4" thick. The handrims have a diameter normally only slightly smaller than the wheels they are attached to. Most wheelchairs have two push handles at the top of the back to allow for manual propulsion by a second person.
Other varieties of wheelchair are often variations on this basic design, but can be highly customised for the user's needs. Such customisations may encompass the seat dimensions, height, seat angle (also called seat dump or squeeze), footrests, leg rests, front caster outriggers, adjustable backrests and controls.
Everyday manual wheelchairs come in two major designs—folding or rigid. The rigid chairs, which are increasingly preferred by active users, have permanently welded joints and many fewer moving parts. This reduces the energy required to push the chair by eliminating many points where the chair would flex as it moves. Welding the joints also reduces the overall weight of the chair. Rigid chairs typically feature instant-release rear wheels and backrests that fold down flat, allowing the user to dismantle the chair quickly for storage in a car.
Many rigid models are now made with ultralight materials such as aircraft aluminium and titanium. One major manufacturer, Tilite, builds only ultralights. Another innovation in rigid chair design is the installation of polymer shock absorbers, such as FrogLegs, which cushion the bumps over which the chair rolls. These shock absorbers may be added to the front wheels or to the rear wheels, or both. Rigid chairs also have the option for their rear wheels to have a camber. Wheels can have a camber, or tilt, which angles the tops of the wheels in toward the chair. This allows for better propulsion by the user which is desired by long-term users. Sport wheelchairs have large camber angles to improve stability.
Various optional accessories are available, such as anti-tip bars or wheels, safety belts, adjustable backrests, tilt and/or recline features, extra support for limbs or neck, mounts or carrying devices for crutches, walkers or oxygen tanks, drink holders, and clothing protectors.
Transport wheelchairs are usually light, folding chairs with four small wheels. These chairs are designed to be pushed by a caregiver to provide mobility for patients outside the home or more common medical settings.
Experiments have also been made with unusual variant wheels, like the omniwheel or the mecanum wheel. These allow for a broader spectrum of movement.
The electric wheelchair shown on the right is fitted with Mecanum wheels (sometimes known as Ilon wheels) which give it complete freedom of movement. It can be driven forwards, backwards, sideways, and diagonally, and also turned round on the spot or turned around while moving, all operated from a simple joystick.
Read more about this topic: Wheelchair
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