Unit 2: Wheelchairs

Question 1

What are the prime functions of wheelchairs

Answer 1

To compensate for locomotor disability

To enable person to move from place to place

Question 2

What are the methods of wheelchair propulsion

Answer 2

Occupant propelled
Attendant propelled
Powered wheelchairs

Question 3

What are the 4 main styles of occupant propulsion

Answer 3

Bilateral arm
One arm
Bilateral legs
One arm one leg

Question 4

Benefits of handrim propulsion

Answer 4

Simple, lightweight, easy to manoeuvre

Question 5

Disadvantage of handrim propulsion

Answer 5

Depends on good hand grip and strong pushing force

Question 6

How can handrim propulsion be made easier

Answer 6

Use larger cross-section handrim tubing
Use indentations/capstan fittings
Use non-slip finish plastic

Question 7

Problems with handrim modifications

Answer 7

Indentations: friction burns

Non-slip finish: splintering

Question 8

Why is handrim diameter usually matched to wheel diameter

Answer 8

Allows user to grip both at same time to aid propulsion

Minimises forces required to propel the chair

Question 9

Benefits and disadvantages of smaller diameter handrims

Answer 9

Increases the max speed

Requires higher force for propulsion

Question 10

Benefits and disadvantages of larger diameter handrims

Answer 10

Less force required to turn wheels

Lower maximum speeds

Question 11

What is the optimum position of the handrim/wheels

Answer 11

As close to the body as possible

Allows arm movement to commence slightly posterior to the trunk and travel to just short of full elbow extension

Question 12

What term is used to describe angling of the wheels to bring them closer to the occupant

Answer 12

Cambering

Question 13

What mechanisms provide the most efficient use of bilateral arm propulsion

Answer 13

Level or crank mechanisms

Question 14

How do you propel a wheelchair with one arm

Answer 14

Grip both handrims to move forwards and backwards

Push one handrim to change direction

Question 15

What are disadvantages of one arm control

Answer 15

Limited speed, range and manoeuvrability

Requires good hand grip, arm strength and control

Question 16

How should a leg-propelled wheelchair design differ

Answer 16

Seat should be lower to allow feet to contact the ground

Ensure max clearance behind the legs to avoid impeding movement

Question 17

How are attendant propulsion wheelchairs usually operated

Answer 17

Push handles at the rest of the backrest

Question 18

What measure is used to give the capacity of a battery

Answer 18

The amp-hour rating

Note: normal ratings are 20-amp hours

Question 19

What are the limitations of powered wheelchairs

Answer 19

Battery operated: heavy, need recharging, finite life

Question 20

What are the 2 types of battery

Answer 20

Lead acid batteries

Gel batteries

Question 21

What are the benefits and disadvantages of lead acid batteries

Answer 21

Benefits: greatest capacity, last longer, cheaper
Disadvantages: heavy, bulky, require regular topping up

Question 22

What are the benefits and disadvantages of gel batteries

Answer 22

Benefits: unspillable, smaller, lighter, more easily transported
Disadvantages: dont have as much capacity as lead batteries

Question 23

What are motors used for

Answer 23

To drive the rear (or front) wheels via belts or gearboxes

Question 24

Describe a beneficial function of motors

Answer 24

Can be disengaged from the wheels to allow the wheelchair to move when the battery is flat

Question 25

How is steering controlled

Answer 25

By feeding differential power to the motors | Note: the wheelchair moves away from the side which is fed more power

Question 26

How are sharp turns achieved

Answer 26

Turn one motor forwards and one in reverse

Question 27

What are the 2 main types of braking

Answer 27

Parking brake Regenerative braking Note: can also brake manually by slowing down the handrims

Question 28

What is regenerative braking

Answer 28

Slowing down the speed of the motors in order to slow down motion of the wheelchair

Question 29

When is parking braking used

Answer 29

When the wheelchair is at a standstill

Question 30

What is the function of the control system

Answer 30

Detects actions of the occupant and translates this into the appropriate operation of the motors

Question 31

What is the 'bang-bang' controller. Give a benefit and a disadvantage

Answer 31

A control system that operates the motors at full power only Benefit: good if no fine control of hand position Disadvantage: creates very fast accelerations that are difficult to control

Question 32

What are the 7 main performance characteristics of the wheelchair

Answer 32

``` Range Max speed Acceleration Stability Obstacle climbing Manoeuvrability Environment protection ```

Question 33

What are the typical max speeds of an indoor and an outdoor wheelchair

Answer 33

Indoor: 2mph Outdoor: 4-8mph

Question 34

What is used as a good indication of the manoeuvrability of a wheelchair

Answer 34

The minimum width of corridor in which a wheelchair can turn to face the opposite direction

Question 35

How is the stability of a wheelchair measured

Answer 35

The steepness of the angle to which a wheelchair can be tipped before it falls over

Question 36

What 2 factors govern the wheelchair stability

Answer 36

The size of its wheelbase and the position of the centre of gravity If the centre of gravity is within the wheelbase then the object remains stable

Question 37

What gives a larger wheelbase: castors in trail or in leading position

Answer 37

In trail

Question 38

Where should the centre of gravity be to ensure max manoeuvrability

Answer 38

As near to the main wheels as possible

Question 39

What adaption may need to be made for a bilateral lower limb amputee

Answer 39

Set the main wheels back a few centimetres to maintain rearwards stability

Question 40

What are anti-tipping levers

Answer 40

Extension to tipping levers that contact the ground before the wheelchair becomes unstable in a rearwards direction

Question 41

What kind of tyres are most prone to instability/slipping when parked on a slope

Answer 41

Smooth hard tyres

Question 42

What do pneumatic-type brakes depend on

Answer 42

Sufficient inflation of the tyres

Question 43

What is an advantage of progressive action running brakes

Answer 43

Work independently of tyre inflation

Question 44

How to ratchet brakes work

Answer 44

Prevent rolling backwards when propelling uphill

Question 45

What factors influence manoeuvrability

Answer 45

The propulsion system | The castors

Question 46

What design characteristics of a castor affect its manoeuvrability

Answer 46

Resilience (hardness of the tyre) Radius of swivel Castor wheel diameter

Question 47

What happens to manoeuvrability as the occupant moves closer to the castors

Answer 47

Manoeuvrability decreases

Question 48

What is castor flutter/shimmy

Answer 48

Impairment of direction control due to castors vibrating widely on their swivels when moving at speed

Question 49

What 5 factors influence rolling resistance

Answer 49

``` Wheel diameter Tyre resilience Bearing friction Wheel alignment Weight ```

Question 50

What happens to rolling resistance as wheel diameter increases

Answer 50

Rolling resistance decreases

Question 51

What happens to rolling resistance as tyre resilience decreases

Answer 51

Rolling resistance increases

Question 52

What is a benefit and a disadvantage of solid tyres

Answer 52

Benefit: less energy required for propulsion Disadvantage: less comfortable when going over uneven ground, cannot climb obstacles

Question 53

What dimension of a wheelchair governs the height of the obstacle that can be climbed

Answer 53

The front wheel diameter | +/- assistance from anti-tipping levers and kerb climbers

Question 54

What are kerb climbers

Answer 54

A pivot structure that hits obstacles and swings down to lift up the front of a wheelchair

Question 55

What environment is the use of solid tyres restricted to

Answer 55

Indoor use on solid surfaces with no obstacles

Question 56

Benefits and disadvantages of foam-filled tyres

Answer 56

Benefit: cannot be punctured Disadvantage: increased rolling resistance and weight

Question 57

What is the most common style of seating used

Answer 57

Sling-type

Question 58

How wide are most wheelchairs

Answer 58

Required seat width +5cm for wheels and frame

Question 59

What are the 3 main types of strength

Answer 59

Static Impact Fatigue

Question 60

Describe static strength

Answer 60

The ability to withstand a constant force e.g. weight of a person in the chair

Question 61

Describe impact strength

Answer 61

The ability to withstand transient loads e.g. blows to the chair when dropped/hitting a kerb

Question 62

What components of the wheelchair are vulnerable to impact strength loads

Answer 62

Castor forks, mountings and frameworks

Question 63

Describe fatigue strength

Answer 63

The ability to withstand variation in load over prolonged period of time (wear and tear)