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Product design
6.1Ergonomics
Ergonomics deals with the interaction of technological and work situations with the human
being. The basic human sciences involved are anthropometry, physiology and psychology,
these sciences are applied by the ergonomist towards two main objectives: the most
productive use of human capabilities, and the maintenance of human health and well-being. In
a phrase, the job must ‘fit the person’ in all respects, and the work situation should not
compromise human capabilities and limitations.
Anthropometry. This is the branch of ergonomics that deals with body shape and size. People
come in all shapes and sizes so you need to take these physical characteristics into account
whenever you design anything that someone will use, from something as simple as a pencil to
something as complex as a car.
Percentiles
Percentiles are shown in anthropometry tables and they tell you whether the measurement
given in the tables relates to the 'average' person, or someone who is above or below average
in a certain dimension.
If you look at the heights of a group of adults, you'll probably notice that most of them look
about the same height. A few may be noticeably taller and a few may be noticeably shorter.
This 'same height' will be near the average (called the 'mean' in statistics) and is shown in
anthropometry tables as the fiftieth percentile, often written as '50th %ile'. This means that it is
the most likely height in a group of people. If we plotted a graph of the heights (or most other
dimensions) of our group of people, it would look similar to this:
First, notice that the graph is symmetrical – so that 50% of people are of average height or
taller, and 50% are of average height or smaller. The graph tails off to either end, because
fewer people are extremely tall or very short. To the left of the average, there is a point known
as the 5th percentile, because 5% of the people (or 1 person in 20) is shorter than this
particular height. The same distance to the right is a point known as the 95th percentile, where
only 1 person in 20 is taller than this height.
So, we also need to know whether we are designing for all potential users or just the ones of
above or below average dimensions. Now, this depends on exactly what it is that we are
designing.
For example, if we were designing a doorway using the height, shoulder width, hip width etc.,
of an average person, then half the people using the doorway would be taller than the average,
and half would be wider. Since the tallest people are not necessarily the widest, more than half
the users would have to bend down or turn sideways to get through the doorway. Therefore, in
this case we would need to design using dimensions of the widest and tallest people to ensure
that everyone could walk through normally.
Deciding whether to use the 5th, 50th or 95th percentile value depends on what you are
designing and who you are designing it for.
Usually, you will find that if you pick the right percentile, 95% of people will be able to use your
design. For instance, if you were choosing a door height, you would choose the dimension of
people's height (often called 'stature' in anthropometry tables) and pick the 95th percentile
value – in other words, you would design for the taller people. You wouldn't need to worry
about the average height people, or the 5th percentile ones – they would be able to fit through
the door anyway.
At the other end of the scale, if you were designing an aeroplane cockpit, and needed to make
sure everyone could reach a particular control, you would choose 5th percentile arm length –
because the people with the short arms are the ones who are most challenging to design for. If
they could reach the control, everyone else (with longer arms) would be able to.
Here are some examples of other situations – state which percentile you would cater for in
each example:
What is it that you
are aiming for with
your design?
Easy reach
Adequate
clearance to avoid
unwanted contact
or trapping
A good match
between the user
and the product
A comfortable and
safe posture
Easy operation
To ensure that an
item can't be
reached or
operated
Design examples:
Vehicle
dashboards,
Shelving
Manholes,
Cinema seats
Seats,
Cycle
helmets,
Pushchairs
Lawnmowers,
Monitor
positions,
Worksurface
heights
Screw bottle tops,
Door
handles,
Light switches
Machine guarding
mesh,
Distance of
railings from hazard
Examples of
measurements to
consider:
Arm length,
Shoulder
height
Shoulder or hip
width,
Thigh length
Users that your
design should
accommodate:
Smallest user: 5th
percentile
Largest user: 95th
percentile
Knee-floor height, Head
circumference, Weight
Maximum range:
5th to 95th
percentile
Elbow height,
Sitting
Maximum range:
eye height,
Elbow height 5th to 95th
(sitting or standing?)
percentile
Grip strength,
Hand
Smallest or
width,
Height
weakest user: 5th
percentile
Finger width
Arm
Smallest user: 5th
length
percentile
Largest
user: 95th
percentile
Whilst ergonomic design is often a compromise, you must never compromise safety. If there is
a real risk of injury, you may have to use more extreme percentiles (1%ile or 99%ile or more) to
make sure that everyone is protected (not just 95% of people).
How do psychological factors (smell, light, sound, taste, texture and temperature) influence
ergonomics?
Individuals react differently to sensory stimuli. Efficiency and comfort are affected by such
factors.
What problems can arise when collecting data relating to psychological factors?
Quantitative data may be used in a design context relating to psychological factors, but
individuals vary in their reaction to the data. For example, one person will find a room
temperature comfortable while another person will find it uncomfortable, though the
temperature is constant.
How do physiological factors affect ergonomics?
For example, bodily tolerances such as fatigue and comfort.
6.2 The designer and society
Read through the following article that gives an example of a “throw-away society”:
By 2002 over 130 million still-working portable phones were retired in the United
States. Cell phones have now achieved the dubious distinction of having the shortest
life cycle of any consumer product in the country, and their life span is still declining.
In Japan, they are discarded within a year of purchase
What are the moral and social responsibilities of designers in relation to green design issues?
Consider issues relating to waste, pollution, resources, market forces and wealth creation.
Read through the following article about the Apple iPod and planned obsolescence.
As often as possible, Apple introduces new, improved, smaller, faster, more
powerful models that make their predecessors seem much less desirable. This is
what we call "technological obsolescence."
Into this classic marketing strategy, Apple then adds "planned" obsolescence.
Lithium batteries sealed inside iPod bodies begin to lose their peak functionality
after a year of use. By year two, you can only play your tunes half of the time. This
makes the newest model your friend owns so much more attractive. Solution: Toss
the old one into the trash and demand the newest iPod for Christmas.
Apple has already sold 100 million iPods. They are chemically complex little things.
Like every electronic device, they are full of poisonous stuff that's truly bad for the
environment. (My favorites include lead, mercury, cadmium, chromium, and barium).
iPods are also so small that it's expensive to disassemble them and quite easy to toss
them into the trash, which then sits in the landfill poisoning our groundwater.
How can planned obsolescence influence the design specification of a product?
Consider materials and construction, durability and ease of maintenance.
Describe the advantages and disadvantages of planned obsolescence to the designer,
manufacturer and consumer.
Refer to consumer choice, value, R&D and product life cycle.
How does the influence of fashion differ from planned obsolescence in the product cycle?
Planned obsolescence has a definite timescale; fashion is less predictable. Both may be
present. For example, a certain colour may be fashionable for a car but this does not affect
materials or technological obsolescence.
Do you think that “designer” products are better quality than cheaper brands of the same
product?
How do aesthetic considerations affect the design of products?
Refer to shape and form, texture and colour.
Designers always compromise when attempting to balance form with function in the design of
products. Where would you place the following products along a form - function line?
Function
Form