The chief divisions
within engineering science, the fundamental areas of
knowledge upon which the creative thinking of the designer is based, are usually
labelled after some such scheme as the following:
These topics may be
used to study examples of engineered environments in a
wide range of categories, five of which are exemplified in Cardiff and the
Vallleys.
Mechanics
Mechanisms are familiar
enough, in clocks, sewing machines, locks and
catches, switches, the human hand, and so on. They can be considered as
assemblages of simple elements, such as pivots and hinges, sliders, gears,
and so on. Their functions generally are to transmit and modify forces and
movements: the object of a door catch is to move a bolt under the action of a
spring so that the door will be held closed, and to convert a turn of the handle
into the retraction of that bolt when it is required to open the door. A door lock
has a rather different function because it requires a very special kind of
movement to withdraw the bolt, which depends on a knowledge of the code (in
the case of a combination lock) or possession of a key which has the required
movements coded into it. Historically, locks represent the human designer's first
traffic in the third of his media, information, about 6000 years ago. They also
exhibit, in a simple form, a crucial design principle, that of stereospecificity,that
is, of actions like unlocking a door which depend on the interaction of
components of very special shape. Stereospecificity is crucial to the highly-
selective chemical processes in which the design of living organisms is founded.
Structures
The term structure
is used very widely for any complex whole showing functional
relationships between its parts, as, the management structure of a company, the
structure of a language, etc. In this chapter its use will be confined to load-
bearing structures, material (but not necessarily solid) bodies that sustain or
resist forces. Most of the designed world consists of structures of one kind or
another; aqueducts and arteries, boilers, bones and bridges, cathedrals and car
bodies, teeth, termitaries, trees, tyres and tennis rackets are all structures
whose design is chiefly dictated by the loads they must sustain.
Very often there is
a conflict between the structural and other functions -the wing
of a bird or an aircraft is best made thick for strength and thin for performance, a
brick will be able to carry more load if it is dense but it will be a better thermal
insulator if it is porous, and so on. Nearly always it is desirable to use as little
material as possible both for reasons of economy, which apply no less in nature
than in human affairs, and also usually for functional reasons. For example, more
stone than necessary in the top of a cathedral would not only have been more
laborious to raise, but might have led to collapse lower down, and bones, car-
bodies, tyres and tennis rackets are all structures in which extra mass requires
extra force to accelerate it, and is therefore undesirable.
Materials
The appreciation of
materials, their special properties, their fitness for certain
purposes, the deep satisfaction given by their cunning and sympathetic use in
articles combining function and ornament, is an important part of human culture.
Scythes and violins, walnut and mahogany furniture, tweed cloth and silver
cutlery, glass and bronze, all show the subtle alliance of craftsmanship and the
nature of the raw material in the creation of artefacts combining beauty and use.
All this was achieved with very little in the way of science, before we enjoyed
anything of the understanding of materials we have now, and it is one of the
fundamental failures of imagination of our age that it does not recognise that this
tradition has not perished, but has flourished and transcended itself in some
modern engineering products. For example, a record-player pick-up cartridge
may marry a tiny precisely-shaped diamond, a fine strip of bronze three times
as tough as anything known 100 years ago, delicate coils of wire as fine as a
spider's web, a powerful little magnet made of rare metals or oxides, whose
existence was unsuspected a century ago, and intricate and perfectly-fitting
parts of strong plastics and metals.
Moreover, all this
was offered, not to kings or bankers, but to any citizen of the
developed world. For perhaps half a day's pay he could buy this triumph of
craftsmanship and ingenuity, beyond anything made by Faberge. Now the vinyl
disc has been displaced by the compact disc, with an optical system in place of
a mechanical one. The materials are not so interesting, but still all-important,
chosen now for optoelectronic rather than mechanical properties, and the value
in terms of design and craftsmanship is perhaps even more remarkable.
Systems
A third manifestation
of design is in systems - combinations of components or
organs for performing particular functions. Thus, the digestive system of an
animal consists of jaws and teeth, salivary glands, gullet, stomach, and so on,
and its function is to process food and extract from it the substances which
support life. A railway system consists of railwaymen, rails, rolling stock, signals,
and so on, and its function is to move people and goods.
These two examples
of systems are of characteristic types. The digestive
system is a process plant, in effect, where material flows through and is
processed to yield some useful product or products. It has a series or line
arrangement of components, one after another, and a flow from one end to the
other. The railway system is a service system, which provides a function,
transport in this case, over an area. It has a network of components, with flows in
both directions down any branch.
Not all systems will
fit into these two categories, but they do provide the key to a
number of important aspects of design in which the ideas of flows, lines, loops
and networks are central.
Energy
An aircraft can fly
the Atlantic because it can store a great deal of energy in
chemical form in fuel and convert that energy reasonably efficiently into other
forms as required. An aircraft or a bird can take off and fly because of its ability
to convert or release energy at a high rate - the rate of conversion or release of
energy is called power.
The ability of a bird
or a mammal to survive in cold weather depends on its
ability to keep down its loss of heat, which is a form of energy, and the
protection that a vehicle offers its occupants in a collision depends largely on
the capacity of its structure to absorb the destructive energy of motion (kinetic
energy). All life depends on energy: plant life draws its energy from the rays of
the sun, and animals in turn obtain energy by eating plants or other animals. At
another extreme, a clothes-peg or a nut-and-bolt depend for their functioning on
their power of storing a little energy.
