5. Examples of engineered environments
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:
  • Mechanics, which deals with the forces between and the movements of solid bodies.
  • Structures
  • Materials
  • Systems, which deals with the flows of heat and mass through
  • Energy
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.
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.
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.
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.
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.
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.