Engineering & Technology
Why, you may be wondering, are engineering and technology classified as Culture and not Science? What is the difference between science & technology?
Science is the exploration of the fundamental laws of nature. Technology is the human application of those laws for the purposes of invention. The latter is based on the former, but science encompasses everything that is naturally occurring whereas technology refers only to those things that are man made.
From the earliest of all human technologies, spirals have been a basic structural element. We may not think of them as technologies today, but baskets and pots were among man’s most useful early inventions. In ancient Egypt, for example, baskets were used for storing and carrying food and other goods as well as for earth-moving during construction.
Like a giant coiled snake, a highway spirals down to meet with other roadways. The advantages of the spiral construction here are the same as for constructions in the man-made and natural world: the layering of the road levels allows the ramp to take up much less space than a straight ramp would and also eliminates crossing conflicts by keeping lines of traffic that are moving in different directions from having to cross paths; traffic can move smoothly and efficiently.
The Turntable is based on spiral grooves.
A cyclotron is a type of particle accelerator. Charged atomic and subatomic particles are accelerated by exposure to high-frequency alternating voltage while following an outward spiral or circular path in a magnetic field. A perpendicular magnetic field causes the particles to travel in a loop, thus re-encountering the accelerating voltage many times. The increased energy of the accelerated particles combined with the force from the magnetic field makes each subsequent loop larger, which means that the path followed by the particles is an outward spiral. Eventually, when the spiral is wide enough, the particles collide with a target at
Biomimicry (from bios, meaning life, and mimesis, meaning to imitate) is a discipline that studies nature’s best designs and processes and then applies (or mimics) them to help solve human problems. The non-human world has already perfected mechanisms for addressing challenges we humans struggle with today, challenges like harnessing natural energy, building durable shelter from materials at hand, finding medical solutions in the natural world, and producing food in an environmentally sustainable manner. Biomimicry is “innovation inspired by nature.”
Not surprisingly, the spiral has been a fertile source of inspiration in biomimicry. Based on observations of fluid dynamics, engineers have designed energy efficient rotors, pumps, and fans. Read more about biomemetic innovation.
Biomimicry methodology promotes the idea that all stages of innovation development, distribution, and usage follow a cyclical process. The Biomimicry Institute explains this metaphor: “We use a spiral to emphasize the reiterative nature of the process—that is, after solving one challenge, then evaluating how well it meets life’s principles, another challenge often arises, and the design process begins anew. For instance, an innovator might design a wind turbine that mimics life’s streamlining principles, but then ask how will it be manufactured? Will the energy use and chemical processing mimic nature too? It can, with another cycle through the design method.”
Gears produce torque, or rotational force, and are used in a wide variety of common machines, including bicycles, cars, and clocks and watches. There are numerous types of gears, and the following are examples of gears that employ spiral designs.
In helical gears (right), the teeth are not parallel to the axis of rotation but are set at an angle. As the teeth are set along the curved surface of the gear, each tooth is a segment of a helix. One useful characteristic of helical gears absent in straight-toothed gears is that they can be aligned in either parallel or crossed orientations (see illustration). Another benefit of helical gears is that, because the teeth engage more gradually than in other types of gears, they run more smoothly and quietly. Helical gears are therefore preferable in applications that involve greater speed, large power transmission, or where reduced noise is advantageous.
Double helical gears (right), also called herringbone gears, eliminate the axial thrust—pressure exerted on the gear’s axis created by the slanted teeth—generated by single helical gears. The two sets of teeth, positioned to form a V, create thrust in opposite directions that cancels itself out. A double helical gear can be thought of as two standard helical gears stacked in mirror image.
Worm gears (right) resemble screws (and are usually used with standard gears, as illustrated). Worm gears are a variety of helical gear, but their teeth are set at much larger than in helical gears—much closer to 90 degrees—and the body of a worm gear is typically longer than that of its helical cousin, thus giving it its screw-like appearance. Worm-and-gear sets are a simple and compact way to achieve a higher gear ratio, which means that the difference in speed between the two gears is increased. One of main reasons for using gears is to increase or decrease the speed of rotation.
Impellers and Pumps
Centrifugal pumps use rotating impellers to increase fluid pressure and propel liquids through a piping system. This illustration of velocity and pressure patterns on impellors demonstrates the spiral characteristics of fluid dynamics.
the edge of the chamber, causing them to fragment. The secondary particles created can then be analyzed to determine various subatomic properties of the material. Cyclotrons have a variety of applications, including nuclear physics research and medicine—for example, they enable diagnostic tools like PET scans and can be used in radiation therapies to treat cancer.
Types of balance springs: (1) flat spiral, (2) Breguet overcoil, (3) chronometer helix, with top view, and (4) early balance springs.
Before the days of batteries, all watches were mechanical and were driven by a spring, called a mainspring, made of metal ribbon. Mechanical watches had to be wound up in order to work: by turning the knob or key, the mainspring twisted tighter, storing energy. As the spring slowly unwound, the force exerted turned the gears and made the clock run. However, as the mainspring untightened, the force it generated slackened. As a result, the clock would run fast after it had been wound and would gradually run slower and slower as the spring released. Thus accuracy was a problem for early watches. In the 1670s, a solution to the problem was presented by Dutch astronomer Christiaan Huygens in the form of a second spring, called a balance spring. The balance spring enabled the even release of energy from the mainspring due to the inherent and regular cycling of its own coiling and uncoiling: “In a modern spring-driven watch, the spring is mounted on a balance wheel, which turns back and forth in sync with the spring's oscillations, simultaneously rocking the pallet from side to side. The pallet controls the turning of the gears connected to the clock's face and thereby maintains a steady transfer of power from the mainspring to the clock's counting mechanism. While the mainspring is being wound, a ratchet and click keep the winding action from disturbing the watch's main gear train.” (from Encyclopædia Britannica Online)
How does the thermostat know when to turn on and off? In electrical thermostats, a metal spiral, known as a bimetallic strip, expands and contracts, thereby opening and closing the electrical circuit that switches the heater or air-conditioner on and off.
The spiral is made of two strips of different metals banded together (usually steel and copper or brass). The two metals expand at different rates when heated, which means that one side of the spiral will increase or retract more quickly than the other side, causing the spiral to tighten or relax. The principle is essentially the same as for curling ribbon: When you pull curling ribbon over the blade of a pair of scissors, the friction generated stretches out one side of the ribbon, and it curls in around the shorter side.
In curling ribbon, this transformation is the result of the molecules reorganizing themselves when they are subjected to the friction, effectively stretching out one side; in the case of the bimetallic strip, the metals are simply expanding and contracting with temperature fluctuations; there is no molecular rearrangement, but the inside and outside of the strip still change in length relative to each other.
The strip curls one way when it is heated and the other when it is cooled. Although bimetallic strips can be flat, they are often coiled for compactness. Coiled strips allow for greater length and thus gives improved sensitivity.
Bimetallic strip wound into a coil. The center of the coil is attached to a rotating post attached to lever (1). As the coil gets colder the moving end — carrying (4) — moves clockwise.
Below: Portrait of an old man dressing a millstone from the collection of the Smithsonian Institute
Millstones are carved with furrows to facilitate the grinding of the grain. Traditionally, furrows are cut to a "harp pattern," so called because the stone is marked off into ten segments, each of which is carved with a set of grooves resembling a harp. The repeated angles of the furrows give the millstone a pinwheel effect. Miller expertise has long held that the harp pattern was the most effective pattern for millstones, and in the late nineteenth century, that tenet was finally substantiated mathematically.
To see an illustration of the pattern of furrows on a millstone and animation of the spiral motion created by the bedstone and the runner, visit: http://www.whitemill.org/z0008.htm.