! Technology Introduction

The technology that we use today is the result of millennia of mankind's ingenuity, persistence and the exploitation of the resources available. Much of this technology is hidden and we usually only pay homage to novelty and the obvious. We live in a world filled with machines that use various forms of energy. Much recent development has utilized electrical energy and electronic mechanisms and the electro-magnetic spectrum. One should not forget that that we are almost totally dependent on electro-mechanical systems for our way of life.

"Because the clock did not start as a practical tool shaped for a single purpose, it was destined to be the mother of machines" Boorstin; The Discoverers, p.64

 NUNET focuses mainly on: Transportation, and Investment and the Time Value of Money relationships.

Of these Transportation depends mostly on past and current technology. However it is impossible to separate most of the aspects of life from these and the interdependence of most current activities.

Transportation is often classified by mode, which tends to identify a set of technologies for each movement of goods and/or people. The modes have developed largely because of the medium and vehicles which they utilize.

Transportation requires work (i.e. force x distance) and consumes energy. Before the 19th and 20th centuries most of the work was performed by human, animal effort, or the natural forces of current and wind. Sailing vessels always have difficulty adapting their desired course to the current wind conditions. Here is an example of a clever sail rig used by the Portuguese in the 16th century that would sail quite close to the wind and which allowed them to become the premier European explorers of their time.

In the 19th century transportation was revolutionized by the steam engine. Steam was first used for pumping water out of deep mines. It was then applied to land vehicle locomotion and to water craft propulsion. During the fuel supply difficulties of the mind 1970's in the US considerable attention was paid to alternative forms of power plants that could be used in transport vehicles. Click on chart as prepared by General Motors for a comparison at that time. Since then there have been improvements in the power to weight ratios of most of the types such as gasoline, diesel, and fuel cell - electric power plants. Many type of engines have been designed and developed over the years. A small sample of some of the engines that have been used is included in these notes.

Steam engines tend to be heavy and not as convenient as internal combustion engines. These have dominated the 20th century. Also appearing towards the end of the 19th century were electric engines. Successful use of electricity requires generators i.e. and engines for converting other forms of energy into electricity, and motors i.e. engines for converting electricity to mechanical motion.

Electricity has the great advantage that it can be transmitted over distances by relatively small conductors i.e. wires. Electric powered transport vehicles have been in use for a variety of transport vehicles for over a hundred years. E.g. early street cars and electric locomotives. The dominant railway locomotive for long hauls currently is the diesel-electric. You will note that its power to weight ratio is poor but it has several advantages for this application. The weight is useful in that it assists in development of the traction needed to move long heavily loaded trains, and the electric drives provide the required high torque and ease of control for starts, etc.

The most common type used in motorcars is the so called four stroke (four cycle) multi cylinder in line or V type engine. It is also used in aircraft and reaches its peak development in the 1940's in the very powerful multi cylinder aircraft engines such as the V type, 12 cylinder Merlin, the H type 24 cylinder Sabre, and the multi row radial like the PWR2800

In a four stroke engine the piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed into the air for this to work.
Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful.
When the piston reaches the top of its stroke, for gas, and gasoline engines the spark plug ignites the air fuel mixture. In Compression Ignition engines, i.e. Diesel, the charge is heated sufficiently by the compression to ignite. This is possible as the fuel is injected into the cylinder as a fine mist at the appropriate time. The charge in the cylinder explodes, driving the piston down.
Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out trough the exhaust system.
Now the engine is ready for the next cycle, so it intakes another charge of air and gas. Additional information on aircraft engines is available at:
http://www.aviation-history.com/index-engine.htm.
Notice that the motion that comes out of an internal combustion engine is rotational. Rotational speeds are usually below 5000 revolutions per minute, but much higher speeds are used for special engines, usually for racing purposes.
Another type of internal combustion piston engine is called a two stroke. The two stroke appears to have an advantage over the four stroke because there are twice as many power strokes for a given number of revolutions. There are many two stroke engines in use, and by clever design they can achieve the same fuel efficiency as the four stroke.
A major modern type of internal combustion engine is the gas turbine. They achieve their widest use as jet engines to provide thrust for larger airplanes. Some gas turbine engines are used to drive rotating systems where high power to weight ratio engines are required, e.g. Turboprop engines for smaller aircraft, helicopter engines, etc. The jet engine revolutionized transport aircraft in the late 1950's, and they now represent the major propulsion systems on larger commercial airliners.
All of the above engines (except electric) require air for combustion. A very old type of engine that has been developed to a high level during the latter part of the 20th century is the rocket engine. They have provided the means for man to leave the earth and visit the moon for the first recorded time.

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End to date: 051221, ams