The invention: Electrically powered time-keeping device with a
quartz resonator that has led to the development of extremely accurate,
relatively inexpensive electric clocks that are used in computers
and microprocessors.
The person behind the invention:
Warren Alvin Marrison (1896-1980), an American scientist
From Complex Mechanisms to Quartz Crystals
William Alvin Marrison’s fabrication of the electric clock began a
new era in time-keeping. Electric clocks are more accurate and more
reliable than mechanical clocks, since they have fewer moving parts
and are less likely to malfunction.
An electric clock is a device that generates a string of electric
pulses. The most frequently used electric clocks are called “free running”
and “periodic,” which means that they generate a continuous
sequence of electric pulses that are equally spaced. There are various
kinds of electronic “oscillators” (materials that vibrate) that can
be used to manufacture electric clocks.
The material most commonly used as an oscillator in electric
clocks is crystalline quartz. Because quartz (silicon dioxide) is a
completely oxidized compound (which means that it does not deteriorate
readily) and is virtually insoluble in water, it is chemically
stable and resists chemical processes that would break down other
materials. Quartz is a “piezoelectric” material, which means that it
is capable of generating electricity when it is subjected to pressure
or stress of some kind. In addition, quartz has the advantage of generating
electricity at a very stable frequency, with little variation. For
these reasons, quartz is an ideal material to use as an oscillator.The Quartz Clock
Aquartz clock is an electric clock that makes use of the piezoelectric
properties of a quartz crystal. When a quartz crystal vibrates, a difference of electric potential is produced between two of its faces.
The crystal has a natural frequency (rate) of vibration that is determined
by its size and shape. If the crystal is placed in an oscillating
electric circuit that has a frequency that is nearly the same as that of
the crystal, it will vibrate at its natural frequency and will cause the
frequency of the entire circuit to match its own frequency.
Piezoelectricity is electricity, or “electric polarity,” that is caused
by the application of mechanical pressure on a “dielectric” material
(one that does not conduct electricity), such as a quartz crystal. The
process also works in reverse; if an electric charge is applied to the
dielectric material, the material will experience a mechanical distortion.
This reciprocal relationship is called “the piezoelectric effect.”
The phenomenon of electricity being generated by the application
of mechanical pressure is called the direct piezoelectric effect, and
the phenomenon of mechanical stress being produced as a result of
the application of electricity is called the converse piezoelectric
effect.
When a quartz crystal is used to create an oscillator, the natural
frequency of the crystal can be used to produce other frequencies
that can power clocks. The natural frequency of a quartz crystal is
nearly constant if precautions are taken when it is cut and polished
and if it is maintained at a nearly constant temperature and pressure.
After a quartz crystal has been used for some time, its frequency usually varies slowly as a result of physical changes. If allowances
are made for such changes, quartz-crystal clocks such as
those used in laboratories can be manufactured that will accumulate
errors of only a few thousandths of a second per month. The
quartz crystals that are typically used in watches, however, may accumulate
errors of tens of seconds per year.
There are other materials that can be used to manufacture accurate
electric clocks. For example, clocks that use the element rubidium
typically would accumulate errors no larger than a few tenthousandths
of a second per year, and those that use the element cesium
would experience errors of only a few millionths of a second
per year. Quartz is much less expensive than rarer materials such as rubidium and cesium, and it is easy to use in such common applications
as computers. Thus, despite their relative inaccuracy, electric
quartz clocks are extremely useful and popular, particularly for applications
that require accurate timekeeping over a relatively short
period of time. In such applications, quartz clocks may be adjusted
periodically to correct for accumulated errors.
Impact
The electric quartz clock has contributed significantly to the development
of computers and microprocessors. The computer’s control
unit controls and synchronizes all data transfers and transformations
in the computer system and is the key subsystem in the
computer itself. Every action that the computer performs is implemented
by the control unit.
The computer’s control unit uses inputs from a quartz clock to
derive timing and control signals that regulate the actions in the system
that are associated with each computer instruction. The control
unit also accepts, as input, control signals generated by other devices
in the computer system.
The other primary impact of the quartz clock is in making the
construction of multiphase clocks a simple task. A multiphase
clock is a clock that has several outputs that oscillate at the same
frequency. These outputs may generate electric waveforms of different
shapes or of the same shape, which makes them useful for
various applications. It is common for a computer to incorporate a
single-phase quartz clock that is used to generate a two-phase
clock.
The invention: Electronic device that reduces the signal-to-noise
ratio of sound recordings and greatly improves the sound quality
of recorded music.
The people behind the invention:
Emil Berliner (1851-1929), a German inventor
Ray Milton Dolby (1933- ), an American inventor
Thomas Alva Edison (1847-1931), an American inventor
Phonographs, Tapes, and Noise Reduction
The main use of record, tape, and compact disc players is to listen
to music, although they are also used to listen to recorded speeches,
messages, and various forms of instruction. Thomas Alva Edison
invented the first sound-reproducing machine, which he called the
“phonograph,” and patented it in 1877. Ten years later, a practical
phonograph (the “gramophone”) was marketed by a German, Emil
Berliner. Phonographs recorded sound by using diaphragms that
vibrated in response to sound waves and controlled needles that cut
grooves representing those vibrations into the first phonograph records,
which in Edison’s machine were metal cylinders and in Berliner’s
were flat discs. The recordings were then played by reversing
the recording process: Placing a needle in the groove in the recorded
cylinder or disk caused the diaphragm to vibrate, re-creating the
original sound that had been recorded.
In the 1920’s, electrical recording methods developed that produced
higher-quality recordings, and then, in the 1930’s, stereophonic
recording was developed by various companies, including
the British company Electrical and Musical Industries (EMI). Almost
simultaneously, the technology of tape recording was developed.
By the 1940’s, long-playing stereo records and tapes were
widely available. As recording techniques improved further, tapes
became very popular, and by the 1960’s, they had evolved into both
studio master recording tapes and the audio cassettes used by consumers.Hisses and other noises associated with sound recording and its
environment greatly diminished the quality of recorded music. In
1967, Ray Dolby invented a noise reducer, later named “Dolby A,”
that could be used by recording studios to reduce tape signal-tonoise
ratios. Several years later, his “Dolby B” system, designed
for home use, became standard equipment in all types of playback
machines. Later, Dolby and others designed improved noisesuppression
systems.
Recording and Tape Noise
Sound is made up of vibrations of varying frequencies—sound
waves—that sound recorders can convert into grooves on plastic records,
varying magnetic arrangements on plastic tapes covered
with iron particles, or tiny pits on compact discs. The following discussion
will focus on tape recordings, for which the original Dolby
noise reducers were designed.
Tape recordings are made by a process that converts sound
waves into electrical impulses that cause the iron particles in a tape
to reorganize themselves into particular magnetic arrangements.
The process is reversed when the tape is played back. In this process,
the particle arrangements are translated first into electrical impulses
and then into sound that is produced by loudspeakers.
Erasing a tape causes the iron particles to move back into their original
spatial arrangement.
Whenever a recording is made, undesired sounds such as hisses,
hums, pops, and clicks can mask the nuances of recorded sound, annoying
and fatiguing listeners. The first attempts to do away with
undesired sounds (noise) involved making tapes, recording devices,
and recording studios quieter. Such efforts did not, however,
remove all undesired sounds.
Furthermore, advances in recording technology increased the
problem of noise by producing better instruments that “heard” and
transmitted to recordings increased levels of noise. Such noise is often
caused by the components of the recording system; tape hiss is
an example of such noise. This type of noise is most discernible in
quiet passages of recordings, because loud recorded sounds often
mask it.Because of the problem of noise in quiet passages of recorded
sound, one early attempt at noise suppression involved the reduction
of noise levels by using “dynaural” noise suppressors. These
devices did not alter the loud portions of a recording; instead, they
reduced the very high and very low frequencies in the quiet passages
in which noise became most audible. The problem with such
devices was, however, that removing the high and low frequencies
could also affect the desirable portions of the recorded sound.
These suppressors could not distinguish desirable from undesirable
sounds. As recording techniques improved, dynaural noise suppressors caused more and more problems, and their use was finally
discontinued.
Another approach to noise suppression is sound compression
during the recording process. This compression is based on the fact
that most noise remains at a constant level throughout a recording,
regardless of the sound level of a desired signal (such as music). To
carry out sound compression, the lowest-level signals in a recording
are electronically elevated above the sound level of all noise. Musical
nuances can be lost when the process is carried too far, because
the maximum sound level is not increased by devices that use
sound compression. To return the music or other recorded sound to
its normal sound range for listening, devices that “expand” the recorded
music on playback are used. Two potential problems associated
with the use of sound compression and expansion are the difficulty
of matching the two processes and the introduction into the
recording of noise created by the compression devices themselves.
In 1967, Ray Dolby developed Dolby Ato solve these problems as
they related to tape noise (but not to microphone signals) in the recording
and playing back of studio master tapes. The system operated
by carrying out ten-decibel compression during recording and
then restoring (noiselessly) the range of the music on playback. This
was accomplished by expanding the sound exactly to its original
range. Dolby Awas very expensive and was thus limited to use in recording
studios. In the early 1970’s, however, Dolby invented the less
expensive Dolby B system, which was intended for consumers.
Consequences
The development of Dolby Aand Dolby B noise-reduction systems
is one of the most important contributions to the high-quality
recording and reproduction of sound. For this reason, Dolby A
quickly became standard in the recording industry. In similar fashion,
Dolby B was soon incorporated into virtually every highfidelity
stereo cassette deck to be manufactured.
Dolby’s discoveries spurred advances in the field of noise reduction.
For example, the German company Telefunken and the Japanese
companies Sanyo and Toshiba, among others, developed their
own noise-reduction systems. Dolby Laboratories countered by producing an improved system: Dolby C. The competition in the
area of noise reduction continues, and it will continue as long as
changes in recording technology produce new, more sensitive recording
equipment.
The invention: An inexpensive shaving blade that replaced the traditional
straight-edged razor and transformed shaving razors
into a frequent household purchase item.
The people behind the invention:
King Camp Gillette (1855-1932), inventor of the disposable razor
Steven Porter, the machinist who created the first three
disposable razors for King Camp Gillette
William Emery Nickerson (1853-1930), an expert machine
inventor who created the machines necessary for mass
production
Jacob Heilborn, an industrial promoter who helped Gillette start
his company and became a partner
Edward J. Stewart, a friend and financial backer of Gillette
Henry Sachs, an investor in the Gillette Safety Razor Company
John Joyce, an investor in the Gillette Safety Razor Company
William Painter (1838-1906), an inventor who inspired Gillette
George Gillette, an inventor, King Camp Gillette’s father
A Neater Way to Shave
In 1895, King Camp Gillette thought of the idea of a disposable razor
blade. Gillette spent years drawing different models, and finally
Steven Porter, a machinist and Gillette’s associate, created from those
drawings the first three disposable razors that worked. Gillette soon
founded the Gillette Safety Razor Company, which became the leading
seller of disposable razor blades in the United States.
George Gillette, King Camp Gillette’s father, had been a newspaper
editor, a patent agent, and an inventor. He never invented a very
successful product, but he loved to experiment. He encouraged all
of his sons to figure out how things work and how to improve on
them. King was always inventing something new and had many
patents, but he was unsuccessful in turning them into profitable
businesses.
Gillette worked as a traveling salesperson for Crown Cork and Seal Company.William Painter, one of Gillette’s friends and the inventor
of the crown cork, presented Gillette with a formula for making
a fortune: Invent something that would constantly need to be replaced.
Painter’s crown cork was used to cap beer and soda bottles.
It was a tin cap covered with cork, used to form a tight seal over a
bottle. Soda and beer companies could use a crown cork only once
and needed a steady supply.
King took Painter’s advice and began thinking of everyday items
that needed to be replaced often. After owning a Star safety razor
for some time, King realized that the razor blade had not been improved
for a long time. He studied all the razors on the market and
found that both the common straight razor and the safety razor featured
a heavy V-shaped piece of steel, sharpened on one side. King
reasoned that a thin piece of steel sharpened on both sides would
create a better shave and could be thrown away once it became dull.
The idea of the disposable razor had been born.
Gillette made several drawings of disposable razors. He then
made a wooden model of the razor to better explain his idea.
Gillette’s first attempt to construct a working model was unsuccessful,
as the steel was too flimsy. Steven Porter, a Boston machinist, decided
to try to make Gillette’s razor from his drawings. He produced
three razors, and in the summer of 1899 King was the first
man to shave with a disposable razor.
Changing Consumer Opinion
In the early 1900’s, most people considered a razor to be a oncein-
a-lifetime purchase. Many fathers handed down their razors to
their sons. Straight razors needed constant and careful attention to
keep them sharp. The thought of throwing a razor in the garbage after
several uses was contrary to the general public’s idea of a razor.
If Gillette’s razor had not provided a much less painful and faster
shave, it is unlikely that the disposable would have been a success.
Even with its advantages, public opinion against the product was
still difficult to overcome.
Financing a company to produce the razor proved to be a major
obstacle. King did not have the money himself, and potential investors
were skeptical. Skepticism arose both because of public perceptions of the product and because of its manufacturing process. Mass
production appeared to be impossible, but the disposable razor
would never be profitable if produced using the methods used to
manufacture its predecessor.
William Emery Nickerson, an expert machine inventor, had looked
at Gillette’s razor and said it was impossible to create a machine to
produce it. He was convinced to reexamine the idea and finally created
a machine that would create a workable blade. In the process,
Nickerson changed Gillette’s original model. He improved the handle
and frame so that it would better support the thin steel blade.
In the meantime, Gillette was busy getting his patent assigned to
the newly formed American Safety Razor Company, owned by
Gillette, Jacob Heilborn, Edward J. Stewart, and Nickerson. Gillette
owned considerably more shares than anyone else. Henry Sachs
provided additional capital, buying shares from Gillette.
The stockholders decided to rename the company the Gillette
Safety Razor Company. It soon spent most of its money on machinery
and lacked the capital it needed to produce and advertise its
product. The only offer the company had received was from a group
of New York investors who were willing to give $125,000 in exchange
for 51 percent of the company. None of the directors wanted
to lose control of the company, so they rejected the offer.
John Joyce, a friend of Gillette, rescued the financially insecure
new company. He agreed to buy $100,000 worth of bonds from the
company for sixty cents on the dollar, purchasing the bonds gradually
as the company needed money. He also received an equivalent
amount of company stock. After an investment of $30,000, Joyce
had the option of backing out. This deal enabled the company to
start manufacturing and advertising.Impact
The company used $18,000 to perfect the machinery to produce
the disposable razor blades and razors. Originally the directors
wanted to sell each razor with twenty blades for three dollars. Joyce
insisted on a price of five dollars. In 1903, five dollars was about
one-third of the average American’s weekly salary, and a highquality
straight razor could be purchased for about half that price.The other directors were skeptical, but Joyce threatened to buy up
all the razors for three dollars and sell them himself for five dollars.
Joyce had the financial backing to make this promise good, so the directors
agreed to the higher price.
The Gillette Safety Razor Company contracted with Townsend&
Hunt for exclusive sales. The contract stated that Townsend & Hunt
would buy 50,000 razors with twenty blades each during a period of
slightly more than a year and would purchase 100,000 sets per year
for the following four years. The first advertisement for the product
appeared in System Magazine in early fall of 1903, offering the razors
by mail order. By the end of 1903, only fifty-one razors had been
sold.
Since Gillette and most of the directors of the company were not
salaried, Gillette had needed to keep his job as salesman with
Crown Cork and Seal. At the end of 1903, he received a promotion
that meant relocation from Boston to London. Gillette did not want
to go and pleaded with the other directors, but they insisted that the
company could not afford to put him on salary. The company decided
to reduce the number of blades in a set from twenty to twelve
in an effort to increase profits without noticeably raising the cost of a
set. Gillette resigned the title of company president and left for England.
Shortly thereafter, Townsend & Hunt changed its name to the
Gillette Sales Company, and three years later the sales company
sold out to the parent company for $300,000. Sales of the new type
of razor were increasing rapidly in the United States, and Joyce
wanted to sell patent rights to European companies for a small percentage
of sales. Gillette thought that that would be a horrible mistake
and quickly traveled back to Boston. He had two goals: to stop
the sale of patent rights, based on his conviction that the foreign
market would eventually be very lucrative, and to become salaried
by the company. Gillette accomplished both these goals and soon
moved back to Boston.
Despite the fact that Joyce and Gillette had been good friends for
a long time, their business views often differed. Gillette set up a
holding company in an effort to gain back controlling interest in the
Gillette Safety Razor Company. He borrowed money and convinced
his allies in the company to invest in the holding company, eventually regaining control. He was reinstated as president of the company.
One clear disagreement was that Gillette wanted to relocate the company
to Newark, New Jersey, and Joyce thought that that would be a
waste of money. Gillette authorized company funds to be invested in
a Newark site. The idea was later dropped, costing the company a
large amount of capital. Gillette was not a very wise businessman and made many costly mistakes. Joyce even accused him of deliberately
trying to keep the stock price low so that Gillette could purchase
more stock. Joyce eventually bought out Gillette, who retained
his title as president but had little say about company
business.
With Gillette out of a management position, the company became
more stable and more profitable. The biggest problem the
company faced was that it would soon lose its patent rights. After
the patent expired, the company would have competition. The company
decided that it could either cut prices (and therefore profits) to
compete with the lower-priced disposables that would inevitably
enter the market, or it could create a new line of even better razors.
The company opted for the latter strategy. Weeks before the patent
expired, the Gillette Safety Razor Company introduced a new line
of razors.
Both World War I and World War II were big boosts to the company,
which contracted with the government to supply razors to almost
all the troops. This transaction created a huge increase in sales
and introduced thousands of young men to the Gillette razor. Many
of them continued to use Gillettes after returning from the war.
Aside from the shaky start of the company, its worst financial difficulties
were during the Great Depression. Most Americans simply
could not afford Gillette blades, and many used a blade for an extended
time and then resharpened it rather than throwing it away. If
it had not been for the company’s foreign markets, the company
would not have shown a profit during the Great Depression.
Gillette’s obstinancy about not selling patent rights to foreign investors
proved to be an excellent decision.
The company advertised through sponsoring sporting events,
including the World Series. Gillette had many celebrity endorsements
from well-known baseball players. Before it became too expensive
for one company to sponsor an entire event, Gillette had
exclusive advertising during the World Series, various boxing
matches, the Kentucky Derby, and football bowl games. Sponsoring
these events was costly, but sports spectators were the typical
Gillette customers.
The Gillette Company created many products that complemented
razors and blades, including shaving cream, women’s raincluding women’s cosmetics, writing utensils, deodorant, and
wigs. One of the main reasons for obtaining a more diverse product
line was that a one-product company is less stable, especially in a
volatile market. The Gillette Company had learned that lesson in
the Great Depression. Gillette continued to thrive by following the
principles the company had used from the start. The majority of
Gillette’s profits came from foreign markets, and its employees
looked to improve products and find opportunities in other departments
as well as their own.
The invention: Arigid lighter-than-air aircraft that played a major
role in World War I and in international air traffic until a disastrous
accident destroyed the industry.
The people behind the invention:
Ferdinand von Zeppelin (1838-1917), a retired German general
Theodor Kober (1865-1930), Zeppelin’s private engineer
Early Competition
When the Montgolfier brothers launched the first hot-air balloon
in 1783, engineers—especially those in France—began working on
ways to use machines to control the speed and direction of balloons.
They thought of everything: rowing through the air with silk-covered
oars; building movable wings; using a rotating fan, an airscrew, or a
propeller powered by a steam engine (1852) or an electric motor
(1882). At the end of the nineteenth century, the internal combustion
engine was invented. It promised higher speeds and more power.
Up to this point, however, the balloons were not rigid.
Arigid airship could be much larger than a balloon and could fly
farther. In 1890, a rigid airship designed by David Schwarz of
Dalmatia was tested in St. Petersburg, Russia. The test failed because
there were problems with inflating the dirigible. A second
test, in Berlin in 1897, was only slightly more successful, since the
hull leaked and the flight ended in a crash.
Schwarz’s airship was made of an entirely rigid aluminum cylinder.
Ferdinand von Zeppelin had a different idea: His design was
based on a rigid frame. Zeppelin knew about balloons from having
fought in two wars in which they were used: the American Civil
War of 1861-1865 and the Franco-Prussian War of 1870-1871. He
wrote down his first “thoughts about an airship” in his diary on
March 25, 1874, inspired by an article about flying and international
mail. Zeppelin soon lost interest in this idea of civilian uses for an
airship and concentrated instead on the idea that dirigible balloons
might become an important part of modern warfare. He asked the German government to fund his research, pointing out that France
had a better military air force than Germany did. Zeppelin’s patriotism
was what kept him trying, in spite of money problems and
technical difficulties.
In 1893, in order to get more money, Zeppelin tried to persuade
the German military and engineering experts that his invention was
practical. Even though a government committee decided that his
work was worth a small amount of funding, the army was not sure
that Zeppelin’s dirigible was worth the cost. Finally, the committee
chose Schwarz’s design. In 1896, however, Zeppelin won the support
of the powerful Union of German Engineers, which in May,
1898, gave him 800,000 marks to form a stock company called the
Association for the Promotion of Airship Flights. In 1899, Zeppelin
began building his dirigible in Manzell at Lake Constance. In July,
1900, the airship was finished and ready for its first test flight.
Several Attempts
Zeppelin, together with his engineer, Theodor Kober, had worked
on the design since May, 1892, shortly after Zeppelin’s retirement
from the army. They had finished the rough draft by 1894, and
though they made some changes later, this was the basic design of
the Zeppelin. An improved version was patented in December,
1897.
In the final prototype, called the LZ 1, the engineers tried to make
the airship as light as possible. They used a light internal combustion
engine and designed a frame made of the light metal aluminum.
The airship was 128 meters long and had a diameter of 11.7
meters when inflated. Twenty-four zinc-aluminum girders ran the
length of the ship, being drawn together at each end. Sixteen rings
held the body together. The engineers stretched an envelope of
smooth cotton over the framework to reduce wind resistance and to
protect the gas bags fromthe sun’s rays. Seventeen gas bags made of
rubberized cloth were placed inside the framework. Together they
held more than 120,000 cubic meters of hydrogen gas, which would
lift 11,090 kilograms. Two motor gondolas were attached to the
sides, each with a 16-horsepower gasoline engine, spinning four
propellers.The test flight did not go well. The two main questions—whether
the craft was strong enough and fast enough—could not be answered
because little things kept going wrong; for example, a crankshaft
broke and a rudder jammed. The first flight lasted no more
than eighteen minutes, with a maximum speed of 13.7 kilometers
per hour. During all three test flights, the airship was in the air for a
total of only two hours, going no faster than 28.2 kilometers per
hour.
Zeppelin had to drop the project for some years because he ran
out of money, and his company was dissolved. The LZ 1 was wrecked in the spring of 1901. A second airship was tested in November,
1905, and January, 1906. Both tests were unsuccessful, and
in the end the ship was destroyed during a storm.
By 1906, however, the German government was convinced of the
military usefulness of the airship, though it would not give money
to Zeppelin unless he agreed to design one that could stay in the air
for at least twenty-four hours. The third Zeppelin failed this test in
the autumn of 1907. Finally, in the summer of 1908, the LZ 4 not only
proved itself to the military but also attracted great publicity. It flew
for more than twenty-four hours and reached a speed of more than
60 kilometers per hour. Caught in a storm at the end of this flight,
the airship was forced to land and exploded, but money came from
all over Germany to build another.
Impact
Most rigid airships were designed and flown in Germany. Of the
161 that were built between 1900 and 1938, 139 were made in Germany,
and 119 were based on the Zeppelin design.
More than 80 percent of the airships were built for the military.
The Germans used more than one hundred for gathering information
and for bombing during World War I (1914-1918). Starting in
May, 1915, airships bombed Warsaw, Poland; Bucharest, Romania;
Salonika, Greece; and London, England. This was mostly a fear tactic,
since the attacks did not cause great damage, and the English antiaircraft
defense improved quickly. By 1916, the German army had
lost so many airships that it stopped using them, though the navy
continued.
Airships were first used for passenger flights in 1910. By 1914,
the Delag (German Aeronautic Stock Company) used seven passenger
airships for sightseeing trips around German cities. There were
still problems with engine power and weather forecasting, and it
was difficult to move the airships on the ground. AfterWorldWar I,
the Zeppelins that were left were given to the Allies as payment,
and the Germans were not allowed to build airships for their own
use until 1925.
In the 1920’s and 1930’s, it became cheaper to use airplanes for short flights, so airships were useful mostly for long-distance flight.
ABritish airship made the first transatlantic flight in 1919. The British
hoped to connect their empire by means of airships starting in
1924, but the 1930 crash of the R-101, in which most of the leading
English aeronauts were killed, brought that hope to an end.
The United States Navy built the Akron (1931) and the Macon
(1933) for long-range naval reconnaissance, but both airships crashed.
Only the Germans continued to use airships on a regular basis. In
1929, the world tour of the Graf Zeppelin was a success. Regular
flights between Germany and South America started in 1932, and in
1936, German airships bearing Nazi swastikas flew to Lakehurst,
New Jersey. The tragic explosion of the hydrogen-filled Hindenburg
in 1937, however, brought the era of the rigid airship to a close. The
U.S. secretary of the interior vetoed the sale of nonflammable helium,
fearing that the Nazis would use it for military purposes, and
the German government had to stop transatlantic flights for safety
reasons. In 1940, the last two remaining rigid airships were destroyed.
The invention: An electromechanical device capable of solving differential
equations.
The people behind the invention:
Vannevar Bush (1890-1974), an American electrical engineer
Harold L. Hazen (1901-1980), an American electrical engineer
Electrical Engineering Problems Become More Complex
AfterWorldWar I, electrical engineers encountered increasingly
difficult differential equations as they worked on vacuum-tube circuitry,
telephone lines, and, particularly, long-distance power transmission
lines. These calculations were lengthy and tedious. Two of
the many steps required to solve them were to draw a graph manually
and then to determine the area under the curve (essentially, accomplishing
the mathematical procedure called integration).
In 1925, Vannevar Bush, a faculty member in the Electrical Engineering
Department at the Massachusetts Institute of Technology
(MIT), suggested that one of his graduate students devise a machine
to determine the area under the curve. They first considered a mechanical
device but later decided to seek an electrical solution. Realizing
that a watt-hour meter such as that used to measure electricity
in most homes was very similar to the device they needed, Bush and
his student refined the meter and linked it to a pen that automatically
recorded the curve.
They called this machine the Product Integraph, and MIT students
began using it immediately. In 1927, Harold L. Hazen, another
MIT faculty member, modified it in order to solve the more complex
second-order differential equations (it originally solved only firstorder
equations).
The Differential Analyzer
The original Product Integraph had solved problems electrically,
and Hazen’s modification had added a mechanical integrator. Although the revised Product Integraph was useful in solving the
types of problems mentioned above, Bush thought the machine
could be improved by making it an entirely mechanical integrator,
rather than a hybrid electrical and mechanical device.
In late 1928, Bush received funding from MIT to develop an entirely
mechanical integrator, and he completed the resulting Differential
Analyzer in 1930. This machine consisted of numerous interconnected
shafts on a long, tablelike framework, with drawing
boards flanking one side and six wheel-and-disk integrators on the
other. Some of the drawing boards were configured to allow an operator
to trace a curve with a pen that was linked to the Analyzer,
thus providing input to the machine. The other drawing boards
were configured to receive output from the Analyzer via a pen that
drew a curve on paper fastened to the drawing board.
The wheel-and-disk integrator, which Hazen had first used in
the revised Product Integraph, was the key to the operation of the
Differential Analyzer. The rotational speed of the horizontal disk
was the input to the integrator, and it represented one of the variables
in the equation. The smaller wheel rolled on the top surface of
the disk, and its speed, which was different from that of the disk,
represented the integrator’s output. The distance from the wheel to
the center of the disk could be changed to accommodate the equation
being solved, and the resulting geometry caused the two shafts
to turn so that the output was the integral of the input. The integrators
were linked mechanically to other devices that could add, subtract,
multiply, and divide. Thus, the Differential Analyzer could
solve complex equations involving many different mathematical
operations. Because all the linkages and calculating devices were
mechanical, the Differential Analyzer actually acted out each calculation.
Computers of this type, which create an analogy to the physical
world, are called analog computers.
The Differential Analyzer fulfilled Bush’s expectations, and students
and researchers found it very useful. Although each different
problem required Bush’s team to set up a new series of mechanical
linkages, the researchers using the calculations viewed this as a minor
inconvenience. Students at MIT used the Differential Analyzer
in research for doctoral dissertations, master’s theses, and bachelor’s
theses. Other researchers worked on a wide range of problems with the Differential Analyzer, mostly in electrical engineering, but
also in atomic physics, astrophysics, and seismology. An English researcher,
Douglas Hartree, visited Bush’s laboratory in 1933 to learn
about the Differential Analyzer and to use it in his own work on the
atomic field of mercury. When he returned to England, he built several
analyzers based on his knowledge of MIT’s machine. The U.S.
Army also built a copy in order to carry out the complex calculations
required to create artillery firing tables (which specified the
proper barrel angle to achieve the desired range). Other analyzers
were built by industry and universities around the world.
Impact
As successful as the Differential Analyzer had been, Bush wanted
to make another, better analyzer that would be more precise, more
convenient to use, and more mathematically flexible. In 1932, Bush
began seeking money for his new machine, but because of the Depression
it was not until 1936 that he received adequate funding for
the Rockefeller Analyzer, as it came to be known. Bush left MIT in
1938, but work on the Rockefeller Analyzer continued. It was first
demonstrated in 1941, and by 1942, it was being used in the war effort
to calculate firing tables and design radar antenna profiles. At
the end of the war, it was the most important computer in existence.
All the analyzers, which were mechanical computers, faced serious
limitations in speed because of the momentum of the machinery,
and in precision because of slippage and wear. The digital computers
that were being developed after World War II (even at MIT)
were faster, more precise, and capable of executing more powerful
operations because they were electrical computers. As a result, during
the 1950’s, they eclipsed differential analyzers such as those
built by Bush. Descendants of the Differential Analyzer remained in
use as late as the 1990’s, but they played only a minor role.
The invention: An internal combustion engine in which ignition is
achieved by the use of high-temperature compressed air, rather
than a spark plug.
The people behind the invention:
Rudolf Diesel (1858-1913), a German engineer and inventor
Sir Dugold Clark (1854-1932), a British engineer
Gottlieb Daimler (1834-1900), a German engineer
Henry Ford (1863-1947), an American automobile magnate
Nikolaus Otto (1832-1891), a German engineer and Daimler’s
teacher
A Beginning in Winterthur
By the beginning of the twentieth century, new means of providing
society with power were needed. The steam engines that were
used to run factories and railways were no longer sufficient, since
they were too heavy and inefficient. At that time, Rudolf Diesel, a
German mechanical engineer, invented a new engine. His diesel engine
was much more efficient than previous power sources. It also
appeared that it would be able to run on a wide variety of fuels,
ranging fromoil to coal dust. Diesel first showed that his engine was
practical by building a diesel-driven locomotive that was tested in
1912.
In the 1912 test runs, the first diesel-powered locomotive was operated
on the track of the Winterthur-Romanston rail line in Switzerland.
The locomotive was built by a German company, Gesellschaft
für Thermo-Lokomotiven, which was owned by Diesel and
his colleagues. Immediately after the test runs atWinterthur proved
its efficiency, the locomotive—which had been designed to pull express
trains on Germany’s Berlin-Magdeburg rail line—was moved
to Berlin and put into service. It worked so well that many additional
diesel locomotives were built. In time, diesel engines were
also widely used to power many other machines, including those
that ran factories, motor vehicles, and ships.Diesels, Diesels Everywhere
In the 1890’s, the best engines available were steam engines that
were able to convert only 5 to 10 percent of input heat energy to useful
work. The burgeoning industrial society and a widespread network
of railroads needed better, more efficient engines to help businesses
make profits and to speed up the rate of transportation
available for moving both goods and people, since the maximum
speed was only about 48 kilometers per hour. In 1894, Rudolf Diesel,
then thirty-five years old, appeared in Augsburg, Germany, with a
new engine that he believed would demonstrate great efficiency.
The diesel engine demonstrated at Augsburg ran for only a
short time. It was, however, more efficient than other existing engines.
In addition, Diesel predicted that his engines would move
trains faster than could be done by existing engines and that they
would run on a wide variety of fuels. Experimentation proved the
truth of his claims; even the first working motive diesel engine (the
one used in the Winterthur test) was capable of pulling heavy
freight and passenger trains at maximum speeds of up to 160 kilometers
per hour.
By 1912, Diesel, a millionaire, saw the wide use of diesel locomotives
in Europe and the United States and the conversion of hundreds
of ships to diesel power. Rudolf Diesel’s role in the story ends
here, a result of his mysterious death in 1913—believed to be a suicide
by the authorities—while crossing the English Channel on the
steamer Dresden. Others involved in the continuing saga of diesel
engines were the Britisher Sir Dugold Clerk, who improved diesel
design, and the American Adolphus Busch (of beer-brewing fame),
who bought the North American rights to the diesel engine.
The diesel engine is related to automobile engines invented by
Nikolaus Otto and Gottlieb Daimler. The standard Otto-Daimler (or
Otto) engine was first widely commercialized by American auto
magnate Henry Ford. The diesel and Otto engines are internalcombustion
engines. This means that they do work when a fuel is
burned and causes a piston to move in a tight-fitting cylinder. In diesel
engines, unlike Otto engines, the fuel is not ignited by a spark
from a spark plug. Instead, ignition is accomplished by the use of
high-temperature compressed air.In common “two-stroke” diesel engines, pioneered by Sir Dugold
Clerk, a starter causes the engine to make its first stroke. This
draws in air and compresses the air sufficiently to raise its temperature
to 900 to 1,000 degrees Fahrenheit. At this point, fuel (usually
oil) is sprayed into the cylinder, ignites, and causes the piston to
make its second, power-producing stroke. At the end of that stroke,
more air enters as waste gases leave the cylinder; air compression
occurs again; and the power-producing stroke repeats itself. This
process then occurs continuously, without restarting.
Impact
Proof of the functionality of the first diesel locomotive set the
stage for the use of diesel engines to power many machines. Although
Rudolf Diesel did not live to see it, diesel engines were
widely used within fifteen years after his death. At first, their main
applications were in locomotives and ships. Then, because diesel
engines are more efficient and more powerful than Otto engines,
they were modified for use in cars, trucks, and buses.
At present, motor vehicle diesel engines are most often used in
buses and long-haul trucks. In contrast, diesel engines are not as
popular in automobiles as Otto engines, although European auto makers make much wider use of diesel engines than American
automakers do. Many enthusiasts, however, view diesel automobiles
as the wave of the future. This optimism is based on the durability
of the engine, its great power, and the wide range and economical
nature of the fuels that can be used to run it. The drawbacks
of diesels include the unpleasant odor and high pollutant content of
their emissions.
Modern diesel engines are widely used in farm and earth-moving
equipment, including balers, threshers, harvesters, bulldozers,rock
crushers, and road graders. Construction of the Alaskan oil pipeline
relied heavily on equipment driven by diesel engines. Diesel engines
are also commonly used in sawmills, breweries, coal mines,
and electric power plants.
Diesel’s brainchild has become a widely used power source, just
as he predicted. It is likely that the use of diesel engines will continue
and will expand, as the demands of energy conservation require
more efficient engines and as moves toward fuel diversification
require engines that can be used with various fuels.