12 June 2009
An electrically powered and hermetically sealed
food-storage appliance that replaced iceboxes, improved production,
and lowered food-storage costs.
The people behind the invention:
Marcel Audiffren, a French monk
Christian Steenstrup (1873-1955), an American engineer
Fred Wolf, an American engineer
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.
09 June 2009
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.