The Blacksmith's Motor
Electricity, magnetism, and motion: A self-taught Vermonter pointed the direction for lighting the world.
By Frank Wicks
In the spring of 1833, a self-educated but impoverished blacksmith in Forestdale, Vt., by the name of Thomas Davenport heard some curious news. This news, as it turned out, would not only change his life but would eventually change the life of almost everyone on earth. Davenport's curiosity led to his invention of the first rotating electric machine. Today, we would describe it as a shunt-wound brush and commutator dc motor.
Thomas Davenport, inventor of the electric motor, was a self-educated blacksmith with a passion for reading.
The momentous news that roused the blacksmith's curiosity was that the Penfield and Hammond Iron Works, on the other side of Lake Champlain in the Crown Point hamlet of Ironville in New York state, was using a new method for separating crushed ore. The process used magnetized spikes mounted on a rotating wooden drum that attracted the millings with the highest iron content. Higher-purity feedstock could be fed to the furnaces, improving their productivity and the quality of the iron they produced. This was important, since the recent introduction and expected rapid expansion of railroads were dramatically increasing the demand for quality iron.
This process had been developed by Joseph Henry of Albany, N.Y. It used an electromagnet that he had designed to magnetize the spikes; in fact, Henry's electromagnet was said to be powerful enough to lift a blacksmith's anvil. Its use in the iron ore separation process was the first time that electricity had been used for commercial purposes, thus beginning the electric industry.
Thomas Davenport had no prior knowledge of discoveries in magnetism and electricity when this new process stimulated his interest. He had been born in 1802 on a farm outside Williamstown, Vt., the eighth of 12 children. His father died when Thomas was 10. Schooling opportunities were minimal, and at the age of 14 Thomas was indentured for seven years to a blacksmith. His room and board and six weeks per year of rural schooling were provided in return for service in his master's shop. The work was hard, but the boy was later remembered for his curiosity, his interest in musical instruments, and his passion for books.
Once he was liberated in 1823, Davenport traveled over the Green Mountains to Forestdale, a hamlet in the town of Brandon, Vt., where there was an iron industry. He set up his own marginally successful shop, married the daughter of a local merchant, and started a family.
His only means of learning was self-education. When the news from the ironworks piqued his curiosity, he acquired books and journals, and started reading about the experiments and discoveries that were beginning to unlock some of the mysteries of electricity and magnetism.
Electric Currents
It was more than 80 years since Benjamin Franklin, in 1752, had experimented with static electricity from Leyden jars and with electricity from the sky, by flying a kite over Philadelphia during a storm.
Davenport's model of an electric "train." The circular track is 4 feet in diameter. Power was supplied from a stationary battery to the moving electric locomotive, using the rails as conductors for the electricity.
A new era had started in 1800, when Alessandro Volta demonstrated an electric pile, which was a battery that produced electricity directly from a chemical reaction between two different metals. Static electricity batteries such as the Leyden jar had provided only sudden electric pulses during discharge. For the first time, investigators could draw a continuous electric current for hours, instead of relying on an erratic spark in a Leyden jar.
In 1820, the Danish experimenter Hans Oersted showed that Franklin had been half-wrong in his conclusion that electricity and magnetism were unrelated. Oersted observed that the needle of a nearby compass moved when he closed the circuit through a wire and battery. This demonstrated that electricity was causing magnetism. Andre-Marie Ampere in France soon showed that the magnetic effect could be multiplied by coiling the wire. William Sturgeon went the next step in 1825 by wrapping an uninsulated coil of wire around an insulated horseshoe-shaped iron core, thus making the first electromagnet, which lifted about 5 lbs.
Now that it was shown that electricity could produce magnetism, the reverse question arose: whether magnetism could produce electricity. The first attempts consisted of holding a magnet near a wire. No electricity was observed. Then, in 1831, Michael Faraday succeeded in producing electricity by means of magnetism when he moved a disc perpendicular to a magnetic field. Almost simultaneously, Joseph Henry, inventor of the ore-separation process that so excited Davenport, used a more powerful lifting magnet of his own design to show that electricity could be produced from magnetism by changing the strength of the magnet.
The discovery that magnetism could cause electricity was a vital step toward the modern electric world. The only previously demonstrated techniques for producing electricity had been the limited-potential static electric generator of von Guericke and the chemical reaction battery of Volta.
Joseph Henry was to become the only American to have his name applied to a unit of electricity: A henry is a measure of electric inductance. Henry had started his pioneering work in electricity and magnetism as a professor at Albany Academy in 1826. In 1833, he moved on to Princeton. He ended up as the founding secretary of the Smithsonian Institution, where he served from 1846 until 1878.
While at Albany, Henry developed an electromagnet that could lift a phenomenal 2,000 lbs. He did this by wrapping a mile of insulated wire in several parallel circuits around a soft iron core that he procured from the Crown Point Iron Works, the company for which he eventually designed the machine that used his ore-separating electromagnet.
The iron separation technique developed by Henry was, in a sense, the magnetic equivalent of the cotton gin. That device, invented in 1794 by Eli Whitney, used spikes on a rotating drum to comb the seed from the fiber. For the first time growing cotton was profitable, because a single worker could produce 50 lbs. of pure cotton per day. Threshing machines were being built on a similar principle. The ancient process of beating the wheat with a wooden flail to separate the grain from the chaff was to be replaced by spikes on a rotating drum.
The Blacksmith's MotorElectricity, magnetism, and motion: A self-taught Vermonter pointed the direction for lighting the world.By Frank WicksIn the spring of 1833, a self-educated but impoverished blacksmith in Forestdale, Vt., by the name of Thomas Davenport heard some curious news. This news, as it turned out, would not only change his life but would eventually change the life of almost everyone on earth. Davenport's curiosity led to his invention of the first rotating electric machine. Today, we would describe it as a shunt-wound brush and commutator dc motor.Thomas Davenport, inventor of the electric motor, was a self-educated blacksmith with a passion for reading.The momentous news that roused the blacksmith's curiosity was that the Penfield and Hammond Iron Works, on the other side of Lake Champlain in the Crown Point hamlet of Ironville in New York state, was using a new method for separating crushed ore. The process used magnetized spikes mounted on a rotating wooden drum that attracted the millings with the highest iron content. Higher-purity feedstock could be fed to the furnaces, improving their productivity and the quality of the iron they produced. This was important, since the recent introduction and expected rapid expansion of railroads were dramatically increasing the demand for quality iron.This process had been developed by Joseph Henry of Albany, N.Y. It used an electromagnet that he had designed to magnetize the spikes; in fact, Henry's electromagnet was said to be powerful enough to lift a blacksmith's anvil. Its use in the iron ore separation process was the first time that electricity had been used for commercial purposes, thus beginning the electric industry.Thomas Davenport had no prior knowledge of discoveries in magnetism and electricity when this new process stimulated his interest. He had been born in 1802 on a farm outside Williamstown, Vt., the eighth of 12 children. His father died when Thomas was 10. Schooling opportunities were minimal, and at the age of 14 Thomas was indentured for seven years to a blacksmith. His room and board and six weeks per year of rural schooling were provided in return for service in his master's shop. The work was hard, but the boy was later remembered for his curiosity, his interest in musical instruments, and his passion for books.Once he was liberated in 1823, Davenport traveled over the Green Mountains to Forestdale, a hamlet in the town of Brandon, Vt., where there was an iron industry. He set up his own marginally successful shop, married the daughter of a local merchant, and started a family.His only means of learning was self-education. When the news from the ironworks piqued his curiosity, he acquired books and journals, and started reading about the experiments and discoveries that were beginning to unlock some of the mysteries of electricity and magnetism.Electric CurrentsIt was more than 80 years since Benjamin Franklin, in 1752, had experimented with static electricity from Leyden jars and with electricity from the sky, by flying a kite over Philadelphia during a storm.Davenport's model of an electric "train." The circular track is 4 feet in diameter. Power was supplied from a stationary battery to the moving electric locomotive, using the rails as conductors for the electricity.A new era had started in 1800, when Alessandro Volta demonstrated an electric pile, which was a battery that produced electricity directly from a chemical reaction between two different metals. Static electricity batteries such as the Leyden jar had provided only sudden electric pulses during discharge. For the first time, investigators could draw a continuous electric current for hours, instead of relying on an erratic spark in a Leyden jar.In 1820, the Danish experimenter Hans Oersted showed that Franklin had been half-wrong in his conclusion that electricity and magnetism were unrelated. Oersted observed that the needle of a nearby compass moved when he closed the circuit through a wire and battery. This demonstrated that electricity was causing magnetism. Andre-Marie Ampere in France soon showed that the magnetic effect could be multiplied by coiling the wire. William Sturgeon went the next step in 1825 by wrapping an uninsulated coil of wire around an insulated horseshoe-shaped iron core, thus making the first electromagnet, which lifted about 5 lbs.Now that it was shown that electricity could produce magnetism, the reverse question arose: whether magnetism could produce electricity. The first attempts consisted of holding a magnet near a wire. No electricity was observed. Then, in 1831, Michael Faraday succeeded in producing electricity by means of magnetism when he moved a disc perpendicular to a magnetic field. Almost simultaneously, Joseph Henry, inventor of the ore-separation process that so excited Davenport, used a more powerful lifting magnet of his own design to show that electricity could be produced from magnetism by changing the strength of the magnet.The discovery that magnetism could cause electricity was a vital step toward the modern electric world. The only previously demonstrated techniques for producing electricity had been the limited-potential static electric generator of von Guericke and the chemical reaction battery of Volta.Joseph Henry was to become the only American to have his name applied to a unit of electricity: A henry is a measure of electric inductance. Henry had started his pioneering work in electricity and magnetism as a professor at Albany Academy in 1826. In 1833, he moved on to Princeton. He ended up as the founding secretary of the Smithsonian Institution, where he served from 1846 until 1878.While at Albany, Henry developed an electromagnet that could lift a phenomenal 2,000 lbs. He did this by wrapping a mile of insulated wire in several parallel circuits around a soft iron core that he procured from the Crown Point Iron Works, the company for which he eventually designed the machine that used his ore-separating electromagnet.The iron separation technique developed by Henry was, in a sense, the magnetic equivalent of the cotton gin. That device, invented in 1794 by Eli Whitney, used spikes on a rotating drum to comb the seed from the fiber. For the first time growing cotton was profitable, because a single worker could produce 50 lbs. of pure cotton per day. Threshing machines were being built on a similar principle. The ancient process of beating the wheat with a wooden flail to separate the grain from the chaff was to be replaced by spikes on a rotating drum.
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