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The BLACKSMITH'S motor , , and motion:

A self-taught Vermonter pointed the direction for lighting Downloaded from http://asmedigitalcollection.asme.org/memagazineselect/article-pdf/121/07/66/6382341/me-1999-jul8.pdf by guest on 25 September 2021 the world. By Frank Wicks

N T HE SPRING OF 1833, a self-edu­ This process had been developed cated but impoverished black­ by Joseph of Albany, N.Y It I smith in Forestdale, Vt., by the used an that he had name of Thomas Davenport heard designed to magnetize the spikes; some curious news. This news, as it in fact, Henry's electromagnet was turned out, would not only change said to be powerful enough to lift a his life but would eventually change blacksmith's anvil. Its use in the the life of almost everyone on earth. iron ore separation process was the Davenport's curiosity led to his in­ first time that electricity had been vention of the first rotating electric used for commercial purposes, thus machine. Today, we would describe beginning the electric industry. it as a shunt-wound and com­ Thomas Davenport had no prior mutator . knowledge of discoveries in mag­ The momentous news that roused netism and electricity when this the blacksmith's curiosity was that new process stimulated his interest. the Penfield and H ammond Iron He had been born in 1802 on a Works, on the other side of Lake farm outside Williamstown, Vt., Champlain in the Crown Point the eighth of 12 children. His fa­ hamlet of Ironville in ther died when Thomas was 10. state, was using a new method for Schooling opportunities were min­

separating crushed ore. The process lllt.I\I \1> Il ~ \TW(l/l'l'. imal, and at the age of 14 Thomas used magnetized spikes mounted was indentured for seven years to a on a rotating wooden drum that at­ Thomas Davenport, inventor of the , was blacksmith. His room and board a self-educated blacksmith with a passion for reading. tracted the millings with the highest and six weeks per year of rural iron content. Higher-purity feedstock could be fed to schooling were provided in return for service in his mas­ the furnaces, improving their productivity and the quali­ ter's shop. The work was hard, but the boy was later re­ ty of the iron they produced. This was important, since membered for his curiosity, his interest in musical instru­ the recent introduction and expected rapid expansion of ments, and his passion for books. rail roads were dramatically increasing the demand for Once he was liberated in 1823, Davenport traveled quality iron. over the Green Mountains to Forestdale, a hamlet in the town of Brand on, Vt., where there was an iron industry. Frank Wicks is a professor of mechanical at He set up his own marginally successful shop, married Union College in Schenectady, N. Y. the daughter of a local merchant, and started a family.

66 J ULY 1999 M EC H AN ICA L ENG I NEE RI NG H is only means of learning was self-educa tion. W hen generator of von Guericke· an d the chemical reaction the news fro m the ironworks piqued his curiosity, he ac­ battery ofVolta. quired books and journals, and started reading about the ] oseph H enry was to become the only American to experiments and discoveries that were beginning to un­ have his name applied to a unit of electricity: A henry is lock so me of the mysteries of electricity and magnetism. a measure of electric . H enry had started his pioneering work in electricity and magnetism as a pro­ ELECTRIC CURRENTS fessor at Albany Academy in 1826. In 1833, he m oved It was more than 80 years since , in on to Princeton. H e ended up as the fo unding secretary 1752, had experimented with from Ley­ of the , w here he se rve d from den jars and with electricity fro m the sky, by flying a kite 1846 until 1878. over during a storm. While at Albany, H enry developed an electromagnet A new era had started in 1800, when that could lift a phenomenal 2,000 Ibs. H e did this by demonstrated an electric pile, which was a battery that wrapping a mile of insulated w ire in several parallel Downloaded from http://asmedigitalcollection.asme.org/memagazineselect/article-pdf/121/07/66/6382341/me-1999-jul8.pdf by guest on 25 September 2021 produced electricity directly from a chemical reaction be­ tween two different m etals. Static electricity batteries such as the Leyden jar had provided o nly sudden electric pulses during discharge. For the first time, investiga tors could draw a continuous fo r hours, instead of relying on an erratic spark in a Leyden jar. In 1820, the D anish experi­ menter H ans O ersted showed that Franklin had been half­ wrong in his conclusion tha t electricity and m agn etism were unrelated. O ersted ob­ served that the needle of a nea rby compass moved when he closed the circuit through a wire and battery. This demon­ st ra te d that electricity was ca using m agnetism. Andre­ Davenport's model of an electric "train." The circular track is 4 feet in diameter. Power was supplied from a M arie in France soon stationary battery to the moving electric locomotive, using the rails as conductors for the electricity. showed that the magneti c ef­ fec t could be multiplied by coiling the w ire. William circuits around a soft iron core that he procured from Sturgeon went the next step in 1825 by wrapping an the Crown Point Iron Works, the company for which uninsulated coil of wire aro und an insulated horseshoe­ he eventually designed the m achine that used his ore­ shaped iron core, thus making the fi rs t electromagnet, separating electrom agnet. which lifted about 5 lbs. T he iron separation technique developed by H enry N ow that it was shown that electricity could produce was, in a sense, the magnetic equi va lent of the cotton m agnetism , the reverse qu es ti on arose: w hether m ag­ gin. That device, invented in 1794 by , used netism could produce electricity. T he first attempts spikes on a ro tating drum to comb the seed from the consisted of holding a near a w ire. No electric­ fiber. For the first time growing cotton was profitable, ity was observed. Then, in 1831, Sll C­ because a single worker could produ ce 50 lbs. of pure ceeded in producing electricity by means of magnetism cotton per day. Threshing nnchines were being built on when he move d a disc perpendicular to a m agnetic a similar principle. T he ancient p rocess of beating the fi eld. Almost simultaneously, ] oseph H enry, inventor of wheat with a wooden flail to separate the grain from the the ore- separation process that so excited D ave nport, chaff was to be replaced by spikes on a rotating drum . used a 1T1Ore powerful lifting magnet of his own design to show that electricity could be produced from mag­ DAVENPORT INVENTS THE MOTOR netism by changing the strength of the magnet. Soon after he learned of the H enry magnet, Davenport T he discovery that magnetism could ca use electricity traveled the 25 miles to Crown Point on a horse to wit­ was a vital step toward the m odern electric world. T he ness the wonders of magnetic lifting power. The amazing only previously demonstrated techniques for producing sight further inflamed his interest. H e decided to travel elec tricity had been the limited-potential static electric another 80 miles south, to Albany, to meet H enry, only

MEC H AN ICA L ENG IN EE R I NG JULY 1999 67 to find out that he had moved down to Princeton. to one of the he could get the to com­ Returning home out of money, D ave nport called upon plete another half- turn. Davenport then devise d what his brother, a peddler, to join him with his cart for an­ we now call a brush and commutato r. Fixed wires from other trip to C row n Point. Once there, they auctioned the fram.e supplied current to a segm.ented conductor the brother's products and traded a good horse for an in­ that supplied current to the rotor-mounted electromag­ ferior one to obtain money to buy the magnet. When net. T his provided an automatic reversal of the polarity they got hom e, the brother suggested trying to recover of the rotor-mounted magnet tw ice per rotati on, re­ the cost by exhibiting the magnet for a fee. sulting in continuous rotation. Thomas D avenport had other plans . H e unwound and The motor had the potential to drive some of the dismantled the magnet as his wife, Emily, took notes on equipment in D avenport's shop, but he had even bigger Davenport traveled 25 miles to Crown Point on a horse Downloaded from http://asmedigitalcollection.asme.org/memagazineselect/article-pdf/121/07/66/6382341/me-1999-jul8.pdf by guest on 25 September 2021 to witness the wonders of magnetic lifting power. its method of construction. H e then started his own ex­ ideas. The era of the steam locomotive and railroa ds was periments and built two more magnets of his own de­ j ust beginning, but already boiler failures and explosions sign. Insulated wire was required, but only bare wire was were becoming frequent, tragic occurrences . Daven­ ava ilable. Emily D avenport cut up her wedding dress port's solution was the electric locomotive. H e built a into strips of silk to provide the necessary ins ulation that model electric train that operated on a circular trac k; allowed for the maximum number of windings . power was supplied from a stationary battery to the mov­ The electricity so urce for the magnets was a galva nic ing electric locomotive using the rails as conductors to battery of the type developed by Volta. It used a bucket transmit the electricity. of a weak acid for an electrolyte. T he bucket contained When D avenport traveled to Was hington to obtain a concentric cylinders of different n1.etals for ; patent, however, his applica tion was rej ected: There these were wired to provide external electric current to were no prior patents on electric equipment. the magnet. H e started a tour of colleges to meet professors of nat­ D avenport mounted one magnet on a wheel; the oth­ ural philosophy who might examine his inve ntion and er magnet was fi xed to a stationary fram e. T he interac­ provide letters of support to the patent office. His travels tion between the two magnets ca used the rotor to turn took him to the new R ensselaer Institute in Troy, N.Y, half a revolution. H e learned that by reversing the wires recently founded (in 1824) as the nation's first engineer­ ing school by Stephen Va n R enss elaer. The las t o f eight generati o ns of land-ow ning pa­ troons, Van R enssela er had been a commiss ioner ove r­ seeing the constructi o n of the E rie and Champlain Which Way canals, opened in 1825. The sc hool had been charged with a mission to qualify teachers for instructing the sons and daughters of farmers and m echanics in devel­ to Turn oping m ethods o f applying science to the common

WHILE ALL ROTATING ELECTRIC MACHINES WORK on purposes of life. the same principle of relative motion between interacting D avenpo rt met R ensselae r's fo unding presid ent, magnets, there are great differences in construction and , a distinguished lawyer, botanist, geologist, the specific mathematical models that describe the oper­ chemist, educator, and innovator, who was amazed by ation. machines are generally easier the motor and by the self-educated blacksmith who had to construct but are more difficult to understand. The built it. Eaton arran ged an additional exhibit for the analysis of electric machines is generally the domain of citize ns of Troy, and Stephen Van R enssela er himself electric power engineers, but the invention and develop­ ment of electric apparatus has traditionally been, and re­ bought D ave nport's m otor for the school. The nation's mains, largely a mechanical endeavor. first engineering school now possessed the world 's first The fundamental requiSites for electrification are the electric motor. generators and motors that allow mechanical power to With the sale of his motor, Davenport was able to buy be converted to electricity and back to mechanical pow­ a quantity of already insulated wire, and he returned er, via the medium of magnetism . Every rotating elec­ home to build another motor. H e traveled to Princeton tric machine has a magnet associated with the rotor and to m eet Joseph H enry and then to the University of another based in the outer frame or . In a motor, the rotor is allowed to turn in the direction of magnetic Pennsylva nia to m eet Professor B enj amin Franklin force and electric power is converted into mechanical Bache, Benj amin Franklin's grandson and an outstanding power. In a generator, an or turbine drives the scientist. rotor against the direction of magnetic force, convert­ T he self-educated blacksmith, having now im pressed ing mechanical power to electricity. the most prominent men of learning in the country, re­ turned to the patent offi ce with letters and a working

68 JULY 1999 MEC H AN ICA L ENG IN E ERI NG m odel. His troubles were not yet over, however. T he model was destroyed by fire before it was examined. H e built anoth­ er and tried again. At last, the first patent on any electric ma­ chine was iss ued to T homas Dave nport for his electric m o­ tor on Feb. 25, 1837. The scientific community and th e m e d ia respo nde d with great excitement and Downloaded from http://asmedigitalcollection.asme.org/memagazineselect/article-pdf/121/07/66/6382341/me-1999-jul8.pdf by guest on 25 September 2021 high expec tations. Benj amin Silliman, th e founder of Silli­ man's j au mal aJ Science, w rote an extended article and con­ cluded that a power of grea t but un kn own energy had un­ exp ecte dly b een pl aced in man k ind 's h ands. T he New Yark Herald proclaimed a rev­ o lution of philosophy, sci­ en ce, art, and civiliza tio n: "The occult and mysterious principle of magnetism is be­ ing displ ayed in all of its mag­ This Patent Office model of Davenport's motor now sits in The Smithsonian Institution in Washington. Reading nificence and energy as Mr. about experiments and discoveries sparked Davenport's interest, and led to his invention of the electric motor. D ave nport runs his w heel." Davenport se t up a laboratory and workshop nea r Wall distribution systems to provide electricity to customers. Street in hopes of attracting investors. , In 1882, his Pearl Street station in lower Manhattan used who in 1844 would commercialize the telegraph, ca me stea m to drive shunt-wound brush and commu­ to observe. To further adve rtise his motor, D avenport es­ tator dc generators of the type that Thomas Davenport tablished his own newspaper, The Electra -Magnet and Me­ had inve nted 45 yea rs ea rlier. R ecognizing that expand­ chanics In telligencer, and used his electric motor to drive ing demand would require a massive new manufac turing his rotary printing press . and service industry, Edison started a manufacturing fa ­ The m otor was a spectac ular technological success, cility in Schenectady that would become the General but it was becoming a commercial failure. N o o ne Electric Co. The company's first products were motors knew how to predi ct the amount of energy in chemi­ and generators that copied the design and principles of cal batteries, and a battery-powered motor could not T hol11.as Davenport's moto r. com.pete w ith a steam en gine. Funds were p romise d When Edi so n di ed in 1931, it was suggested that all bu t not delivered. Bankrupt and distressed, D ave nport the electricity should be turned off for five minutes in returned to Vermont and started writing a book de­ recognition of the great inventor, bu t such an action scribing his work and his vision for his electric motor. was judged to be practically impossible. The ultimate. H e died in 18 51 at the age of 49, leaving only a tribute to Edison was that w ithin his lifetime the ben­ prospectus. efits of his inventions had become such a vital part of dail y life. THE MOTOR KEEPS RUNNING D avenport died 30 years before the world was rea dy What Davenport could not anticipate, and w hat no one for his inve ntion. Today, the electrificati on of the world else would describe for an other 20 yea rs, was that his and electricity's myriad of now-vital uses can be seen as motor would be turned by wa ter or steam power and the g rea tes t technological marvel in human history. would operate in reverse, as an . With­ Electric light has extended full human activity to 24 in 40 years of his dea th, electric-powered trains and trol­ ho urs per day. Electric-powered refr igeration is now leys had become commo n, with Davenport's machine taken for granted. Air conditioning has-made the m ost crea ting electricity at the power station and his motor inhospitabl e regions com fortable for year-round living then converting this electricity back to mechanical pow­ and spawned new maj or cities . O ur communicati ons, er to move the cars. computing, and inform ation sys tem s could no t exist T homas Ediso n invented the electric lightbulb in 1879, without elec tricity. Thomas D ave nport, though little using a chemical battery to power his experiments, but remembered today, played a vital part in making all of he recognized the need for ceritral generating plants and this possible. _

M EC HAN IC AL ENG INEER ING JULY 1999 69