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The Invention of the History and Demonstration

An Interactive Qualifying Project Submitted to the Faculty of WORCESTER POLYTECHNIC INSTITUTE in partial fulfilment of the requirements for the Degree of Bachelor of Science

Authors: Barry Aslanian Sam Milender Jianqing Zhu

Date Submitted: May 30, 2019

Report Submitted to:

Professor John A. Goulet Worcester Polytechnic Institute

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Abstract

The purpose of this project is to help high school level students learn about the basics of , and the history behind the subject. This document contains the fundamental concepts of the behind an electric motor and provides a comprehensive background of the history of electromagnetism. The topics in electromagnetism were demonstrated by creating a working replica of Thomas Davenport’s original DC motor, based on his 1837 patent. The building process is described and illustrated in this document to enhance the educational experience.

Acknowledgements

Our team would like to thank our project advisor, John Goulet, for providing us with necessary materials and helping us along the way throughout the building process and Ryan Breuer for being invaluable in learning how to forge the cores.

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Executive Summary

There are many great minds behind the invention of the electric motor. All of the early pioneers that discovered the uses of and deserve credit for the work they did, and the foundations they have laid for those who came after them. Thomas Davenport, the inventor of the electric motor, is often forgotten, but it was he who made the monumental discovery of creating constant mechanical from electromagnetism. This is one of the most important discoveries in all of science, and deserves significant recognition. The first section is a historical background of electromagnetism that can aid in sparking a student’s interest in the subject. It starts with William and his experiments with the compass in the late 1500s, and goes through the contributions of , Hans Christian Ørsted, André-Marie Ampère, and Joseph , all of which formed the foundation on which Davenport built his motor. It is helpful to know how these discoveries were made, and it is only proper to give credit to the individuals who discovered this physics that has led to the invention that benefits humanity so much today. Studying the physics behind an electric motor is a fantastic learning experience for anybody interested in electricity and magnetism. This document contains descriptions of some of the fundamental concepts behind an electric motor. The Right-Hand Rule is used to illustrate how the flow of electrical current in a wire interacts with a to create a force. The form of each component within an electric motor is described along with a basic description of what they do. Using the right-hand rule, the description of the components, and a simple two-pole motor as an example, it is straightforward to understand how each component fits together within the electric motor to create the desired motion. The current goes through a into the and through the poles, which produces a force as per the right hand rule. When the armature reaches the point where this force no longer has a tangential component (and therefore no longer induces rotational motion), the commutator stops the current flow through the armature, and only resumes it once the armature’s inertia has carried it to the point where the electromagnetic force would again have a tangential component. When current is resumed, the commutator has caused the current to invert direction through the poles, causing the force to also invert, and enable a constant rotational motion The motor replica represents a perfect project for students to complete to reinforce the electromagnetic concepts they learn in physics. This re-creation was completed how Davenport would have created his original, completely by hand from raw material, before the assembly into a functioning motor. A student would benefit from an in-class project of the assembly of a motor, as it was an incredibly beneficial project in deepening the understanding of electromagnetism.

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Table of Contents

Abstract 2

Acknowledgements 2

Executive Summary 3

Table of Contents 4

Table of Figures 6

Introduction 7

The History of Electromagnetism 7 William Gilbert 7 Alessandro Volta 8 Hans Christian Ørsted and André-Marie Ampère 9 9 Thomas Davenport 10 Understanding the 10 Applying for the patent 11 After the invention 11 Model Railroad 12 Death 13

The Physics of the Electric Motor 14 and Magnetic Fields 14 Composition of a Motor 15 Field 15 Armature 16 Poles 16 The Commutator and Brushes 16 The Physics 17

Building the Motor 20 In the Forge 20 The Wrought Iron Billet 20 The Final Shaping 22 The Frame 24 The Armature 24 The Brushes and Commutator 24

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The Finished Motor 25

Education 26

Conclusion 27

Authorship 28

Bibliography 28

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Table of Figures

Figure 1: J oseph Henry’s Electromagnet 9

Figure 2: M ap of Thomas Davenport’s Locations 10

Figure 3: First Electric Motor 1837 US Patent 11

Figure 4: D avenport’s Electric Railway Model 12

Figure 5: T he Direction of a Magnetic Field 14

Figure 6: T he Right-Hand Rule 14

Figure 7: C omposition of a DC brushed motor 15

Figure 8: B asic Electric Motor Diagram 17

Figure 9: Electromagnetic Forces that Induce a Rotational Motion. 18

Figure 10: E lectromagnetic Forces that would not Induce a Rotational Motion 18

Figure 11: The Split Between Commutator Pads 19

Figure 12: T he Electromagnetic Forces 19

Figure 13: Clean, Partially Clean, and Uncleaned Pieces of Wrought Iron 21

Figure 14: T he Welded Wrought Iron Billet 21

Figure 15: T he Now-Broken Billet of Wrought Iron 22

Figure 16: F orging Together the Two Pieces of the Armature Cores 23

Figure 17: T he Final Shape of the Armature and Field Cores 23

Figure 18: Finished Motor Showing Field Windings and Armature Windings 25

Figure 19: A Replica of Davenport’s Motor from the Smithsonian 26

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Introduction

Electromagnetism is a difficult subject for a student to master. Even with a teacher with an established curriculum and a working knowledge of the subject, it is incredibly difficult to conceptualize electricity and magnetism, how they work together as a single force, and how to apply this force for everyday life. Despite how difficult it is to teach and understand, there were individuals who originally discovered the phenomena of magnetism and then electricity, all without a reference or teacher of any sort. These individuals, representing some of the brightest people humanity has ever seen, conducted numerous experiments, tested numerous hypotheses, and were able to set humanity on the path to the level of technological sophistication it has today. One of the best ways to go about assisting students in understanding electromagnetism is to re-create the experiments those electromagnetic pioneers conducted many years ago that allowed them to become the first people to truly begin to understand it. One of the most basic and most important of electronic devices is the electric motor. It demonstrates electrical flow, the creation and interaction of electromagnetic fields, and, most importantly, how all of those things are applicable in everyday life. The construction of one of these motors would be an incredibly useful project for students to complete during their study of electromagnetism. This project attempts a re-creation of the very first electric motor, created by a man by the name of Thomas Davenport in the early , and goes significantly more in depth into the history and process of the design of the motor than the average high school physics student would need to get in class, but it also serves as a proof-of-concept: such a re-creation deepens the creator’s understanding of the physics behind it, and having a physical object demonstrating the theory taught assists in cementing those same topics.

The History of Electromagnetism

It all started with the invention of the compass. The very first compasses are attributed to Song dynasty in around 1040 CE [1][2], where a scholar by the name of Shen Kuo wrote that, by rubbing a needle on a lodestone (naturally magnetized piece of magnetite) and suspending by a thread in a calm environment, it will always point south. The first European compass is commonly attributed to 14th century merchants in Amalfi [3], an important trade hub in the south of the Italian peninsula, although its European origin is not definitely known. It was one of the inventions, along with ocean-faring ships, that allowed the rise of the European colonial and trade empires. It was also the invention that began studies into the field of electromagnetism.

William Gilbert

It was in the late 16th century that a man by the name of William Gilbert began to experiment, and more importantly, document his experiments, with electromagnetism. It was thought by many that compass needles were attracted to Polaris, the north star, or to mountains in the north [4]. Gilbert, intrigued by these contradicting claims, among others, conducted

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experiments with compasses, lodestones, and Earth’s yet-to-be-discovered magnetic field. While the majority of his work was done with relation to testing antiquated theories of what attracted a compass’ needle, he also studied produced by rubbing a piece of amber (and coining the adjective “electricus” in the process, which would give rise to the modern word “electricity”), and conducted experiments with lodestones. He discovered magnetic poles and disproved many of the antiquated misconceptions about lodestones and what is now called magnetism, paving the way for future developments in the field of electromagnetism [4].

Alessandro Volta

There was then a three-hundred year gap during which no developments in the field of Electromagnetism were made; that is, until Alessandro Volta began his work. While William Gilbert is the father of magnetism, it could be said that Alessandro Volta is the father of Electricity. He was an Italian professor of Physics at the Royal School of whose early work included an improvement to the , a device used to generate a static charge, and the discovery and isolation of gas [5]. In 1791, one of Volta’s peers, the president of the Bologna Academy of Science , discovered that by touching frogs’ nerves with a scalpel that had a static charge, or by touching a frog’s spinal cord with a hook attached to an iron railing, the frogs’ legs could be made to twitch [6]. This led Galvani to conclude that animal motion was caused by a phenomenon he called “Animal Electricity” [7]. Volta disagreed, and believed this so-called Animal Electricity to be no different than any other electricity, and so set out to disprove Galvani’s theory. His experiments led him to discover that, while touching a frog’s leg or the human tongue with pieces of two different metals, the leg or tongue spontaneously jumped or experienced a tingling from the electrical flow [8]. There was no animal, or human, element required to generate this response in the animal or human, just two pieces of metal, so Volta concluded that Galvani’s so-called “Animal Electricity” was no different from any other sort of electricity. With this experiment, he achieved two things: firstly, he succeeded in his goal of disproving Galvani’s theory, and secondly he discovered that by connecting two pieces of metal on one end by a conductor and on the other by a certain kind of liquid, an electric current could be generated. Using this newfound knowledge, Volta went on to build the first form of a chemical battery by layering alternating disks of copper, tin, and paper soaked in salt water. One diode was connected to the top-most disk, and one diode to the bottom-most disk (which should each be different metals) [8], and, if connected by a conductor, an constant electrical current will flow from one diode to the other. It was the first instance of a device that could create a constant , and both allowed Hans Christian Ø rsted and André-Marie Ampère to continue research in the field of electricity, and would be the inspiration for the power source used by Thomas Davenport in the construction of his motor.

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Hans Christian Ø rsted a nd A ndré-Marie Ampère

During one of his lectures in 1820, a Danish physics professor at the University of Copenhagen by the name of Hans Christian Ø rsted noticed that the needle on his compass deflected when brought near a copper wire through which flowed a current from one of Volta’s devices, but did not when brought near a copper wire through which no current flowed, thereby proving a link between electricity and magnetism. André-Marie Ampère, a french Professor of Mathematics at École Polytechnique in Palaiseau, France, and namesake of both the SI unit for current and Ampere’s Circuital Law, heard of Ørsted’s discovery, and conducted experiments on his own, eventually quantifying the behavior Ørsted first noticed [9], a nd it was Ampère’s writings that inspired Joseph Henry in his creation of the electromagnet.

Joseph Henry

Joseph Henry was an intellectual from Albany, whose interests laid in the sciences. While most in the early focused mostly on , Astronomy, and Geology so as to be of practical help to the settlers, Joseph Henry was entranced by all forms of science. He read his way through , and would eventually stumble upon the writings of A ndré-Marie Ampère, where he would discover that his true passion laid with Electromagnetism. Driven by rumors of being built in Europe, Henry began building his own. Eventually, he would build one that could lift 750 lbs with only a modest-sized battery [10]. These magnets would eventually be used to facilitate the separation of iron from the ore in Ironville, New York [11]. News of this incredible invention spread, and came upon a small town in Vermont, and to the ear of one Thomas Davenport [12].

Figure 1: Joseph Henry’s Electromagnet [19]

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Thomas Davenport

Thomas Davenport was born in Williamstown, Vermont, in 1802. He became an apprentice to a blacksmith at age 14, and, after his apprenticeship was complete, set up his own blacksmith shop in Brandon, Vermont. It was there that news of Henry’s electromagnet reached him, and his journey to develop the first electric motor began[13].

Figure 2: Map of Thomas Davenport’s Locations [20]

Understanding the Electromagnet At age 29, Davenport visited the Penfield Iron Works in Ironville, New York, where he observed the first commercial electromagnet in use. This powerful electromagnet was built by Joseph Henry and could lift up to 750 pounds of iron. It was being used to separate the higher-quality, more magnetic iron from the lower-quality, less magnetic iron. The rapidly-expanding railroad system needed the highest quality of iron possible, so this electromagnetic solution was incredibly profitable. This marvel of modern technology enchanted Davenport, and when he discovered Henry was selling an electromagnet, sold his brother’s horse and used all of his savings to purchase it. After walking home to Brandon, he and his wife Emily carefully took it apart, taking care to note how it was assembled, to study how it worked. Using the knowledge from Henry’s magnet, Davenport reverse-engineered and built several of his own electromagnets. Two of these he mounted to a pivot, and another two were mounted to fixed poles nearby. Connecting a commutator to the pivot (a device that allows the current to invert at known intervals, see the “The Commutator and Brushes” section under “Composition of the Motor”) and creating an electrical circuit by hooking the magnets and commutator up to a lead-cup battery resulted in Davenport’s very first motor. He exhibited his

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invention in December of 1834 to Professor Turner of Middlebury College, and to the public in 1835 in Springfield, Massachusetts. Further refining would result in a four-pole armature (four magnets mounted on the motor shaft) with two field magnets (fixed to the frame), and a model electric railroad that was powered by one of his motors. [14]

Applying for the patent Thomas Davenport attempted to patent his device but was refused because the patent office officials had never patented an electric device before. Davenport returned home to seek out letters of recommendation from academics and to support his cause. He traveled to Princeton, NJ, where he met with Joseph Henry, and then to the University of Pennsylvania where he met Bache, both of whom offered their support [14]. On Feb 25 1837, with help of his wife and his to-be business partner Ransom Cook, and all of the support he garnered, he again applied for, and was this time granted, a patent. [15]

Figure 3: First Electric Motor 1837 US Patent [21]

After the invention Having successfully acquired a patent on his motor, Davenport moved to New York City and set up a workshop close to Wall Street. He made Ransom Cook his business partner, who maintained control of Davenport's New York shop when Davenport himself traveled back to his workshop in Brandon, which he did frequently. He built many versions of his motor, and was

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even able to build an electric-powered piano. Davenport main focus was finding ways to use the motor for weaving silk, harvesting grain, lathe, and milling lumber, bark milling, sugar grinding, plowing, and printing. In 1840 he was able to build a more powerful motor to run a printing press. He used this press to publish a work entitled T he Electromagnetic and Mechanics Intelligencer. Unfortunately, he was not able to make the motor profitable because the batteries at the time were of poor quality, provided fairly inconsistent power, and were expensive.

Model Railroad While the words “model railroad” typically conjure images of little, scale plastic locomotives with railroad cars that connect to them running around a track, that was obviously not the case at Davenport’s time. His model railroad sought to do more than be his hobby and project; he aimed to provide a practical demonstration that his electric motor could be used in practical applications. It consisted of a circular track on which sat a wheeled cart that held one of his motors.

Figure 4: Davenport’s Electric Railway Model [18]

It does not run as fast as a modern model train, but it does run smoothly. This motor has a two-pole armature with a fixed field electromagnet below the armature. The motor drives a belt via a bevel gear that causes the frame holding the cart on the rail to spin, moving the

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motor-cart combination around the track. He made many more models such as this, demonstrating the practicality of motors from transportation to cotton refining to machining [18].

Death July 6, 1851, Davenport passed in Salisbury due to overwork and poor psychological condition. The steam proved to be significantly more practical for industrial uses than was his electric motor, but it was eventually used by innovators like to develop more advanced inventions, but never in Davenport’s life did his motor see widespread use [16].

Thomas Davenport envisioned the future as being full of large electric motors working for man, but eventually, he returned home to Vermont a broke man and decided to write a book about his ideas for the future of the electric motor. However, he passed away before finishing it. His legacy lives on, albeit not as well known as some other electromagnetic innovators, in just about everything humanity uses on a day-to-day basis, from cell phones to industrial machinery.

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The Physics of the Electric Motor

Electric Current and Magnetic Fields

When a current flows through a wire, a magnetic field is produced around said wire. This magnetic field, when it interacts with other magnetic fields, creates an electromagnetic force between the two objects that are generating the magnetic fields. Mathematically, the vector representing this force can be determined by doing calculations with the current vector I and the magnetic field vector B , but there is a much easier and faster way of determining the direction of this force than going through the mathematics. This method is called the “Right-Hand Rule”, and is depicted in figure 6 below. If one were to extend their right thumb and forefinger to form a ‘finger-gun’, and then extend their middle-finger straight towards the left (so it is perpendicular to the other two), they would have a physical representation of the relationship between the current (I ) along the forefinger, the magnetic field (B ) along the middle-finger, and force (F ) along the thumb. To determine the direction of this force, simply point the forefinger in the direction of the current, the middle finger in the direction of the magnetic field, and the thumb will be pointing in the direction of the force. This rule may also be used to determine the current if given the force and magnetic field, or the direction of the magnetic field if given current and force. The current (in a circuit) flows from the positive of the power source to the negative electrode, and the direction of the magnetic field is a straight line, pointing from the North pole (positively-charged pole) towards the South pole (negatively-charged pole). In reality, the magnetic field lines do curve, but for the purposes of this, the above explanation is sufficient. This information, albeit useful, is useless unless the parts of a motor all work together.

Figure 5: The Direction of a Magnetic Field [22]. The top plate is the north pole, and the bottom plate is the south Figure 6: The Right-Hand Rule [23].

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Composition of a Motor

Figure 7: Composition of a DC brushed motor [24]

Field Magnets The field magnets (called magnets in figure 7 above), which can be either electromagnets or permanent magnets, are the source of the magnetic field with which the motor’s poles interact. There are two kinds of motors in which the field magnets are electromagnets: Series Motors and Shunt Motors. In a Series Motor, the current flows through the field magnets and then to the poles (or vice versa); the field magnets and poles are connected in series. In a Shunt Motor, the current is split when it goes into the motor: roughly half goes through the field magnets to produce the magnetic field, and the other half goes directly to the poles; the field magnets and poles in a shunt motor are connected in parallel. In a , the only current that is used goes into the poles, as the field magnets do not require a current to produce their magnetic field.

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Armature The armature is the piece of the motor that spins. It consists of the motor shaft, the poles, and the commutator pads (everything in the motor except the field magnets and the motor housing). The motor shaft acts as the axis of rotation for the armature, providing a solid frame for the rotation and transferring the rotational energy to the outside of the motor so it may be used. The function of the poles and commutator are discussed below.

Poles The poles of the motor are the internal wires or wire coils and their ferric cores (as they are in figure 7 above) that produces the spin of the armature. When current is run through them, as was discussed above in the “Electric Current and Magnetic Fields” section, the wire in the poles interact with the magnetic field to produce a force, and because the poles are attached to the motor shaft, this force causes them to spin about the shaft’s axis. Poles range from being a single segment of wire to tightly-bound coils of wire. The advantage of more coils is that, while the current flowing through the pole may stay the same, there is a greater length of wire for it to flow through that is in the magnetic field. Because the amount of force applied to a wire depends upon the length of the wire through which current passes. The more wire there is, the greater the overall force will be, and the faster the armature will rotate. The disadvantage is, however, the poles become heavier, and therefore need more force to move. To make a stronger, more efficient motor, one must balance the length of wire with the weight of the poles. There must always be an even number of poles on a motor (with the exception of a three-poled motor, but those are rare). Each opposing pair of poles must have an electrical connection and their overall current flows must be going in opposing directions. If the poles are single segments of wire, the direction of the current is simple to determine, but is a little more confusing when dealing with motors whose poles are coils of wires. To determine the overall current flow through a coil, one must treat the coil as a single wire, starting where the current enters the coil and ending where it leaves. Thinking about the coil in this way allows for easier understanding of the direction of the force that will be acting on the armature, as well as a better understanding of the benefit of coiling the wire. With a coil, one simply extends the length of the wire on which the force can act without increasing the size of the pole too much. The opposing direction of these current flows, as per the right-hand rule, creates opposing forces on either pole, creating a rotation.

The Commutator and Brushes The commutator is, arguably, the most important part of the motor. It is what allows the current going through the poles to invert. The commutator is a cylinder of a conductive substance (frequently copper or brass) around the shaft that is divided into radially-symmetric segments (pads). Each of these pads is insulated from the others and from the motor shaft. There are always an equal number of commutator pads as there are poles on the motor’s armature, and each pole is connected to one pads. There are two conductive brushes, one

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connected to the positive electrode of the power supply and the other connected to the negative electrode. These brushes are held against opposing sides of the commutator but are fixed to the frame of the motor. As the armature rotates, the commutator rotates with it, but the brushes stay static. As the commutator pads rotate under the brushes, different pads come into contact with the brushes, allowing different pole pairs (on a motor with more than two poles) to receive current and therefore produce a force.

The Physics

The simplest form of a DC motor is a loop of wire in a magnetic field that rotates about its axis, with a commutator and power source (see figure 8 below).

Figure 8: Basic Electric Motor Diagram [25]

In this motor, there are two poles, one for each pass the wire loop makes through the magnetic field. Using the right hand rule discussed in section “Electric Current and Magnetic Fields” above, it can be determined that the force acting on the pole closer to the North of the magnetic field is acting up and out of the page, while the force acting on the pole closer to the South of the magnetic field is acting down and into the page. These complementary forces will cause the poles to spin about an axis (see figure 9 below). However, as the rotation continues, the forces that were tangential and induced a rotational motion become forces that pull the poles away from each other (see figure 10 below). In figure 8 above, this occurs when the wire loop is vertical, rather than horizontal. As per the right-hand rule, the force acting on the pole that was once closer to the north of the magnetic field pulls it straight up, while the other force pulls the other pole straight down.

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Figure 9: Electromagnetic Forces that Induce a Rotational Motion [26]. The black arrows are the Electromagnetic forces, the blue arrows represent the , and the red arrows the current.

Figure 10: Electromagnetic Forces that would not Induce a Rotational Motion [26]. The black arrows are the Electromagnetic forces, the blue arrows represent the electromagnetic field, and the red arrows the current.

It is this situation that makes the commutator so important. As can be seen in the figures 9 and 10 above, the commutator pads are connected to the armature and will therefore rotate as the armature does. When the armature reaches the point where the forces no longer induce a rotational motion, (when the forces act along the same plane, see figure 10 above), the split between the two commutator pads (the black band on the commutator in figures 9, 10, 11, and 12) causes current to stop flowing through the wire loop, so no force is induced to pull the wires apart (see figure 11 below). The inertia will keep the wire loop rotating for just long enough so the commutator pad that was once touching the positively-charged brush to now be touching the

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negatively-charged brush, and vice versa. Because of this, from the point of view of the armature, the current has inverted, which causes the acting forces to invert. The force is acting in the opposite direction, which pulls the pole that would be at the top of the motor down in figure 8 above, and the pole at the bottom of the motor up (see figure 12 below). This completes a half of a rotation. This cycle will repeat for as long as there is power coming from the power source that is connected to the commutator brushes, inducing a fairly constant rotational motion.

Figure 11: The split between commutator pads interrupting the flow of current through the armature [26].

Figure 12: The Electromagnetic Forces after the inertia allows the commutator pads to resume the current flow through the armature [26].

The intermittent moments where there is no force applied to the armature can cause the rotation to be jerky and inconsistent, accelerating when force is applied, and decelerating when

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there is none. The solution to this problem is to increase the number of poles on the motor, because when one pair of poles is in the situation where the commutator prevents a current from passing through them and inertia would be the only force maintaining the rotation, current is allowed to pass through another pair of poles, creating a force that acts on them, decreasing the amount by which the armature will decelerate. The more poles that are added to the armature, the less it will decelerate when one pair of poles has no current, and the smoother the rotation will be.

Building the Motor

In the Forge

The Wrought Iron Billet The piece of metal from which the motor’s armature and field cores would be forged was an old eighty inch long by three inch wide by one-quarter inch thick piece of wrought iron. This piece was interrupted roughly every seven inches by a rivett, so in order to create a piece of workable material that could be forged into the required shapes, the stock piece was cut into seven inch segments, removing the one inch of material on either side of those seven inch pieces that housed the rivetts, creating fairly uniform rectangles of wrought iron, without many irregular protrusions that would have to be ground away later. The wrought iron was fairly old, and was pockmarked and covered in a thick layer of rust, so after they were cut, the rust was ground off each surface of each of the seven-inch pieces. These imperfections would have made it nearly impossible to successfully forge weld these pieces into a single billet, so the surfaces were ground as close to perfectly smooth as possible. However, due to the severity of the pockmarking, grinding each surface down to a perfect finish would have taken half of the material of each piece, so all the rust was easily removed, but it was only practical to remove about half of the pockmarks.

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Figure 13: Clean, Partially Clean, and Uncleaned Pieces of Wrought Iron

After grinding, the surfaces of each piece were each cleaned of skin oils and dust with acetone. These cleaned pieces were stacked into a pile, and welded into a single billet. The forge had, at this point, been warming up for several hours, so the next step involved welding a handle to the billet, sticking it in the forge, and waiting for it to heat. Periodically throughout the heat, the billet would be removed and borax would be spread along the surfaces such that, when it melted, it could flow in-between the not-yet forge welded pieces. Borax helps the forge weld successfully fasten the two pieces of iron together.

Figure 14: The Welded Wrought Iron Billet

The metal must heat until it is white-hot and almost burning before a forge weld will succeed. When the billet reached the proper temperature, it was brought to the nearby hydraulic press and pressed. If successful, the separate pieces of wrought iron would have

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fused into one, and could be forged into the proper shapes for the motor. If unsuccessful, the pieces would separate under the immense pressure of the press and the process would have to be restarted. Below is a picture of the result of the press:

Figure 15: The Now-Broken Billet of Wrought Iron

The forge weld, unfortunately, failed, and due to time constraints, the process could not be restarted. It was assumed that, due to their similarly low carbon content, wrought iron and mild steel have similar magnetic properties, and a piece of stock mild steel was easily accessible in the required dimensions, so the wrought iron forge weld was scrapped in favour of a more-easily workable piece of mild steel. If the forge weld had been successful, the next step would have been to, using the same hydraulic press and the nearby power hammer, draw the billet out into a three-quarter inch square bar. Besides this step, all the following steps would have been identical.

The Final Shaping The final design for the motor required two three-inch pieces of the bar for the armature cores, and a eight-inch diameter circle in two pieces for the field cores. The lengths for the armature were cut, and then two one-foot pieces for the field cores. Due to the shape of the final design of the field magnets, each piece of the field cores would have to be forged into a semicircle. This was completed, once the metal was hot enough, holding one end of each piece in a vice, putting a pipe around the other end, and bending the piece. The diameter of each semicircle would be checked with a ruler, and then each piece’s shape and size would be touched up with a hammer, if needed. Because the armature cores had to sit on the same plane, material had to be ground away from both pieces that would make up the armature cores so they could fit together properly. Due to time constraints, this had to be done outside the forge, so it was done on a radial arm saw with a grinding wheel attachment. Once the material was ground out properly, and the pieces could just barely not fit together snugly, they were heated with a hawk heater until they were forgeable, and then hammered together. Once the pieces cooled, while not forge welded together, the centres of each piece were deformed in such a way that the pieces

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could not come apart. A one-quarter inch hold was then drilled into the centre of the now-completed armature cores to house the shaft.

Figure 16: Forging Together the Two Pieces of the Armature Cores

Figure 17: The Final Shape of the Armature and Field Cores

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The Frame

The frame of the motor is made of two horizontal wooden supports. The lower support acts as the base of the motor, where the commutator rests and the armature is supported by a brass disc acting as a lower bearing. The base has dimensions of 1’x3’. The upper support rests upon four approximately 4” long wooden pillars that are fixed to both the base and support using wood screws. The upper support is a circular-support with a cross-sectional shape L, and its purpose is to support the semi-circular field magnets. The upper support is composed of two 1” thick pieces of wood cut into circles with an outer diameter of 11”. The two wooden circles are stacked on top of each other, one having an inner diameter of 7”, the other having an inner diameter of 9”. Together, they create a circular shelf of width 1” between the circles. The difference between the inner diameters of the two circles is the “shelf” and the larger inner diameter of the top piece acts as a wall to hold the field magnets in place. The brass bearing is located on the base in the center of the circular support. The upper part of the armature is supported by a horizontal bar that is about 4” above the circular-support that houses the field magnets. The horizontal bar is attached to the sides of the upper support using wood screws.

The Armature

The motor shaft is a ¼” steel rod, onto which the armature core is soldered. A propane torch was used to heat the core and shaft to the required soldering temperature and melt the flux before a silver solder was applied to fix the two pieces together.

The Brushes and Commutator

Two copper pads were soldered onto two semi circular brass substrates to act as a commutator. The substrates were made out of a brass disc that was about 1.25” in diameter and 0.25” thick. Wires were soldered onto the substrates so that current would be able to enter one pad and exit the other. The pads were mounted at the base of the motor where the armature shaft was supported. Brushes were made from the poles of small steel utility flags. The brushes were bent to stay sprung against the copper pads and remain in contact, and they were attached to the shaft but insulated from it electrically. The top ends of the brushes were spliced to the ends of the armature windings. Current was then able to flow through the brushes via the brushes making contact with the commutator. Current would enter the copper pad, travel through one brush, through the armature windings, and out of the other brush through the pad. When the armature would complete half of a turn, the positions of the brushes would switch and thus the magnetic poles of the armature would flip, resulting in another half of a turn.

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The Finished Motor

The finished motor consisted of all of the parts mentioned above. Electromagnets wrapped with about 50 convolutions of 16 gauge varnish coated wire were used as field magnets instead of permanent magnets because it makes very little difference in the function of the motor, but it was significantly easier to make electromagnet fields than it would have been to make permanent magnet fields.. The armature poles were wrapped with the same wire - about 50 convolutions per pole. The motor was tested on two different power supplies. The first tests were done using a 120 VAC to step down the , and then connected to a rectifier that provided the necessary DC voltage. The motor ran on as little as 6 , and performed better as the voltage increased to about 12 volts. The second test was done using a 12 battery, where the brushes began to heat up due to high current.

Figure 18: Finished Motor Showing Field Windings and Armature Windings

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Figure 19: A Replica of Davenport’s Motor from the Smithsonian [27]

Education

Experiential projects such as this always make the best teachers. It is one thing to learn the theory behind electromagnetism in the classroom; perform calculations with Ampere’s law and determine the theoretical force one electromagnet would have on another when certain currents flow through them, but it is a completely different thing to take these calculations and apply them to a physical, actual system. With an actual, physical motor, the only right answer is the one that works. Nothing a teacher teaches in a classroom lecture can compare to understanding and appreciating the intricacies of electromagnetism. The original motor, as well as this one, were both built and tested, for the most part, by hand, using tools that anybody could have or build in their backyards (the exceptions for this are, of course, the hydraulic press and power hammer used to forge the magnet cores, but that could have been done by hand as well). Granted, the motor for this project went quite a bit more in-depth and took more time than a typical physics teacher would have to spare for such a project, and focused far more on the history of electromagnetism than a physics teacher would need to, but in giving students the opportunity to, in class, a place they are r equired t o be, have hands-on experience building a mechanism that applies the theory that they had been learning would get significantly more students interested in the sciences.

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A high-school physics teacher would have pre-built components because forging is dangerous, to provide more of a focus on the electromagnetic aspects of the motor, and to reduce the amount of time needed to spend on the project. The motors would have to be small, probably palm-sized, to reduce cost and ensure every student was able to work on their own or in partners to build it. It would not cause too much of an upset to the average class plan, because all that would be needed is a single class period. A physics teacher would go through their standard routine of going through the theory behind electromagnetism, with assigning homework and quizzes, and at the end of the unit would have a class period or two dedicated to this project. If not already completed, the teacher would need to go through the basics of how an electric motor works (how electromagnetic fields interact, the need for a commutator, &c.). On the day of assigning the motor project, the professor would need to explain what each component is and how they fit together. Walking students through the process is not detrimental to their learning, as it is not the actual building of the motor that will help them learn and understand the material. It is in troubleshooting problems as they arise and it is seeing how the theory they have been learning applies to the real world that would get students excited to learn, and an excited student has a significantly easier time processing information.

Conclusion

The goals of this project were to study and expound on the history behind the invention of the electric motor by Thomas Davenport, to re-create a working replica of his original patented design from 1837, and to determine why completing a similar project is of benefit to students of basic physics. The invention of the electric motor has had a significant impact on society. The ability to convert electrical energy into mechanical energy has and shall continue to benefit society in many ways. Electric motors are found in everyday items, and range in size from the small motors in electric toothbrushes to the larger motors that power electric cars or trains. Thomas Davenport’s contribution to humanity by discovering a way to achieve rotational motion from electromagnetism deserves, and yet does not get enough, appreciation. The replica created for this project was difficult enough to make even with Davenport’s design easily accessible for reference, an in-depth understanding of the physics, and mail-order components. For Davenport, a poor man who wagered his entire livelihood on an the idea of this motor, to figure out what he needed to do, come by the components he needed, and assemble them in a way that actually functioned as he imagined it would is incredible. Creating a DC motor is a fantastic learning project for physics students. The motor is a great place to start learning about the applications of electromagnetism in machines such as motors and generators. Creating the replica not only provides a much deeper sense of appreciation for what Davenport has done for humanity with his invention, but is also a fun and engaging way to learn about electromagnetism.

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Authorship

Section Author

Abstract Barry Aslanian

Executive Summary Barry Aslanian

Introduction Sam Milender

The History of Electromagnetism Sam Milender, Jianqing Zhu

The Physics of the Electric Motor Sam Milender, Jianqing Zhu

Building the Motor Barry Aslanian, Sam Milender

Education Sam Milender

Conclusion Barry Aslanian, Sam Milender

Bibliography

● [1] "Compass Invention - The Development of the Compass", H istoryofcompass.com, 2019. [Online]. Available: http://www.historyofcompass.com/compass-history/invention-of-the-compass/. [Accessed: 22- Apr- 2019]. ● [2] G. He, "The Compass", C hina Today, 2016. [Online]. Available: http://www.chinatoday.com.cn/english/culture/2016-02/16/content_712997.htm. [Accessed: 22- Apr- 2019]. ● [3] J. Vardalas, "History Lesson: The Magnetic Compass", I EEE Spectrum: Technology, , and Science News, 2013. [Online]. Available: https://spectrum.ieee.org/the-institute/ieee-history/history-lesson-the-magnetic-compass. [Accessed: 22- Apr- 2019]. ● [4] W. Gilbert, D e Magnete. 1600. ● [5] "Alessandro Volta | Biography, Facts, & Invention", E ncyclopedia Britannica, 2019. [Online]. Available: https://www.britannica.com/biography/Alessandro-Volta. [Accessed: 22- Apr- 2019]. ● [6] B. Dibner, "Luigi Galvani | Italian physician and ", E ncyclopedia Britannica, 2019. [Online]. Available: https://www.britannica.com/biography/Luigi-Galvani. [Accessed: 22- Apr- 2019]. ● [7] L. Galvani and M. Foley, "A Translation of Luigi Galvani's De viribus electricitatis in motu musculari commentarius. Commentary on the Effect of Electricity on Muscular Motion", J ournal of the American Medical Association, vol. 153, no. 10, p. 989, 1953. Available: 10.1001/jama.1953.02940270095033.

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● [8] A. Volta, "On the Electricity Excited by the Mere Contact of Conducting Substances of Different Kinds", P roceedings of the Royal Society of London, vol. 1, 1800. Available: 10.1098/rspl.1800.0016. ● [9] A. Ampère and Babinet, E xposé des nouvelles découvertes sur l'électricité et le magneétisme. Paris: Chez Méquignon-Marvis, 1822. ● [10] "Joseph Henry 1797-1878", H istory.aip.org, 2019. [Online]. Available: https://history.aip.org/history/exhibits/gap/Henry/Henry.html. [Accessed: 22- Apr- 2019]. ● [11] F indagrave.com. [Online]. Available: https://www.findagrave.com/memorial/101397298/allen-penfield. [Accessed: 22- Apr- 2019]. ● [12] C. Center, "Joseph Henry - Engineering Hall of Fame", E disontechcenter.org. [Online]. Available: https://edisontechcenter.org/JosephHenry.html. [Accessed: 22- Apr- 2019]. ● [13]Thomas Davenport Archived October 16, 2008, at the Wayback Machine ● [14]Davenport, W. Rice. (1929). Biography of Thomas Davenport: the "Brandon blacksmith", inventor of the electric motor. Montpelier, Vt.: The Vermont historical society. Chapter XI-XII ● [15]Dr.Frank Wicks:As published in Mechanical Engineering magazine in July 1999. © 2010 ASME. Used with permission. ○ Also this: h ttp://edisontechcenter.org/ironville.html ● [16]Patent "IMPROVEMENT IN PROPELLING MACHINERY BY MAGNETISM AND ELECTRO-MAGNETISM". Google. Retrieved 27 February 2011. ● [17]Getting Electricity to Work for Man: h ttp://www.hbci.com/~wenonah/history/edpart2.htm- ● [18]Ethw.org. (2019). A rchives:The Inventions of Thomas Davenport - Engineering and Technology History Wiki. [online] Available at: https://ethw.org/Archives:The_Inventions_of_Thomas_Davenport [Accessed 30 May 2019]. ● [19]https://upload.wikimedia.org/wikipedia/commons/0/02/Joseph_Henry_electromagnet_closeup. jpg. (2019). [image]. ● [20]https://edisontechcenter.org/DavenportThomas.html. (2019). [image]. ● [21]United States Patent Office (1837). I mprovement in Propelling Machinery by Magnetism and Electro-Magnetism. United States Patent Office. ● [22]Khan Academy. (2019). W hat is ?. [online] Available at: https://www.khanacademy.org/science/physics/magnetic-forces-and-magnetic-fields/magnetic-flu x-faradays-law/a/what-is-magnetic-flux [Accessed 30 May 2019]. ● [23]Arbor Scientific. (2019). Three Right Hand Rules of Electromagnetism. [online] Available at: https://www.arborsci.com/blogs/cool/three-right-hand-rules-of-electromagnetism [Accessed 30 May 2019]. ● [24]Mouser.com. (2019). D on't Ignore the Humble Brushed DC Motor| Mouser. [online] Available at: https://www.mouser.com/applications/dont-ignore-the-brushed-dc-motor/ [Accessed 30 May 2019]. ● [25]Explain that Stuff. (2019). H ow do electric motors work?. [online] Available at: https://www.explainthatstuff.com/electricmotors.html [Accessed 30 May 2019]. ● [26]Fendt, W. (2019). D irect current electrical motor. [online] Walter-fendt.de. Available at: https://www.walter-fendt.de/html5/phen/electricmotor_en.htm [Accessed 30 May 2019]. ● [27]Wicks, F. (1999). The Blacksmith's Motor. M echanical Engineering, 121(07), p.66.

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