Design Life-Cycle

Life Cycle of Brushless Motor

Noe Segundo

DES 40A

Professor Christina Cogdell

December 5, 2018

Raw Materials

Direct Current (DC) Motors today can be found inside millions of products, machinery, and other forms of technology. The first DC Motor being created in 1832 by William Sturgeon turned electrical energy into mechanical energy. This invention from 1832 gave foundation to hundreds of different types of motors today that can be applied to many products for all kinds of uses. One major variant that was created is the brushless direct current motor (BLDC) motor that as its name implies, is just a DC motor without any brushes. In the following paragraphs I will speak about the needed creation of the BLDC motor and materials that it is composed of which was able to increase efficiency inside some products by overall making the life of the motor last longer without much maintenance as well as drastically help the environment.

The first thing to understand is that direct current motors are a better alternative to achieving mechanical/kinetic energy. Using a DC motor you are transforming electrical energy into mechanical energy without the use of fossil fuels or other harmful byproducts being released into the air other than those released in production. The creation of BLDC motors is just another step-forward to using clean energy. In this present day, one of the main focuses or problems is trying to incorporate as much “clean energy” into everyday uses. An example of this would be the major rise in electric cars that has been becoming more popular as well as electric skateboards. Direct current motors which are reusable as well as recyclable has led to many alternatives to relying on fossil fuels and other harmful chemicals to the environment to use for transportation, manufacturing, and tools.

BLDC Motors are not manufactured by one single company, meaning that there are different forms of BLDC motors which can have different materials used. However, all BLDC motors are separated into three different parts, the casing, the rotor, and the stator. Different from a regular motor as stated before, BLDC motors do not have brushes. These brushes,made from carbon and graphite, can be found on the stator of a regular DC motor and are used to create an electric current. What replaces these brushes on an BLDC motor is an permanent magnet in its external rotor (Motion Control And Motor Association). Getting rid of the brushes on the DC Motor allows for a smoother rotation of the motor that is capable of being spun at higher speeds.

Metals make up nearly all of the material that are inside of a BLDC motor, some of these metals are iron, copper, tin, and steel but there are also other non-metal primary materials such as silicon. While iron is known to be found on the earth’s crust along with other elements it can also be found inside of hematite a black mineral found in Yellowstone and other parts of North America (Royal Society of Chemistry). Copper is one of the most popular metals used as a conductor that can be found in nearly any electronic or cable, and is mined mainly from Utah in the United States, it is then sent to a manufacturing factory that turns the copper into cable which is then sold. Tin is gathered from the ore Cassiterite which is found throughout China, Thailand, and Indonesia (Royal Society of Chemistry) then shipped to US factories. While iron, copper, and tin are natural materials there are other materials such as steel (alloy) used in motors that are created from iron combined with carbon. Motors aren’t necessarily dangerous for the environment because they are almost completely made out of metal, meaning they are recyclable and reusable.

While there are primary materials (mostly metals) there are also secondary products such as lubricants, solder, and glues/insulations. Lubricants which I will later explain what they are used for in motors, can either be synthetic or natural made from base and mineral oils. Solder is often used in a motor driver chip. This solder is a lead-free product of tin and copper. Glues and insulations are used to keep together the components that are inside of the motor, whether it is the driver chip or keeping the copper wire together as well as holding together the permanent magnets. BLDC motors don’t use very much byproducts but rather first materials meaning that there isn’t a very long complicated process when it comes to the creation of the materials or the production of the motors themselves.

 BLDC Motors aren’t a complicated product by any means, about 90% of the motor is metal  and while there has been improvements in the motors since they were first discovered, a BLDC motor must still have the foundation layout because if it doesn’t the electromagnetic s will not function properly. It is important for all the materials to be precisely cut whether its through machinery, with lasers, or high pressure water. Understanding the layout of a motor by separating the motor into its three different parts: The casing, the rotator, and the stator can help better understand the product and create it.  The casing is usually molded from aluminum or iron, sometimes depending on the size of the motor and its applications a motor can have a plastic casing. Moving onto the rotator, it consists of steel and iron bearings as well as a rod with a steel center. Steel is the product of an iron alloy implemented with carbon. Around the steel body there are permanent magnets which can either be Samarium Cobalt, Neodymium, or ferrite magnets depending on the amount of torque or speed wanted. These magnets are especially popular magnets used for applications in motors. Finally moving on to the stator, the part inside the casing of the motor that doesn’t move, consists of a few different types of materials. The center of the stator is made from iron which copper wire that has been shaped is put over. This copper wire  is used as a conductor and is often covered with grease to act as a lubricant that can prevent corrosion or wear, this lubricant may either be synthetic or oil-based. In the stator there is a Hall element, which is a transducer made from metal and silicon that transmits speed and positioning of motor into an electrical signal output. Because there is speed and positioning being turned into an electrical signal output, there has do be some kind of circuit or motor drive. This circuit (which may vary in position on the motor) is composed of many smaller electrical components but all which are either created from Silicon, tin, and copper with thin layers of steel. Overall, it is important to remember that although there are new kinds of motors designed for all types of purposes they must all have near the same set up in order for each part of the motor to be able to perform its task of using electromagnetism to spin the motor.

As previously stated motors can easily be reused by opening them up and giving them maintenance or replacements on the parts they are composed of. Often magnets can be replaced or demagnetized using electric current. However if a motor is no longer reusable there is no need to worry. The iron, steel, copper, tin, and silicon can all be recycled which will later be used for other electronics. The best part about these motors is that you simply just need to take off the casing or simply give a product that has a BLDC motor to a company who would simply take it apart.

The Brushless Direct Current motor is a revolutionary invention that does minimal damage to the environment that turns electrical energy into mechanical through the process of electromagnetism. The copper which creates an electric field along with the magnets makes the armature of a motor rotate creating mechanical energy. Without BLDC motors today there wouldn’t be as much advances towards a world where clean energy can be used rather than relying on fossil fuels and other harmful chemicals for power, transportation, machinery, and tools.

Annotated Bibliography

“US6034493A - Brushless DC Motor Control.” Google Patents, Google, patents.google.com/patent/US6034493A/en?q=motor&oq=brushless dc motor.

This isn’t an article but instead the patent for a Brushless DC Motor which is the product we will be analyzing the life cycle of. The patent’s main purpose is to protect the product from being replicated without properly giving credit to the owner. The patent describes what their product is made out of, how the product is made, and finally how the product works. Looking at patents makes my research easier because DC motors have been around for a long time, so looking at a particular model (brushless) helps us better research the life cycle of our product more accurately.

“Raw Materials.” Raw Materials for Motion Control Applications - MCMA, www.motioncontrolonline.org/product-raw-materials.cfm.

This article was created by the MCMA (Motion Control & Motor Association) which focuses on the way that the motors work. I will use this article in my research to gain better understanding of the way that motors work. It is important for me understand how the motors work in order for me to find out what kind of metals and magnets are needed and what other components are used inside the motor to get it to turn.

“Brushless DC Electric Motor.” Wikipedia, Wikimedia Foundation, 19 Oct. 2018, en.wikipedia.org/wiki/Brushless_DC_electric_motor.

This Wikipedia page is composed of many sources. The main purpose of the page is to describe the types of motors that there are, how they’re used, and the characteristics that they have to have in order to perform the task they are meant to do. Different metals and different magnets can be used depending on the job. The more strength (torque) you want in your motor, the higher quality magnet and metal you want. However for our research we will be looking at the most common type of motors for electric skateboards.

Daware, Kiren. “How a DC Motor Works?” Electricaleasy.com, www.electricaleasy.com/2014/01/basic-working-of-dc-motor.html.

Kiran Daware, the author of the article explains that a motor converts electrical energy into mechanical energy. Daware explains the magnetism of a motor and how exactly it rotates. This information is crucial when wanting to understand the types of magnets needed and used in brushless dc motors. There are different motors an example being a regular DC motor and another being a brushless DC, as the name implies the brushless DC motor does not have any brushes unlike the regular DC motor. In my research there will be no need to find the materials needed to create brushes.

“Recycling Electric Motors.” Interco Trading Company, 21 Mar. 2018, www.intercotradingco.com/recycling-electric-motors/.

This source isn’t an article but instead a website created by the Interco Trading Company. On this website you can arrange to recycle your unwanted electronics and equipment which might have DC motors inside of them. This website is useful because it describes the process of scrapping the motors and why it is important to scrap them. While describing the scrapping and recycling process, the webpage names some of the components that make up the motor and where it can be found.

“Build Your Own Brushless Motor.” Hackaday, 13 July 2016, hackaday.com/2016/07/13/build-your-own-brushless-motor/.

This “How To” by AI Williams gives you instructions on how you can build your own brushless motor. While the materials aren’t necessarily the same as used in regular brushless dc motor, the project helps you create a large motor that you can see and make it easier to understand how magnetism works. Inorder for someone to truly understand how a product is made it is very important to understand how it works and why.

“Magnets for Motor Applications.” Magnets for Motor Applications | Adams Magnetic Products, www.adamsmagnetic.com/markets/magnets-motor-applications.

The purpose of this source is to understand the types of magnets that there are. The website titled “Magnets for Motor Applications” meaning that all the magnets listed in this website are used inside motors. Here I can find the magnet I need to research on how it is extracted.

“How Are Samarium Cobalt Magnets Made.” first4magnets, www.first4magnets.com/tech-centre-i61/information-and-articles-i70/samarium-cobalt-magnet-information-i85/how-are-samarium-cobalt-magnets-made-i111.

In this article by First4Magnets, a website that specializes in magnets, gives us a step by step guide on how the main magnet used in motors is made. Through the detailed process of how Samarium Cobalt magnets are made, it is possible to trace and recognize the different types of energy needed to make the magnets for use inside motors.

Mills, Richard. “About Us.” Ahead of the Herd, aheadoftheherd.com/Newsletter/2011/Mine to-Magnet.htm.

In this article by Richard Mills, the process of mining for natural elements is described. There are countless natural earth metals and elements that are mined for many uses, rare earths are some of the components that make up the magnet and metal casing of the motors. In his article, Mills, adds a graph that shows where the rare earths can be found and in how many quantities.

Greene, Jay. “Digging for Rare Earths: The Mines Where IPhones Are Born.” CNET, CNET, 26 Sept. 2012, www.cnet.com/news/digging-for-rare-earths-the-mines-where-iphones-are-born/.

Jay Greene in this article describes what “rare earths” are and the many products that these rare earths are used for. In my research I have found out the rare earths that are needed to make a brushless DC motor. This website helps me understand how these rare earths used in my product are mined and the amount/type of energy that is needed to acquire the materials.

“Iron - Element Information, Properties and Uses | Periodic Table.” Royal Society of Chemistry - Advancing Excellence in the Chemical Sciences, www.rsc.org/periodic-table/element/26/iron.

Raama Srivatsan

Christina Cogdell

Des 40A Fall 2018

6 December 2018

DC Motors

A DC motor is a device run by direct current that has the ability to convert electrical energy into mechanical energy.  This type of motor can be controlled over a large range by either variable supply voltage or by changing the strength of current in the motor itself.  These motors are being used more because of their advantages over AC motors. The most common motors are three-phase AC induction motors because of their low cost, reliability, and simple design.  However, brushless DC motors conquer all of the negatives that AC motors come with. DC motors firstly are put in miniature machines and other equipment dependant on speed such as automotives or other battery powered machines.  In today’s age, there are many reasons for the popularity of DC motors. DC motors, for example, provide improvements in the performance of automobiles. Coreless DC motors have a tendency to have low inertia, making them useful as automobiles need to be moving constantly.  According to an article from Engineer Live, “The prototype ENV motorbike from Intelligent Energy features a fuel cell that generates electrical energy from hydrogen and oxygen. To make best use of the limited supply of electrical energy, the bike is equipped with a high-efficiency Lynch axial-gap DC motor.  This type of low-voltage, high-torque, permanent magnet DC motor has the added advantage of a high power density.” (“DC Motors Deliver higher performance and efficiency”). Lynch motors is based in the United Kingdom by the Lynch Motor Company, and is a main manufacturer for motors supply not only in the UK, but around the world as well. Like AC motors and products, DC motors have energy intensive production and recycling processes. Unlike AC motors though, DC motors not only use energy, but are also capable of producing their own through generation.

The inventor of Lynch, Cedric Lynch, currently works alongside Agni Motors in India.  He has improved the design for applications in a variety of industries. “The latest version of the Agni Motor is said to offer higher torque per amp and lower speed per volt, which makes it possible to use a simpler and cheaper transmission in some applications, as well as slightly more efficient.  Two Agni motors are being installed in a Ducati 600 Supersport, which is intended to be the fastest, road-legal, emission free motorcycle in Europe. Power will be supplied by a LiFePO4 (lithium iron phosphate) battery developed by LIfebatt.”

In the United States, Lynch motor technology is licensed to manufacture the Etek motor for use primarily in boats and motorbikes.  “This time the company is Electric Motorsport of the USA, with its Electric Motorsport GPR-S using 3.3kWh Lithium batteries rather than the fuel cell of ENV.  The GPR-S is claimed to have a maximum speed of 112km/h (70mph) and a range of 80km (50miles). While the bike is equipped with the Etek-RT motor, the company says that the industry-standard motor mounting would make it straightforward to retrofit a different motor (and controller) to take advantage of regenerative braking.  An alternative to the Lynch, Agni and Etek motors is the PMG 132 high-performance disc armature motors from Perm Motor in Germany, which operate from 24-72V and have a rated power output of 2.2 to 7.2kW. Depending on the operating conditions, these can achieve a peak efficiency of 90 per cent or more.”  

Another company called PML Flightlink has been making armature motors for around 40 years.  This motor is different, in the way that it is “essentially an ironless disc with coils punched from sheet copper and formed onto non-magnetic disc insulators.  Brushes contact on two or more points to create a path through the copper, thereby creating a magnetic field that interacts with the permanent magnets to cause motion.”  Because there is no magnetic material in the armature, the motion process is very smooth. Torque is continuous and not limited by saturation. Recently, PML Flightlink developed the Hi-Pa Drive in wheel unit that incorporates the motor and drive electronics in a common housing.  Basically, they created a Nano Wheel which incorporates a brushless motor inside a wheel hub. The first item this was used on was a power assisted suitcase. Nano Wheel claims to be more compact, have a simpler design, increase energy efficiency and maximize battery life.

“Compact DC motors are also being manufactured in ever-increasing volumes for even smaller applications.  These include solar-powered devices, toys and mobile telephone handsets - for the vibration function. Apart from those systems in which the dc motor is connected directly to a switched power supply, the motor is only one half of the DC powertrain.  Industrial applications and those calling for precise control of speed or torque require a DC drive. Given the increased demand for DC motors, it is not surprising that there have also been developments recently in the field of DC drive technology” (“Dc Motors Deliver Higher Performance and Efficiency”).

Another DC motor drive launched at the 2008 SPS/IPC/Drives show in Nuremberg was the Mentor MP.  The company that created it, Control Techniques, claims that this drive sets a new world standard for excellence in DC motor control.  “Control Techniques has a patent (pending) to protect an innovative aspect of the Mentor MP’s design. Galvanic isolation between power and control is a standard feature in AC drives and, in the case of a power-side failure, it protects the control circuits and connected equipment.  According to Control Techniques, other DC drives feature a form of isolation that relies on impedance-only isolation, which has limitations. In contrast, the Mentor MP uses novel technology to achieve galvanic isolation without compromising performance or reliability”(“Dc Motors Deliver Higher Performance and Efficiency”).  Giving these factors it should come to no surprise that direct current motors are far superior in terms of durability material usage and recyclability and of course energy usage, then their alternating current Motor counterpart.

Given the market that is prevalent today, it's more vital than ever for development and technology to progress in the motor area with our world is becoming increasingly automated and electrically driven. Throughout history there have been two main forms of electricity. Alternating current and direct. Overtime direct-current has taken a more battery-based approach and it has made it more mobile and more easy for a mass amount of people to use on a daily basis. Due to the increasing amount of efficiency that research is putting out, DC motors we'll most likely become the number one biggest powerhouse that fundamentally drives the world. As stated before due to the nature of this device and the fact that it is capable of producing its own energy, the DC motor holds a different place in the life cycle chart and can actually end up tipping the scale onto the positive side of the carbon footprint much like a solar panel are a windmill. However, given the finite amount of resources in this world it's more important than ever to recycle and reuse as much as possible and to sustain this lifestyle.

Works Cited

“Dc Motors Deliver Higher Performance and Efficiency.” Engineer Live,

www.engineerlive.com/content/21559.

“What Are Brushless DC Motors.” Renesas Electronics, www.renesas.com/us/en/support/technical-resources/engineer-school/brushless-dc-motor-01-overview.html.

Moog Inc. “Brushless Motors & Servomotors Overview.” Moog, Inc. - Precision Motion Control Products, Systems, Servovalves, Actuators, www.moog.com/products/motors-servomotors/brushless-motors/.

“Brushless DC Motors.” NANOTEC, us.nanotec.com/products/156-brushless-dc-motors/.

Brain, Marshall. “How Does a Brushless Electric Motor Work?” HowStuffWorks, HowStuffWorks, 15 Dec. 2006, electronics.howstuffworks.com/brushless-motor.htm.

“Brushless DC Motors.” PCA9564|NXP, www.nxp.com/pages/brushless-dc-motors:WBT_MOTORBLDCTUT_WP.

“What Is Brushless DC Motor (BLDC)? Structure, Working & Applications.” Electrical Technology, Electrical Technology, 16 Nov. 2018, www.electricaltechnology.org/2016/05/bldc-brushless-dc-motor-construction-working-principle.html.

“Brushless DC Motors – Part I: Construction and Operating Principles.” EDN, www.edn.com/design/sensors/4406682/Brushless-DC-Motors---Part-I--Construction-and-Operating-Principles.

“Brushless DC (BLDC) Motor - Construction and Working.” Electricaleasy.com, www.electricaleasy.com/2015/05/brushless-dc-bldc-motor.html.

“Brushless DC Motor.” All About Circuits, www.allaboutcircuits.com/textbook/alternating-current/chpt-13/brushless-dc-motor/.

Yuejia Zhu

Christina Cogdell

DES 40A

Dec. 1th 2018

Recycling Electric Motors

Typically, electric motor work under a fundamental principle that involves the conversion of the electrical energy to mechanical energy.  A decision to recycle motors is significant since the majority of the electric motors are broadly utilized in many organizations and are prudent for commercial value. Among the gadgets that highly employ the use of electric motor encapsulates blowers, pumps, disks drives, industrial fans, and many machine instruments. It is also important to note that the electric motors are significant in engendering mechanical force via interaction and interfacing with the magnetic field as well as windings. Electric motors constitute many elements and components which are embedded in the device. It is through these components that electric motors can convert electrical energy into mechanical energy (Hanselman, Duane, 231). Such components constitute armature, case, commutator, copper windings, shaft, commutator, stator, and the bearings. The components are the one that makes the electric motor to work more effectively in the conversion.

The electric motor recycling process is profoundly important. In the event of damage and electrical surge on any part of electric motors, the recycling process should be initiated for the damaged components to bring them back to use. The reason why recycling of the electric motors should be fully considered for recycling is that a significant percentage of the materials that form electric motors are metallic subject to recycling.

A large percentage of electric motors are utilized to generate multiple devices in contemporary society. As such, in the event when such materials are rendered to damage and are not subjected to the recycling process then eventually may result in a landfill. This implies that the recycling of electric motors is essential in preventing pollution caused as a result of solid waste and landfills. To some extent, recycling of the electric motors can be a holistic strategy to valuable natural resource for instance copper (Slade, Margaret, 21). In actuality, principal components that constitute electric motors are the copper windings.

Copper is regarded one among the most precious and treasured material that take important role in making electrical components. It is unreasonable to advocate for depleting such a valuable component through not recycling.

Recycling Process

The process of recycling is usually carried out on a large-scale basis since the majority of the electric motors lack sufficient copper windings. In regards, the recycling process should be direct and unswerving. Recycling process takes a unique course that should be followed to the latter to ensure a successful operation.

1. First, the people concerned with recycling should decide on gathering and collecting electric motors to make sure that the probable course of sustaining enough copper is enhanced. (“Recycling Electric Motors” ).

2. The second step involves hammering using a hammer to eliminate the metallic casing that is embedded on the copper component (“Recycling Electric Motors” ).

3. The third phase entails the extrication of the elements as well as the classification based on the materials (“Recycling Electric Motors” ).

4. Finally, the fourth step requires positioning of the extricated materials to their different recycling positioning and execute the recycling process of the electric motors (“Recycling Electric Motors” ).

People can engage in promotion of recycling materials through disposing of the damaged electric motors, and in return, they might make money. In essence, the electric motors are typical materials that can be recycled at all times. People should know that categorically almost all the electrical products that are involved in the mechanical movements that are commonly used in homesteads tend to utilize electric motor. For instance, typical electric motors components that are present include computers, hand tools, microwaves, air conditioners, power supplies, washing machine, and power supplies. Besides, conventional electrical motors majorly used in industries include pumps, transformers, machinery, and manufacturing equipment (Vlad, Just, www.youtube.com/watch?v=5sZe1fZkIm8). Among the automotive products that are made of electric motors entails generators, starters, and generators.

Majority of the electric motors are made of these valuable copper and aluminum products. The casing which is an insulator that covers most of the electric motors include the steel alongside with a robust shell that serves as a protector. In some extreme circumstances, some of the motors contain aluminum instead of copper as both are used as good conductors of electricity and hence ideally applied in most of the electrical appliances. Those motors that include copper are the one easy to be recycled. Aluminum also contained non-ferrous metal (Inboard Technology). Steel can also be recycled although it is not attributed to the same value as that of Aluminum and Copper. More importantly, merging such precious metals such as copper and aluminum with specific components like plastic and works may lead to contamination as they are attributed to the lower value (Gockmann, Klaus, 150). For the recycling process to be a success, the people concerned with recycling should categorize the materials collected in three core classifications such as size, weight, and nature of the article.

Benefits of Recycling Electric Motors

The is a lot of value that comes as a result of recycling of electric motors.

1.The Conserving Energy

Under this segment, recycling of electric motors is essential in the case as the energy that could be employed to copper and aluminum from the earth as it is secured through recycling the metal. The conserved energy is then directed to other important areas such as commercial activities and industrial processes. It is typical that resources are directed into waste in the method of drilling on the earth surfaces (Alonso, Elisa, et al. 3414). Hence, the benefit of the recycling electric motors is that energy that could be used for drilling could be directed to other relevant activities and processes such as agriculture and it also has positioned the environment to appear more natural. Recent research stipulates that approximately 99% of the energy may be lost extracting copper and aluminum hence the process of recycling is deemed essential (Ruhrberg, Martin, 141).

2.Conserving Raw Materials

It is right to say that metal ore is a rare and valuable resource. The course of mining may consume all the resources in the long run which then put forth the threat to the environment. In regards, most of the precious metals such as copper and aluminum are difficult to mine even though they are rare cases. In the advent of the technological revolution regime, the demand for these materials was growing at a largely increasing rate, and hence there was continuous mining that threatens the future existence of the mineral reserves. It is through the strategy of recycling such metals that the metallic reserves can be conserved to the most significant extent (“Recycling Electric Motors.2018). Taking caution on this matter is a serious concern based on the fact that all the metallic reserves are essential in the healthy living of people. Everybody requires metal for power-driven cables, electric motors, copper wiring, brass products, and electric radiators (Waste management (New York, N.Y.), 67). These are among the necessities that are essential in the contemporary world. In particular, copper and aluminum are limited material compounds that are subject to depletion under uncontrollable circumstances. Constant mining and extraction of such metals may result in a reduction hence recycling plays a vital role in conserving them.

3. Reduced Pollution

In regards, the most metallic commodities in many landfill areas signify the presence of pollutants to the environment. Such contaminants then discharge harmful chemical into the atmosphere for an extended period.  The severely toxic substances can abolish the more substantial part of the ecosystem making it unfit for human survival. The chemicals released in the environment are dangerous to human, and hence the only way to avert this is through initiating a recycling program for the copper and aluminum. The society should be aware of the extent of value these metals are and get insights about the dangers of allowing these particular metals to be released in the environment. Recycling of metals will not only end pollution but also advance the effective and efficient use of natural resources (Magno, Marcelita, 32). Similarly, the extraction process demands the availability of energy. In this process, the greenhouses gases are also released into the atmosphere which also releases toxic waste in the air making the environment unfit for human survival. Recycling permits minimization of secondary impacts which results from greenhouse gases for instance formation of acidic rain and the effect of global warming. However, the process has prompted to recycle the Copper and Aluminum as opposed to higher depending on the extraction process to eliminate the most significant percentage of environmental pollution. It is also worth knowing the recycling such valuable metals is a bit cost-effective than mining them.

Works Cited

“Recycling Electric Motors.” Interco Trading Company, 21 Mar. 2018, www.intercotradingco.com/recycling-electric-motors/.

Alonso, Elisa, et al. "Evaluating rare earth element availability: A case with revolutionary demand from clean technologies." Environmental science & technology 46.6 (2012): 3406-3414.

Gockmann, Klaus. "Recycling of copper." Canadian Mining and Metallurgical Bulletin(Canada) 85.958 (1992): 150-154.

Hanselman, Duane C., "Brushless Permanent Magnet Motor Design" (2003). Faculty and Staff Monograph Publications. 231. 

Inboard Technology, www.inboardtechnology.com/products/m1-electric-skateboard.

Magno, Marcelita C. "Recycling Scrap Copper." The Science Teacher 57.3 (1990): 32. ProQuest. 30 Oct. 2018.

Ruhrberg, Martin. "Assessing the recycling efficiency of copper from end-of-life products in Western Europe." Resources, Conservation and Recycling 48.2 (2006): 141-165.

Slade, Margaret E. "An econometric model of the US secondary copper industry: Recycling versus disposal." Journal of Environmental Economics and Management 7.2 (1980): 123-141.

Vlad, Just, director. YouTube. YouTube, YouTube, 24 Dec. 2017, www.youtube.com/watch?v=5sZe1fZkIm8.

Waste management (New York, N.Y.), ISSN: 0956-053X, Vol: 25, Issue: 1, Page: 67-74