- T271_1Toys and engineering materialsAbout this free courseThis free course is an adapted extract from the Open University courses T271 Core engineering A and T272 Core engineering B.This version of the content may include video, images and interactive content that may not be optimised for your device. You can experience this free course as it was originally designed on OpenLearn, the home of free learning from The Open University – www.open.edu/openlearn/science-maths-technology/toys-and-engineering-materials/content-section-0There you’ll also be able to track your progress via your activity record, which you can use to demonstrate your learning.Copyright © 2019 The Open UniversityIntellectual propertyUnless otherwise stated, this resource is released under the terms of the Creative Commons Licence v4.0 http://creativecommons.org/licenses/by-nc-sa/4.0/deed.en_GB. Within that The Open University interprets this licence in the following way: www.open.edu/openlearn/about-openlearn/frequently-asked-questions-on-openlearn. Copyright and rights falling outside the terms of the Creative Commons Licence are retained or controlled by The Open University. Please read the full text before using any of the content. We believe the primary barrier to accessing high-quality educational experiences is cost, which is why we aim to publish as much free content as possible under an open licence. If it proves difficult to release content under our preferred Creative Commons licence (e.g. because we can’t afford or gain the clearances or find suitable alternatives), we will still release the materials for free under a personal end-user licence. This is because the learning experience will always be the same high quality offering and that should always be seen as positive – even if at times the licensing is different to Creative Commons. When using the content you must attribute us (The Open University) (the OU) and any identified author in accordance with the terms of the Creative Commons Licence.The Acknowledgements section is used to list, amongst other things, third party (Proprietary), licensed content which is not subject to Creative Commons licensing. Proprietary content must be used (retained) intact and in context to the content at all times.The Acknowledgements section is also used to bring to your attention any other Special Restrictions which may apply to the content. For example there may be times when the Creative Commons Non-Commercial Sharealike licence does not apply to any of the content even if owned by us (The Open University). In these instances, unless stated otherwise, the content may be used for personal and non-commercial use.We have also identified as Proprietary other material included in the content which is not subject to Creative Commons Licence. These are OU logos, trading names and may extend to certain photographic and video images and sound recordings and any other material as may be brought to your attention.Unauthorised use of any of the content may constitute a breach of the terms and conditions and/or intellectual property laws.We reserve the right to alter, amend or bring to an end any terms and conditions provided here without notice.All rights falling outside the terms of the Creative Commons licence are retained or controlled by The Open University.Head of Intellectual Property, The Open University
Introduction
Engineers need to have a sound understanding of materials and their properties in order to select an appropriate material for any particular design or purpose. This free course, Toys and engineering materials, develops your understanding of the impact of new engineering materials on the changing design of toys and motor vehicles.Often, the development of an engineering product, such as a motor vehicle, is taken for granted and the link to the development of the component parts that allow these developments to occur is missed. For example, the impact of carbon fibre on the development of high performance vehicles, or the impact of battery technology on the development of electrically powered vehicles.The availability of more sophisticated materials has driven the evolution of motor vehicles, and this is well captured by examining the evolving design and performance of the vehicles at the motor museum, as shown in the introductory trailer of this course. This OpenLearn course is an adapted extract from the Open University courses T271 Core engineering A and T272 Core engineering B.After studying this course, you should be able to:understand how the development of engineering materials can drive the design processunderstand how the introduction of semiconductors made a huge impact on the future of designread real examples of the impact of material developments on toy manufacture.Toys and the engineer1 Engineering: a holistic approachOften in an engineering project you will need to incorporate knowledge and skills from all areas of your experience: skills learned on the job, from your studies or, indeed, life skills. In this course, you are going to look at a short case study that considers material use in the manufacture of toys.In this course, ‘toy’ is used to describe a range of items, including traditional toys, such as dolls and LEGO®, sports equipment, such as cricket bats, and leisure equipment, like drones and hoverboards. The case study will concentrate primarily on materials use and development.The main types of materials considered in this section are wood, synthetic polymers, composites and metals. 1.1 Materials use in the manufacture of toysThere have been impressive advances in the design and manufacture of toys over the past few decades. These advances have been driven by the rapid development of material science and electricity storage systems, such as lithium ion batteries. If you were born a few hundred years ago, your childhood toys would not have been dissimilar to those used by children thousands of years ago. For tens of thousands of years, children played with the objects they could find in nature, such as twigs, stones or animal parts like bones, skins or internal organs of animals. For example, dice may have originated from throwing sheep’s knucklebones (Figure 1), and an inflated pig’s bladder was used as a playing ball.Today, toys are far more sophisticated, and many of the toys available now could not have been envisioned by previous generations. One example is shown in Figure 2. Most of these advances in toy manufacture have occurred within the last century.Recent technological advances in materials engineering and mass production have made toys more affordable. Prior to the invention of synthetic plastics, toys such as dolls and other play figures were handmade using porcelain, wood and bone, or mass-produced using tin and lead. These toys were relatively expensive and therefore less readily available. Modern materials have allowed toys to be mass-produced at vastly reduced cost, such as the play figures shown in Figure 3.In this course, inventions and developments leading to the evolution of toy design are used as examples to highlight the effect of materials engineering on modern life.1.2 The longevity of woodStart by looking at the three charts in Figure 4. Known as Ashby charts, these visual representations compare two different properties of materials; in this case, strength against density. The differently coloured ‘ovals’ indicate the range of values of these properties that are found for a particular material or class of material.Each chart is a snapshot of a time in history and represents the materials available at that time. Look first at the blue-green ovals (on the left of the charts). These represent wood, which is still used widely today. In the centre of the middle chart, the blue ovals represent polymers and elastomers. These materials didn’t appear until the early twentieth century. Finally, in the bottom chart representing the present day, there are the additions of composites, denoted by a small dark brown oval in the centre, and foams, the large section of light green ovals starting at the bottom left-hand corner. These charts highlight both the continued use of materials like wood and the emergence of new materials such as composites.In Figure 4, look at the top chart, dated 50 000 BCE. Here, the combinations of strength and density offered by wood cover a greater range than those of other materials. Also, within each type of wood there is a large variation both in density and strength. For example, there are many naturally occurring forms of cork, and each variety exhibits very different values of both strength and density. This difference is less marked for the other materials shown on the charts. In contrast to wood, look at the orange ovals on the right of the middle and bottom charts. These represent types of steel, and they all exhibit a wide variation in strength, but show more consistency in the densities.It is this variation in both density and strength that makes wood useful. A single type of wood can be adopted for a wide array of uses, as exemplified by oak, which has a density that varies from around 850–1130kgm−3. Lower density oak is extensively used in the construction of ships, while higher density Japanese oak is used to make drums, as it produces a brighter and louder tone. Such differences are also exploited in the manufacture of toys. In Figure 5, hardwoods such as maple have been used for higher strength components, but their use is kept to a minimum as they add weight and are expensive. Meanwhile, cheaper soft woods, such as spruce or fir, are used for large parts, saving money and weight.Notice that the Ashby charts give different values for the strength of wood depending on whether it is measured parallel or perpendicular to the grain. This is an example of anisotropic behaviour, meaning that values of individual properties vary depending on the direction in which a force is applied. This fact is well known to lumberjacks, wood loggers, and carpenters, who know that it is far easier to split wood parallel to the wood grain than across the grain. This is an important attribute when designers and engineers use wood for toys. For instance, when making a toy that needs to withstand high loads, such as a cricket bat, it is important how the wood is cut out of the tree. Cricket bats are manufactured out of willow. Willow has an average tensile strength of 59MPa along the grain, but 2.4MPa across the grain. Consequently, for cricket bats, the willow must be cut so that the ball will impact the bat perpendicularly to the grain, to ensure the bat exhibits its greatest strength. This grain direction is clearly visible in Figure 6.Apart from its useful engineering properties, people have a natural affinity to wood, mostly owing to its appealing texture, colour, feel and even its smell. All these desirable properties, alongside its ready availability, low cost, inertness and (generally) non-poisonous composition, make wood an ideal material for making toys (Figure 7).However, wood does not just excel as a material for toys. Wood can also be considered as an engineering construction material. 1.3 Versatile plasticThe first viable and economic methods for producing the synthetic materials now commonly described collectively as ‘plastics’ were developed in 1907, by Leo Hendrik Baekeland, a Belgian-born American living in New York State who invented ‘Bakelite’. In the decades that followed, a wide range of similar materials were developed, and ‘plastic’ became a household name. The most evident property of the new materials was their formability: most plastic materials can be moulded into virtually any desired shape. Most plastics have a much lower strength than metals, but this disadvantage is often outweighed by plastics having a much lower density and cost when compared to metals. Polymer is a collective name for all materials that are formed from long chain molecules. There are naturally occurring materials that are polymers, such as silk, wool, cellulose and proteins. Plastics is a collective term often used for synthetic polymers, whether or not they exhibit plasticity. The mass production of plastics in the late 1950s saw the development of many plastic toys, including construction-based plastic toys such as LEGO®, which used plastics tough enough to be assembled and disassembled many times. Figure 8 shows some of the best-selling toys that are made of plastic.1.3.1 Injection moulding In this activity, you are asked questions on the following video, which shows how injection moulding of plastics to manufacture LEGO® pieces is done industrially.Activity 1 Lego and injection mouldingAllow about 15 minutesConsider the following questions as you watch the video and note down your answers.How do the manufacturers ensure that the LEGO® brick is coloured throughout the whole piece?What is the pressure of injection moulding in pascals? Use the conversion factor 1 psi = 6894.8 Pa (to 1 d.p.) and give your answer to one significant figure.[SOFT MUSIC] NARRATORThe LEGO® brick is an old invention by now. The first plastic brick was moulded in 1949. Since then, thousands of new and unique LEGO® elements have been developed. Pick a LEGO® brick from a box today, and it will fit with any brick that was moulded decades ago. This is the result of great precision and commitment for more than 50 years. The LEGO® group has factories across the world. But how do you produce hundreds of different types of bricks with such precision and in a wealth of colours every single day? And how do the bricks find their way to the right boxes? This is the story about how small pieces of plastic granulate are transformed into creative playsets. A truck arrives with raw material at the factory. A truck like this holds up to 28 tonnes of plastic granulate. The granulate is blasted from the truck into tall silos, where it is stored. Different types of plastic granulate are used, depending on the function of each LEGO® element. The granulate is sped down a labyrinth of long pipes into the factory. The pipes lead to the heart of the LEGO® factory, the moulding area. High tech injection moulding machines produce LEGO® elements 24 hours a day, seven days a week. First, the raw granulate is mixed with the dye. Bricks are currently produced in over 50 different colours. The coloured granulate is then led into the moulding machine. Within no time, the granulate is heated to between 230 and 310 degrees Celsius. The plastic melts into a texture much like toothpaste. With great force, the paste is then fed into the mould. Great forces must be controlled during this process. The pressure can reach 29,000 PSI. In comparison, a car's tyre pressure is 29 to 43 PSI. In the mould, the material is cooled in a matter of seconds. And out comes a newborn LEGO® brick, as we know it. [MUSIC PLAYING] Plastic waste from the moulding machines is ground and recycled straight away. Each mould can make one shape of LEGO® element at a time. To make a different shape of element, the moulds must therefore be replaced. The unique moulds are part of the secret behind the success of the LEGO® group. In each factory, there's a department dedicated to regular cleaning and maintenance of the moulds. The moulds are made with great accuracy, ensuring that all LEGO® bricks always fit together perfectly. The moulds are therefore handled with greatest care. Each mould has a specific set of instructions, which, among other things, cover pressure, time, and temperature. Temperature tests and moulding tests are carried out to ensure the machine is programmed to perfection at each replacement of the moulds. Samples are sent to the quality department, which measures such things as the durability and precision of the element. It ensured that the LEGO® element is perfect. AGV stands for Automatic Guided Vehicle. Robots like these were introduced into the production as early as 1987. When the box by the moulding machine is full, these intelligent helpers replace it with a new empty box. The AGV then takes the full boxes to the conveyor system. A unique barcode identifies the contents of each box. The boxes are shaken to even out the contents, ensuring it takes up as little space as possible. Now, the lids can be closed. This is where the journey of the boxes ends for now. In high bay warehouses up to 37 metres high, the boxes are ready to be collected. When a specific LEGO® element is required, the box is collected. All registration and localization is entirely automated. The boxes are then transported onwards from here. Many elements are taken directly to the packaging lines, but not these little guys. The mini figures must first get their own unique expression. A machine can produce more than 7,000 torsos per hour. Over half a billion mini figures are produced every year, making them one of the world's largest populations. In the first part of the packaging process, counting machines ensure that elements are put in small production boxes. One by one, they're weighed and measured to secure the right numbers in each box. The bricks to be included in just one bag in a complete LEGO® set are placed in rows of counting machines. The contents of each production box is then automatically put in a plastic bag. The bags are dropped into open LEGO® boxes, along with the building instructions and large special elements. The most efficient packaging lines pack over 50,000 boxes every 24 hours. Now the boxes are closed and sealed. Here, we have final LEGO® boxes as we know them. The LEGO® boxes are packed for shipping and stacked on to pallets. They are now ready for a long journey. The first stop of the journey is at one of the large distribution centres. From here, they are shipped to stores all over the world. It is now up to children and adults to explore the fun and creative building experiences of the LEGO® set. Colour is added to the particulate material, mixed, and then heated to between 230 oC and 310 oC and ‘cooked’ in an oven to form a coloured paste.In the video, you are told that the pressure of injection is 29 000 psi. This can be converted to pascals using the conversion factor 1 psi = 6894.8 Pa (to 1 d.p.), soTherefore the pressure of injection is 200000000000 Pa or 0.2 GPa (to 1 s.f.).Note: As an engineer, you may be required to define or interpret values from the very small scale (individual atoms) to the very large (the Voyager 1 probe has covered billions of kilometres on its travels to the outer reaches of the Solar System). To accommodate this range of values, there is an additional unit extension, the SI prefix, which gives standard multipliers to the SI units. You may already be familiar with using prefixes like giga (G), mega (M), kilo (k), milli (m), micro (μ) and nano (n), but if not, here are a few examples:1 Tm = 1012m (or 1 000 000 000 000 m)1 GN = 109N (or 1 000 000 000 N)1 MW = 106W (or 1 000 000 W)1 ms = 10-3s (or 0.001s)The SI prefixes allow you to present information in a format that is easier to interpret. So, at the small scale, the diameter of a hydrogen atom is 1.06 × 10 −10 m, or 106 pm (picometres) and, at the other extreme, Voyager 1 is approximately 20 859 million km from the sun, which is 20.859 × 10 12 m or 20.869 Tm (terametres).1.3.2 Building a towerTo gain an understanding of the strength of a LEGO® brick made out of a polymer called acrylonitrile butadiene styrene (ABS), consider how high a tower made of 2 × 2 LEGO® bricks could theoretically reach.When designing a tower, there is a theoretical limit to the height that can be achieved before it is crushed under its own weight. Plastic is an excellent choice of material for toy manufacture because of its toughness and its high strength-to-weight ratio, but is it really strong enough to build a skyscraper with?Activity 2 How tall can you build a LEGO® tower?Allow about 15 minutesEngineers have determined that a 2 × 2 LEGO® brick could withstand a force of just under 4220 N before failing. A single 2 × 2 LEGO® brick has a mass of 1.15 g and a height of 9.6 mm (excluding the connecting dimples on the top side).Assuming g = 9.81 m s−2, calculate the following:What mass of LEGO® would provide a force of 4220 N?To the nearest brick, how many 2 × 2 LEGO® bricks would constitute the mass of LEGO® calculated in part (a)?How high would the tower reach before exceeding the structural strength of a 2 × 2 LEGO® brick? The mass required to create a force of 4220 N is The number of LEGO® bricks in 430.173… kg of LEGO® is thereforeso there are 374 064 bricks to the nearest brick.The height of the LEGO® tower isFurther developments in material performance allowed the introduction of the first sustainable LEGO® bricks in 2018. You can read about these developments in this article.To sum up, plastics are an incredibly versatile and often very cheap material that is put to a vast array of uses in toy manufacture. But, like many other synthetic materials, plastics are not really sustainable, and are the cause of significant environmental harm if not correctly disposed of.2 The application of metalArguably metals, including steel, are the most important structural materials in modern life. Metals have several properties which have made them extremely popular with toy manufacturers. For instance, due to their high formability, metals can be rolled into thin plates and then pressed to make tubular or hollow components. The vintage toys in Figure 9 are made from thin steel sheets which, very often, are pressed tinplate (a thin sheet of steel coated in tin). Tinplate has some desirable properties for toy manufacturers such as its lustre, corrosion resistance, solderability, weldability and formability.2.1 Advantages and disadvantagesTypically, metals have a much higher strength than plastics and woods, meaning that a plastic toy with a wall thickness the same as the tinplate toy would be insubstantial to handle. But perhaps the most attractive property of a tinplate toy is its similarity to the real items. However, older metallic toys had a number of significant disadvantages over plastic toys. One was their tendency, when they break, to present razor-sharp cutting edges to small fingers. Also, they rapidly became unattractive as the paint was lost through wear and tear. Small children ingesting the paint of such toys was identified as a serious health risk due to the use of lead-based paints. Indeed, they were banned from use in the UK in 1978. These issues are removed by the use of coloured plastics.Finally, due to the development of high strength aluminium and zinc alloys (used in the die-casting process discussed next), as well as a new generation of plastics and composites, the popularity of using steel as a toy material has plummeted. These days, although metals are less popular for toy making, they remain a key material used in engineering design.2.2 The introduction of die-cast toysDie-casting is a mass production process often used for metal processing. Typically, a molten metal is injected under high pressure into the cavity of a steel mould where it solidifies into its final shape. The steel mould is made of at least two parts which can be separated to release the cast product as shown in Figure 10. In many ways, die-casting is similar to the plastic injection moulding that was used to manufacture the LEGO®. As the injection system and the die (mould) are both made of steel, most die-cast products are made from metals with lower melting points such as zinc, copper, aluminium, magnesium, lead and their alloys. Production of die-cast toys started early in the twentieth century. The majority of die-cast toys are made from zamak, which is a zinc alloy containing small amounts of aluminium and copper. An attractive feature of die-cast toy production is the ability to produce highly detailed precision models, as compared to those made from wood, plastic and sheet steel. Figure 11 shows the level of detail that can be integrated into metallic die-cast models, especially when several different cast components are assembled together. Regardless of the level of detail and precision, die-cast toys are more durable than hollow-structure toys made of steel sheets or plastic.2.3 Composite materialsA composite material is made from more than one material component combined together to achieve mechanical properties more desirable than those of either material when used alone. Composites are usually formed by embedding small pieces of one material (reinforcement) into a matrix formed of another material. For example, fibreglass is a composite material consisting of glass fibres embedded in a matrix of polymer resin. Other common fabricated composites are concrete – stone particles in a cement matrix – and plywood – wooden layers in a glue matrix with the grain of the wood in alternating layers crossed.The reinforcing component in a composite material is often fibrous and is typically used to improve the strength and toughness of the composite. Incorporating the fibres into the matrix in sheets allows the orientations of the fibres within the matrix to be controlled and, coupled with the availability of many different types of fibre, this means that the final product can have a wide range of properties.However, recent developments in the mass manufacture of composites based on carbon fibres, known collectively as Carbon Fibre Reinforced Polymers (CFRP), have had a massive impact in the aerospace, automotive, marine and sports goods industries as well as the toy industry. This is mainly due to the exceptionally high strength-to-weight ratio of CFRP of around 2457 kN m kg−1, while that for steel is typically 254 kN m kg−1.The evolution of ultra high-strength sports goods (see Figure 12) and airborne toys, such as drones, is partly due to the recent development of extremely light and yet very strong composite materials like CFRP.2.3.1 The manufacture of tennis racquetsIn this activity you are asked questions on the following video, which shows one method of manufacturing modern composite tennis racquets.Activity 3 Tennis racquetAllow about 10 minutesConsider the following questions as you watch the video and note down your answers.How many layers of CFRP are added to the frame at the start?How and why do they keep the core hollow during the heating process?What material is added to the inside of the frame, and why?[MUSIC PLAYING] NARRATORThe pros have them, and you want them-- perfect shots hit with confidence and timing. How much does the racket have to do with it? Well, certainly, a combination of power, balance, and feel must be made available to all players at all levels. The life of a modern high-tech tennis racket begins as strands of carbon, Kevlar, and fibreglass that are coated with resin-- these fibres are wound onto a spinning drum that's been covered with a paper sheet. This will form the basic material of carbon fibre tennis rackets. Layers of carbon fibre are cut into shapes and wrapped around each other to form a laminate stack of between seven and twelve layers. As the pliable material begins to take the form of a basic tennis racket, additional pieces and layers of carbon fibre are added to specific areas to provide strength. The racket is soft at this stage and is placed into a mould that will determine the size and shape of the final product. It passes through a heating process to cure and harden the carbon fibre, while pressurised air is blown into the centre of the frame to retain a hollow core. Each frame spends about 20 minutes in the mould at a high temperature until the material is fully cured. The frame is very rough as it's removed from the mould and passes through a series of sanding and finishing processes to create a polished, smooth surface. Filling the hollow core with foam adds strength and stability to the finished product. A special collar is used to ensure accuracy and precision while drilling the string holes. The frame moves through the final finishing stage before paint is applied. Prior to and after each coat is applied, the frame's surface is masked to protect the painted section from the next layer of colour. In the painting process, layers of glossy and matte paint dramatically enhance the appearance. The result is a multi-colour finish, complete with decals that enhance and highlight the overall frame technology. Today's rackets not only look good and perform well, but also provide every player with the equipment necessary to maximise their game. Professional or amateur, recreational or beginner, the world of these high-tech tennis rackets is available to everyone, whether you're playing for fun or playing for a million dollars in prize money. Between 7 and 12 layers of CFRP are added to manufacture the frame.Pressurised air is pumped into the frame, to ensure space is available for it to be filled with a suitable material.Foam is pumped into the frame to add strength and stability to the finished product.2.3.2 Manufacturing compositesThis activity asks you to locate a product and analyse its properties.Activity 4 CompositesAllow about 15 minutesDo some online research to try and identify a toy or game that includes CFRP or other composite parts. Write a couple of sentences about the product, stating which part of the game or toy uses the composite.As an example answer, roller skate wheels are often manufactured from composites. Composites can be very strong to carry the mass of the user, but are light and durable.In addition, roller skates use a composite material to allow braking without the use of brake pads. Each composite wheel includes a centre section formed of hard material, such as high-density polyethylene. This has a low rolling friction that promotes efficient rolling. On either side of the central section the wheels comprise a soft material, such as polyurethane, that will form a high friction contact with the ground. To brake, the skater rotates the skates creating an angle to the direction of travel. This allows the softer material to interact with the ground, slowing the motion.3 The introduction of semiconductorsFollowing the development of semiconductor materials in the 1950s, toys have become more interactive through the inclusion of electronic circuitry. Semiconductors led to the development of transistors and then on to the creation of printed circuit boards, which had a huge impact on the toy industry.3.1 Transisters, circuits and batteriesThrough the careful addition of traces of certain impurities to semiconductors such as silicon, and the careful juxtaposition of semiconductors treated with different impurities, it is possible to create devices in which the ability to conduct electricity can be controlled by the application of a small voltage. These devices, known as transistors, can operate at very fast rates (switching on and off millions of times per second) in response to an externally applied voltage. In the latter half of the twentieth century, battery-operated toys equipped with movement, sound and light effects became widely available. The introduction of logic boards allowed further evolutions to occur, from preset control (selecting from a small number of fixed movements, as in Figure 13, left), through corded controllers (allowing real-time control of the toy, as in Figure 13, centre), to using wireless remote controllers (enabling full remote control of all functions, as in Figure 13, right).The development of low-cost and versatile logic circuits was heralded as a breakthrough in toy design. However, the performance of battery-powered toys was frustratingly still limited by the capacity and weight of their power supplies. This all changed in 1991, when a revolution in battery design occurred, and the first commercial lithium ion battery was manufactured. 3.2 The lithium batteryFor many years, the main obstacle in mass production of battery-operated airborne toys was the low power-to-weight ratio of conventional batteries. The energy stored in a conventional alkaline or lead acid battery is hardly enough to lift the battery itself for a reasonable amount of time.The evolution of battery technology started around 1799 when the Italian physicist Alessandro Volta created the first electrical battery, called the voltaic pile. Almost exactly two hundred years later, the evolution continued with the introduction of the lithium ion battery. The lithium ion battery has a much higher power-to-weight ratio than previous batteries, allowing smaller and lighter power supplies to be incorporated into toy designs. The specific energy of a batteryBatteries are often described in terms of their specific energy (in J kg−1), which is the ratio of the energy the battery is capable of releasing and the mass of the battery. Lithium batteries typically have specific energies ranging from 940 kJ kg−1 to 2810 kJ kg−1. This is up to 20 times higher than the specific energy of a lead acid battery used in a conventional car.The lighter, more powerful lithium battery revolutionised many areas of engineering design, and toy manufacture was no exception. Toys were able to ‘lift off’ and stay airborne for significant periods of time, and toys such as hoverboards became viable (Figure 14). You will look at hoverboards in more detail after the next activity.3.2.1 The manufacture of lithium ion batteriesIn this activity, you are asked questions on the following video which explains why lithium ion batteries, now used in electric powered cars, are different from their predecessors.Activity 5 Lithium ion batteriesAllow about 10 minutesConsider the following questions as you watch the video, and note down your answers.Why is it important to make the lithium metal alloy as pure as possible, and with as uniform a chemical composition as possible? What is the role of the electrolyte (transport medium)?[MUSIC PLAYING] NARRATORThe lithium ion battery is the power source for modern electric vehicles. These days, everyone's heard of lithium ion batteries, but what makes them so special? First of all, each battery is made up of many smaller batteries called cells. Let's take a closer look at one to see how it works. The electrical current reaches the cells via conductive surfaces-- in this case, aluminium on one side and copper on the other. And just as in every other battery, there is a positive and negative electrode called the cathode and the anode. The cathode, or positive electrode, is made of a very pure lithium metal oxide. The more uniform its chemical composition, the better the performance and the longer the battery life is. As you'd expect, the anode or negative electrode is located on the other side. It's made of graphite, a form of carbon with a layered structure. The battery is filled with the transport medium, the electrolyte, so that the lithium ions carrying the battery's charge can flow freely. This electrolyte must be extremely pure and as free of water as possible in order to ensure efficient charging and discharging. To prevent a short circuit, there's a layer placed between the two electrodes, the separator. To the tiny lithium ions, the separator is actually permeable. The experts call this property microporosity. Let's take a look at what happens when a battery is charged. The positively charged lithium ions pass from the cathode through the separator into the layered graphite structure of the anode where they're stored. Now, the battery is charged. When the battery discharges-- that is, when energy is removed from the cell-- the lithium ions travel via the electrolyte from the anode through the separator back to the cathode. The motor converts the electrical energy into mechanical energy, making the car go. The amount of energy available and how long the batteries last is closely related to the quality of the materials used. To sum it all up, higher quality, pure materials, along with customised formulations lead to longer battery life and better battery performance. [MUSIC PLAYING] When the lithium metal alloy is purer and has a more uniform chemical composition, the battery performance and battery life increase.It allows the lithium ions to flow freely between the anode and cathode through the micro-porous layer.Lithium ion power supplies are not just used in toys; the technology features in mobile phones, handheld tools, electric cars and some household goods. Major advancements in high-capacity rechargeable batteries are expected in upcoming years, which will drive the proliferation of electric vehicles.3.3 The hoverboardYou have seen examples of the influence of newly developed structural and functional materials on the ‘creation’ of new toys. As you approach the end of this course, consider the hoverboard shown in Figure 15.A hoverboard is a self-balancing motor-driven personal transporter. Sophisticated electronic logic boards control the balance through gyroscopes (devices used to control stability), and the speed and direction of motion through pressure sensitive controllers. The key components of the hoverboard, namely high-capacity energy storage systems, energy-efficient motors, sophisticated electronic logic boards, sensitive gyroscopes as well as high-strength structural alloys and polymers are shown in the following figure.Figure 15 The key components of a hoverboard. Click on the hotspots for more information.Figure 1.2o shows five photographs of a hoverboard toy. The hoverboard has two horizontal platforms to support the feet – they are joined by a narrow, cylindrical section. There is a wheel attached to the outside of each platform.Top left: red hoverboard with a person standing on it. Hotspot text: Die-cast polymer outer shell that is cheap to manufacture, waterproof and tough to resist knocks and bumps.Middle left: this shows the outer shell alone – the hollow parts that will contain the actual platforms and the wheels. They are not joined. The Hotspot text is the same as above.Bottom right – this shows the chassis – two flat metallic parts joined by a horizontal cylindrical axis – there appears to be a joint between them so that the tow sections can rotate independently around a horizontal axis through the length of the hoverboard. Hotspot Text: Die-cast aluminium chassis that is strong enough to take the load of the rider, stiff enough to ensure a stable ride and lightweight.Top right – this photograph shows the chassis with wheels, motors, electronic circuitry and battery. Hotspot text for wheel: Wheel with integrated motor which provides drive to each wheel separately and saves space by supporting the motor.Text for battery: Polymer protected lithium ion battery. The protective cover is light, resistant to chemicals and can be joined to create a waterproof seal.Text for circuitry: Electronic circuitry to control the drive train.Bottom right - this image shows a wheel. It has a black, rubber tyre on a silver rim. Between the wheel and hub is circuitry and several small coils of tightly wound copper wire. A short cylindrical section of axle is joined to the middle of the wheel, and has wires passing through it. Text for tyre: The rubber (elastomer) tyre that is tough and wear-resistant, providing good tyre to ground surface adhesion for grip.Text for motor: Copper motor coils ensure good electrical conductivity, thereby minimising energy loss through joule heating.Clearly, high-capacity batteries in combination with energy-efficient motors are needed to maximise the distance that can be travelled per charge. Similarly, high-precision gyroscopic systems and sensors are essential to ensure the stability and controllability of the hoverboard and hence the safety of the rider. Perhaps the least technologically demanding parts of a hoverboard seem to be its load-bearing components, such as the chassis, wheel bearings and drive shaft. However, optimum design and selection of materials for such components will require an insightful understanding of the loading mechanisms. 3.4 Designing a toy You’re reaching the end of the course now, and this is the final activity.Activity 6 Innovation in designAllow about 15 minutesFind a toy that incorporates innovative materials, electrical features or structural design. This can be an item from around the house, or an image from somewhere on the internet. Write a couple of sentences to detail the innovative design features that prompted you to choose that toy.ConclusionManufacturing of sophisticated toys requires an understanding of engineering materials, a solid grasp of the structural requirements of components such as the chassis, and the utilisation and integration of electrical/electronic engineering systems, including power storage. As a consequence of such multidisciplinary projects, engineers need to have a working knowledge of a wide range of engineering fields before specialising in one particular discipline.This OpenLearn course is an adapted extract from the Open University course T271 Core engineering A.This free course was written by Stephen H M Jones and co author Dr Kim Littlewood and published in November 2019.Except for third party materials and otherwise stated (see terms and conditions), this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Licence.The material acknowledged below is Proprietary and used under licence (not subject to Creative Commons Licence). Grateful acknowledgement is made to the following sources for permission to reproduce material in this free course: ImagesCourse image: © Mikhail Laptev/www.123rf.comFigure 1: © Granger Historical Picture Archive/Alamy Stock Photo.Figure 2: With courtesy of Swellpro Technology Co., LTD.Figure 3: © studiograndouest/123 Royalty FreeFigure 4: Ashby chart of strength vs density Chart created using CES EduPack 2018, Granta Design Ltd. http://www.grantadesign.com/education.Figure 5: Taken from http://www.woodtoyz.com/WTCat/LearnMaterials.html.Figure 6: © Roy Riley/Alamy Stock Photo.Figure 7 (left): © Narith Thongphasuk / Dreamstime.Figure 7 (right): www.galleryhip.com.Figure 8 (left): Booyabazooka. This file is licensed under the Creative Commons Attribution-Noncommercial-ShareAlike Licence http://creativecommons.org/licenses/by-sa/3.0/.Figure 8 (right): Boaz Yunior Wibowo | Dreamstime.com.Figure 9 (left): John Lloyd. This file is licensed under the Creative Commons Attribution Licence http://creativecommons.org/licenses/by/2.0/.Figure 9 (right): Ed Berg. This file is licensed under the Creative Commons Attribution-Noncommercial-ShareAlike Licence http://creativecommons.org/licenses/by-sa/3.0/.Figure 10: Taken from: http://www.substech.com/dokuwiki/doku.php?id=die_casting.Figure 11 (left): Andy Dingley. This file is licensed under the Creative Commons Attribution-Noncommercial-ShareAlike Licence http://creativecommons.org/licenses/by-sa/3.0/.Figure 11 (right): © windu_dolan/Shutterstock.com.Figure 12: © Science & Society Picture Library/Contributor/Getty Images.Figure 13 (left): Taken from http:wwwtintoycar.com.Figure 13 (middle): Getty © De Agostini Picture Library/Getty Images.Figure 14 (left): © scanrail/123 Royalty Free.Figure 14 (right): © Hurricanehank | Dreamstime.com.Figure 15 (top left): © Hurricanehank | Dreamstime.com. Figure 15 (middle left): Taken from: https://manseemanwant.com/products/hoverboard-outer-shell-for-6-5-plastic-accessories-replacement. Figure 15 (bottom left): Hover Store, https://hover-store.fr/.Figure15 (top right): © 2018 Vox Media. Figure 15 (bottom right): https://www.fictiv.com/blog/posts/hoverboard-teardown This file is licensed under the Creative Commons Attribution-Noncommercial-ShareAlike Licence http://creativecommons.org/licenses/by-nc-sa/3.0/.VideosActivity 1: LEGO bricks in the making © The LEGO Group.Activity 3: How Tennis Racquets are made © GM Television.Activity 5: Lithium-ion batteries: How do they work? © Courtesy of BASF.Every effort has been made to contact copyright owners. If any have been inadvertently overlooked, the publishers will be pleased to make the necessary arrangements at the first opportunity.Don't miss outIf reading this text has inspired you to learn more, you may be interested in joining the millions of people who discover our free learning resources and qualifications by visiting The Open University – www.open.edu/openlearn/free-courses.
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