Group 20 - Ford Mustang Power Wheels - Gate 3

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Contents

Introduction

After the complete dissection and documentation of the Ford Mustang Power Wheels, Group 20 was tasked with performing a thorough engineering analysis of the product. In order to accomplish this, the group must examine the Ford Mustang’s components individually, as well as analyzing them together in their respective subsystems. This allows the group to better understand the engineering decisions and considerations that factored into design and production of the product. Each component or subsystem has certain characteristics that can be used to identify not only the function, but other attributes such as material composition and the manufacturing processes used to create the part. In addition, the engineering analysis performed in Gate 3 address the global, economic, societal, and environmental concerns with the specified manufacturing procedures. This analysis allows Group 20 to make informed design decisions and revisions as to which features or components should be revised, removed, or added in order to improve the Ford Mustang Power Wheels.

Project Management: Coordination Review

Upon starting Gate 3, Group 20 assessed the project management aspect of the project in order to identify potential challenges and provide solutions to said problems. This Coordination Review is detailed below.

Cause for Corrective Action

Overall, the dynamic of the group has continued to function extremely well in working on the project. Each group member has done the work assigned as promptly and efficiently as possible. While groups may not be able to be completely efficient, Group 20 has continued to work at a very efficient pace and has continued to produce professional work. However, this is not to say that Group 20 has faced no challenges. Although most of the major challenges that have caused potential roadblocks for the group have been addressed, Group 20 still faced a few unresolved problems. One of the major challenges with this gate was the large volume of work that needs to be completed for the gate and the relatively short time frame to complete it in. Gate 3 has several extensive components which each take a long time to adequately answer all of the questions for each part. This will prove to be extremely difficult due to the fact that there is less time before the due date of this gate as opposed to the previous gates. Group 20 plans to meet more often in order to assure that each portion of the gate is adequately completed.

Another major challenge that the group currently faces is the ability to get the work complied farther in advance of the deadline. The group has always finished the work before the deadline, however, it usually was the product of a long and stressful day before. To overcome this, the group plans to develop a strategy to attack this issue. The group hopes to continue to do individual work as before but wants to make an “imaginary” deadline, approximately a day or so prior to the actual due date, that will allow for extra time to modify the project if problems arise. This “additional” time will ease stress and will allow the group members to work more clearly and efficiently.

In addition to these problems, another major challenge the group faces is the amount of work assigned for other classes in conjunction with the work for the gate. At this point in the semester, the members of Group 20 all have several tests and large assignments in the weeks preceding the due date of Gate 3. This could lead to a very large increase in stress levels and the potential for decreased group performance. In order to overcome this challenge the group has attempted to break up the workload amongst group members in order to be as efficient as possible. By doing small portions of the work over a larger period of time, work from other classes can be done in parallel with the Gate’s assignments. By adopting this work regimen, the group hopes to further its progress in completing the gates in a timely and efficient manner. It is the hope of Group 20 that these adjustments will aid in the group’s performance and ultimately result in a better final product.

Although the Group has encountered some challenges throughout the course of this project and Gate 3, Group 20 has done an extremely good job of resolving said issues. The majority of the previously addressed challenges have been overcome by analyzing the situations and proposing the best solution to each problem. Ultimately, Group 20 has performed well as a group and thus has been able to adequately complete a the gates of the project in a timely and professional manner.

Meeting more often prior to the deadline of the gate was proved to be extremely beneficial to the timely completion of Gate 3. It resulted in better quality material and less stress to the group members. However, there is still room for improvement which the group worked on in Gate 4. Ultimately, the success of this course of action proved to be beneficial to the group and is something that Group 20 will implement in later gates.

Project Archaeology: Product Evaluation

After analyzing the dynamics and performance of the group, Group 20 was able to evaluate and assess the Ford Mustang Power Wheels at the component level. Doing so builds on the dissection process and analysis detailed in Gate 2 and allows the group to better understand the design choices and procedures for the Power Wheels. In the following sections, Group 20 provides a component by component summary of the Ford Mustang, including a detailed component analysis for several of the more important components of the car. In addition, the group presents a solid model assembly of one of the Ford Mustang's subsystems and its corresponding components, and details an engineering analysis and potential design revisions for the product.

Component Summary

Group 20 has compiled a component list to accurately and succinctly describe each component used in the Ford Mustang Power Wheels. In order to make this database detailed enough the group decided that the information compiled would include: Component Name, Component Number, Quantity, Size, Color, Functions, Material, Manufacturing Processes, Complexity, and Notes of miscellaneous information. By including each of these categories, the group felt that the Component List would be very useful when conducting the Product Analysis, considering the information it contained in such an organized manner.

Under the Complexity heading for each component there are 4 sub-categories under which the component was judged. These four subcategories are the complexity of: Geometry, Manufacturing Processes, Material, and Function. Each is given a rating on a scale from one to three as set by the following standards:

Geometry

  1. The component has very few features and is composed of a few basic shapes.
  2. The component has a moderate number of features and/or the features are of moderate complexity.
  3. The component has many features and/or the features are very complex.

*Simple features consist of extrudes, holes, fillet, and chamfers.
*Moderately complex features are sweeps, revolves, and lofts.
*Very complex features are coils, surfaces, ribs, and threads.

Manufacturing Processes

  1. The component requires very few manufacturing processes.
  2. The component requires has a moderate amount of processes.
  3. the component requires many processes.

Material

  1. The component consists of one material.
  2. The component consists of 2 materials.
  3. The component consists of 3 or more materials.

Function

  1. The component performs one or two simple functions.
  2. The component performs multiple simple functions functions and/or a few complex functions.
  3. The component performs many complex functions.

*Simple Functions consist of support of other components or systems, energy transfer, etc.
*Complex Functions consist of energy conversions, signal outputs, etc.

It should be noted that for all component summaries and analysis, the dimensions and weights of the components are approximations used solely to give the reader an approximate size of the part. The dimensions represent the outermost dimensions of the part, and do not reflect the fact that all parts of the component do not necessarily reach the full dimension listed. For example, the Headlight Lamp was measured as a rectangular prism in order to obtain its outermost dimensions, when in reality, much of the part is well within the "maximum" dimension range. Also after researching to determine the type of plastic used for much of the product, Group 20 has decided to document the components using the description ABS Plastic. This is much more specific than just plastic and prevents choosing a particular type of ABS Plastic and being incorrect. This choice will still accurately describe properties observed by group 20 of the plastic components and thus is acceptable.

A complete catalog of all of the components of the Ford Mustang Power Wheels and their respective summaries can be found in Table 10: Component Catalog.

Table 10: Component Catalog
Component 1: Hood Component 13: Left Headlight Lens Component 25: Left Interior Door Trim Component 37: Steering Column Component 49: Speed Selector Switch
Component 2: 12 V Battery Component 14: Left Headlight Frame Component 26: Center Console Component 38: Retainer Cap Component 50: Speed Selector Housing
Component 3: Seats Component 15: Left Headlight Lamp Component 27: Spoiler Component 39: Sprocket Component 51: Gas Pedal
Component 4: Steering Wheel Cap Component 16: Key Component 28: Trunk Lid Component 40: Back Axle Component 52: Pedal Switch
Component 5: Steering Wheel Component 17: Right Mirror Component 29: Rear Light Panel Component 41: Wire Cover Component 53: Pedal Support
Component 6: Exhaust Pipe Component 18: Left Mirror Component 30: Center Caps Component 42: Battery Holder Component 54: Johnson Motor
Component 7: Lower Grille Component 19: Dashboard Component 31: Hubcaps Component 43: Car Frame Component 55: Gear Box Cover
Component 8: Upper Grille Component 20: Windshield Component 32: Right Tire Component 44: Front Support Component 56: Fourth Stage Gear Reduction
Component 9: Front Bumper Component 21: Windshield Frame Component 33: Left Tire Component 45: Steering Support Bar Component 57: Third Stage Gear Reduction
Component 10: Right Headlight Lens Component 22: Lower Right Body Panel Component 34: Bushing Component 46: Front Axle Component 58: Second Stage Gear Reduction
Component 11: Right Headlight Frame Component 23: Lower Left Body Panel Component 35: Front Bumper Support Component 47: Speed Selector Cover Component 59: First Stage Gear Reduction
Component 12: Right Headlight Lamp Component 24: Right Interior Door Trim Component 36: Steering Column Retainer Component 48: Speed Selector Knob Component 60: Gear Box Housing
Component 61: Pretend Radio

Product Analysis

Left and Right Tires

Component Function
The purpose of the left and right tires of the Ford Mustang is to allow the vehicle to move in a linear motion via rotational energy, steer the car in different directions, and to support the combined weight of the vehicle itself, and the passengers. The rear tires receive the rotational energy from the gear boxes located towards the rear of the car. The fourth gear reductions turn, rotating the wheels in the desired direction which propels the car forward or reverse. The front tires do not receive this energy from the gear boxes; however they, unlike the rear wheels, are not fixed and can be rotated about the z axis from a steering system. The signal and energy from the steering wheel is transferred to the steering column, which causes a linear movement of the linkage connected to the tires. The linear motion causes the tires to rotate either left or right based on the signal from the user. Lastly, the wheels keep the body of the car off the ground, and are able to sustain the weight of a child and the car itself, allowing the child to safely ride in the vehicle. The tires are an end process and therefore do not assist any other components carry out their functions, however these components do help in the overall steering system as well as the drive train system perform the duty of moving the vehicle. The wheels of the Ford Mustang are associated with energy flows, both the receiving, transferring, and transforming of energy from the gear boxes to the linear motion of the Ford Mustang, and the rotational energy of the steering wheel, to the rotational energy of the tires themselves. The tires also work with signal flows, and though do not give off signals themselves, the front tires receive signals from the user input to the steering wheel to the steering column, to the linkage, to the tires, and then perform the desired output based on that input. The tires are meant to be used in an indoor or outdoor environment, with fairly smooth ground, dry weather, and in non-extreme temperatures.

Component Form
The left and right tires are both cylindrical shaped with a diameter of 12 inches and are 5.5 inches wide and weigh approximately 2 lb. The front side of both the left and right tires are mirror images (except for the writing around the perimeter of the front of the tire), however the back of the left tire has eight ribs for support, while the right tire only has four. The shape of the tires are coupled to the conversion of rotational energy to translational motion of the vehicle due to their round shape. This allows the system to rotate 360 degrees without running into any corners, which without would make the car uncomfortable even dangerous to ride, and would quite possibly be unable to rotate at all. Also the outside of the tires that rotate against the ground are textured, which provides more friction for the tires to grab and push the car forward. The left tire has the eight ribs in order to provide extra support because the left side of the car will always have the driver when being used. The weight is concentrated on the left side and therefore requires extra support that right tires do not need. The front and rear tires of each respective side are identical. The most important material properties for the wheels would be strength and ability for the wheel to keep its shape. If the plastic could bend or deform easily, it could be dangerous and cause damage to the vehicle in a short amount of time. Therefore the wheels are most likely made of ABS plastic. This was most likely chosen because of its high availability, the ease to melt and perform injection molding processes with it, and the relative strength that ABS plastic has. This is important because many tires must be produced and therefore a cheap and easily accessible material would be desired. Another consideration for the material is how well it can withstand the forces exerted on the product, and still be safe for a child to be in contact with as it is not toxic. If more strength is needed, ABS can easily be modified by the use of additives to improve impact resistance and toughness. The Ford Mustang tires all have treads molded into the wheel, along with text that provide the tires with a more realistic feel. This includes text such as “Max. Tire Pressure 0 PSI,” etc. The tires perform very important functions in driving and steering systems, but also in the aesthetics of the vehicle. Wheels are obviously very important in a car, and the more realistic the tires on the Power Wheels, the more a child will see their toy as an actual Ford Mustang. Not only do just the physical components give the tire a more realistic look but the tire is black, giving it the “expected” appearance of a real tire. While the wheel has a relatively smooth finish overall, as stated before, the tread is still rough enough to provide a higher coefficient of friction, and have the physical appearance of a normal tire.

Manufacturing Methods
The tires appear to be one piece, however are actually made of two halves. Each half is made via injection molding, and then fused together to form a hollow, yet sturdy single tire. This was the assumed method for manufacturing as riser marks can be seen on both halves of the tire, and at the center a line can be seen, along with a small amount of flash where the tires were fused together. The fact that the material is ABS plastic made this a very good way to produce the tires, and in actuality, a different material would have been chosen if ABS could not be injection molded, probably not a different process to get ABS to work. The shape of the tire was very easy to injection mold, and because of the size of the tire, and amount of material needed, that probably aided in the decision to produce the tires in two halves. Also, the shape was probably also made so that it could be injection molded, as it is made to easily be removed from the mold, and be injected into a mold of only moderate complexity. Injection Molding was chosen most likely more for economic, societal, and environmental reasons and not so much global. Injection Molding is legal everywhere, and there are no issues in any of countries or groups of people that would not buy a product because it was injection molded. Societal concerns however are important, especially with regards to the safety of the child. If the process produced a part that was unreliable, many countries would not except the product. Injection Molding does produce parts that can have small differences, however overall, the integrity of the parts are not compromised by using this process. Therefore, it is very safe to produce the tires in this manner, without the worry that a tire will fail and damage the product or hurt the child. Environmental reasons only make a small part of why Injection Molding may have been chosen. The process of injection molding uses electricity on most machines, and deals with the melting of plastics, however there is little waste besides thermal waste, and some excess plastic that can be thrown out. The plastic waste is not going to help the environment, however does small enough harm that it causes no issue with any regulations that could prohibit this process for the Ford Mustang tires. The economic reasons are the most important in choosing which manufacturing process should be used for the tires. Injection Molding produces many parts with little waste, and can make multiple tires at once. Also, all that is needed is the machine, and the plastic to be melted, and many parts can be produced in a short time. Though the initial cost for the tire die, and the machine itself is expensive, in a relatively short time, the money savings will outweigh the cost to start injection molding for the tires.

Component Complexity
The left and right tires are fairly complex parts. They both have multiple shapes from the treads, to concentric circles, and on the back half of the wheels, there are a number a ribs. On the previously described complexity scale, the tires have a rating of 2. The component function requires a fairly complex part as the wheels need to be able to produce a higher coefficient of friction in order to move the car forward, but also, the tires must be able to withstand high forces from the car. The interactions of the tires with the rest of the vehicle are also somewhat complex with a rating of 2 on the pre-described scale for component function. This is due to the fact that the tires transform linear energy into rotational energy, and rotational energy into linear energy.

Motor

Component Function
The motor in the Ford Mustang takes the electrical energy that is provided form the battery, and signals that are provided from the gear selector and foot pedal, and based on the signals, rotates clockwise or counterclockwise. The motor performs only one function, which is transforming electrical energy into rotational energy, and transferring that to the gears to drive the wheels and move the vehicle in the desired direction. The motor is coupled with energy and signal flows, taking in electrical energy, and sending out rotational energy, and taking in multiple signals. The first signal that the motor is receiving is from the gear selector. Based on which switch the selector has depressed, the motor will move forward at either 2.5 mph, 5 mph, or reversed at 2.5 mph. The second signal is from the foot pedal, which when the user depresses the pedal, sends a signal to the motor to turn on and provide an output that matches the input from the gear selector. The motor is protected by the car frame and all the surrounding parts, and therefore is not directly in contact with any environment other than the car, however, the motor should remain under dry conditions, and out of extreme conditions to work properly.

Component Form
The motor has multiple shapes which include a cylindrical body, a gear, rod, and many unseen internal components. The motor is primarily 3 dimensional, with a diameter of 1.50", a length of 3.35", and an approximate weight of 1 lb. The body of the motor is a cylinder, as the body not only holds the components of the motor, however also is used to help produce the magnetic field from the magnets in the motor to chart the flow of the magnetic force [1] and the shape is the most ideal for the desired field combined with a easy shape to obtain and work with. The gear is extremely important in the motor as the shape of the gear allows it to mesh with the gears in the gear box, and drive those gears to drive the tires. If the shape was different, the gear would not properly rotate the gears and could damage the motor, the gears, or become extremely inefficient. The motor is made from a variety of materials including steel, copper, and ABS plastic, along with others that cannot be identified without dissecting and therefore permanently damaging the motor. These materials were chosen for a multitude of reasons, partly from manufacturing decisions in cost, output, and mass production, and specific properties of the materials. The casing of the motor must be metal in order to be conductive enough to produce a magnetic field, and copper wires are an ideal to send signals and power throughout the motor. The gear is also made of steel, which provides higher strength and keeps the gear from deforming and becoming inefficient or damaged. In the motor, the most important material properties are conductivities of the metals, magnitude of the fields produced by the magnets, and the strength of the different materials to be able to perform their functions for long periods of time without destruction of the motor. The motor does not have any aesthetic properties except for an ID on the body of the motor. Because the motor is out of view and only has the function of taking inputs and putting out the corresponding outputs, the motor does not have a need for aesthetics or a purpose to have any. The motor is multiple colors, which are dictated by the natural colors of the materials used, and have otherwise no meaning to the reasons behind their color. The motor has a smooth finish in both the body and the gear. This is to keep any fragments from getting stuck between the gear and causing issues when the gear is meshed with the gear box and provides a clean surface to drive the gears. The body itself is smooth, however that is more of a property of the steel to be smooth, more so than a functional or aesthetic reason behind it. There were no global factors that paid any kind of role in the selection of the materials used. However, all the materials chosen were nontoxic and safe to be in contact with children. Though the motor is not reachable by the child, however it is still important that the motor is safe in case the user was ever able to gain access to it.

Manufacturing Methods

Figure 24: Johnson Motor

The motor is made out of many different parts and therefore multiple manufacturing methods were used. The outside casing was cut from stock sheet metal and rolled onto the inner casing of the motor, shown by the thin metal sheet that is the outer casing, and the fact that the casing is not a solid piece shown by Figure 24. This means that the outer casing was rolled onto the inner casing making a tight grasp on the casing. The inner casing was sheet metal that was pressed into a mold. This is known because the casing is a circle that is the entire casing. To obtain the desired shape, it would have to be pressed into a mold by force. The gear was extruded through a die and then cut from stock, which allows a clean surface and a cheap rapid method to produce many parts. This is assumed to be the process used because of the pipe lines running along the gear, which points towards manufacturing by extrusion. Because the gear is a uniform shape and a relatively small diameter, extrusion would be the best way to produce the gear. The copper wires are drawn from an ingot, which is the usual method for creating wire. The magnets cannot be seen, and therefore no supporting evidence can be used, however, magnets usually go through a cutting machining process, which can be assumed for this case as well. A small exhaust fan can also be seen, which is presumed to be made from ABS plastic, and most likely is made from injection molding, though once again, no supporting evidence can be drawn. Lastly the armature is known to be inside the motor, however cannot be seen. This is made from some sort of metal, and will most likely be extruded. Global and societal factors only played a minor role in the manufacturing methods and materials of the parts. None of the parts can be toxic, and safety is a major issue. All of the methods listed above give the proper strength, toughness, conductivity, and other properties desired for the material. There were also little environmental factors that went into the creating of the motor. All the materials are standard to create the motor, and therefore the company did not have to worry about breaking regulations in the creation of the motor. Economic factors, like the left and right tires, are the biggest factors in creating the motor. The extrusion of the different metals allows many pieces to be made with relative accuracy and speed, while producing very little waste. The injection molded exhaust fan allows many pieces to be made cheaply, and will produce a piece that is strong enough for the job, yet very cheap to make. The rolled outer casing is cheap, rapid, and secures the casing onto the inner casing without any difficulty, creating a strong bond without the need of welding or bonding agents. The inner casing being forced into a mold provides a near perfect circle and requires no welding or heat. The magnets are cut, which is cheap in itself, but also, there are few other ways to make magnets the right size unless they are formed when they are originally created to be a specific size.

Component Complexity
The motor is the most complex part of the Ford Mustang Power Wheels, being made of multiple smaller pieces, different materials, different manufacturing processes, the motor itself could even be called its own system, and therefore is a 3 on our complexity scale. The motor has to be made from these different materials to be able to conduct properly, create the right magnetic field, and perform its function without damage over time. Because of the different materials and shapes, the motor had to be made with different processes, making it more complex. The motor’s functions are also complex, as it takes in electrical energy, the signals from that, transforms and then translates that energy into rotational mechanical energy as an output. Therefore, the motor is also a 3 on our Function Complexity Scale.

Steering Column

Component Function
The steering column takes the rotational energy from the steering wheel and transfers it to the linkage. The steering column only performs this transferring in the steering system, and has no other function in any other system. The flows associated with the column are energy and signal. The steering wheel receives a signal from the user, and the wheel causes the steering column to turn in the direction desired by the user. After the column receives the signal, the column rotates the linkage. The energy flow is similar and a direct result from the signals the column receives. The rotational energy from the steering wheel is transferred down the column to the linkage.

Component Form

Figure 25: Steering Column

The column is basically a long rod weighing around 1 lb, however at the end that connects to the linkage, the column bends 90 degrees, then after a distance of one inch, bends 90 degrees back, being parallel to the original path of the rod (See Figure 25). The steering column has a diameter of .350”, but is primarily two dimensional. This is because in actuality the main features of the column are the length (23.75”) and the width (1.4”). The column’s length directly relates to its function because the steering column’s only purpose is to transfer the energy from the steering wheel, to the linkage, putting distance between the user, the steering wheel, and the linkage/tires. The bend at the end of the linkage keeps the steering column in place and allows it to rotate, but not move linearly. The column is made from steel, which is relatively easy to extrude and manipulate under the right conditions. The material was probably chosen and the machining processes were built around the column due to the benefits that could be gained by using steel. The most important property for the steering column are probably the strength of the material, as if the steering column became bent or damaged, it would ruin the vehicle and if the vehicle was in motion, could pose a danger for the user from their loss of ability to steer. Steel is a readily available material, and poses no danger chemically to the user, even under extended contact. Also, due to the strength of steel, the column will not break under forces from the user and so can be considered to be safe. There were not any global factors considered in the material used as steel poses no issue in any country. Environmentally, steel causes no pollution, and so also the environmental factors were not taken into account. The cost of steel is relatively cheap, especially compared to other materials of similar strength so economically is a good choice. The steering column cannot be seen from the user, and is used for functional purposes only. Because of this, no aesthetics were added. The column is silver, but that is due to the coloring of steel, and serves no purpose otherwise. The rod is smooth, but does not have any sort of machined finish other than what came out of the extrusion and stock, as the surface doesn’t have much effect on the function of the column.

Manufacturing Methods
The column is only made of one material; however, multiple manufacturing processes were used to produce the shape desired. In order to get the rod itself, the steel was extruded through a die. Along the side of the column, uniform lines can be seen along the length of the column, including the angled parts, showing that at one time the rod was completely straight. The angled part of the column was bent, as can be seen be the corners of the bend, which are built up at the inner corners, and stretched at the outer corners. This was the easiest method to have the rod bent, without having to heat up the steel. Towards the top of the steering column are two fins, which were most likely made during a forming process produced by a press that pinches the rod and forms the two fins. The uniform lines can be seen in the fins that match the rest of rod, which points to the fins once being part of the rod itself. This process is the most obvious way to produce the fins, and uses the material itself, eliminating waste. Lastly, the rod has two holes that were drilled in it. This is known because the holes aren’t incredibly precise and some extra material is taken out around the holes, further pointing towards a drilling process to make the holes. All the above processes were aimed more towards the economic and societal factors than environmental and global. Extrusion, bending, pressing, and drilling are all relatively cheap processes, as none require molds except for extrusion, and they all have fairly cheap start ups. These processes are working with steel, do not change the strength of the material much, and therefore can still be considered safe after the column has been produced, keeping the user from harm.

Component Complexity
The steering column is made of one material, however has multiple geometric attributes and therefore is rated a 2 on the complexity scale. The column had to be bent and pressed in order to transfer the rotational energy without coming lose from the steering wheel or sliding out of the linkage. The function of the steering column is rated a 1 on the complexity scale. This is due to the fact that the only function of the column is to transfer the rotational energy from the steering wheel to the linkage.

Car Frame

Component Function

Figure 26: Electrical System Path

The function of the car frame is vital to the functionality of the Ford Mustang Power Wheels. The frame of the car supports all of the subsystems within the car, providing a central hub to house all the systems so that they can properly work together. Each subsystem combines together to achieve the higher level function of transporting the user from point A to B. One example is how the electrical system starts from the front of the car and woven throughout the car in order to connect to the motors and gearboxes in the rear of the car as seen in Figure 26. Without the car frame, the car would be unable to perform this function. The frame also serves as a way to keep the user safe by keeping harmful parts hidden and out of reach. For example, the wires of the vehicle are obviously dangerous to the user. The car frame serves as a way to inhibit these wires from being reached without proper dis-assembly and keep the user safe. In addition to the function of the car frame, material flow is also associated with the frame. The car frame serves as a way to import the user and the battery. The battery must be imported to the car frame in order to power the subsystems that require electrical energy. Without the battery being imported, the rest of the functions will not work. The car frame also supports the user, allowing the user to physically ride in the vehicle. The car frame is meant to function inside or outside depending on the users preference, and though the frame itself is able to be under most conditions, the systems inside should not be under the stress of extreme temperatures or weather conditions.

Component Form
The general shape of the car frame is highly irregular. It has multiple curved portions (body panels) and has many holes to allow for the connection of other subsystems. A notable property of the car frame is the thickness of the plastic. This is because the frame must be able to withstand the weight applied by the user. This component is primarily three dimensional at 50” x 29.5” x 12” and weighs approximately 20-30 lb. The shape of the component is coupled to the performance of the function by allowing space for the other subsystems to be connected without them being overlapped or too close to one another. The frame is made solely from ABS plastic. The manufacturing decisions likely did not impact the choice of material. However when designing the car, the choice of material likely did influence the process of manufacturing. By choosing plastic the manufacturers had many routes in which they could turn. In this case the manufacturers chose injection molding. Aesthetic properties of the car frame include the smooth finish on the exterior portion of the frame and the semi-rough finish on the interior portion of the frame. Another property is the relative shine on the exterior while the interior is relatively dull. These properties serve no purpose to the functionality of the component and are purely for aesthetic purposes. It is meant to give the look of the real Ford Mustang. The overall choice of red for the frame was purely a design choice.

Manufacturing Methods
The manufacturing method used to make the car frame was injection molding. Evidence to support this is the riser marks and parting lines located on the underside of the car frame. The choice of ABS plastic influenced the overall choice of injection molding. Had plastic not been chosen and say metal was, the manufacturing process would have been much different and would have been more expensive. The car frame has many curves, extrusions and holes. By choosing injection molding the shape of the frame can easily be achieved. Global factors did not influence the decision to choose injection molding for the car frame. Societal factors are very important in the decision, mainly because of safety factors. With injection molding it creates a very durable product for which the user can rely on. If the process did not create a product that was reliable, then consumers would not feel safe in purchasing the product. Economic concerns related to chose of injection molding is the most important aspect. Manufacturers are always looking for a way to create parts in the most efficient and cost effective manners. The initial costs of the machinery and molds can be expensive but the overall process is relatively cheap and will eventually repay itself back in the long run. Its one limitation is that the machine can only produce one part at a time, so the process can be time consuming. Environmental concerns have little impact on the choice of injection molding. The process uses heat and electricity to inject the plastic into the mold. When the product is finished the excess plastic can be recycled.

Component Complexity

Figure 27: Shifter Intrusion

The car frame is very complex. The curvature of the body panels is very detailed. The design was meant to recreate the look of the exterior of the real Ford Mustang. Also the interior of the frame is very complex as well. The extrusions made are designed to allow for certain subsystems to be hidden in a more reliable and convenient manner. For instance the shifter housing is placed in an intrusion within the interior of the car frame as seen in Figure 27. Also the location of the battery is placed inside of a well within the car frame that is hidden by the hood. By creating these spaces in the car frame it allows for components to be connected easily to the frame without having to create more parts that would ultimately do the same thing. The overall function, material, and manufacturing process made for the complexity of the car frame to be as high as it is; a 3 on the previously described scale. Being that it is modeled after the Ford Mustang the idea is that the product look as real as possible, creating the high complexity of the part. However, when considering the interactions with other components the car frame loses its complexity factor. The parts are connected with screws and other simple fasteners.

Gear Box

Component Function
The only flow associated with this subsystem is energy. The overall function of the gear boxes is to take the rotational energy from the motors and then create a gear reduction to increase the torque of the motors which will then be used to rotate the wheels and move the car. There are four gears inside the gear box, each which increase the torque of the motor and allow for the movement of the car. The gear box is intended to function outside and inside, depending on where the user actually uses the car.

Component Form
The general shape of the gear boxes is an irregular. Notable properties of the gear box are the thickness of the plastic and use of metal components. The thickness and durability of the plastic is notable because the gear boxes need to be able to withstand the high amounts of torque from the motors. The metal components are notable because they are needed for the stability of the gears rather than plastic shafts. These gear boxes are primarily 3-dimensional at 4.5” x 3.5” x 5” and weighing roughly 1.5 lb each. The shape of the gear box is coupled with the performance because it allows for all four different gears to properly translate its energy to the next gear. Multiple gears equal a lot of space, so in order to keep the gear box compact the gears need to overlap yet still function in a way that will increase its performance. Each gear box shell is made of ABS plastic while the four gears inside each is also ABS. Each gear is then supported by a steel shaft which keeps it firmly in place. When deciding on manufacturing processes, plastic is a good choice because it is easily formed into complex shapes, while the metal rods are chosen because of the torques applied to each shaft. The shell of the gear box must be a durable ABS plastic that can handle the forces applied when the car is in motion. Also the gears must be made of a hard plastic in order to keep them from dulling. The added lube in each gear box also keeps the wear down on the gears. Also the shafts must be made of metal in order to handle the forces applied. If plastic were used the amount of torque applied could possibly break the plastic thus making the gear box unusable. Global factors that helped make these material decisions would be the acquisition of the resources. Economic factors relating to these material decisions would be the overall costs of each material. Plastics are generally cheap and the steel used for the rods is also cheap as well. The aesthetic properties of both the gear box shell and the gears are smooth and relatively shiny. The shafts are also smooth. Each gearbox does not have an aesthetic purpose. They are hidden within the car itself when the car is fully assembled. The gearbox itself is black while the gears are white and the metal shafts are silver.

Manufacturing Methods
The methods used to create this component were injection molding and turning. Injection molding was used for the plastic components and turning was used for the metal shafts. Notable evidence that supports this is the riser marks and parting lines visible on the exterior shell of the gear box. Also riser marks are visible on all of the gears. Evidence that shows that the shafts were turned is the visible circular marks on the end of each shaft. The choice of plastic of had influence on the manufacturing process. The use of injection molding is the easiest process when it comes to the complexity of the gear box and the gears. And the choice of steel for the shafts made the choice for turning apparent. This is because the rough piece of stock and turning it to a constant diameter then cutting it to the desired length. Shape also influenced the method chosen. Injection molding allows the creation of very complex geometry which is needed for both the shell of the gear box and the gears. Also turning allows for the precise symmetrical dimensions needed for the shafts used in each gear box. Global factors that influenced these decisions would be the acquisition of materials. Societal factors include the safety within the overall product. The process of injection molding creates a very durable product which is needed for the gear box and its gears. If the gear box or its gears were poorly made they could break which would render the gear box useless. Initial costs of the injection molding process are relatively high, but in the long run the costs of production are cheap and will eventually pay itself off. Environmental concerns of the injection molding process are rather limited. The process is safe and gives off thermal energy and some plastic waste. This plastic waste can then be recycled and then reused again in later processes.

Complexity Analysis
The gear box and its respective gears are made of multiple materials and many different geometric shapes, and therefore was given rating of 3 on the complexity scale. The gear box had to be compact in order to keep its envelope to a minimum, and because a four gear reduction was needed, the gears had to be placed over each other in order to have them properly mesh and carry out their function. So a complex shape was needed in order to house the gears in their particular order. The interactions of the gears themselves was given a rating of 2 on the function complexity scale because the gears took a rotational energy and through a reduction, brought down the rotational speed and increased the torque, providing more power to the wheels of the Ford Mustang.

Solid Modeled Assembly

Figure 28: The Steering Wheel System consists of components such as the steering wheel (Left) and the Steering Wheel Column (Right)

Upon analyzing the Ford Mustang Power Wheels, Group 20 determined that the Steering Wheel assembly (See Figure 28) is an integral subsystem. The Steering Wheel system, which channels an imported human energy and control signal from the user and converts it to rotational mechanical energy, is one of the most important portions of the product because it gives the user control over the direction of the vehicle. By providing a solid model of the Steering Wheel System and its components, the group would be better able to understand how the assembly functions and therefore be able to further analyze the system as a whole. With this in mind, Group 20 felt that this system was of adequate complexity to solid model given the abilities and time constraints set forth by the gate criteria. Although some of Group 20 does have prior experience with various solid modeling software packages, it was determined that it would be best to model a system with relatively simply shaped components, yet these components should have an important higher function. A combination of the above factors led to Group 20’s decision to create solid models of the Steering Wheel System.

With this in mind, Group 20 chose to use the Computer Aided Design (CAD) software package known as Autodesk Inventor in order to develop a solid model of the Steering Wheel System and its individual components. Analyzing the group’s capabilities produced three viable CAD software packages for this task: Autodesk Inventor, AutoCAD, and SolidWorks. The decision to use Autodesk Inventor was made by the Product Managers, Mike and Zach, after consulting with the group as a whole. It was determined that Autodesk Inventor would be the best choice to create solid models of the system for reasons of familiarity and ease. Seeing as the solid models needed to be 3D models as opposed to CAD drawings, the group ruled out using AutoCAD since the group’s only experience with this software was 2D sketching. While SolidWorks does have 3D modeling capabilities, the group did not feel confident in its abilities to accurately model the parts with this software, nor did any group member possess the program. In contrast, since Mike and Chris have previous experience creating solid models with Inventor and Mike currently has the CAD package installed on his laptop, it was the ideal choice.

Using Autodesk Inventor, Group 20 was able to develop solid models of the Steering Wheel System and its individual components. The components that make up the Steering Wheel System are listed below:

  • Steering Wheel Cap (Part #: 4)
  • Steering Wheel (Part #: 5)
  • Steering Column Retainer (Part #: 36)
  • Steering Column (Part #: 37)
  • Steering Linkage Bar
  • Steering Wheel Pin (Hardware #: 3)

The following table (Table 11) illustrates the solid models of each of the above components, as well as an assembly that shows the individual components being assembled in sequence: Figures 29, 31, 33, 35, 37, 39, and 41 illustrate the physical components of the Steering Wheel System which was modeled while Figures 30, 32, 34, 36, 38, 40, and 42 depict the solid models of each respective component in the system.

Individual Components

Table 11: Individual Solid Models of Steering Wheel System
Part Name Part Picture Solid Model of Part
Steering Wheel Cap
Figure 29: Steering Wheel Cap
Figure 30: CAD Model of Steering Wheel Cap
Steering Wheel
Figure 31: Steering Wheel
Figure 32: CAD Model of Steering Wheel
Steering Column Retainer
Figure 33: Steering Wheel Cap
Figure 34: CAD Model of Steering Column Retainer
Steering Column
Figure 35: Steering Column
Figure 36: CAD Model of Steering Column
Steering Linkage Bar
Figure 37: Steering Linkage Bar
Figure 38: CAD Model of Steering Linkage Bar
Steering Wheel Pin
Figure 39: Steering Wheel Pin
Figure 40: CAD Model of Steering Wheel Pin
#8 x 0.75" Screw
Figure 41: #8 x 0.75" Screw
Figure 42: CAD Model of #8 x 0.75" Screw

Steering Wheel Assembly and Procedure

Once all of the Solid models of each of the individual components of the Steering Wheel System were created in Autodesk Inventor, they can be constrained together in order to form the solid model of the Steering Wheel System assembly. The following procedure outlines the steps that must be performed in order to create this assembly model.

Step 1: Placement of Parts

In order to create an assembly of the Steering Wheel System, one must first place all of the solid models into the same assembly file as seen in Figure 43. For this assembly, one needs to place:

  • One Steering Wheel
  • One Steering Wheel Pin
  • One Steering Column
  • One Steering Linkage Bar
  • One Steering Column Retainer
  • One Steering Wheel Cap
  • Two #8 x 0.75” Screws
Figure 43: Step 1 - Part Placement
Step 2: Insert Column into Linkage

Once all of the individual solid models have been placed into the assembly file, the first step to assemble the system is to insert the short end of the Steering Wheel Column into the 0.375” hole in the Steering Linkage Bar as seen in Figures 44 and 45. Since the Steering Column is supposed to be able to be rotated, it does not need to be constrained in any other ways.

Figure 44: Step 2: - Insert Column to Linkage Hole
Figure 45: Close up of Step 2
Step 3: Insert Retainer onto Column

Next, one must insert the Steering Column Retainer onto the short end of the Steering Column in order to lock the Steering Column into place (Figure 46). The open end of the retainer should be inserted in such a way that the hole of the retainer is concentric with the small hole on the short end of the Steering Column as seen in Figure 47. This effectively secures the Steering Column into the Linkage bar so that it will not slide out of the hole

Figure 46: Step 3 - Insert retainer cap onto column
Figure 47: Close up of Step 3
Step 4: Insert Wheel onto Column

Once the lower portion of the system assembly has been constrained, one must then attach the Steering Wheel to the long end of the Steering Column as seen in Figure 48. The long end of the Steering Column should be completely inserted into the bottom part of the Steering Wheel until the fins on the Steering Column latch into the corresponding groove in the Steering Wheel. Since the Steering Wheel is supposed to be able to be rotated, it does not need to be constrained in any other ways.

Figure 48: Step 4 - Insert Wheel onto Steering Column
Step 5: Insert Pin into Column

In order to secure the Steering Wheel onto the Steering Column, the Steering Wheel Pin must be inserted into the 0.162” hole on the long end of the Steering Column. The Steering Wheel Pin is inserted into the hole thus locking the Steering Wheel in place as seen in Figure 49. The pin fits into the groove on the top of the Steering Wheel in order to keep the pin itself in place.

Figure 49: Step 5 - Insert Steering Wheel Pin into Steering Wheel Column
Step 6: Insert Cap onto Wheel

Once the Steering Wheel Pin and Steering Wheel are constrained in place, the Steering Wheel Cap needs to be place on the center of the Steering Wheel in order to cover the open section where the Steering Wheel Pin is located (Figure 50). The Steering Wheel Cap has two cylindrical extrusions that line up with the two screw holes in the Steering Wheel. The Steering Wheel Cap must be mated onto the cylindrical center of the Steering Wheel so that the entire center piece is covered as seen in Figure 51.

Figure 50: Step 6 - Insert Steering Wheel Cap onto Steering Wheel
Figure 51: Close up of Step 6
Step 7: Insert Screws into Cap

The last step of the assembly procedure is to secure the Steering Wheel Cap onto the Steering Wheel with two #8 x 0.75” screws. As previously stated, the holes in the Steering Wheel Cap line up with the holes in the Steering Wheel in order to allow the screws to be screwed into the Steering Wheel (Figure 52). To secure the Cap in place, each screw needs to be fully inserted into the holes in the top of the Steering Wheel Cap as seen in Figure 53. Once this is completed, the Steering Wheel System is fully assembled.

Figure 52: Close up of Step 7
Figure 53: Close up of Step 7

Completely following the above steps results in the completely assembled Steering Wheel System as seen in Figure 54. In order to illustrate how each component connects with the other components in the system, Figure 55 shows an exploded view of the final assembly. In addition to this, Group 20 provided an Animated Assembly of the Steering Wheel System in order to better illustrate how the Steering Wheel System is assembled.

Figure 54: Final Assembly of the Steering Wheel System
Figure 55: Exploded view of the Final Assembly of the Steering Wheel System

Engineering Analysis

Introduction

In order for engineers to validate the design of a product and make sure it meets expectations, an engineering analysis may be preformed. When performing these analysis’ engineers are seeking maximum and minimum standards of the product. With these standards met, the company will feel confident in producing and selling the product to consumers. The Ford Mustang Power Wheels must have undergone many function and component analysis’ to meet the standards set forth by various laws as well as Fisher-Price’s own standards. One such example of an engineering analysis is testing the stalling load of the product to ensure the ability to preform the function of moving the user from point a to point b. If this value is not at an adequate level, design revisions may need to be implemented. This will also ensure that the product will not fail and possibly become a safety hazard under expected circumstances. Engineering analysis is a very important part of engineering design and must be completed thoroughly.

1) Problem Statement

Determine the maximum weight of the user/user’s in lbf in which the car can move. Each wheel has a separate motor and transmission. This situation will put each motor at its stalling torque. As stated in the motor spec sheet, the stall torque of each motor is 400.13 mN-m. Each transmission has an overall gear ratio of 139.3:1. The weight of the car is 72.6 lbf, and each wheel’s diameter is 1 ft.

This Problem Statement provides the proper information and parameters for testing the higher limit of the usability for this product. By clearly defining what needs to be analyzed along with the given parameters, the engineer can accurately provide a solution within the proper context.

2) Diagrams of the System

Figure 56: Free Body Diagram of the Car
Figure 57: Gear Train Ratios


The diagram of the system provides visual support and physical relationships between the variables in the analysis. This also allows for loads to be seen visually and give context to them and their associated geometry. In this analysis the positions of both the weights of the user and Car is easily seen along with the direction of frictional forces in order to help with proper set up of the equilibrium equations. A free body diagram of the car is shown in Figure 56. The varying gear ratios are shown in Figure 57.

3) Assumptions

  • 25% torque loss due to friction in the gearboxes
  • Coefficient of static friction between plastic wheels and carpet is 0.45
  • Weight of car is at the center
  • The Car does not break
  • User’s weight is 2/3 from the front of the car
  • Each rear wheel is stalled at the same torque
  • g = 32.2 ft/s2

Assumptions are necessary in every engineering analysis. This can further help simplify the problem by ignoring small differences and simplifying geometry. In this analysis, the position of the weight of the user and car does not need to be exact. These assumptions place these loads in areas close to the exact placement. These assumptions should not influence the end result too largely as the estimated locations should be fairly close to the real coordinates.

4) Governing Equations

Figure 58: Governing equations for Engineering Analysis

Within analysis, governing equations must be define for use during the calculations. These equations document the mathematical relationships that will be used for the analysis. Various equations could be used to relate geometry, loads, energies, flows, etc. In this analysis, the car is in static equilibrium requiring the equations related to that such as the sum of moments, forces in the y, and the forces in the x, all that will equal zero. Rotational conversions are also utilized in order to quantify the energy transfer between the wheels and ground.

Design Revisions

Figure 59: Key Revision
Figure 60: Gear Box Revision
Figure 61: Center Console Revision

When analyzing the Ford Mustang Power Wheels, Group 20 has developed proposals for potential design revisions for this product. In order to increase utility, performance, safety, and longevity for the product, features and/or components must be added, changed, or combined with economic, societal, global, and environmental concerns in mind. The three design revisions Group 20 proposes are the addition of an on and off switch, better connection of the gear boxes to the car frame, and simplification of the center console. These design revisions are outlined below.

Addition of ON/OFF Switch

The addition of an on and off switch would address societal concerns for the product. By adding this component, the overall safety of the Ford Mustang Power Wheels would be improved. As of the present, as long as the battery is plugged in, the product is ready to drive the motors. If the gas pedal is pushed and the pedal switch is closed, the car will begin to drive. If the pedal or the switch malfunctions and becomes locked in place, the car would continue to drive until either the battery is depleted, the car is physically stopped with a large force, or the battery is removed. For the user, many of these procedures would be difficult to preform quickly in the event of an emergency. A simple on off switch could be used to prevent accidental motion of the car but also provide an emergency power cut off for the user. The proposed location for this switch would be where the current "key" is located as shown in Figure 59. This addition would in turn give the "key" another function instead of just aesthetics and would be easily recognized by the user. In a real car the key is used to start the engine and would therefore would translate well to the toy car. By adding this safety measure, consumers will feel better about the product as well as the brand. In the event of a malfunction, this addition with decrease the chance of injury and will therefore keep the image of the brand in high regard. By taking this societal concern into consideration, Group 20 believes that the addition of an on/off switch would be a product design revision which is beneficial to both the user and the company.

Connection of Gear boxes to the Car Frame

By changing the connection between the car frame and the gear boxes, another societal concern would be addressed. Consumers expect a product to be well built and last an appropriate amount of time. For the Ford Mustang Power Wheels, the function of moving the user from point A to point B, the operation of the gear boxes is critical. By not attaching the gearboxes, there is a lot of excess movement and stress on these components. Figure 60 shows the interface between the car frame and gearbox and the inherent lack of mounting holes. It would make sense that this extra concentrated stain may cause these components to break. If these components break, the main function of the product would be hindered and the consumer would be unhappy with the performance. This would then could lead to the image of the company being damaged as a “low-quality” vendor. By adding a physical connection between the gearboxes and the car frame, there will be little movement and torquing in single areas. Group 20 proposes that extra material is added to the car frame so that the gear box housing must snap into position and held tightly from all sides. Therefore no more fasteners would be required and the excess movement would be eliminated. These stresses would then be better distributed to the surrounding material rather than the single point of contact in the current design. By redistributing the stresses the results could potentially lower the chances of failure.

Simplification of the Center Console

In terms of economic concerns, Fisher-Price could have possibly cut costs by altering the design of the center console component. The reasoning behind this revision is that the simplification of this component most likely would not have a large effect on the user experience. The child operating this product does not expect the “cup holder” or “e-brake” to be modeled in the car as shown in Figure 61. Rather, the exterior would be the most likely attract the most attention to detail. Regardless of whether or not these interior features are present will not impact the main function of the product. The ability to transport the user from point A to point B would not be hindered by the omission of these features. By simplifying this component, the number of features is decreased greatly and therefore the number of dimension decreases as well. The costs associated with production will decrease, for example one source estimated that for every 100 dimensions of a part reduced the production costs are decreased at around $4000 [2]. The mold made for this product with the proposed revision would be easier to machine and therefore would be cheaper when doing production runs. By taking this into account the omission of these features could have a definite impact on the cost for production.

After considering the design of each component, one can develop various design revisions that could potentially impact economic, societal, global, or environmental concerns. Group 20 has evaluated the Ford Mustang Power Wheels and developed the aforementioned revisions to improve the cost and performance of the product.

References

All of the photographs used in this gate were taken by Group 20.


[1] Johnsonmotor.com . Main Components of a PMDC Motor, Retrieved November 15 , 2010, http://www.johnsonmotor.com/Main-Components.267.0.html
[2] kazmer.uml.edu . Early Cost Estimation for Injection Molded Parts, Retrieved November 15 , 2010, http://kazmer.uml.edu/Staff/Archive/XXXX_Inj_MOld_Cost_Estimation.pdf
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