Group 20 - Ford Mustang Power Wheels - Gate 2

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Group 20 - Ford Mustang Power WheelsGroup 20 - Ford Mustang Power Wheels - Gate 2
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G20 fordmustang main edited.jpg {{#if:Figure 1: Fully assembled product. Photo courtesy of Zach Wilson. |
Figure 1: Fully assembled product. Photo courtesy of Zach Wilson. }}
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Name of Artifact Ford Mustang Power Wheels
Manufacturer Fisher Price
Built in {{#if: |{{#if: |, }}|}}{{#if: |{{{bldstate}}}warning.png"{{{bldstate}}}" cannot be used as a page name in this wiki.{{#if: |, }}|}}{{#if: |{{{bldcountry}}}warning.png"{{{bldcountry}}}" cannot be used as a page name in this wiki.|}}
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Cost $300.00 USD
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Contents

Introduction

Following the initial planning stage of the project detailed in Gate 1, Group 20 was tasked with assessing the work and management proposals in addition to dissecting and documenting the physical product in Gate 2. Analyzing the group’s cause for corrective action will allow the group to evaluate the quality and success of the management plan over the first month of the project. By evaluating what was successful and what points needed to be amended, Group 20 can maximize the efficiency of its team. The second part of Gate 2 details the group’s complete dissection and documentation of the Ford Mustang Power Wheels. The disassembly procedure is meant to provide a non-expert with the tools and information needed to easily disassemble the product as well as provide an analysis of the process.

Preliminary Project Review

In order for a successful completion of this project, it is necessary to analyze our work and management proposals in order to determine it’s successes and failures. With this in mind, Group 20 determined that the management plan, as a whole, has gone as the group intended, with only minor issues arising.

Project Successes

In accordance with the aforementioned idea, Group 20 found that the Management and Work proposals provided an appropriate and efficient course of action for the dissection and documentation of the Ford Mustang Power Wheels. The initial analysis of each group member’s capabilities and weaknesses proved to be quite accurate and useful in appropriately dividing tasks among group members. In regard to the division of tasks, the group performed exceptionally well. Each group member retained their assigned roles and worked well together. The role designations of each member has proven to be beneficial to the timely and completion of the project. By keeping each group member accountable for certain tasks and responsibilities, the group has been able to stay on schedule and efficiently complete all portions of the project in a timely and professional manner. This division of labor created a system to efficiently dissect and properly document the disassembly process, allowing for minimal time wastage.

When a group member was not present, the project managers could assign an appropriate amount of work to that individual in order to ensure that the workload was being fairly distributed and completed on schedule. In addition, this prevented group members from falling behind and kept each individual up to speed with the project. This proved to be extremely useful because it allowed group members to remotely progress on their portion of the project if they had a conflict with a group meeting time. However, this was not a major issue for Group 20. In fact, the meeting times set forth in the Management proposal allotted the proper opportunities for the group to maintain the established goal time frames. The Gantt chart proved to be extremely useful in ensuring the timely completion of each part of Gate 2 and the group was able to successfully follow the planned schedule of dissection and “write-up”. Overall the group has performed each aspect of the project extremely well, which clearly demonstrates that Group 20’s management proposal was well developed and executed.

Project Failures

While most elements of the management proposal have been successfully utilized, some aspects required either revision or deletion. For the planned meetings, various aspects were altered in order to provide a more convenient and efficient meeting process for the group. For example, the team meeting agendas were dropped because of the high number of short meetings and low level of complexity in the tasks that needed to be completed. Since all six group members share a similar class schedule and often see one another in other classes and on campus, short discussions about the project were able to be had more frequently than expected. Yet, the group did not think that every mention of the project and its plan of action warranted a formal agenda and meeting notes. The group also decided to change where the dissection took place. Due to the nature of the group’s product, the dissection process required minimal and simple tools, yet requires a large amount of space to document in an organized manner. in addition to the fact that the amount of space required is large. Group 20 determined that the dissection lab did not provide sufficient space for disassembly due to the fact that other groups would also need to use the lab and its tools. Based on this, the group decided to work in the Lehman 306 common room of the Governors dormitory (with the permission of the instructor) with self supplied tools. Also, by changing the management and work proposals in respect to the dissection setting, the group was not constrained to the dissection lab’s schedule and thus could work on the project at the group leader’s discretion.

Project Challenges

Initially the group originally expected few challenges with respect to the dissection and analysis of the Ford Mustang Power Wheels. However, the group did believe that “the fact that none of the individuals in our group have much experience or knowledge with how real cars function.” could potentially cause some problems during dissection. Fortunately, thus far this low level of automobile knowledge has not presented any major issues with the project including the dissection of the Ford Mustang. The main issue associated with no group member possessing knowledge of cars, was that it made it more difficult to determine appropriate names of for each component and subsystem. The group compensated for these problems by trying to utilize all resources, such as general Internet searches and the user manual, based on observation of the components in order to generate names for all of the parts and hardware. The group kept names technical while still providing descriptive names based on the more familiar workings of a car. By working collaboratively, the group overcame this challenge and continued to function smoothly for the remainder of project. With respect to avoiding future challenges, Group 20 plans to continue meeting reguarly and dividing work equally amongst the group members. This division of labor will be allocated based on each group member's capabilities and assigned roles. For example, Joe Glab will handle the majority of uploading content to the wiki as it is finished because he is the most experienced with the wiki. Ultimately, by learning from past mistakes, the group's performance and efficiency will improve.

Project Additions

In order to facilitate group work at a distance, the group decided to implement the use of Google Documents by all group members. This allows members to edit each other’s work in real time, thus making the final result much more refined. Before information is put on the Wiki, it must first be uploaded to Google Documents to have it be proofread by the other members of the group. Once the approval is given by all group members, it will be formatted for Wiki and uploaded by the Head of Web Development. This allows group members to work on the project from any location as long as there is Internet access while allowing for documents to be editted and exchanged between group members as new ideas come to mind.

Product Dissection

After analyzing its Management and Work Proposals, Group 20 completely dissected the Ford Mustang Power Wheels. The purpose of this dissection was to provide the group with a better understanding of how the product is connected and functions, both in respect to individual subsystems and components, as well as the product as a whole. The entire process, including the tools used, components and hardware found in the product, and a detailed disassembly procedure was documented and recorded below.

Parts, Hardware, and Tools

Based on the initial product assessment performed by Group 20 in Gate 1 of the project, many of the individual components of the Ford Mustang Power Wheels could be observed and described with no dissection. This being said, upon disassembly, the Power Wheels proved to contain many more parts than just those which were initially visible. during the dissection process (detailed below), Group 20 encountered a plethora of components and hardware within the Ford Mustang, including several items that were not included in the Fisher-Price manual. Since the group performed a complete dissection of the product, including the disassembly of several items which were not intended to be removed, the group created its own unique Parts List (Table 5) and Hardware List (Table 6). These tables provide the user with a complete inventory of all of the components and hardware that make up the Ford Mustang Power Wheels. Tables 5 and 6, the Parts List and Hardware List can be accessed below.

  • Table 5: Parts List details the components that were observed and documented during the dissection process.

Tools List

Since the Ford Mustang Power Wheels is a relatively simple product, a small amount of tools were required for the complete disassembly of the vehicle. In fact, according to the Fisher-Price manual, the only tools needed to assemble (or disassemble) the Power Wheels are the Included Wrench and a Phillips Head Screwdriver. However, as the dissection included parts that the user was not meant to disassemble, there were more tools that needed to be used in order to fully disassemble the Ford Mustang. This list of tools can be seen in the Tools List (Table 7) shown below.

  • Table 7: Tools List details the tools used during the dissection process.
Table 7: Tools List
Tool Number Tool Name Primary Use Picture
1 Safety Glasses To protect the user’s eyes from objects that may come towards and potentially damage the eyes
G20 SafetyGlasses.JPG
2 Needlenose Pliers To remove slip rings from the rear and front axles
G20 Pliers.JPG
3 Safety Gloves To protect the user’s hands from sharp objects that could damage the hands
G20 Gloves.JPG
4 603-4 inch #2 Phillips Head Screwdriver To remove Phillips head connecting screws that fastened components together
G20 6034.JPG
5 3/16 inch Flathead Screwdriver To remove center and retainer caps from the wheel systems
G20 FHead.JPG
6 Included Wrench To remove the locknuts from the wheel system
G20 wrench.JPG

Disassembly Process

The dissection of Group 20s Ford Mustang Power Wheels was not very complicated, although, at times, some aspects of the dissection proved to be very difficult. When Group 20 started dissection the initial plan was to start with the outer dissection of solely components, then move on to the chassis and finally on to the dissection of the subsystems.

Figure 13: The lock nuts were difficult (Level 3) to remove

On day 1, Group 20 started dissection by removing both the hood and the battery. The battery removal step was planned in our work proposal due to safety reasons and was implemented. The group moved on to the front bumper where the first setback was encountered, it was apparent that other parts would need to be taken off in order to remove the bumper. The group next took off the seats and the steering wheel from the steering column. This path was taken to see what could be found beneath the seats and formulate a new plan of attack. Next the group removed the exhaust pipes from the rear bumper to try and eliminate extraneous pieces of plastic on the body. Continuing with this plan, the group moved back to the front and took off both the upper and lower grilles from the front bumper, revealing more screws connecting the front bumper; the group removed the front bumper. The group continued dissecting the front bumper by taking both the right and left headlights out. The windshield/dashboard was removed as one subsystem. Dissecting this subsystem, the radio along with the key which was solely for aesthetic purposes was removed from the dashboard. Following the separation of the dashboard from the windshield, both mirrors were removed. The windshield was next removed from its frame. Moving to the interior, the left and right side door trim was removed. While doing so the left and right side lower body panels were also removed along with the center console. The trunk lid, spoiler, which was attached to the trunk lid, and the rear light panel were all taken off of the car frame. After each of these steps most of the outer aesthetic plastic components were removed. This now left the chassis along with the the electrical system, drive train, steering system, and wheels still attached.

Figure 14: The electrical system of the Ford Mustang Power Wheels prior to removal
Getting back to work on day 2 of disassembly, the group began with the removal of the front tires, but some challenges came about when removing the lock nuts, making the process a little longer than anticipated. The lock nuts required the use of the included wrench and proved to require a significant amount of force to loosen them from the front axle as shown in Figure 13. After noticing how the steering subsystem was connected to the chassis, the group went on to removing the front support the car frame and then removed the front bumper support from the front support. After isolating the steering system from the car frame, the removal of the steering column from the linkage followed. Once this step was completed the group moved on to the rear tires. Again some challenges came about in removing the slip rings from the back axles. This challenge is discussed later on. After doing so the tires came off with ease. Once the removal of the rear tires was complete the sprockets interfacing the gearbox to the rear tires could then be removed. The axle could be removed from the gearboxes and set aside. Sliding the gearboxes from the car frame, the group planned to isolate the whole electrical system as shown in Figure 14. In order to accomplish this, the wire cover was removed from the frame along with the pedal enclosure. After that the entire electrical system could be removed to be later dissected. The battery holder was then removed after this.
Figure 15: The housing and inner components of the gearbox with the cover removed
Turning to the previously separated steering system, the front support was taken off from the front axles removed from the steering support bar. Once that was complete we removed the front axles from the linkage. Following this the only remaining system to be dissected was the electrical and drive train systems.


Day 3, the final day, was disassembly of the electrical system along with the gear boxes. First the group started by separating the Molex connectors from the speed selector assembly. This assembly was taken apart by removing the speed selector cover and the knob from the speed selector housing. After that we removed the speed selector switches from the housing, but it took some force to get them out. Then after spending some time on that the pedal Molex connector was removed from the pedal support. Once that was complete both the pedal and pedal switch from the pedal support were separated. One of the motors was detached from its respective gearbox and the cover was separated from the gearbox housing. After doing so the group took out the 4th stage reduction gear then the 3rd, 2nd, and 1st which left us with an empty gearbox housing filled with a lot of lubricant as illustrated in Figure 15. These steps were then repeated for the second gearbox. The final step for dissection was separating the two pieces of the radio in order to see the inner workings of this subsystem. Once that was complete, dissection of Group 20’s Ford Mustang Power Wheels was finished.


For a detailed step-by-step procedure for the dissection of the Ford Mustang Power Wheels, refer to Table 8: Disassembly Procedure.


Ease of Disassembly

Figure 16: Shane and David work collaboratively to remove the pedal enclosure

In order to for an individual to be able to completely, safely, and correctly disassemble the Ford Mustang Power Wheels, Group 20 documented each step of the dissection process in Table 8. Table 8 details the dissection procedure, the approximate time and tools needed for each step, and the difficulty of each portion of the disassembly process. Based on the dissection, the group was able to measure the difficulty of the procedure and determine which parts of the Ford Mustang were actually meant to be disassembled.

Difficulty Level

In order to define a meaningful scale to measure the difficulty of each step, Group 20 incorporated the following scale into the dissection procedure:

1 - Very easy to disassemble; Requires little time and/or effort to perform this step; One person recommended. An example of a step with a difficulty level of 1 is: Step 1: Removal of the Hood. This step is extremely simple to perform.
2 - Easy to disassemble, Requires some strength, time, maneuvering, or effort to perform this step; One person recommended. An example of a step with a difficulty level of 2 is: Step 40: Removal of lower left body panel from car frame. Due to clips attaching the two parts together, this step required a small amount of force to perform.
3 - Medium difficulty in disassembling; Requires average (more than levels 1 or 2) effort, strength, and multiple attempts to perform this step; Two people recommended. An example of a step with a difficulty level of 3 is: Step 9: Removal of steering wheel from steering column. Due to clips attaching the two parts together, this step required an average (more than in step 40) amount of force to perform.
4 - Difficult; Requires a large amount of time, effort, and strength to perform this step. This step should be properly assessed before one completes it and will most likely require multiple attempts; Two people recommended. An example of a step with a difficulty level of 4 is: Step 71: Removal of retainer caps from back axle. A flathead screwdriver and a large amount of force was required to perform this step.
5 - Very Difficult; Requires an exceedingly large amount of strength, effort, and planning to perform this step; This step should be properly assessed before one completes it and will require multiple attempts to complete; Two or three people recommended. An example of a step with a difficulty level of 5 is: Step 72: Removal of slip rings from back axle. This step required a long time and an incredible amount of strenth to perform. It ultimately resulted in deformation of the slip rings.

It should be noted that steps designated with a difficulty level of a 4 or 5 are most likely dissection steps that are not meant to be performed by the user such as removing the pedal enclosure (Figure 16). These steps are both exceedingly difficult to perform and cause some damage to the product.Since these dissection steps are not meant to be performed, if one chooses to attempt these steps, all safety precautions and procedures outlined in Group 20’s Work Proposal should be implemented.

Extent of Intended Disassembly

Based on the dissection of the Ford Mustang Power Wheels, Group 20 was able to determine which components of the products were actually intended by Fisher-Price to be disassembled. Since the Power Wheels is not very complex, most of the components can be removed from the car without much difficulty. Most of the disassembly can be performed by any individual with a standard Philips Head screwdriver, and can be done without being a trained technician. However, some steps and components proved to be extremely difficult to remove and thus were labeled as parts that were not meant to be disassembled. Also, many of the parts were assembled in the factory and sent pre-assembled to the consumer. These parts are simply labeled “Vehicle” by the manufacturer, and generally speaking, those parts that are in this component were those that were harder to remove. Group 20 determined the following items as components that were not intended to be disassembled:


Slip Rings
The slip rings hold together different components of the Ford Mustang and are impossible to remove unless they are bent and destroyed. The slip rings have a locking feature consisting of outwardly angled “teeth” that allows them to be easily put on the axle, yet makes them extremely difficult to remove from the axle. When pressure was applied to remove the slip ring, the “teeth” dug into the axle and would not come off the shaft they were connected to. Due to the difficulty of removing the rings, it was determined that when a slip ring was found holding back a part, that particular part was not meant to be disassembled.


Restraining Caps
The restraining caps were found on multiple components and usually were covering the slip rings. These caps were very difficult to gain access to, and required much force to remove. As a result, there would be a lot of damage to the caps, and the surrounding parts from the prying force to remove them. Because of the “one way” use of the restraining caps, it was determined that like the slip rings, whatever component the restraining caps held was not meant to be disassembled.


Steering Wheel
The steering wheel was the only part that did not come pre-assembled that was determined to be meant not to be disassembled. The factor in the steering wheel that seemed to prove this was the fact that the steering wheel had multiple clips and when the steering wheel was pushed into the body of the car, the clips would engage. They would then be impossible to access and “unclip” and therefore, the only way to remove the steering wheel would be to apply a great enough force on the wheel until the clips bent and the wheel would then slide out. The reason the steering wheel is made not to be removed is that the steering wheel is the only way the user is able to steer the vehicle. If the wheel could come out easily, then mid-drive the user could accidentally pull out the wheel and have no way to turn the car. This is a very dangerous situation, and with the clips, this prevented this from happening.


Linkage
The linkage was also located in the “vehicle” section of the Ford Mustang, This was the bar that linearly moved to rotate the front tires in order to provide steering. The linkage was a very large problem because the entire system was press fitted together. Because of this, it was not only near impossible to separate the linkage into it’s components, but if it was taken apart, we would not have the proper equipment in order to put the linkage back in working order. The linkage is a very important part of the car because it kept the tires from moving on their own, and provided the means to convert a child’s rotating of the steering wheel, into the actual turning of the wheels in the desired direction. Because of this, the linkage would have to stay together at all times, and do to much strain on the linkage constantly turning, a screw or bolt holding the linkage together could very easily loosen, and easily be tampered with. With being press fit however, the linkage can’t fall apart, and is very difficult to manually separate without totally being destroyed.


Rear Wheels

One of the most difficult parts that were not user assembled/disassembled, were the rear wheels. Unlike the front tires, which were connected with simple lock nuts, the rear tires had slip rings holding them in place, and over those were retainer caps. These caps were very hard to remove, and a flat head screwdriver had to be used in order to pry them off. This caused damage to the hubcaps of the mustang, and the slip rings had to be broken in order to be removed. The rear wheels are proposed by our group to not be intended to be disassembled due to the fact that they are restrained by slip rings, came pre-assembled, and the retainer caps cannot be removed without causing damage to the vehicle. The reason that the real wheels were chosen to be pre-assembled is because of the fact that the entire driving system is being held together by the wheels. When the wheels are removed, the whole drive system is easily removed, which not only can bring damage to the vehicle, but to the user as well. Also, unlike the front wheels which are only for steering and so can be easily attached and work fine, if the rear wheels are not attached properly,
Figure 17: The motor-gearbox assembly prior to dissection of the gearbox
they can cause damage to the vehicle, user, or break after a small strain is applied. Therefore, for liability and safety, the Fisher-Price determined that the rear wheels being assembled by the factory and keeping them from being able to be taken off, or fall off after use.


Motor/Gear Box
The motor and the gear box (Figure 17) were restrained by the rear wheels, and unless the whole process of removing the wheels is done, it is impossible to even get to the motor and gear box. This shows the fact that the manufacturer did not want the motor nor the gear box to be accessed. Once they are removed however, it is fairly simple to remove the motor and disassemble the gear box. The reason that the gear box and motor aren’t wanted from Fisher-Price to be disassembled is because of the complexity of both, the difficulty of assembling them so that they work correctly, and the danger of dealing with the motor and the gear box. Also, the gears are lubricated and if they could be easily accessed, not only could there be the danger of a child ingesting them, or the mess that the lubricant could cause, but also, if enough came off the gears, the friction between them would greatly increase and deteriorate the gears at a much faster rate.

Documentation of Connections of Subsystems

Table 9: Subsystems
Subsystem Number Subsystem Name Description Function Performed Picture
1 Steering System Consists of Steering Wheel and Steering Wheel Column as well as the Front Wheel System. Channel human energy and control signal to rotational mechanical energy.
G20 Sub1.JPG
1a Front Wheel System Consists of the front axle, linkage, and front tires. Convert rotational mechanical energy to translational mechanical energy; Move vehicle.
G20 Sub1a.JPG
2 Drive Train System Consists the Electrical System and Rear Wheel System. Convert electrical energy and control signal to rotational mechanical energy.
G20 Sub2.JPG
2a Rear Wheel System Consists of the back axle, slip rings, gearboxes, and rear tires. Convert rotational mechanical energy to translational mechanical energy; Move vehicle.
Car underbody.JPG
3 Chassis and Body System Consists of the Car Frame and all plastic components of the vehicle. Support and protect other subsystems.
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4 Pretend Radio System Contains logic circuits and hardware needed to output audio and light signals. Convert electrical energy and control signal to acoustic and electromagnetic energy.
G20 Radio.JPG
5 Electrical System Consists of the gearboxes, pedal switch, motor, and various wires and connectors. Transport electrical energy to the drive train system.
G20 Sub5.JPG


Within the Ford Mustang Power Wheels, there are several subsystems that must interface to one another. The major subsystems include the drive train, chassis, steering system, electrical system, front and rear wheels, and pretend radio which are detailed in Table 9. Each subsystem may interface with one or more systems to perform the higher function. When interfacing, not only are they physically connected, but mass, signals, and energy are involved through these connections. Figures 18 and 19 show the connections of these subsystems in terms of mass, energy and signals. Physical interfacing can also be described by examining the physical connections. The chassis is connected to all subsystems as it provides a base for them all to function. The steering system is attached by 1/4"x1-1/4" screws. The radio is attached with #8x3/4” screws. The electrical system is contained within channels of the chassis and plastic covers that are attached by screws. The electrical system also has quick disconnects at the battery and both of the motors. The connector at the battery is a large block connector while the motors have simple spade receptacles that are soldered to the spade terminal on the battery. While the front and rear wheel systems are similar in function, they differ slightly in their physical connections to the rest of the car. The rear wheels are slid onto the back axle and held in place by two slip rings which are press fitted onto the axle. In addition, on the inside of the wheels, two sprockets prohibit the wheels from freely rotating about the axle unless enough force is applied to overcome the resistance of the gearboxes (or if the motors are operated). Conversely, the front wheels are not connected to sprockets, instead, bushings are used as space holders which prevent the wheels from "wobbling" on the axle. Both wheel systems are connected to corresponding hub caps and center caps. In addition, the gearboxes do not directly interface with the rear axle, but rather are connected directly to the sprockets which are slid onto the rear axle and connected to the rear wheels. As stated before, these systems are all connected to perform the highest level function of: “Moving the user from point A to point B”(Figure 18). In order to perform this function the subsystems must input energy, mass, and signals to convert them into the proper output of mass, energy, and signals to achieve the highest level function.

Mass, Energy, and Signal Flows

Figure 18: Overall and first level functions.
Figure 19: Second level functions.

Connections Between and Within the Subsystems

The connections between and within each subsystem are impacted by global, societal, economic, and environmental concerns. Fisher-Price must have taken these concerns into mind when they developed the connections within the Ford Mustang Power Wheels.

Global Concerns
When looking at global concerns that influence the connections of the subsystems, there is a distinct lack thereof. This product is not intended to be sold globally and therefore will not take global concerns such as laws, cultures, or climates for other countries into consideration. Fisher-Price does not sell the Power Wheels globally and other online retailers will tend not to ship outside of the continental United States.[3]


Economic Concerns
In terms of economic concerns, the type of connecting hardware is influenced. By looking at the fasteners involved in much of the product, one can see the reuse of just a few different sized screws multiple times. The #8x3/4” screw is used the most out of any fastener. By reusing this same fastener multiple times as opposed to many different sizes, the company producing our product will save by buying those screws in larger quantities. Designing many of the plastic pieces to snap together, the company will also save on production costs. In many instances it may be cheaper to add an interfacing feature to a part than producing it to accept a fastener that also may be purchased.[2] This is evident in this product due to the many places where plastic snaps are present. Economic factors also influence the design of the drive train. In most cars, there is usually one motor that drives the back axle. This requires a transmission that connects the motor to the rear axle. In this instance the Fisher-Price decided to develop a system that has two independent motors and transmissions at each rear wheel. While this may appear to be more complicated, it is not due to the fact the rear axle does not spin, but rather just supports the weight of the vehicle to the wheels. By doing this type of system, the complexity of the required components in this motor and transmission is much simpler than using one motor and transmission to drive an axle and therefore will be much more cost effective. Tolerances are also another economic factor companies consider when connecting system. The lower the tolerance on a part the higher the cost. An example of saving costs by not requiring low tolerances are the wheels and interfacing them with the front axles. The wheels themselves are produced with large cavities where the axles go. Instead of producing this very large part with a hole that needs a small tolerance to interface with an axle, they instead produce a smaller bushing that fits well at the axle. By making the large wheels using a cheaper less accurate method and the smaller bushing with the low tolerance, the Fisher-Price saves on production costs. It is clear that when designing connections, FIsher-Price takes economic factors heavily into account.


Societal Concerns
Societal concerns also influence the connection between the subsystems as well. One of the most obvious examples is the quick disconnect to the battery. In the past there have been recalls due to the wrong size connector. By having too small of contacts and insulation, there is a risk of over drawing current and overheating the connector possibly causing a fire. To combat this, the Fisher-Price uses a much larger connector than needed to ensure that there is virtually no chance of over drawing current. By doing this, people feel better about buying the product and the safety for their child and property. The hardware used to connect the wheels to the axles are slip rings for the rear wheels and nylon lock nuts for the front wheels. The slip rings are very difficult to remove as documented earlier and the lock nuts are designed to prevent backing out and falling off. If these connections fail, the wheels will fall off and could injure the user. The usage of the slip rings and lock nuts are preventative measures to ensure safety. In order to keep consumers happy about safety, societal concerns were definitely involved when Fisher-Price designed the connections within and between the subsystems.


Environmental Concerns
For many companies environmental concerns are influential factors when deciding how subsystems interface and the connections used. In this product most of the components are composed of ABS plastics. When Fisher-Price developed this product they probably took into account environmental concerns when developing these components and their connections. Plastic, because of the properties, has a much higher energy efficiency when being recycled as compared to steel. By making most of the connections involve plastic the later life of the product will be much more energy efficient if it is recycled.[1] Again perceived environmental consciousness is an important part of consumer attitude and will influence the connections within the product.


Figure 20: Front end view of the car showing the steering, chassis, and electrical systems

Performance Factors
Performance is another factor that influences the connection types within the product. In the steering system, the tolerances on the parts involved are very high. These high tolerances allow for a lot of “slop” in the system itself. This “slop” was allowed because the user, as a child, does not expect high level precision when operating.The level of precision does not effect the enjoyment of the product so therefore was kept low in regards to performance. The connectors within the electrical system are also influenced by performance. Each Molex connector is high quality and the contacts are large and strong; this ensures a tight connection between electrical components. The disconnects at the motors are soldered as well making sure neither separate. By making all of these electrical connections strong, the performance that is expected should be achieved and maintained regardless of use. If any of those connections fail, the product would cease to function properly and interfere with the expected level of performance.


Subsystem Arrangement
The arrangement of the subsystems is depicted in Figures 18 and 19. Some subsystems function in series, such as the chassis-body system, steering system, and the electrical system (Figure 20), while others act in parallel. The individual function of these subsystems may require input which is the output of another system, however other systems can be independent and perform their specific function simultaneously. For example the pretend radio functions in parallel with the drive train. Neither system must come first to allow the other to function and therefore are independent. Another example of parallel subsystems is the drive train and steering system. Neither relies on the other to fulfill their function and can run simultaneously. On the other hand the, the front and rear wheel system must be in series with the steering system and drive train respectively in order to function. The wheels’ input relies on the output of the steering system or drive train to function. Likewise, the front and rear wheel systems can not be adjacent to each other because if they were the car would not function correctly. This includes the fact that the drive train system and the steering system can also not be adjacent for similar reasons. All of the other defined subsystems can, and in most cases are, adjacent to one another.By analyzing the flows and functions of the subsystems one can see how each are arranged in terms of one another.

Challenges

Figure 21: The left interior door trim proved to be difficult to remove from car frame due to interconnecting parts and fasteners

Parts are Interconnected

A problem that occurred multiple times was the fact that many of the components and systems were interconnected. While trying to remove a certain component, it was found that the part was being blocked by other parts, which may have some surrounding parts. This was a large problem because as a certain component was removed, it was found that it wasn’t possible at that time. This problem was overcome by looking at the vehicle as a whole and taking note of which parts were connected to which. The vehicle could then be disassembled layer by layer and properly access all components that were needed. For example, the left interior door trim could be loosened, yet not completely removed from the Ford Mustang until the lower body panel was first removed from the system (See Figure 21).

Hard to reach Screws/Components

As the Ford Mustang was dissected, it was found that some of the screws and components were very hard to reach or had to be accessed within tight confines. This was a problem because it became very difficult to apply a sufficient force to remove the screws, or to properly place the tool to remove the screws or parts. There was not much of a technical way to overcome this issue, other than trial to get the tool placed on the screw or part, and brute force to loosen the component.

Clips, Slip Rings, and Restrainers

Figure 22: Removing the slip rings resulted in permanent damage to both the slip rings (left) and hubcaps (right)
Figure 23: The linkage(bottom)could not be further dissected because of press fit(top)

Many of the parts were connected to the other components by clips, slip rings, and restrainers. This became a very large problem because these different features were very difficult to remove, and many times in order to remove them, damage to the surrounding components occurred, along with the destruction or damaging of the clips, slip rings, or restrainers. Because of the very high difficulty there was a necessity to analyze the situation and come up with a way to remove the slip rings. The conclusion was drawn that it was impossible to remove the slip rings without damaging the slip rings. With this in mind, needlenose pliers were used to squeeze each slip ring in order to deform and loosen them from the axle. Then using the pliers to grip the rings, a very large force was able to be applied to the ring while the Power Wheels was held in place in order to remove the slip rings from the back axle. Removing the slip rings from the back axle permanently deformed both the rings and to some extent, the hubcaps as depicted in Figure 22. This proved to be one of the most difficult challenges that was faced during dissection. In order to remove the clips, either brute force would be used until the clips gave way and the part successfully came loose, or the clips would be pushed in using a screw driver and then the part was pulled out. The restrainers, like the clips, were very hard to access and so a screw driver was used to pry them loose.

Press Fitted Parts

The only press fitted part that was encountered was the linkage system. Unlike the other parts, which were connected with screws, bolts, clips, or slip rings, the linkage system was connected using a press fitted metal slab as illustrated in Figure 23. This was a problem because in order to remove the slab, it would require a very high amount of force that wasn’t able to be applied, and would require a special tool in order to put back together, which was not accessible. Because of these reasons, it was decided that the linkage would not be taken apart.




References

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


[1] Economist.com (2007). The Truth About Recylcing Retrieved October 25, 2010, http://www.economist.com/node/9249262?story_id=9249262

[2] Zheng,M . Tolerances of Injection Molding Parts. Retrieved October 25, 2010, http://www.articlerich.com/Article/Tolerances-of-injection-molding-parts/1007025

[3] Fisher-Price.com.Ford Mustang Power Wheels User Manual. Retrieved October 20, 2010, http://www.fisher-price.com/inst_sheets/P5920pr-0920.pdf

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