Group 18 - Barbie™ Ford Mustang/Gate 2

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Gate 2

Project Management: Preliminary Project Review

Overall, our work proposal has worked fairly well with a few exceptions. It has worked well because every group member assisted in the product dissection and the dissection was completed in a timely manner. The one aspect of the dissection that proved to be more difficult than we had anticipated was the removal of the rear wheels and engines of our product. In the end, we resorted to using large amounts of force (and a hammer) to remove the rear wheels, which we didn't anticipate in our proposal. While many of the other parts in our product appeared to be designed for easy installation and removal, the rear wheels appear to have been designed specifically not to be removed.

Our management proposal has also worked fairly well except for a few conflicts, which include: managing the Wiki, following the Gantt chart, and group members coming late to meetings. In regards to the Wiki, we have had difficulty formatting the items we add; we have also procrastinated the process of editing and adding information. Particularly with the Gantt chart, we didn’t know the proper way of formatting it onto the Wiki, which caused our Gantt chart to be presented in an unprofessional manner. We also haven't followed the schedule laid out in our Gantt chart, we overestimated the time required to dissect the product, and underestimated the time it took to document the information. In addition, the difficulty in formatting caused our first gate to have inconsistencies leading to the appearance of unprofessionalism. Pertaining to group members coming late to meetings it has been a minor issue, but an issue nonetheless. There has been no reason for corrective action because the group handled the issue internally and it was resolved with little difficulty. We overcame the challenge of formatting the Wiki by refering to the tutorial provided by Professor Cormier. We overcame the challenge of group members coming late to meetings by speaking the member(s) as a group and informing them that if their tardiness continued we would inform Professor Cormier. We will overcome or avoid future challenges by remaining disciplined as a group and sharing the work load of each gate.

Project Dissection

This chart provides a step by step description of the dissassembly process our group went through to take apart our product. Please note that the difficulty scale is described in detail below the chart, and that all images can be clicked on to be seen at a larger size.

Step No.	Work Performed	Tools Used	Difficulty (1-10)	Picture
1	Removed hood, was attached by two screws	P2 Phillips head screw	2 out of 10
2	Removed battery	None needed	1 out of 10
3	Removed plastic seats. Involved taking out 3 screws located throughout seat	P2 Phillips head screwdriver	2 out of 10
4	Removed both headlights. Involved using screwdriver to take of one screw for each headlight and pulling out headlight	P2 Phillips head screwdriver	2 out of 10
5	Removed two screws holding steering wheel in place and pin holding the wheel and the steering shaft together.	P2 Phillips head screwdriver	2 out of 10
6	Removed front dashboard including window shield. Remove screws throughout outside dashboard. There are two screws holding on the dashboard and 4 screws in the window shield.	P2 Phillips head screwdriver	3 out of 10
7	Removed center plastic console and gear shifter. 10 screws need to be removed	P2 Phillips head screwdriver	2 out of 10
8	Removed plastic coverings over bolts, used screwdriver to work off plastic	3/16 flat head screwdriver	4 out of 10
9	Removed lock nuts on front axle allowing wheels to be free. Used socket wrench and loosening lock nuts	3/8” socket wrench	3 out of 10
10	Removed front wheels, Pulled off wheels	None needed	1 out of 10
11	Removed screws on front grill, They are hidden inside the grill, This allows the plastic covering and support on bottom to be removed, 2 visible screws	P2 Phillips head screw	3 out of 10
12	Removed rear wheels held on by permanent lock washer, Involved taking off plastic covering over wheels then hitting end of metal axle with hammer while another person holds wheel in place	Hammer	9 out of 10
13	Pulled rear axle with one wheel still attached away from car, sliding it out from frame and motors	None needed	1 out of 10
14	Removed motor and gears from rear axle, pulled from plastic body of car. Once axle is off there are no attachment pieces	None needed	3 out of 10
15	Separated motor and gears, Pulled from inside car	1/8" screw driver	2 out of 10
16	Took apart gear compartment, 5 sets of screws need to be removed. Also plastic snaps need to be pushed back for proper separation of gear. Actual interlocking gears are visible once disassembled.	P1 Phillips head screwdriver	4 out of 10
17	Removed steering shaft, Pulled out from where dashboard was	P2 Phillips head screw	2 out of 10
18	Removed plastic covering wiring in front of car, Contained in front center of car connecting the accelerator and battery along with speed changer and motors	None needed	3 out of 10
19	Removed acceleration pedal, involved flipping car over pushing back 4 snap holders.	P2 flat head screwdriver	8 out of 10
20	Removed stereo from dashboard	P1 Phillips head screwdriver	3 out of 10
21	Took apart radio, Removed screws on outside perimeter of radio allowing radio to be pulled apart into two halves	P1 Phillips head screwdriver	3 out of 10

Ease of Disassembly

Defining difficulty

Difficulty for these steps was rated on a 1 to 10 rating. 1 being extremely easy and 10 being extremely difficult. Ratings for this system are only rating the difficulty of disassembly. The rating system is only comparing the difficulty compared to other disassembly or assembly steps in regards to the Barbie Mustang. These ratings are based off the time it took to disassemble the part, the number of tools used, the force needed to put back together part, the amount thought needed, and the number of people needed. A value of one would mean that component disassembly was extremely easy and fast. A value of 2 would be slightly harder but still fast. A value of 3 would start to take some more time but only involve the use of 1 tool. A value of 4 might involve multiple people being needed to disassemble part but still is not too time consuming. A value of 5 might involve multiple tools and people would not involve more than 5 minutes for disassembly. A value of 6 might involve multiple tools and people would take 15 minutes. A value of 7 might involve multiple tools and people would take 20 minutes. A value of 8 might involve multiple tools and people would take 25 minutes. A value of 9 might involve multiple tools and people would take 30 minutes and would require lots of force and be extremely irritating. A value of 10 would involve multiple tools and people would take over 30 minutes and would involve lots of irritation. To actually define difficulty of each step different factors were taken into account. Time was a major factor in deciding difficulty. The longer each step took the higher the number of difficulty it was given. Another factor that was taken into account was the force needed to take apart the part. Some screws and nuts were much harder to remove then others. The number and complexity of tools used in taking apart the car was also considered. Since the car was relatively elementary all the tools required were rudimentary . The final consideration taken in account in measuring difficulty was the number of people needed to disassemble the part. Some parts specifically the rear axle required multiple people working at the same time together to accomplish that subsystems disassemble.

Intention of disassembly of part

Rear Wheels and axle
Almost all parts on the Barbie Mustang are meant to be disassembled with relative ease. They virtually all just require one person using a Phillips head screwdriver to remove the screws and pull the pieces out. There is one major exception though, the rear axle. To actually be able to remove the motors and gearboxes located above the wheels the rear axle has must be removed. A fitted lock washer holds on the wheel to the rear axle. This lock washer is angled with an outward concavity allowing it to be put on relatively easily but makes removal extremely difficult. There is no easy means to remove the lock washer and we had to resort to hitting with extreme force the rear axle while supporting the wheel against the table. This finally made it come off after 20 hits. This component is not meant to be taken off by the customer. This is because Fisher Price does not want people tampering with the gears and motors. This would create a liability and possible failure of their product. This is easily seen through the permanent lock washer put on the end of the axle.
Accelerator
While this subsystem was easier to disassemble then the rear axle it still required a large amount of work and multiple people helping. To remove the accelerator pedal there were no screws but there were 4 pieces of plastic angled on the back. These pieces of plastic simply snap in place but to remove them they all have to be pushed back in synchronization. This required lots of time and multiple hand to succeed at. Fisher Price might not have specifically designed this component so that customers could not tamper with it but it was extremely difficult to take apart. Fisher Price might have designed this so the electronics weren’t tampered with and broken in the accelerator pedal or maybe just for the ease of assembly.

Tools used in dissection

Tool Name	Tool Picture	Tool Name	Tool Picture
P2 Phillips head screwdriver	Tool Fig. 1[1]	Wooden claw hammer	Tool Fig. 2[2]
3/8" Socket wrench	Tool Fig. 3[3]	P1 Phillips head screwdriver	Tool Fig. 4[4]

Connection of Subsystems

Fig. 1: the first level of subsystems showing the functions done in order to get the desired output.

A subsystem is said to be a coherent and somewhat independent part of a larger system. The overall function of the vehicle is to transport a child from one place to another, in the process providing a similar experience as a driver of an actual vehicle would get while driving it. The subsystems involved to accomplish this goal are best illustrated in figure 1. For any system to work it would have to import energy from somewhere, transform this energy into another form of energy that is required by the system to perform its function and then supply it to the component that will give us the desired output.

For this vehicle the main source of energy is the electrochemical battery that has to be charged and connected to the car to provide electrical energy; another source of energy is the human energy that comes into the system when the user rotates the steering wheel.

The transformation of energy takes place in the motor (converts electrical energy to rotational mechanical energy) and connecting rod (converts rotational mechanical energy to translational mechanical energy).

The components involved in transferring energy are electrical wires (for electric energy), gear box (for rotational energy), connecting rod (for rotational energy) and tire rod (for translational energy).

The final component to which all the transformed energies are supplied to are the wheels; rotational energy to the rear wheels and translational energy which is again converted to rotational energy by the front wheels to provide the change in direction required.

The overall system requires only three signals to work effectively; these signals comes from the pedal(to turn system on and off), shifter (to tell the system what speed is required) and the last one is combined with the energy input that comes when the user turns the steering wheel.

We categorized our subsystems into three sections:

a) Those responsible for translational motion.
b) Those responsible for rotating wheel left and right.
c) Radio.

Translational Motion

Fig. 2: The components responsible for translational motion and their relative position.

Figure 2 shows the layout of the components that makes the translational motion of the vehicle possible (Note this is the layout as found in the vehicle. Note also that the component marked motor is not just the motor but also a gear box connected to it). The battery is the power source; it has electro-chemicals in it that can store up to 12 V of potential difference when fully charged. Therefore the energy input comes from the battery. Pedal can be treated as the signal provider or an on/off switch. The user has to press the pedal to tell the system that it is now supposed to work (i.e. pressing the pedal means to turn on the switch). Releasing the pedal tells the system to stop providing power to the motors, which then slows the car as the internal resistance of the motor acts to slow the car. Our product had no brake system that could be compared to a braking system on a conventional car. The shifter acts as a speed selector; it is the mechanism by which the user can tell the system what speed is required (only three speeds are possible, two forward and one reverse). When the pedal is pressed, the motors (which are connected in parallel to each other) will get some electric energy which it will convert to rotational mechanical energy. This energy is passed to the wheels through a series of gears. And when the wheels start rotating, the friction force between the ground and the wheels makes the vehicle move forward (i.e. we get translational motion in vehicle). This concept can be best understood by a simplified electric circuit diagram as shown in Figure 3.

Fig. 3: Electric circuit equivalent of the components responsible for translational motion. R is a resistor that limits the current flowing through the circuit and hence the electric power across the motor that in turn limits the rotational power that the motor can supply to the gears and wheels.

Steering

The main components required in rotating a wheel are Steering Wheel, Connecting Rod and Tire Rod. Their connection with each other is demonstrated in figure 4 (a). In this subsystem the main source of energy input and the signal are both provided by the user. This is done by rotating the Steering Wheel in the direction required. This rotational energy is then transferred through the Connecting Rod to the Tire Rod. The connecting rod is not a straight rod as shown in figure 4(a), it is actually bent in such a way to convert the rotational energy into the translational energy for the tire rod. The Tire Rod is connected to the wheels in parallel to the axle and the distance between the axle and the Tire Rod is approximately 5cm. This way when the Tire Rod translates left/right, the wheels rotate with the axle as the pivot; as shown in figure 4 (b) and (c). Rotating the wheels will make the vehicle turn in the direction of rotation.

Fig. 4: (a) figure shows the components responsible for rotating a wheel and their relative position to each other. (b) initial position of wheels and tire rod. (c) position of wheels and tire rod after the steering wheel has been rotated to the left.^[5]

Radio

The radio is located on the right side of the car’s dashboard. It needs 3 AA batteries to function. To install the batteries the user has to first remove the screws connecting the radio to the dashboard using P1 type Phillips-head screwdriver and then remove another screw that holds the battery covering in place (using the same screwdriver) and then insert the batteries and replace everything again. The user can now listen to prerecorded songs and tunes whenever he/she wants to by press the button with the music symbol on it. The radio has nothing to do with the overall function of the product.

Reason for Subsystem Connections

Petroleum is a non-reusable resource that is widely used around the world. Since the Industrial Revolution in the 19th century, petroleum has been used frequently. Being used for two centuries plus, it is hard to believe that it is still being used. In a research that was done by Roberto Aguilera in 2009, there are 1,653 billion BOE left in the world; this is enough for about 50 years. In a country that consumes plenty of oil, the availability of petroleum is very high. Most of the Fisher's Power Wheels products are made in Mexico. Mexico did not have much problems with petroleum until recently. Since the turn of the century the consumption and the availability has been going down. If the trend continues, then the availability of petroleum in Mexico will be very low. The Barbie Mustang is mostly composed of plastics. Change in price of plastics will make the price of the car increase or decrease drastically. Also the manufacturers must keep in mind that some plastics are dangerous, especially for children. If the company chooses to use cheap plastics, the price of the product will go down, but there will be high risk of damaging the children who ride the products. If an expensive plastic is used for the vehicle, then the price of the car would go up too much with lower risk of damage. Depending on what plastic Fisher's uses, the type of consumers will be different, but as of right now regular middle class family can afford the toy. Plastics are widely used for basically every consumer product, so it will be hard to find a replacement for it. The plastics of the Mustang could be replaced by metal, but it will be too heavy, and more expensive. The only real replacement is a different type of plastic, like bio plastic. Cereplast plastic is a plastic that is environmentally friendly, because it will remove 70% of the petroleum used to make a plastic. The words "environmentally friendly" usually comes with the word "expensive". However, cereplast plastic is not expensive at all; it is basically made out of starch materials, such as potatoes and corn.

Implementation of the Different Connections Between Subsystems

The main connections between subsystems occurs between the subsystems for translational motion and those for steering; the radio subsystem does not interact with the other two subsystem categories. In fact, the radio unit can operate completely independent of the rest of our product; for this reason the connections between subsystems will not focus on the radio. The only true connection between the two subsystems discussed here comes from the body of our product itself, the rigid plastic framework of our car holds our two subsystems together. The steering subsystem, which consists of the steering wheel, connecting rod, and tire rod operates entirely on the front two wheels, while the driving subsystem operates on the rear wheels. While both of these systems are necessary to operate our product correctly, the subsystems are not dependent on each other in any way, and each could function normally without the other. The only connection that exists between these two subsystems, as specified earlier, is the body of the car. When the manufacturer determined what material the body of our toy car would be made out of, they had to consider several factors, some of which are detailed in the chart below. Please note that only a few specific factors to consider were given in each category, this is for simplicitys sake. In reality, there are quite a few factors that are not listed here.

Considerations for Subsystem Connections Using Plastic
Category	Factor
Global	What is the availability of petroleum? (Plastic is a petroleum product)
	Will manufacturing materials be available where this product will be manufactured?
Societal	How will choosing plastic influence cost, and therefore who can purchase the product?
	Is this form of plastic considered safe to be around children?
Economic	What is the cost per product of using plastic versus an alternative?
	Will choosing plastic over an alternative affect the terms of the warranty? (and possibly incur additional costs to the company?)
Environmental	How does plastic decompose compared to alternatives?
	Is plastic more or less environmentally friendly to produce than alternatives?
Performance	Can plastic withstand the loads and forces that will be applied to it?
	Can plastic be manufactured to the necessary tolerances to ensure correct product function?

Arrangement of Subsystems

The main purpose of subfunctions is to get the car moving. The human action signals to start everything in the system. The signal comes from the human pushing the accelerator. This signal tells the battery to release electrical energy to act out the command. However, before taking out energy from the battery, first the battery needs to be charged and be put into the car. Next step is the motor, which converts the electrical energy into mechanical energy to gears. Before converting any energy, the motor gets its work rate instructions from the transmission, and then it starts to convert the energy. The gears let the system know what rate it needs to operate in. After going through the gears, the energy finally ends up on the wheels. The wheels convert the rotational energy in the axle into translational energy of the car. Another system of subfunctions is turning the car. Just like the first subsystem, human action is applied as a form of energy onto the steering wheel. Once the rotational energy is brought in, the steering wheel turns it into mechanical energy to steer the car. The energy then goes through the axle which leads to the wheels themselves. The axle holds the wheels to support the car, and it transfers power from the motors to the wheels.

Reason for Each Subsystem’s Placement

The battery comes next to the human action, because going straight to the motors means a person will have to spin the motor directly. The motor must be before gears, because gears work using mechanical energy not electrical energy. The gears should be before wheels, because without the control of the speed of the car, it is hard to maneuver the vehicle and potentially the life of the operator may be in danger. Wheels must come after gears, because the spinning axle does not have enough of a radius to reach the ground therefore the car will not move. The Steering wheel has to come after human action to turn the wheel, because without it the operator will have to turn the shaft, which is harder to turn. This comes from the basic of torques acting on a shaft; the larger the radius the less force needed. After the steering wheel, the wheels must come next, because the axle is not meant to spin, therefore it cannot turn the car.

Subsystems Which Cannot Be Adjacent

Most subsystems in the Barbie Mustang are suitable being adjacent to one another. There are several subsystems which cannot be adjacent. The Steering wheel cannot be beside the energy from the battery or the motor. The Steering wheel requires different type of human energy and does not use any electrical energy, so being beside the battery or the motor would be unnecessary. Another non-adjacent subsystem is that the pressing action to start the battery. It cannot be together with the axle, because the axle uses different human motion that comes from the steering wheel. If the motor was connected to the wheels directly without having the gears in between them, the functionality in the wheels would be lost, because the motor gives out mechanical energy while wheels operate with a rotational energy. Another subsystem which cannot be adjacent is the battery being next to any metal components specifically the metal axle or steering shaft. This is because the battery has the possibility of discharging and electrify the car if it was next to an metal component. therefore the battery must be isolated. Another set of subsystems which cannot be adjacent is the human energy of turning to control the direction of the car and the rotational mechanical energy of the steering shaft. There must be some sort of steering wheel between them. This allows more force to be applied to the axle allowing the wheels to be steered with less work required. This allows a small child to oppurate the car and steer it.

References

1. Fig. 3 is a modification of one image hosted on the following website
2. "Assessing Oil Resources in the Middle East and North Africa" physics.harvard.edu
3. "Trends in Mexican Petroleum Production and Consumption" mexican-petroleum-consumption.html
4. "Creplast - Nature's Renewable Plastic" Creplast