Group 11 - Weed Eater Featherlite 20C - Gate 2

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Group 11 - Weed Eater Featherlite 20CGroup 11 - Weed Eater Featherlite 20C - Gate 2
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Figure 1: Fully assembled view of the product. }}
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Name of Artifact Featherlite 20C string trimmer
Manufacturer Weed Eater
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 [[[|v]]  [[|d]]] 

Group 11 - Weed Eater Featherlite 20C String Trimmer

Contents

Introduction

After creating and developing a plan for how to go about completing the project in Gate 1, the group performed the physical dissection of the product documenting each step of the process followed by assessing the success of our management and work proposals. The cause for corrective action allows the group to examine what aspects of the plans are going well and what needs to be altered in order for the group to perform at its optimal level and to complete tasks with higher quality and in a more timely manner. The physical dissection and documentation of the Weed Eater Featherlite 20C string trimmer is designed to make the group more knowledgeable on their product as well as to allow them to analyze it in order to determine why the product was designed in the way that it was.

Preliminary Project Review

Work Proposal Assessment

The work proposal created in Gate 1 gave our group a strong reference for how to go about dissecting the Weed Eater Featherlite 20C string trimmer. Determining individual strengths and weaknesses was beneficial when dividing up the work and assigning tasks in order to most efficiently and thoroughly complete the project. We have also tried to improve our individual weaknesses by exposing everyone to every aspect of the project. For example, the group members who are experienced in engines have been explaining to Erika what the different parts look like and what they contribute to the overall function of the engine. We have also been trying to improve the technical writing skills of the group as a whole. We have done this by having everyone contribute to writing up the information for the Wiki and critiquing the work of other group members.

Our tools list was extremely helpful for our outer dissection and the majority of the subsystem dissection. When removing all of the outing casing, we found that a few additional tools were needed to remove certain screws that could not be seen during the initial analysis of the product. This did not pose an issue though because we had the tools available to us. The product was very consumer friendly when disassembling the main components, but required two people on certain occasions for hard-to-reach screws and removing particular subsystems. Overall, the work proposal provided a sound guideline for dissecting the string trimmer.

Additional problems have been faced with individual quality of work standards. The submissions from the group members for the part of the gate they were responsible for varied greatly in detail and overall quality and thus had to be revised by the adding additional work to one of the members of the group. This disrupts the work distribution balance that the group tries to achieve - the group tries to ensure that each member is doing the same amount of work, but this is proving to be more difficult than anticipated and needs to be addressed in future meetings for the upcoming gates. A way in which this issue might be solved is to have each member read the final gate submission to see what the quality of the submission and how it varies with their original submission to see how they have to improve or alter their assigned tasks.

Management Proposal Assessment

The management proposal outlined and described in Gate 1 was successful in some aspects and failed in others. The biweekly meetings have been extremely beneficial because they allow each group member to present what they have been working on as well as sets additional deadlines for when specific tasks should be completed. They also allow for the members to compile their work and complete tasks that require the entire group. Since every member has almost the same schedule, changing the dates and times of the meetings when necessary has not posed any problems.

The Gantt chart also provides the group with advanced deadlines that must be followed, which has proved to be successful thus far. Although we scheduled the cause for corrective action before the actual dissection of the string trimmer for this gate, we realized this was not plausible because no work had yet been done to be analyzed.

Although the work for the project has been evenly divided between the group members, it has not been divided according to the position described in Gate 1. Instead of strictly performing the tasks outlined for each position, everyone has taken turns dissecting the string trimmer, documenting the process, and writing up the information and analysis for the Wiki. We find this more beneficial than performing the specific tasks because it allows each member to get hands-on experience in the dissection and gain knowledge on the product as well as improve their analysis and technical writing skills.

Future problems that the group faces will be addressed during the weekly meetings. This allows each member to give their opinion on the issue and the group to collaborate on how to be solve it. If the issue requires immediate attention, an additional group meeting can be held to discuss it. The group predicts the most prominent problem to be the distribution of work throughout the project, which can be addressed during every meeting in the future. Each group member will have to agree upon who is doing what tasks and when they will be due to make sure that everyone believes equal work is being assigned.

Product Dissection

In order to obtain a better understanding of the design of the Weed Eater Featherlite 20C and how it works, the group completed a thorough dissection of the entire product. This section shows a documentation of the steps, parts, and tools used throughout the process.

Difficulty Scale

In order for the person disassembling the product to more knowledgeably disassemble the product, a difficulty scale was creating that is based on how much force was required for the task, how much time it consumed, and how many tools were used. The difficulty scale is as follows:

1 - Level 1 difficulty refers to a task that requires the minimal amount of work to complete. No tools are required to reassemble this part and can be done with a small amount of force. An example of this difficulty level is connecting the cutting shield to the bottom of the drive shaft housing. This only requires the person to remove a wingnut needing little force to complete.

2 - Level 2 difficulty describes a task that requires the use of tools. Only a small amount of force is needed to complete the task and the parts being disassembled are located in a convenient area. An example of this difficult level is detaching the throttle housing handle from the drive shaft housing. An Allen wrench is needed, but a large amount of force is not needed to sufficiently remove the part.

3 - Level 3 difficulty signifies a task that requires the use of tools, more than one step, and a considerable amount of force. An example of this is disconnecting a screw or nut that is very tight and in a very difficult place to reach. The drive coupling, step 15, was attached to the flywheel which rotates making it difficult to hold the flywheel still and loosen the nut shaped base.

Dissection Steps

Table 2-1: Dissection Process
Step Description Tools Required Photo Difficulty (1-5)
1 Before beginning the actual dissection of the product, we emptied the fuel tank in order to make sure that the string trimmer would not accidentally be started. This was done to ensure the highest level of safety throughout the entire dissection process. Hands
Figure 2-1: Rear view of engine
1
2 Using a torque screwdriver, three T-20 torque screws were removed from the exhaust shield, the shroud. This protects the user from the heat that is produced by the engine during usage. The removal of this part allows for the rest of the engine to be disassembled because it is essentially a cover over its entire back side. Hands, Torque Screwdriver
Figure 2-2: Shroud removal
2
3 In order to remove the engine from the drive shaft of the string trimmer, the throttle housing/hand grip was separated and removed disconnecting the throttle and its connecting wire from the drive shaft allowing the dissection of the engine to continue. The two components (the left and right side) of the hand grip were held together by four H-4 socket head screws that were removed with the use of a Alan wrench of the correct size. Hands, Alan Wrench
Figure 2-3: Throttle housing disassembly
2
4 To be able to reach the inside of the engine from all sides, the other side of the engine casing had to be removed. This step required the removal of four T-20 torque screws, and one socket head screw. After the removal of the screws with their respective screwdrivers, the kill switch had to be removed. This was difficult because it was connected to the engine casing and its wires were connected to the motor. As a result, this step required the effort of three people. While one person removed the kill switch with the use of pliers, one person held the drive shaft, and the final person held the engine up. Hands, Torque Screwdriver, Alan Wrench thumb|center|200px|Figure 2-4: Removal of outer casing]] 3
5 The removal of the fuel tank was the next step. Using a torque screwdriver, two T-20 torque screws connecting it to the rest of the engine were removed. The fuel tank was still not completely disconnected after removing these screws. Still held together by the large and small fuel line, they had to be removed from the primer and the carburetor with the use of pliers. Hands, Torque Screwdriver, Needle-nose Pliers
Figure 2-5: Removal of fuel tank
2
6 Utilizing a #1 Phillips head screwdriver, four screws were removed in order to disconnect the bottom component of the carburetor. Removing the bottom component then the primer in that order is not necessary, but just personal preference. Step 6 and Step 7 are interchangeable. Hands, #1 Phillips Head Screwdriver
Figure 2-6: A component of the carburetor
2
7 The primer was removed from the top of the carburetor by utilizing a size 2 Phillips head screwdriver. After unscrewing the two connecting screws, the primer was easily removed exposing a side of the carburetor beneath it. However, the carburetor cannot yet be removed because it is also connected to the air box as well as to the throttle control. Hands, Size 2 Phillips Head Screwdriver
Figure 2-7: Removal of Primer
2
8 The air box was the next component to be removed in order to further expose the carburetor and allow for it to be removed. Disconnecting this part was quite difficult because the screws were located in areas that were hard to reach and required some maneuverability. A size 4 Alan wrench was utilized and two screws were removed. Within the air box is the air filter, which filters the air that is getting input into the carburetor to be combined with the gasoline/oil mixture. Hands, Size 4 Alan Wrench
Figure 2-8: Bottom view of the air box
2
9 After the removal of the bottom portion of the carburetor, the primer, and the air box, the remainder of the carburetor could finally be disconnected. The two socket head screws that went through the entire carburetor connecting it to the throttle control were removed by the use of a size 4 Alan wrench. Once this was completed, the carburetor was easily detached from the motor. Hands, Size 4 Alan Wrench
Figure 2-9: View of the bottom side of the carburetor
2
10 The throttle control, connected to the carburetor on one side and the motor on the other side, could be easily detached after the previous removal of the carburetor. The two torque screws were removed by using a T-20 torque screwdriver detaching it from the motor. Hands, Torque Screwdriver
Figure 2-`0: Throttle Control
2
11 True to its name, the magneto was connected to the flywheel assembly by a magnetic force. As a result, the removal of this part required only hands because it could simply be pulled away from the flywheel with minimal force. Hands
Figure 2-11: Magneto
1
12 The exhaust and the exhaust housing (muffler assembly) were detached from the cylinder head by removing two T-30 torque screws with a torque screwdriver. The exhaust system is attached to one side of the motor and provides an outlet for the unwanted air to leave the engine. The screws in this part are located deep into the part making it difficult to reach with a screwdriver. Hands, Torque Screwdriver
Figure 2-12: Muffler Assembly
3
13 Located on the top of the motor, the next part disassembled was the spark plug. Using an adjustable wrench to unscrew it, the removal of this part was difficult because it required extensive force. Hands, Adjustable Wrench
Figure 2-13: Removal of the spark plug
3
14 The piston, located within the cylinder head, was connected to the crankshaft by two socket head screws. By using a size 4 Alan wrench, these screws were removed detaching the piston from the system. This was challenging because the socket head screws were located deep within the cylinder head making them difficult to reach and required extensive force to remove. Hands, Size 4 Alan Wrench
Figure 2-14: Piston
3
15 The drive coupling was connected to the crank and the crankshaft through the flywheel. With the use of a 9/16 inch wrench, the drive coupling was unscrewed detaching it from the remainder of the engine. This step was difficult because it required more than one person to complete - one person was needed to hold and utilize the wrench while another person was needed to whole the flywheel in place allowing the unscrewing of the drive coupling to take place. Hands, 9/16 Wrench
Figure 2-15: Group removal of drive coupling
3
16 The engine housing holds the pull start assembly, which consists of the spindle, string, and spring. Using a size 4 Alan wrench, two socket head screws were removed detaching the spindle and string from the housing and releasing the spring from its confinement. Hands, Size 4 Alan Wrench
Figure 2-16: Removal of the pull starter
2
17 The kill switch, located in the engine housing, was removed by being pulled out. This was easy to do because it required no tools and minimal force. Hands
Figure 2-17: Removal of the kill switch
1
18 After dissecting the engine, the round handle used by the user to hold the trimmer up was removed. This was done by unscrewing wingnut, which only required the use of hands, and sliding it off of the driveshaft. Hands
Figure 2-18: Vertical Grip
1
19 The shaft is composed of two sections, which connect right below the round handle. These were disconnected by unscrewing them from each other with our hands with little force. Hands
Figure 2-19: Section of the drive shaft
1
20 The blade shield covering the head was detached from the drive shaft by using just your hands to remove one wingnut that was attached to a square bolt. Hands
Figure 2-20: Blade Shield
1
21 The spool containing the line in the head was detached by pulling it off with minimal force. This exposes the compression spring and the retainer/clip that will be disconnected along with the spool. The final part of the head, the hub, can be removed from the drive shaft by unscrewing it from a bolt that extends out of the end of the driveshaft. Hands
Figure 2-21: Components within the head
1

Challenges Encountered

Throughout the dissection process, very few challenges were encountered. The initial problem the group faced was not having the necessary tools out and available. This was easily solved with getting a tool kit that had various screwdrivers. Aside from this, the main challenge faced was hard-to-reach screws. Some components of the engine have the connecting screws locating deep within the part making it difficult for the screwdriver or Allen wrench to reach. In these cases, the long part of the Allen wrench had to connect to the screw which made generating the necessary force to loosen the screw difficult. To overcome this challenge, the group improvised such as inserting the Allen wrench into the hole and using another tool to help generate the force as shown in Figure 2-15. The other challenge faced was removing the knot from the string in the pull start because it was extremely and the ends were burnt to keep it from coming undone. The group decided to just cut off the knot and to retie a knot when having to reassemble the trimmer.

Intended Disassembly

In performing the disassembly of the Weed Eater Featherlite 20C, our group was able to determine which components were designed to be disassembled and which parts were not. Since this product is not complex, dissecting the majority of the parts was simple. However, a selection of parts were quite difficult to remove requiring extensive force and occasionally more than one person. This small group of parts are the parts that have been deemed not intended for disassembly.

Cutting Head/Shield:
The spool with line is easy to remove and can be done so without the use of tools because the operator has to remove it in order to replace the line. The cutting shield can also be removed without the use of tools because it often gets covered with grass and this allows for it to be easily cleaned if desired. However, the remaining parts of the cutting head are screwed in place and are not intended for disassembly because they should never need to be repaired or altered in any way.

Engine Outer Casing/Shroud:
The shroud and fan housing hold the entire engine. Both parts are intended for disassembly because they allow the person to be able to reach the different parts of the engine if any repair is necessary. The fan housing can be detached from the drive shaft housing and the shroud can be detached from the fan housing completely exposing the engine for any need.

Fuel Tank:
Unless repair is needed on the inner parts of the engine, the fuel tank never needs to be disassembled. The only component of the fuel tank that repeatedly gets used is the fuel cap that needs to be removed and put back on every time the fuel tank is filled with the gasoline/oil mixture. The fuel tank is screwed onto the engine as well as has fuels lines attached to the carburetor that typically do not need to be removed.

Air Box Assembly:
The air box assembly consists of the air box itself and the air filter and air filter cover. The air box should never ever need to be removed, but the air filter cover needs to be opened in order to change the air filter. As a result, the air filter cover is designed to be removed simply by the user pulling it open with slight force.

Pull Start:
the pull start is located in front of the engine. Therefore, the engine has to be removed prior to reaching the pull start assembly. When removing the line and its housing as shown in Figure 2-16 the spring easily comes unwound and is difficult to properly get back into place. As a result, the pull start assembly was not designed to be disassembled.

Piston:

As one of the more difficult components of the engine to remove, the piston is located within the cylinder, and not intended for disassembly. The screws to removes this part were located
Figure 2-22: The drive coupling attached the the rotatable flywheel
deep within the cylinder making them difficult to reach. Although the longer end of the Alan wrench was able to reach that deep of a distance, it left the small end of the Alan wrench exposed, which made it difficult to generate sufficient force.

Primer & Carburetor:
Both of the parts are attached to more than one component. In order for them to be removed, the other parts have to be removed first. Although the steps to remove these parts are simple, numerous steps are required, making it not intended for disassembly. These parts would also not have to be removed unless repairs on the engine are needed, which is rare with this product.

Spark Plug & Drive Coupling:
The spark plug and drive coupling are both parts that protrude out from the engine when having to be removed. Both parts were very tightly secured in place making it difficult to remove. The drive coupling was also attached to a rotating component, as shown in Figure 2-22, making it more difficult to gain the sufficient force needed for its removal. The only reason to remove the spark plug is if it needs to be replaced.

Throttle Control:
Connected between the motor and the carburetor, the throttle control can be easily removed with the use of a torque screwdriver. However, since it is located between these two parts it cannot be detached until both the carburetor and the air box are removed. This makes the throttle control not intended for disassembly simply because of the order in which the dissection of parts must follow.

Overall Dissection:
Although some of the part are easy to disassemble, they should not dissected unless there is an issue and a certain part needs to be replaced. Certain parts like the air box are designed to be disassembled because it allows the operator to replace the air filter. The cutting head is also designed to be disassembled because the spool of line has to be replaced when it runs out. The other parts within the engine, although capable of being disassembled, should not be unless necessary.

Connection of Subsystems

The main function of the Weed Eater Featherlite 20C is carried out by converting combustion energy to rotational "cutting energy." This is done by a series of connected subsystems that allow for the transfer of mass, energy, and signals between them. The subsystems carry out their own individual tasks that contribute to the overall function of the product.

Ways of Connection

Physically
The parts are connected physically mainly by a combination of different types of screws that hold the parts together in a certain arrangement and order. The main subsystems - the engine, drive train, and cutting head - are connected by screws. Within just the engine, the majority of the parts are connected by screws. For example, the piston is connected to the crankshaft by two socket head screws because the rotation of the crankshaft causes the vertical movement of the piston. The piston is housed within the cylinder because the spark plug, which is attached to the top of the cylinder, ignites the fuel before it enters the piston. Screws are what are mainly used for these connections because they are strong, last for a long time, and will not weaken as a result of the heat of the engine. Another form of physical connection in the engine is with fuel lines. The fuel tank is connected to the primer and carburetor by two fuel lines that transport mass. The throttle control connects the engine to the trigger of the drive shaft by a cable. This allows the user to control the speed of the engine by altering the location of the cable on the engine by pulling on the trigger.
Signals
The component of the product that involved signals is the kill switch. When an problem occurs where the string trimmer will not turn off the kill switch it utilized. The user simply hits the switch that sends a signal to ignition module ending the rotation of the flywheel and thus stopping the engine from running. The kill switch consists of a lead wire and a ground wire that must be connected to the kill switch itself and the ignition module correctly in order to successfully function.
Mass
The transfer of mass occurs primarily within the engine assembly, but also inside the spinning head. Once the engine is in motion, the carburetor allows air to enter by way of the air box, flowing towards the engine. As the air travels, a vacuum is created, forcing fuel from the fuel tank, along the lines and into the carburetor where it is mixed with gasoline and oil for combustion. While this occurs, a second line, running from the fuel tank to an external part of the carburetor allows air to flow in from the surroundings into the fuel tank in order to compensate for the fuel removed for ignition. The fuel and air mixture burns, and after one cycle of engine operation, the waste gases and unburnt fuel are exhausted out of the exhaust assembly, and through the shroud. In the spinning head, the mass is introduced before operation in the form of cutting line. As the line is worn down from contact with objects such as rocks and fence-posts, the cutting like will decrease in length. When this occurs, the only way to increase the length of the line to that of an effective cutting surface is to release small amounts of line from the excess initially installed inside of the head.
Energy
All of the subsystems work together to transfer energy to achieve the final task of rotating the cutting head to trim grass and weeds. Human energy is inputted in the system by putting fuel into the fuel tank, pushing the primer, pulling the pull start, and holding the string trimmer in position to be used. The initial input of human energy allows for the flow of mass to occur until the spark plug sends ignition energy into the cylinder to combine with the fuel to convert the energy to rotational energy. This rotational energy is produced by the piston, which is connected to the crankshaft. The rotational energy is transported by the drive train to the cutting head where it is expanded and converted into "cutting" energy. This cutting energy is used to trim the grass, which is the overall function of the product.

Why They are Connected

  • The drive shaft is connected to the engine and the cutting head because it transfer the rotational energy produced by the engine to the cutting head that results in the line spinning. This allows the string trimmer to perform its overall function of trimming grass.
  • The fan housing and shroud are connected to the engine because they hold it in place and protect the operator from the engine heat and its moving parts. The shroud also allows for the hot exhaust to escape into the atmosphere to keep the engine from overheating.
  • The fuel tank is connected to the primer and carburetor by two fuel lines because it allows for the transport of mass. One of the fuel lines transports the gasoline/oil mixture while the other transports air used to pressurize the gas. The fuel tank is necessary for the engine to operate, and the tank needs to be big enough to allow for the engine to run for an ideal amount of time.
  • The air box is connected to the carburetor on the engine because it contains an air filter, which cleans the air prior to it entering the carburetor. After the air has been filtered, it directs it into the carburetor, which regulates the amount of fuel and air that gets used by the engine.
  • The pull start is connected to the fan housing because it is close to the operator making it convenient to use. It is also connects to the crankshaft through the flywheel because the pull actuates the flywheel and thus gets the engine running. In order to start the engine without an electric start element, a pull start has to be implemented to spin the crankshaft.
  • The piston, housed within the cylinder, is connected to the crank shaft assembly because the movement of crankshaft causes movement in the piston. When the crankshaft spins it moves the piston up and down in the cylinder, which is necessary for the engine to operate.
  • The cylinder is located in the middle of the engine because it is the location of combustion. It also connects numerous components together. Since the cylinder houses the piston, which connects to the crankshaft the cylinder and the crankshaft need to be located adjacent to each other.
  • The primer is connected to the carburetor, which is also connected to the air box and throttle control because they work together to regulate the amount of fuel and air that is used by the engine for it to operate properly.
  • The spark plug is attached to the cylinder because it ignites the fuel before it enters the piston. Instead of it being directly connected to the piston, it sends a spark through the cylinder chamber that reaches the piston.
  • The throttle control is connected the the engine and carburetor because it regulates the ratio of fuel and air that is used by the engine in order to make the engine run faster or slower. It also wraps down the driveshaft because it is a convenient place that is easy for the operator to reach in order to maintain control of the engine speed.

How the Connections are Implemented

The subsystems in the Weed Eater Featherlite 20C string trimmer are connected in a couple different ways. The components of the engine are connected to each other by fasteners, namely various screws, that tightly secure the components in place and can withstand the heat produced by the engine. For example, the cylinder where combustion takes place is screwed to the crankcase. The components are also held in place simply being slid into place. An example of this is the piston and crankshaft - the crankshaft slides into the hole in the connecting rod of the piston and the base of the piston slides into a hole in the cylinder. Only one component, the kill switch, utilizes an electrical wire. This electrical wire is connected to the ignition module and is a crucial safety aspect of the product. This allows for the signal and electrical energy to be transmitted to the engine signalling for it to turn off. The components of the cutting head are also connected with screws with the screws being used to connect a series of parts together. Not only are the components within a system mainly connected by screws, but the systems are also connected to each other mainly by screws. This is allows the different components to work together to complete the task. After the operator pulls the pull start to actuate the motor, the connections within each system and between the systems allow for the initial human energy to be transferred into different forms of energy ending as rotational "cutting" energy. These connections allow the energy inputs keep the string trimmer functioning long after the initial input.

Mass, Energy, and Signal Flow

Figure 2-23: Overall and first level functions
Figure 2-24: Second level functions
Figure 2-25: Second level functions

Subsystem Arrangement

The engine shroud must be placed on the rear end of the engine in order to protect the user from the heat that is given off from the engine. The fuel tank is located on the opposite side of the engine away from the cylinder and piston in order to keep the heat away from the highly combustible fuel. There is also a small space between the fuel tank and any of the other parts to ensure that it stays cool and allows the hot air to escape through the shroud. The engine block is placed in front of the heat shroud in the back in order to allow the hot air to directly leave while still protecting the user from getting burned by the hot metal parts. The engine block consists of the cylinder, piston, spark plug, and crankshaft assembly all put together. These parts must all be connected in that order in order for any power to be produced. The carburetor pulls fuel out of the tank and pumps it into the engine block using air pressure created from the primer and the air box. The carburetor is also connected to the throttle control, which dictates the amount of fuel that is fed into the engine block. The engine block is also connected to the exhaust system which expels heat and gasses produced when the engine is running. Although the exhaust system and entire carburetor assembly can switch sides it makes the most sense for a person who is right hand dominant to use the original settings. The crankshaft assembly connects to the driveshaft which goes down the entire metal shaft in order to transfer the rotational energy produced by the engine. The rotational energy is transferred to the cutting head, which is bolted to the bottom of the driveshaft. The cutting head is essentially what cuts the grass and weeds. The shield is attached to the end of the shaft in order to protect the user from the spinning blades. The specific arrangement of these parts and the tasks they complete is what allows the string trimmer to function as a whole.

Global, Economic, Societal, and Environmental Influences

The biggest concerns when designing a product and determining the connection of subsystems are cost and safety. Companies are constantly try to design products with the same level of quality but for a cheaper price. The Weed Eater Featherlite 20C was designed with the intention of providing a product of high quality at a low price for consumers. To achieve this, the connections used over the entire product and within specific systems are simple and uniform. As a result, the parts and systems are mainly connected together by different types of screws. This is a cheap yet durable way to connect the parts together. In places where the durability is not as important, such as attaching the shield to the driveshaft, a plastic wingnut used to connect to the bolt reducing the cost of production even further. The system that has the greatest effect on keeping the cost of the product down is the cutting head. These parts along with the two grips are not exposed to heat and are therefore made of plastic as opposed to metal, which is the material used for the majority of the parts within the engine.

The shield is connected to the driveshaft in a position that protects the operator from the high rotating speed of the cutting head and from getting hit by any grass or other objects that go through the spinning line. The product also has a vertical grip that makes it easier and more convenient to hold. This handle along with the curved driveshaft causes less strain on the user thus allowing the trimmer to be used for a longer period of time. The use of plastic for the outer casing and grip also reduces the effect of the vibration that is caused by the engine, which keeps the operator from getting tired. Using plastic for these different systems make the string trimmer lighter in weight thus easier to hold. Within the engine, the larger parts are made of aluminum while the smaller parts are made of steel. This is because aluminum is 1/3 the weight of steel, which also helps make the trimmer easier for the operator to use. The overall design of the product allows for it to be easily and cause little strain.

Since the string trimmer has a two-stroke gas-powered engine, it releases emissions into the air making it not very environmentally friendly. However, the different systems are all made of plastic and metal, which can be recycled and reused. Since the connections between the systems are simple, a single part or system can be replaced without having to replace the entire product saving both money and materials. Utilizing non-permanent joints also greatly contributes to the simplicity of replacing parts - since the parts are screwed together and not soldered together, a broken part or system can simply be unscrewed from the surrounding parts and be replaced. This is especially evident in the engine where a component is most likely to break. Attached to the engine system is the throttle, which allows the operator to control the speed of the engine; a lower speed can be chosen which will release less emissions when not being used for heavy duty jobs.

The most obvious connection that affects global concerns is the fasteners, which are present in all of the systems but is most prominent in the engine. Weed Eater is an American company and therefore designs and manufactures its parts in English units limiting its use to only the United States. Although English unit tools are available in Canada and can be ordered by other countries, this product was designed solely for American use. This mainly pertains to the vast amount of socket head screws that can only be removed with an Alan wrench in English units. Weed Eater creates products to appeal for its target consumers: American homeowners.

Performance Influence on Connection Type

Performance not only influences the type of connection used, but it also influences the materials used. The connections are made mainly through fasteners. Since the engine gets hot during use, the fasteners are made out of metal that will not be effected by the heat. However, fasteners used on the vertical grip handle and the shield are held together by a plastic wingnut. Although one might think that this makes the product "cheap", the plastic is durable enough to effectively hold the parts in place. Metal fasteners in this case are not necessary because they are not being exposed to heat. The use of plastic also has an impact on the weight of the overall product, making it lighter. The foundation of the product is made of metal parts because they are exposed to the heat produced by the engine and are sturdy for long term use. The engine is directly connected to the head through the drive shaft with screws. This direct connection also for the energy to be transported efficiently with the loss of only a small amount of energy due to friction. The overall connection of the parts allows for the engine to only take up a small amount of space, which takes the use of the string trimmer into consideration. The smaller size of the engine makes the product easier for the operator to use.