Group 8 Gate 3

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Contents

Abstract

The purpose of this project gate is to document a detailed analysis of the Craftsman 16” 32cc chainsaw. The chainsaw was dissected and observations were made. From the observations, a thorough analysis of the design considerations for the chainsaw was developed. Design revisions were suggested to improve the overall functionality of the chainsaw.


Cause for Corrective Action

Overall, the project team works well together, the most significant challenges the group faces is lack of manpower. Initially the group started with five members, however before the project began, two members of the team were lost. The remaining three group members have had to take on several extra responsibilities in order for tasks to be completed on time. Due to conflicting schedules and other unforeseen circumstances, much more time than initially anticipated was required for completion of this gate.

The group has responded to this issue by adjusting the work schedule on a day-to-day basis. All tasks are completed by the group now in a collective effort rather than individual tasks being assigned to each person. The group worked more individually based of their schedules rather than trying to all meet up together to work.

Overall the productivity of the group has improved by reevaluating the time management and work schedule. The intent is to proceed to completing gate 4 in a similar manner.


Product Archaeology and Evaluation

Component Summary

Table 1: Component List
Component # Image And Name Function Material Manufacturing Process Model or Part # Other Information
1
Figure 1: Handle
Allows user to hold onto, carry control, and direct the chainsaw. Plastic Injection Molding 530-057888 Wraps around from top a chainsaw to side. Screwed to body with four #2 screws.
2
Figure 2: Screw
Used as a fastener to hold parts together. Steel Forged, Threaded, and Machined 530-016432 Used several times in the entire chainsaw mainly to fasten large parts together like the Handle and the Pull Start component. Designed to be used by star or flat head screw driver. Fully threaded.
3
Figure 3: Bar Knob
Screws down and locks chain bar in place. Loosened for chain adjustment. Plastic molded around metal nut. Injection Molding 545-035001 Several parts connected by steel bar. Small spring allows level to lock knob into place rotationally. Nut is placed in center to allow to screw down and secure chain bar. A small red level is used to lock down the the knob.
4
Figure 4: Tightener and Case
Whole part is held in place by the Bar Knob. User driven screw can be adjusted to control the chain bar. Plastic and Steel Injection Molding and Die Casting 545-027601 Large plastic case holds steel piece where screws go into to secure it to chainsaw body. Steel hook is threaded to ride along screw which moves chain bar left or right according to user input of the screw.
5
Figure 5: Chain
Provides the teeth for removal of material. Steel Punched, Riveted, and Machined 71-3629 Several pieces are punched out and riveted together.
6
Figure 6: Chain Bar
Provides guide for chain. Steel Punched and Heat Pressed. Gear is riveted. 530-044692 Three flat pieces heat pressed together with a flat chain gear riveted down between two outer pieces.
7
Figure 7: Chain Bar Spacer
Provides space between chain bar and chainsaw body. Steel Punched and Shaped 530-057910
8
Figure 8: C Clip
Holds down washers and clutch drum onto crankshaft. Steel Punched 530-071945
9
Figure 9: Washer
Provides space between C clip and chain washer. Steel Punched 530-071945
10
Figure 10: Chain Washer
Large washer keeps chain on drive gear. Steel Punched and Shaped 530-071945
11
Figure 11:Clutch Drum - Drive Gear
When clutched is engaged the drum/gear turns which drives the chain. Cast Iron Die Casting 530-057905 Clutch drum and gear is molded into one single piece which moves freely around crank shaft.
12
Figure 12: Centripetal Clutch
The centripetal clutch is the the part that drives the gear to drive the chain. At a certain speed of the crankshaft the centripetal force over comes the force of the spring holding in the arms which allows the arms to open up and contacts the inside of the clutch drum. When that happens the clutch drum begins to spin and therefore the chain. Cast Iron Investment Casting and Machined 530057907 Two arms are held down by a spring. The Clutch is fixed to the crankshaft and turns as the crankshaft does.
13
Figure 13: Pull Start Casing
Covers pull start mechanism and fly wheel. Plastic Injection Molding 530-058817 Holds the pull start mechanism in place. Held down by four #2 screws (part #530-016432).
14
Figure 14: Pull Start Mechanism
Allows user to manually start the chainsaw. Plastic, Nylon Rope, Steel Injection Molding, Drawing and Weaving, Forged respectively 545-05820 Nylon rope wraps around and is connected to a plastic wheel which turns the flywheel in one direction. A plastic handle is at other end of rope to allow user to pull.
15
figure 15: Top Casing
Covers and protects top of chainsaw. Plastic Injection Molding 530-058838 Held in place by three #2 screws (part #530-016432).
16
Figure 16: Safety Clutch
When engaged the device tightens a metal band around outside of the clutch drum locking the chain in place. Plastic and Steel Injection Molding, Punched, Shaped, Riveted 530-057899 Lever mechanism pulls the band tight when the safety clutch bar is pulled into position. Used to lock chain down when the chainsaw is running to adjust bar or other settings. Held in place by four #2 screws (part #530-016432).
17
Figure 17: Safety Clutch Lever
Controls safety clutch and protects user from large debris. Plastic Injection Molding 530-057897 Held in place by two plastic rods protruding from chainsaw body.
18
Figure 18: Air Filter Cover
Protect air filter from large debris and holds filter in place. Plastic Injection Molding 530-058687 Snaps into place.
19
Figure 19: Air Filter
Filters incoming air for combustion. Polyurethane Pressed 530-057925 Mesh of polyurethane threads.
20
Figure 20: Air Filter Screw
Holds Air Filter Casing to the Carburetor. Steel Forged and Threaded 530-016425
21
Figure 21: Air Filter Nuts
Holds the Air Filter Casing and the Carburetor to the Carburetor Adapter. Steel Injection Molding and Threaded 530016101
22
Figure 22: Air Filter Casing
Holds filter in place. When screwed down it holds the carburetor in place. Also is the base for the kill switch mechanism. Plastic Injection Molding 530-057892 Held in place by a #19 screw (part #530016425) and two #20 nuts (part #530016101).
23
Figure 23:Kill Switch
When pressed down it completes a circuit making electricity flow through that instead of the spark plug killing the engine. Plastic Injection Molding 530-057891 Screwed down onto air filter casing.
24
Figure 24: Trigger Bar
Connects the trigger to the carburetor to control throttle. Steel Drawn and Shaped 530-057909 Slides into slots and is held in by pressure.
25
Figure 25: Choke Lever
Controls the choke. Plastic Injection Molding 530-057893 Slides into slot and is held down by Air Filter Casing and Chainsaw Body.
26
Figure 26: Carburetor
Controls air intake. Steel and Brass Die Casting, Punching and Machined 545-070601 Rods turned by choke and trigger bar control circular plates which alter airflow into combustion chamber. Springs surround rods restoring air flow to idle when not in use. Fastened down by the air filter casing.
27
Figure 27: Primer
The Primer is used before the engine is started to import gas into the carburetor. This allows the engine to immediately start once the Pull Starter is pulled because gas is immediately imported into the combustion chamber. Plastic Injection Molding 530047721 The primer is connected to two tubes once form the Gas Tank and one to the Carburetor. The bulb itself snaps into the side of the chainsaw body.
28
Figure 28: Carburetor Adapter Screw
Holds the Carburetor Adapter to the Engine Block. Steel Forged and Threaded 530016426
29
Figure 29: Carburetor Adapter
Transfers air from carburetor to combustion chamber. Plastic and Rubber Injection Molding 530-057748 Held down to engine block by four #26 screws (part #530016426).
30
Figure 30: Spark Plug
Creates spark inside combustion chamber to ignite fuel. Sintered Alumina, Nickel, Steel Investment Casting R7
31
Figure 31: Cord Clip
Holds wires to Engine Block. Steel Punched and Shaped 530-016136
32
Figure 32: Ignition Mechanism
Magnets in the fly wheel pass this apparatus and create a current which allows the Spark Plug to fire. Wires transfer the current from the mechanism to the Spark Plug and to the Kill Switch. Plastic and Copper Punched and Die Casted 530-039238 The kill switch is also connected this. When the kill switch is engaged the current passes through that instead of the spark plug stopping the combustion cycle. This mechanism in held down by two #2 screws (part #530-016432) very close to the flywheel.
33
Figure 33: Cords
Wires transfer the current from the mechanism to the Spark Plug and to the Kill Switch. Copper and Plastic Drawn 530-071905 and 530-057943
34
Figure 34: Flywheel Nut
The Flywheel Nut screws done onto the crank shaft holding the Flywheel to the crank shaft. Steel Forged and Threaded 530-021179
35
Figure 35: Flywheel
Tranfers energy from the pull start to start the engine. Also provides the motion of magnets that pass the Ignition Mechanism to create a current. Fins come off which moves air by the engine block keeping it to a controllable temperature while in use. Iron Die Casting 530-071905 Two small steel arms made by Punching and Shaping are on two rivets attached to the flywheel. Springs keep them against the starter mechanism to allow them to catch and turn the flywheel. When the flywheel is in motion after the engine starts the arms are allowed to pull back from the starter.
36
Figure 36: Engine Block Screws
Holds the Engine Block together and to the chainsaw body. Steel Forged and Threaded 530-016417
37
Figure 37: Engine Block
The Engine Block\'s function is to provide a combustion chamber where the burning of the fuel can occur. It also provides a path for the piston to follow and an area for the crankshaft to attach and operate. In addition at completes a circuit for the Spark Plug to fire and areas for the Cord Clip, Spark Plug, Muffler kit and Carburetor Adapter to attach to it. It is fastened to the chainsaw body by four #36 screws (part #530-016417). Steel Die Casting and Machined 530-071884 and 530-057941
38
Figure 38: Piston
Rides inside the Engine Block and is pushed by the energy produced by combustion and transfers that energy to the Crankshaft. Steel Die Casting, Machined, and Turning 530071883
39
Figure 39: Crank Shaft
The Crank Shaft takes the linear energy from the piston and converts it to rotational energy turning the Flywheel and Centripetal Clutch. Iron and Steel Middle portion and Die Casted Iron and the shafts that extend out connecting to the Flywheel and Clutch are Lathed the Threaded Steel. Some portions are Machined. 545-112901 The whole Crank Shaft resides in the bottom of the Engine Block and is lubricated by the oil in the gas/oil mixture used as fuel.
40
Figure 40: Muffler Screws
Holds down the Muffler, Muffler Shield and Muffler Spacer to the Engine Block. Steel Forged and Threaded 530-016338
41
Figure 41: Muffler Shield
The Muffler Shield protect the Muffler from overheating. Steel Punched and Shaped 530-057942
42
Figure 42: Muffler Spacer
Provides a space between the Muffler and Muffler Shield. Lead Punched 530-071894
43
Figure 43: Muffler
Dampens noise created by the engine and transfers exhaust away form the combustion chamber. Steel Punched, Shaped and Welded 545-006007 This is not covered by any kind of casing.
44
Figure 44: Muffler Nut
Holds down the Exhaust Director and Spark Arrestor to the Muffler. Brass Forged and Threaded 545-006056 Screws down onto a bolt extruding from the Muffler.
45
Figure 45: Spark Arrestor
Catches all sparks or flame from the combustion Chamber and eliminates them. Brass Drawn and Weaved 545-006056 The Spark Arrestor is a screen of brass wire.
46
Figure 46: Exhaust Director
Directs exhaust from the muffler to the right of the user. Steel Punched and Shaped 545-006056
47
Figure 47: Chainsaw Body
Provides a structure for various components of the chainsaw to attach to it. Also creates a chamber for the Gas and Chain Oil. Plastic Injection Molding 545-028307 Two Halves snap together.

Product Analysis

Complexity Scale

1- Not complex

2- Fairly Complex

3- Very Complex

Chain Bar

\'\'\'Component Function:\'\'\'

The chain bars function is to hold the chain as it turns and acts as the extended cutting portion of the chainsaw. The chain bar is held on by the bar bolts that come out and attach to the bar knob which tightens the chain. It functions on the outside of the chainsaw very close to the cutting area.

\'\'\'Component Form:\'\'\'

The chain bar is a two-dimensional object that is an elongated oval. It has notable properties of symmetry because the chain must smoothly turn around it. The chain bar is 16 inches long, the width is 3/16 of an inch and the height is 2.5 inches. The components shape is tapered at the end to allow smooth movement of the chain around it. It weighs about 2 pounds and is made of painted steel. It needs to be made of a strong material like steel because the chain bar requires a lot of force to be used against it while cutting. If it weren’t a strong material then it would bend when the force was applied for an extended amount of time. When producing the chain bar, economic factors of producing the chain bar in mass production must be taken into account. Steel is not very expensive when mass-producing something and produces the right strength for the amount of force used.. The chain bar is painted black because Craftsman wants to keep the colors consistent throughout the whole chainsaw. The chain bar has a smooth and clean finish to it for aesthetic reasons. If it were a plain steel color it would not look as uniform and proper compared to the logo and brand reputation they have kept.

\'\'\'Manufacturing Method:\'\'\'

The manufacturing process that was used to make this part was heat pressing. From the look of it, there is 3 pieces of steel heat pressed together with an internal piece of steel that is smaller in height and length to create a groove for the chain to run around. When looking at it flush, there are marks on it that shows where the press was used and there are signs of where the steel has been welded together.

\'\'\'Component Complexity\'\'\'

The chain bar was a rated at a complexity of 1 because it is not complex. The component is two dimensional and very simple without any other internal or external components. The chain bar is just attached to the chainsaw via bar bolts and then the chain is wrapped around it.

Chain

\'\'\'Component Function:\'\'\'

The function of the chain is to turn at a high speed around the chain bar to cut into the object. The flow that is associated with the chain is the energy from the gear function. The chain does not have multiple functions; its main use is just to cut whatever object is needed to be cut. The component can function in any environment because it is made to be used all year long to cut wood outdoors when needed.

\'\'\'Component Form:\'\'\'

The general shape of the chain is a strand of hinged components all attached to one another to create a loop of chains. Each individual cutting link has one blade angled to cut to the left of the chain bar and the other has a blade angled to cut to the right of the chain bar. It is primarily two-dimensional because it is steel that has been punched out. Each individual cutting link is about a half-inch and the chain as a whole is around 32 inches long because it has to wrap around a 16 inch chain bar. The shape of the cutting links are angled so that they can cut through anything being that one is angled in one direction and the next is in another direction. The chain is made from stainless steel cutting links and then held together by rivets. The chain itself is about a pound in weight, which makes the external load of the chain bar and chain together about three to five pounds. The chain is made from stainless steel because it needs to be able to withstand high speeds and pressure to cut wood. Also the chain is made from stainless steel so it can be sharpened when it becomes dull and worn down. This is an economic factor because it is a cheaper material to mass produce and can be reused because it can be sharpened. Also it is affected by an environmental factor because it needs to be able to cut through wood all season long, so the wood can be wet from rain or snow and other weather changes. There are no aesthetic properties that have been changed on the chain. This means after the chain was manufactured nothing else was done to change its looks. If it were painted the paint would quickly wear off during use.

\'\'\'Manufacturing Method:\'\'\'

The individual cutting links are made from a press machine that stamps them out of steel. After they are all stamped out, rivets attach all the cutting links. There is most likely a machine used to punch the rivets because they mass produce the chains and it would take a long amount of time to individually attach each link together by hand. They are made out of stainless steel because they need to be able to cut through wood and have a high strength, while keeping an edge. They also need to be sharpened once they are dull and stainless steel is a metal that can be sharpened with ease. The chain also needs to be able to withstand moisture and other environmental factors because it is used outdoors for the most part. It needs to be able to avoid rusting so the chain can function properly.

\'\'\'Component Complexity:\'\'\'

The chain is rated at a 2 for complexity because it is fairly complex. It does not have different components within it but how it’s made and operates is fairly complex. Each cutting link has a shape and has to be able to pivot around the tapered end of the chain bar. The cutting links are held together by a lot of rivets, which make it more complex.


Pull Start

\'\'\'Component Function:\'\'\'

The function of the pull start is when pulled it starts the engine. It does this by pulling on a rope that\'s wound around a spring-loaded pulley. When you pull the rope out, the pulley engages the clutch on the crankshaft of the engine and spins the crankshaft to start the engine. The flows that are associated with this is the convert crankshaft function, which turns into rotational energy. This component can function in any environment.

\'\'\'Component Form:\'\'\'

The shape of the pull start is a little complex. The pulley is circular with a plastic shell around it. The pulley needs to be circular so the cord can wrap around it. The pulley itself is about 3 inches in diameter and an inch in width. The shell surrounds it and has a hole for where the cord runs through to the external part of the chainsaw. The pulley is three-dimensional and is symmetric. The component as a whole with the casing and cord weigh about a pound. The pulley is made from a plastic and the cord is made from nylon. There is a screw and cap in the center of the pulley to allow for it to turn. For this pulley to be functional, it needs to be light and able to spun with a hard force coming from the cord. When looking at the pulley, it is made from plastic, which is a cheap material to make especially when mass producing from injection molding. This is an economic factor and it also has a societal factor of being incased within the chainsaw because it could be a safety hazard if ones hand got caught in the pulley as the cord is being snapped back. The component is white and the casing is black, the pulley is white and not painted because the user can’t see it from the outside but the casing Is painted black to keep the look of the all black Craftsman chainsaw which is aesthetic.

\'\'\'Manufacturing Method:\'\'\'

The pulley and casing were made from injection molding, like most of the components on the chainsaw. It’s economically smart and is mass produced by Craftsman. Its shows signs of injection molding by part lines and riser marks on the pulley. Material choice impacted this decision because the material needed to be light and cost efficient and plastic is the perfect choice for that and the function that it needs to produce.

\'\'\'Component Complexity:\'\'\'

This component is rated at a 2 because it is fairly complex. It involves a pulley that has a string wrapped around it and a spring that makes it pull back.

Centrifugal Clutch

\'\'\'Component Function:\'\'\'

The outside portion of the clutch free spins, while the inside portion is connected to the crankshaft and operates centrifugally. The clutch is composed of a spring, two counterweights and two friction pads. The spring holds the counter weights in while it is idling at low rpm’s and then as the Rpm’s increase the counter weights exceed the spring and slides outward, applying friction to the outer housing.

\'\'\'Component Form:\'\'\'

The general shape of the centrifugal clutch is circular. The internal weights and friction pads are half circles are separated by a spring that is circularly wrapped throughout it. Both friction pads and weights are symmetrical because they need to balance each other out to get an even spin on the clutch. The clutch is three-dimensional because the spring is rounded and the internal components have width to them. The clutch as a whole in diameter is about 4 inches and the components are within it. The components shape is a circle because the function is to spin. The clutch is made from steel because it needs to be strong enough when connected to the crankshaft. The spring is made of steel too and is wound in a certain way because it needs to have a specific spring coefficient in order for the clutch to work properly. The color of the component is the basic unfinished steel. The clutch has a smooth finish because the friction pads need to be smooth and uniform when rubbing against the housing. None of the components of the clutch are painted because they are hidden within the housing and casing in the chainsaw.

\'\'\'Manufacturing Methods:\'\'\'

The components of the clutch are made by die casting. Each part shows signs of machining too, to get dimensional accuracy of the part. The spring is made by being wound by a machine in order to create the right spring coefficient for the clutch to engage at a certain rpm.

\'\'\'Component Complexity:\'\'\'

The clutch as a whole is a complex component and an important one in the operation of a chainsaw. The clutch is rated at a three for complexity because of its internal components and the accuracy that each part needs to be for it to run properly. The clutch has three different internal components with the inner part of the clutch connected to the crankshaft, which is a very important part of the chainsaws engine.

Fly Wheel

\'\'\'Component Function:\'\'\'

The function of a Flywheel is to control the speed of the engine and at the same time cool the engine. The flywheel is weighted to help control the speed. The fins on the flywheel allow for airflow to be pulled into the engine and cool it down.

\'\'\'Component Form:\'\'\'

The flywheel is a weighted circular wheel with fins and has symmetry to allow for it to spin evenly at high rpm’s. The flywheel is three-dimensional and has a diameter of 4 inches and depth of 2 inches. The fins are all evenly spaced out to receive the proper airflow to cool the engine down. The flywheel weights roughly a pound to two pounds and is made from aluminum. The flywheel is made of aluminum to be light while still holding strength properties of metal. The flywheel is an important component because it regulates the engines speed. The color of the component is silver and is not painted because it is an internal component of the chainsaw. The flywheel has a smooth finish to allow maximum airflow and speed when spinning.

\'\'\'Manufacturing Method:\'\'\'

When looking at the flywheel, it shows signs of die casting from its riser marks. Since it is made of aluminum die-casting would be the most effective and cost efficient way to mass-produce this. It shows signs of good part detail and a fine surface finish, along with high dimensional consistency on the fins.

\'\'\'Component Complexity:\'\'\'

When evaluating the flywheel on its complexity, it has been determined that is it rated at a 1 for not complex. It is a circle with fins that exceed outward toward the user in order to draw in air to cool the engine. There are no internal components and it is one solid piece made from aluminum.

Carburetor

\'\'\'Component Function:\'\'\'

The function of the carburetor is to accurately mix tiny quantities of fuel and mix it with the air coming into the engine to allow for it to run smoothly. If there is not the right amount of fuel mixed with the air, the engine will not run properly and can become damages. The carburetor is a very important component of the chainsaw because it is directly connected to the main component, which is the engine.

\'\'\'Component Form:\'\'\'

The shape of the carburetor is a not a simple one and is mainly a square with fuel lines and different screws and components coming off of it. It is about a 2.5 inch square on each side and has a faceplate that is attached. The carburetor is mostly made of aluminum except for the throttle plate, which regulates the airflow. The throttle plate is made up of brass because of its shiny gold color and shiny finish. The carburetor itself has the normal silver finish to it and is smooth to the touch as well. As a whole the carburetor weights a little less than a pound when the fuel lines are detached. When manufacturing the carburetor, it needs to be cost efficient and light to cut down weight throughout the chainsaw. It has to hold properties of metal to be able to withstand high heat but not as much as steel because the air coming in will help cool the aluminum down as well.

\'\'\'Manufacturing Method:\'\'\'

The carburetor shows signs of being die casted due to its high dimensional accuracy and part lines. Some portions of the carburetor show signs of being machined to get the right hole sizes for fuel lines and other components to fit in. The throttle plate within the carburetor looks to be machined due to its very smooth surface finish and small dimensions. When assembly the carburetor, it could be done by hand or machine but for some components like attaching fuel lines, it would probably be easier to inspect and make sure that it would run properly if some of the components were attached by hand. While concluding this, it could be said that the cost in producing a carburetor would be higher than most of the other components in the chainsaw because it is made of a few different materials and needs to be looked at closer to make sure it will perform the task that is needed. This is an economic factor when producing the chainsaw because having human labor and inspection, over a machine just manufacturing it would make the component cost more.

\'\'\'Component Complexity:\'\'\'

When rating the carburetor on its complexity, it has been determined to be a 3 because it is a very complex component. Its task is a couple different functions and has different components within it to be able to make sure that the air intake and fuel intake is the proper amount for the engine to run smoothly. This component is a very important one in the overall design of the chainsaw.

Engine

\'\'\'Component Function:\'\'\'

When the engine starts up, it moves the piston and that’s what moves the crankshaft. The piston moves up and down which makes the crankshaft rotate. The crankshaft moves the clutch, which is connected to the chain and chain bar. The engine is the main source of power and the most important component of the chainsaw. The engine is designed to work in all conditions, from the heat to the freezing cold and uses oil to lubricate it so it can always have easy motion.

\'\'\'Component Form:\'\'\'

The general shape of the engine is a rectangle with cooling fins. It is a three dimensional component with dimensions of 6 inches in width and 8 inches in height. The engine block is a rectangle because it has to house the piston that moves up and down within it. The engine is a 2-stroke engine and is small and simple because it needs to fit within the casing of the chainsaw. The engine block weights about 3 pounds and is made of aluminum. The engine block needs a specific material property of being light to cut down on weight of the chainsaw, while being able to withstand high heat coming from the piston. A societal factor of the engine is it needs to be able to house the piston without it breaking the engine block and causing damage to the user and the rest of the chainsaw. It has cooling fins to try and cool the engine heat down and it is not painted any color besides the natural color of the metal because it is within the chainsaw and cannot be seen from the outside.

\'\'\'Manufacturing Methods:\'\'\'

The engine block was done by die-casting and some machining where the fins are. The internal parts of the engine, including the piston are made from die casting and machining too. These pieces need to be machined in certain places in order to get the correct dimensions for the engine to run smoothly. The shape of the engine impacts why it was die casted because it would take too long and cost too much money for it to be machined by hand for every chainsaw. It is more cost efficient for an engine block to be die casted for mass-production.

\'\'\'Component Complexity:\'\'\'

The engine is a very complex so it’s rated at a 3. The engine is the most important component in the chainsaw because it’s where all the power comes from to move the chain. When looking at the chainsaw it has an engine block, piston and crankshaft, which are all separate components, which make up the engine and have it run properly.

Handle

\'\'\'Component Function:\'\'\'

The function of the handle is to allow the user to comfortably hold the chainsaw and use it for guidance when applying pressure to whatever material is being cut. The handle is made to be durable and strong during all seasons.

\'\'\'Component Form:\'\'\'

The handle is in the shape of a U and it has symmetry in order for the user to adjust their hand position throughout it. It is primarily 2 dimensional and has dimensions of 9 inches in width and 4 inches in height. It connects to the main base of the chainsaw and allows movement forward and back to activate the kill switch. This is a societal factor because it is a safety feature for the user to stop the chainsaw if is needed without having to remove his/her hand from the handle. The handle is made from plastic and is painted black to match the rest of the Craftsman design. It has a smooth finish for functional reasons, so the user can hold it comfortably. The handle is made from plastic because it is a cheaper and lighter than using metal and can still be strong enough for the amount of pressure that would be applied.

\'\'\'Manufacturing Methods:\'\'\'

When manufacturing the handle, it can be seen that is made from injection molding. There are part lines and riser marks throughout. It would be cost effective to use injection molding because the same mold can be used for when mass-producing the handle. The plastic is very strong and solid and has a very trusting feel to it so the user cannot worry about dropping it or the handle cracking.

\'\'\'Component Complexity:\'\'\'

The handle is not a complex component and is rated at a 1. This being said does not mean that it is not an important component. It serves a dual purpose of allowing the user to hold the chainsaw comfortably and also as a kill switch when pressure is applied to push it forward. It is one of the more important components because it allows the user to be able to hold the chainsaw without holding the body directly.

Spark Plug

\'\'\'Component Function:\'\'\'

The function of a spark plug is to create spark and ignite the fuel in the engine to start it. This component is important is starting the engine and the overall function of the chainsaw. The spark plug is associated with the spark plug function, which its input is energy and its output is spark.

\'\'\'Component Form:\'\'\'

The shape of a spark plug is a cylindrical shape that has threads on the end of it, which screws into the engine block. The spark plug for the chainsaw is 2.5 inches in length and a half of inch in width. The component is a three-dimensional shape because it is cylindrical and it is also symmetrical. The component is very light because it is a small component that is half made ceramic and the other half is threaded copper because it is a good conductor of electricity. Between the copper and ceramic parts of the spark plug, the central part of the spark plug is steel and the tip is made of alumina. The ceramic part of the spark plug serves a purpose to be an insulator to prevent the spark plug from shorting. The spark plug has a societal factor associated with it, being it is partially made of ceramic, which stops the spark plug shorting out and causing a fire within the engine and chainsaw. The components has a white ceramic color and has the natural colors of the copper and steal. The component is not painted because it is internal and attached to the engine block, which isn’t seen by the user.

\'\'\'Manufacturing Methods:\'\'\' The spark plug contains several parts that were all forged in some way. The outer casing is also threaded to allow for it to screw down onto the engine block. Also many parts of the spark plug are machined very precisely to ensure they fit together properly when pressed together and so they can operate smoothly under high temperature like the inside of an engine.

\'\'\'Component Complexity:\'\'\'

The spark plug is a fairly complex component that is composed of a few different materials, which is why it is rated at a 2. It’s a small component but still serves a lot of purpose in the overall function of the chainsaw.

Muffler

\'\'\'Component Function:\'\'\'

The function of a muffler is to dampen noise that is created by the engine and transfer exhaust away from the combustion chamber. The muffler is part of the export muffler function and its input is noise, heat and exhaust. The muffler exports heat, exhaust and less noise.

\'\'\'Component Form:\'\'\'

The shape of a muffler is a three-dimensional component with a rectangular shape and rounded edges. The dimensions of the muffler are it is 2.5 inches in length, 1.5 inches in width and 3 inches in height. The components material is steel and has to have qualities of being able to withstand high heat without melting. The muffler is hollow so it does not weight much but it weights roughly less than a pound. When developing the muffler there is a societal factor taken into account because the manufacturer wants to dampen as much sound as possible coming from the chainsaw to make it better for the user and the people around the user. It also transfers the exhaust away from the combustion chamber to avoid the chainsaw from blowing up and causing harm to the user. The color of the component is the natural color of steel and has a smooth finish to it because of the way it was made.

\'\'\'Manufacturing Method:\'\'\'

The muffler was made by being punched out of steel and then shaped. There are two sides of the component so each side is punched and shaped and then welded together to form one solid component. This manufacturing process is used because the inside of the component is hollow to dampen sound.

\'\'\'Component Complexity:\'\'\'

The muffler is not a complex component, which is why it is rated at a 1. The muffler serves a societal purpose to dampen the sound and transfer exhaust away from the combustion chamber. It is a simple component that is very effective and important in the overall function of the chainsaw.



Solid Modeled Assembly

The following six figures were made in Autodesk Inventor Professional 2010. This program was chosen because the group member assigned to design the parts already has the program installed on his laptop and was thoroughly prepared to use it from past experience last year and from high school. The Clutch component of the chainsaw was chosen because it did not involve complicated geometry and could be easily assembled and dissembled. Figure 48 through 51 contains the parts mainly involved with the clutch. The spring has been left out due to the complexity of its design. The spring would lie in the channel in the clutch arms underneath the inner clutch. Figure 52 shows the clutch as it operates inside the chain saw and figure 53 presents how the parts are assembled into each other.

The following zip folder contains all of the six files shown below. Group_-8_CAD_Files.zip


Figure 48: Crank Shaft
Figure 49: Clutch Drum - Drive Gear
Figure 50: Inner Clutch
Figure 51: Clutch Arm
Figure 52: Assembled Clutch
Figure 53: Exploded Clutch
























































































































































Engineering Analysis

One vital component of the chain saw is the centripetal clutch. Centripetal forces expand the clutch as it spins while spring forces resist the expansion. Selection of a spring with an adequate spring coefficient is vital to ensuring the clutch works properly. Too strong of a spring will not allow the clutch to expand as well as too weak of a spring will not keep the components of the clutch held together. Below shows the engineering analysis for how an adequate spring coefficient is determined.

Problem Statement:

Determine the spring constant of the spring in the centripetal clutch.

Diagram:

Figure 54


\'\'\'Symbols:\'\'\'

Fc- Centripetal Force

Fs- Centripetal Force

ω- Angular Velocity

Assumptions:

1) The throttle is engaged only enough to begin spinning the chain

2) Clutch is fully extended to the inner diameter of the gear drum.

3) The centripetal force that extends the clutch is equal to the centripetal force at the throttle specified above.

4) Neglect all friction.

Governing Equations:

ƩF=Fc-Fs=0

Fc=Fs

mrω^2=kx

k=(mrω^2)/x

Design Revisions

Based off the analysis of the chainsaw, three design revisions have been suggested:

1. The engine is a 2 stroke engine. As a result of this the fuel must be mixed with oil in order to lubricate the engine. As a result, emissions from the exhaust include gas and oil which has negative effects on the environment. This type of engine increases the cost to the user as well. Every time the user fills the gas tank, the cost includes gas and oil. To reduce emissions and user costs, the use of a four-stroke engine will allow for this. The oil does not have to be mixed in with gas which reduces fuel costs for the user and burns cleaner than a fuel-oil mixture.

2. The rip cord is required to start the engine. This requires a work input from the user where moderate physical strength is needed. In order to make the input from the user easier, it is suggested that an electric starter is added to the chainsaw. The addition of the starter relieves fatigue on the user which creates additional appeal.

3. The current position of the kill switch requires the user to have let go of one of the handles in order to push the kill switch. This creates a potentially hazardous situation for the user where the awkward hand positioning could lead the blade to swing toward the user, leading to injury. To prevent this, it is suggested that the kill switch should be moved to the handle near the throttle. This allows the user to keep both hands firmly on the handles and the ability to kill the engine safely.





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