Revision as of 17:02, 16 November 2012

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Now that our chainsaw is dissected, we will look individually at each part, evaluate their purpose and how they were made. We will catalog every dissectible part with essential parts will be more closely scrutinized. We will model the drive train to better show how it works. We will also consider the chainsaw weaknesses and suggest design revisions.

Cause of Corrective Action

The group has been working together for several weeks now. During this time, problems have arisen and been solved and new problems have come up and been dealt with. This section reviews both the problems during this project and how the group has worked thus far.

Project Analysis

Working in a group can be a good way to accomplish a task, but it also comes with its own types of problems. For example if one member is not fulfilling his share of work, then it becomes a burden on the whole group. One of the members of the group has a very busy schedule and it is difficult for him to make it to all of the meetings. Because of that, he doesn't always pull his weight. To overcome this problem the rest of the group as a whole had to work harder. This problem was not apparent initially because at this point, we did not give each member specific jobs to accomplish; we instead worked together on each section as a group. To address this problem we gave each member of the group a specific task, realizing that some of the members of the group are very task oriented and need specific duties.

One of the obstacles for this gate was that the work load put upon us was very large during the time this project was needed to be worked on. This is not an excuse for poor work but merely an obstacle that needed to be overcome. To overcome this problem we consolidated our work time into a few days so that the other days could be concentrated on other work.

Another obstacle that occurred was a technological problem. Our CAD technician had trouble accessing the program due to lab scheduling and lack of access to the computers containing said program. He attempted to solve the problem a few different ways before finding the appropriate solution. He downloaded Autodesk Inventor from the company website onto his computer so that he could work on the solid modeling on his own time.

One obstacle that may arise for Gate 4 is the fact that Thanksgiving break occurs right in the middle of the time when we would be working on the gate. There are a few ways to fix this problem. First each member of the group could be given a task to accomplish over the break and they will be expected to have that done by the time they come back from break. Another way to overcome this obstacle would be to collaborate on the project on a single file such as a Google Doc or even on the Wiki itself. Either one of these options will be employed to overcome the obstacle that Thanksgiving break will create.

Component Summary

Evidence of Manufacturing Methods

Die Casting- Metal part with parting lines, draft and riser marks

Injection Molding- Plastic part with parting lines, draft and riser marks

Investment Casting- Molded part with no parting lines. Riser marks and undercuts are possible

Rolling- Any flattened sheet of malleable substance

Forging- Metal part with flash. normally flash shows evidence of being filed down

Extrusion- Metal part of constant shape over an extended length

Drawing- Metal part in thin, drawn out shape such as wire

Sawing- Saw markings on cut side of manufactured part

Turning- Symmetrical shape about a single axis

Milling- Any sort of intricate design having been cut into part

Grinding- Smooth, clean finish, often times used as a secondary method to file down flashes or other small imperfections

Components

#	Component Name	Image of Component	Part #	# of Times Used	Function	Materials Used	Manufacturing Processes Used
1	Flathead Screw		N/A	1	This specific screw was used to connect the handle and the body of the chainsaw together, while allowing it to be disassembled if required.	Steel	The head was forged, and the threads were added using thread rolling.
2	Oval Head Screw		N/A	1	This screw was used to hold the trigger throttle screw in place, while allowing it to be disassembled if required.	Steel	The head was forged, and the threads were added using thread rolling.
3	Allen Screw		N/A	4	These screws were used to hold the filter in place , while allowing it to be disassembled if required.	Steel	The head was forged, and the threads were added using thread rolling.
4	Fillister Screw		N/A	2	These specific screws were used to hold the front and side casings in place, while allowing it to be disassembled if required.	Steel	The head was forged, and the threads were added using thread rolling.
5	Pan Head Screw		N/A	4	These specific screws were used in the intake casing and the alternator, while allowing it to be disassembled if required.	Steel	The head was forged, and the threads were added using thread rolling.
6	Hex Cap Screw		N/A	13	These specific screws were used to hold all the casings, handle, and drive shaft in place, while allowing it to be disassembled if required.	Steel	The head was forged, and the threads were added using thread rolling.
7	Hex Bolt		N/A	4	These specific screws were used to hold the casings, and handle in place, while allowing it to be disassembled if required.	Steel	The head was forged, and the threads were added using thread rolling.
8	Plate Washer/Washer		84520-01	3	Acts as a seat for the screw that goes into the brake handle.	Stainless Steel	The primary manufacturing process used to make washers is called stamping. There may have also been some additional heat treating, and surface coating of gold metal.
9	Spacers		N/A	2	To hold screws and bolts in place.	Aluminum	This component was made through extrusion, then cutting.
10	Nut		N/A	5	To fasten in bolts and screws.	Steel	This component was made through forging, and then threads were added using thread rolling.
11	Chain		N/A	1	Uses rotational energy to cut through materials like wood, etc., with it's numerous small blades.	Steel	The individual links were die casted separately. These links were then joined together by machine.
12	Muffler		215411	1	Quiets the sound of exhaust.	Steel	Exterior housing was cast in a die in two separate sections and then the edges were welded together to form a permanent connection.
13	Exhaust Deflector		92961	1	It Is placed over the muffler. It prevents from an excessive amount of exhaust to come out of the chainsaw all at once.	Steel	The muffler cover was forged.
14	Choke Knob		83870	1	Its purpose is to restrict the flow of air, there by enriching the fuel-air mixture while starting the engine.	Black Plastic	This component was processed through injection molding.
15	Trigger Throttle		217909	1	When the trigger throttle is pressed, more gas is introduced to the engine, causing the engine to speed up, and for the centrifugal clutch to connect the engine to the cutting action. When the operator takes their finger off the throttle trigger the engine returns to idle speed, and the clutch automatically disconnects the engine from the cutter.	Black Plastic	This component was processed through injection molding.
16	Magneto		217030	1	The spark plug wire conducts spark energy from the ignition source to the spark plugs. It converts the rotational energy of the flywheel, which has magnets on it, into alternating current. There is a ground wire that when the switch is closed, provides a path of lower resistance. This stops the spark plug from receiving power keeping the engine off.	Steel, copper and rubber. The wires were drawn out through a manipulative process then wrapped in rubber tubing and heat shrunk. The actual magneto contains a coil of wire and an aluminum casing which was also wrapped in rubber and heat shrunk.	The rubber parts were made with injection molding. The metal piece was forged. Unknown processes may have been used to manufacture internal parts.
17	Oil Tube		N/A	1	Connects the gas tank to Carburetor to transfer oil.	Rubber	This was made from an extruder and sliced to length. The straight tube was then put around a mold and heated till it assumed the mold's curved shape. A hole is then cut in the side of a straight piece of tube and then the two pieces were then molded together under high heat.
18	Oiler Rod Lever		217759	1	Pumps oil onto the chain.	Steel	A long wire of steel was forged and sliced into lengths. The wire was then bent into the desired shape.
19	Trigger Return Spring		83940	1	Pumps oil onto the chain.	Steel Alloy	The metal wire was processed by drawing. The wire was coiled into shape.
20	Spark Plug-DJ8J Champion		62345	1	Delivers electric current from the ignition system to the combustion chamber to ignite the compressed fuel/air mixture by an electric spark, while containing combustion pressure within the engine.	Ceramics/Steel	It went through die casting, extrusion, and machining.
21	Air Filter		216905	1	Prevents unnecessary dirts, and other materials from entering the engine.	Plastic	It was made through injection molding.
22	Starter Assembly-Pull Chord		213255	1	Provides the user with an outlet to exert energy that is converted into rotational energy of the crank shaft, thus starting the chainsaw.	Plastic, nylon	The plastic parts were made through injection molding, and the chord itself is braided nylon.
23	Air Filter Cover		91853	1	Protects the air filter from becoming damaged, and also helps filter the air that flows into the air filter.	Plastic	The plastic was made through injection molding.
24	Gas Tank		217761	1	Holds both the oil, and gas supply needed to fuel the engine.	Soft and hard Plastic	The tank was made through with a soft plastic by injection molding of two parts, then combining them together under high heat. Holes were also drilled in the tank. Gas caps where also injection molded but from a harder plastic. They are then screwed onto the assembly.
25	Fly Wheel		94737	1	Spins two magnets to power the magneto.	Aluminum, Magnetite, plastic	The flywheel was processed by investment casting. Then it was drilled in the center and milled where the magnets go. The magnets were cut into the desired shape and force fit into the flywheel. The plastic pieces where injection molded and pressed into the flywheel with a spring that was rolled.
26	Centrifugal Clutch		213278	1	The clutch system uses centrifugal force to automatically engage the clutch when the engine rpm rises above a certain point, and to automatically disengage the clutch when the engine rpm falls under a certain point.	Steel	The clutch system is processed by die casting. The spring inside it is drawn and coiled under high heat. Other parts in this assembly where pressed from sheet metal and riveted into place.
27	Main Casing		N/A	1	Holds the entire engine system directly inside, and hold the pull chord.	Aluminum	The case was made by die casting.
28	Front Casing		N/A	1	Holds the gas tank inside, and has the brake handle attached to it.	Aluminum	The case was made by die casting.
29	Side Casing-Brake Assembly		N/A	1	Holds the brake assembly, and brake handle.	Aluminum	The case was made by die casting. Assembly also includes a spring that was coiled and a slice of sheet metal that was rolled. It is all assembled with a force fit fastener.
30	Metal Handle		214505	1	Gives user something to hold while using the chainsaw.	Aluminum	The handle was extruded, cut, then bent into its shape. One end was bent and holes where drilled in each end.
31	Main Handle		217908	1	Handle attached to main casing. Has a safety trigger for user to press.	Plastic	The handle was processed by injection molding.
32	Guide Bar		N/A	1	Holds the chain in place. Acts as a guide for the chain as the chain rotates.	Alloy Steel	Two pieces of where punched from sheet metal and riveted together with spacers in-between.
33	Piston head		N/A	1	Piston head absorbs the combustion from the gas and turns the energy into translational energy.	Aluminum, Chromium	Piston cut from a rod of aluminum. The inside was forged through a high heat pressing process. The piston was then cut on a lathe. Holes were drilled and the sides were also milled.
34	Crank Shaft		N/A	1	Converts translational work into rotational work.	Aluminum	Crankshaft was cut from a rod of aluminum. It is then water jet cut from on a CNC machine. Threads are then rolled on to each side.
35	Combustion Chamber		N/A	1	Houses combustion and high pressure system that pushes out on piston.	Steel	Combustion Chamber was injection molding in a mold then later drilled.
36	Crank Shaft Casing		N/A	1	Houses the crankshaft.	Steel	Crank shaft casing was die cast in a mold then drilled to fit airtight on top of the combustion chamber.

Product Analysis

Various components of the chainsaw were examined in great detail for the purpose of better understanding the engineering and manufacturing processing that were involved in the making of the Eager Beaver chainsaw. These parts were selected for a number of reasons, each part has an important job and is vital to the chainsaw's operation, function flow, user interaction, or safety. As we will explain, the components are influenced by the GSEE factors. Some of the parts that we will describe will be incorporated into various other parts of the gate such as the solid modeling assembly and the engineering analysis for example.

A scale can be a useful to define a component's complexity. It is based on several factors. First the function of the component. Second the component geometry. Third the manufacturing methods used to create the component.

Function Complexity:

• 1. The component performs one function that requires no flows (mass, signal, or energy).
• 2. The component performs one function that receives one flow during use.
• 3. The component performs two or more functions or receives two or more flows.

Geometry Complexity:

• 1. The component is primarily two dimensional and consist of basic shapes (circle, square, etc.)
• 2. The component is primarily two dimensional and consist of complex shapes
• 3. The component is three dimensional and consist of basic 3-D shapes (cylinder, cube, etc)
• 4. The component consist of numerous planes and complex shapes

Manufacturing Processes Complexity:

• 1. The component is manufactured using only one process.
• 2. The component is manufactured using two different processes.
• 3. The component is manufactured using three or more processes.

Piston Head

The piston head is a very important component, responsible for taking the force of the combustion and converting it to mechanical energy. Its factors are:
Societal: The piston head must be durable to ensure that the explosion is contained and therefore is essential to user safety.
Economical: The piston head must be made to very high tolerances to ensure that energy from the explosion doesn't escape and the chainsaw is as efficient as possible.
Environmental: This also ensures that the chainsaw uses the least amount of gas possible. Also, it is made of metal which can be recycled.

Analysis

Component Function: The function of the piston head is to take the force of the combustion and convert it to translational mechanical energy. The pressure of the explosion pushes on the top surface of the head and drives it downwards. It operates within the combustion chamber and therefore, is in an environment with very high heat and pressure. The primary flows associated with this are the energy from the explosion in and translational energy out.

Component Form: The piston head's main shape is a cylinder that is hollow from the bottom with a hole though it about halfway down the cylinder. It is three dimensional with a height of about 1.4" and is approximately 1.4" in diameter. It is axially symmetrical and has two grooves near the top that have rings of different material in them. These rings expand when exposed to the heat of the explosion to fill any gap between the piston and the chamber, ensuring a tight seal. The piston head is a cylinder because it has to fit into the combustion chamber cylinder. It is hollow so the connecting rod can be connected within it using the hole. The piston head is fairly light, weighing less than a pound and is made of aluminum. This material is used because it is strong, durable, lightweight, and performs well in high heat environments. Aluminum is a relatively cheap metal which decreases manufacturing costs. The piston head is simply silver in color and has no aesthetic purpose because it is hidden. It has a very smooth and shiny surface finish which decreases friction between it and the chamber and also ensures a tight seal.

Manufacturing Method: The piston head was manufactured by a number of methods. The inside was forged through a high heat pressing process. This produced the rough finish and strengthened the metal by compressing it. It was used because it is a quick and relatively cheap way to hollow out the inside. The piston is then turned on a lathe because of its axial symmetry. This creates a good surface finish and high precision. The hole through the head is drilled because drilling is quick and provides decent precision. There are other processes that would be quicker than turning, but they would not provide the surface finish and precision needed for this to function most efficiently.

Component Complexity:

• Function Complexity:2
• Geometry Complexity:3
• Manufacturing Complexity:3

Connecting Rod

The connecting rod takes the translational energy from the piston head and transfers it to the crankshaft. Its factors are:
Societal: The connecting rod has to work in harmony with the piston head and the crankshaft to keep the engine running smoothly.
Environmental: It is made of metal which can be recycled.

Analysis

Component Function: The function of the connecting rod is to hold the crankshaft and the piston head together. It also transfers the translational energy from the piston head to the crankshaft. It operates within the combustion chamber and has to withstand the heat. It deals with the mechanical (translational) energy flow.

Component Form: The connecting rod is mainly two-dimensional and is fairly flat and straight. At each end it widens out and becomes circular with a hole in each end. It is 3" long, .25" thick and .4" wide in the middle. At the end that connects with the piston head, the rod widens to about .75" and at the other end it is 1.25" wide. It is shaped this way to most efficiently connect the crankshaft and piston head. The circular shape and holes at the ends are to connect to the other components. at the end connected to the crankshaft, the circular part is split in the middle and held together by two screws. This is for the assembly, allowing the rod to be easily connected to the crankshaft. The rod is made of steel because it has to be strong and durable. This metal is cheap and decreases manufacturing costs. Since the rod is hidden, it has no aesthetic purpose. It is brown in color and has a very rough, dull finish.

Manufacturing Method: The connecting rod was manufactured mainly by forging. Evidence for this can be seen in the rough shape that isn't excessively detailed and the parting lines along the sides. Forging compresses the metal which makes the connecting rod stronger. Also, the connecting rod's main shape doesn't have to be extremely precise which makes forging possible. At the ends, the holes are drilled because they need to be very precise to prevent any unnecessary gaps between the rod and other components. At the end connected to the crankshaft, the circular part is sawed in half and there are two holes drilled for screws to hold the two halves together.

Component Complexity:

• Function Complexity:2
• Geometry Complexity:1
• Manufacturing Complexity:2

Combustion Chamber

The combustion chamber is where the explosion happens that drives the piston and initiates the mechanical energy resulting in the rotation of the chain. Its factors are:
Societal: The chamber has to be strong enough to contain the explosion and ensure safety.
Environmental: The chamber is made of metal which can be recycled.
Economical: The chamber has to contain the combustion and use as much of that energy as possible to drive the piston to maximize efficiency.

Analysis

Component Function: The main function of the combustion chamber is to contain and control the explosion. It takes mass flow in from the carburetor in the form of air and gas. It also takes electrical energy from the spark plug. It outputs mass flow in the form of exhaust and mechanical energy to the piston. This component operates within the casing of the chainsaw and withstands high heat and pressure.

Component Form: The combustion chamber is three-dimensional and roughly a rectangular prism but is a very complex shape. It is approximately 4.5" long, 4" wide at its widest point, and 3" thick. Its chamber is about 2.5"x 1.5" and narrows down to a cylinder with a diameter of 1.4". It is fairly heavy and weighs approximately 3 pounds. At one end, it has a threaded hole to hold the spark plug. On the other end, a cylinder is hollowed out to hold the piston and guide its movement. This cylinder is also where the explosion happens. On this end there are four threaded holes which is where the crankshaft casing is screwed on. The outside has many groves in it to increase surface area and dissipate heat faster. One one side there a medium sized hole with smaller threaded holes around it. This is where the carburetor goes and the air and gas mixture enters the chamber through the hole. On the other side, there are two medium sized holes with two smaller threaded holes on either side. This is where the exhaust screws on and the exhaust exits through the two medium sized holes. There are a few more threaded holes on the chamber where various other components are screwed on. The chamber is made of steel which is strong, durable, and can handle the high heat and pressure of the combustion. This metal is relatively cheap so it reduces cost and also is recyclable. The combustion chamber is not visible so it has no aesthetic purpose. It is silver in color and has a fairly rough finish. The inside of the chamber has a very smooth finish to reduce friction and create a solid seal with the piston.

Manufacturing Method: The main body of the combustion chamber is die cast. The evidence that indicates this is a parting line along the body, riser marks and a fairly dull finish. This was done to quickly and cheaply produce the chambers with a complex shape. After the main body was die cast, the chamber was milled. This was done to create the precise cylinder needed and the smooth surface finish required. The exhaust and carburetor holes were also milled due to their irregular shapes. The final manufacturing process used was drilling to create all of the screw holes. This progression was the cheapest and most efficient way of manufacturing such a complex component. The die casting also creates less waste than if the whole thing was machined.

Component Complexity:

• Function Complexity:3
• Geometry Complexity:4
• Manufacturing Complexity:3

Crank Shaft

The crankshaft takes the translational energy from the connecting rod and turns it into rotational energy. Its factors are:
Societal: The crankshaft has to be weighted properly to maintain constant rotation and keep the chainsaw running efficiently.
Environmental: It is made of metal which is recyclable.

Analysis

Component Function: The main function of the crank shaft is to take the translational movement of the connecting rod and change it into rotational energy. This is done through a crank and slider mechanism. The crankshaft is connected to the flywheel and the centrifugal clutch. It spins these and causes the rotation of the chain. The crankshaft takes translational energy flow from the rod and outputs rotational energy flow. It operates within the crankshaft casing.

Component Form: The crank shaft is three-dimensional and fairly complex. One side is an axis which is cylindrical and 2.5" long. It tapers from .5" in diameter to .25" in diameter. The other side is also a cylindrical axis and it is 2" long. It starts with a diameter of .5" and after .75" it drops to .3" in diameter. There are threads on both ends which are for nuts to hold on the flywheel and the clutch. In the middle there are two counterweights that are parts of circles with a radius of 1". These counterweights are .5" apart and there is a cylinder between them which is where the connecting rod is connected to. The counterweights ensure a smooth rotation and enough momentum to bring the piston back up to its starting position. The crankshaft is made of aluminum which is strong, durable and recyclable. It is also relatively cheap to reduce cost. Since the crankshaft is not visible, there is no aesthetic purpose. The crankshaft is silver and the axes have a very smooth finish to reduce friction between them and the spacers. The counterweights have a rougher finish due to the manufacturing process.

Manufacturing Method: The different parts of the crankshaft are manufactured separately and welded together. Welding marks are evident at all the connections. The two axes and the cylinder that connects the counterweights are all manufactured by turning which is evident in the axial symmetry and the smooth, shiny finish. The turning also created the threads on the axes. This smooth finish is needed to decrease friction between the axes and the spacers and between the cylinder and the connecting rod. The counter weights were die cast. There are parting lines and riser marks on them which indicates casting. The casting of the counter weights was the cheapest, fastest, and least wasteful way to produce them. The performance requirements made turning necessary for the axes.
Component Complexity:

• Function Complexity:2
• Geometry Complexity:4
• Manufacturing Complexity:3

Fuel Tank

The fuel tank serves one very important function; it stores all of the fuel and oil for the chainsaw. Without the fuel, the chainsaw would not run, so the tank serves a crucial function to the whole product. The GSEE factors are as follows:
Global:The tank has no fuel marking lines because different countries used different units to measure volume. The tank is designed to be universal so that different markets can use the chainsaw and not be confused by any volume markings.
Societal:The tank is fairly small and does not hold a large amount of fuel because the chainsaw needs to be kept small and light weight so a large variety of people can use it for home use.
Economical:"The tank is made out of a plastic material because it is a much cheaper material to use to hold the fuel than a metal. Both would get the job done but plastic is much cheaper. The tank holds both the fuel and oil in one vessel that is divided. This was done to prevent manufacturing two different tanks and having to attach two tanks to the chainsaw, saving both time and money.
Environmental:The plastic used to make the fuel tank is a recyclable material, this factor considered the disposal of the chainsaw after its life cycle, so that the material may not be wasted but reused. The fact that there is only one tank holding both the fuel and oil also cuts down on material use so it saves material.

Analysis

Component Function:The primary function of the fuel tank is to hold the fuel and the oil for the chainsaw. The fuel for this product is a gas/oil mixture. That means that the fuel powers the engine but also lubricates it as the fuel runs through the machine. Along with the fuel, the tank also has a reservoir for oil. This oil is separate from the fuel and serves its own purpose. It is the lubricant for the chain, which experiences a lot of friction just like the engine. The oil for the chain is not a continuous flow that is constantly being pulled from. Instead is it designed so that the user has the power to determine how much and when the chain is oiled. There is a black rod that the user pushes to pump the oil onto the chain. The primary flow that is associated in the tank is the mass flow of the fuel and the tank. The tank is the first component of the product that interacts with the flow of the fuel and oil. The user inputs the mass into the tanks and from there the chainsaw controls the flows of the fuel and oil. The tank stores the fuel until the product requires it.

Component Form:The tank has a very complex shape. The general shape can be called an extruded "C." It is flat on one side of the tank and on the opposite side it is shapes so that it can fit around the rest of the chainsaw. It is three dimensional and consists of numerous planes on one of the sides. The components rough overall dimensions are as follows: the height is 6", the length is 3", and the width changes from 4" at the top to only 1" at the bottom. This component takes up a reasonable amount of the product's volume yet its weight with nothing in it is only about a pound. The tank is not a solid block. The component has two separate chambers to hold two different liquids. On the top of the tank their there are two holes, one for each of the separate chambers. The mouths of the holes are very wide, making it easier to pour fuel and oil into the tank. The holes are also threaded on the outside so that caps can be screwed on to prevent any of the liquid from spilling out of the holes. The material used to make the tank is plastic and there are a number of reasons for this. From an economic standpoint, plastic is cheaper than metal, which could have been used to hold the fuel and oil. Furthermore, plastic is more durable than metal because it won't rust or corrode. A big concern is that the plastic may melt from the heat at the engine, but the plastic has a high enough melting point that it won't become a fluid from the heat generated from the engine. The fact that plastic can become fluid is important in its selection as the material of choice because the component was manufacturing using casting techniques. It is clear that the tank was created using injection molding because there is a very distinct parting line on the outside of the component. Environmentally, the plastic used to make the tank can be recycled by simply remelting it. The user was also considered in the material selection because plastic is much lighter than metal and can do the job just as well. The tank serves no aesthetic purpose because the user never really sees most of the tank. The only part of the tank that the user sees is the holes that are used to fill the tank. The color of the tank is white, which is probably the color of the plastic without any dyes in it. The caps that cover the holes are black to match the majority of the chainsaw's other components. Since the tank is not seen by the user there are no aesthetic finishes or any functional finishes for that matter. The parting lines are not even ground down. There are no aesthetic considerations in the making of this part. It was designed solely to fulfill its functional duty.

Manufacturing Method:The primary method used to manufacture this component was injection molding. The evidence that points to this conclusion are all the parting lines and riser marks. It would appear that the tank was created by piecing together a couple different cast parts. This also is the most likely method to be used to create the separate chambers in the one tank. There are very subtle parting lines on the various parts of the tank that suggest it was cast and then there is one larger, more distinct line that is where they pieced the segments of the tank together. The pumping system used to pump the oil onto the chain was put in the oil part of the tank before the pieces of the tank were put together. The holes have threads on the outside of them for the caps to screw into. Those threads were created during the casting process. There is further evidence to suggest that injection molding was the primary manufacturing method. The material choice, plastic, is often shaped using casting methods, that is because plastic is nearly impossible to machine. Plastic can take the fluid state when heated and be poured into a mold. The complex geometry of the tank suggests that it was cast as separate parts and then pieced together. The two chambers of the tank were created on one of the pieces that created three of the sides and then another piece was put on to create the last side of the chambers.

Component Complexity:

• Function Complexity:2
• Geometry Complexity:4
• Manufacturing Complexity:2

Clutch Handle

The clutch handle serves important safety functions. It is also one of the few components of the chainsaw that the user can interact with. The GSEE factors are as follows:
Global:There is a safety sticker on the handle to show proper use and what to avoid. It is displayed in pictures because it can be understood by people that speak different languages.
Societal:The purpose of the handle is to provide added safety. Since this is a chainsaw for household use, it may not always be handled by experienced users. Because of that, it has to have these added safety features.
Economical:A portion of the handle along its length is subtracted out. This was done not only for a better feel but also so there was less material. The handle is also made of hard plastic which is a cheaper material than metal.

Analysis

Component Function:The primary function of the handle is to engage and disengage the clutch. The location of the handle also serves as a hand guard. The clutch is the device that transfers the motion of the crankshaft to the component that rotates the chain. If it is engaged the chain will not move, but the engine will continue to run. When it is disengaged the engine will turn the chain. Because of this feature, the handle that operates the clutch is very important. If it wasn't there, then the chain would have no way of stopping except for turning off the engine, which would become a hassle for the user. So the handle serves both a safety function and a convenience function. A secondary function of the handle is as a hand guard. This handle is not the component of the chainsaw that the user holds while operating the chainsaw. Its location is in between the handle the user holds and the front of the chainsaw where the chain is. This is to protect the user in case his hand slips by accident. Both of these functions serve as a safety feature, which is important to the typical household user.

Component Form:The general shape of the handle resembles a horseshoe with one of the sides of the "U" missing. The component is largely two dimensional with three dimensional features at both ends. The rough overall dimensions are the following: height is 8", the length is 10", and the width is 1/4". The weight of the component is approximately one pound. The geometry of the component works well with the function of the handle. It is taller than it is wide, because it is supposed to stop the user's hand if it slips. Since it is taller, it has a larger surface area for the hand to hit. The component is made of a hard plastic material. There are a few reasons for this material choice. First, economically, it is made of plastic because it is cheaper than metal and does its job just as well as if it was made of metal. Furthermore, it is very skinny because the component does not need as much material to perform its function, just as long as it can be grabbed to engage and disengage the clutch and stop a hand. Less material is both an economical benefit and an environmental benefit because less material means less strain on the earth. Plastic was used because of the manufacturing method as well. Plastic when heated can take a liquid state, which means that a casting method can be used to form the component. The styling of the chainsaw as a whole is very simple. As a result of this, the aesthetic properties of this component, even though it is seen by the user, is very simple. The color of the component, like much of the outside of the chainsaw, is black; however, this helps to emphasize the safety sticker on the handle because it stands out more against the black background. The component is not painted black so the surface is that of the plastic. It has some roughness to it for a better feel when the user is grabbing it to engage and disengage the clutch. There are not many aesthetic properties of this component.

Manufacturing Method:The handle was manufactured using primarily one method. The majority of the handle was made using injection molding. Then the ends, which feature holes, were machined, drilled to be exact. There is evidence to suggest both of the claims. First, a subtle parting line is noticeable along the length of the component. The holes were drilled as evident by the rings around each hole, which suggests a drilling machine was used. Additionally, the material chose, which is plastic, points towards injection molding. The material that is used for injection molding must be able to become liquid and plastic has that ability. A simple shape like this handle would be very easy to create using a mold given the material choice. Plastic is very difficult to machine so casting is the likely choice. Investment casting could have been used to create the component, but this process would have been more expensive, so economic consideration factored into the choice of manufacturing method. Likewise, investment casting has a large amount of waste in every mold that is destroyed, so the environment was considered when selecting the manufacturing method as well.

Component Complexity:

• Function Complexity:2
• Geometry Complexity:2
• Manufacturing Complexity:2

Outer Casing

The outer casing serves several functions for the overall use of the chainsaw. Additionally, it is one of the parts that the user interacts with, sees, and touches. It servers a purpose both for the chainsaw and the for the user. The GSEE factors are as follows.
Global: The important information about the chainsaw appears right on the outer casing. It is applied using a sticker. This may have been done so that different stickers with different languages could be applied.
Societal:The outer casing protects the user from the moving parts and hot surfaces of the engine, providing increased safety. The outer casing also is where the emergency on/off switch is located, which is colored red to stand out against the black metal.
Economical:" This section of the outer casing covers most of the chainsaw's engine and moving parts in one single metal sheet. This was done to decrease the number of parts that needed to be manufactured, which would save on build cost.
Environmental: The single sheet metal piece requires less material to make then making multiple parts and then piecing them together.

Analysis

Component Function: The primary function of the outer casing is to house all of the moving parts in a single area. It protects engine and other moving parts from the environment. It helps to keep dirt away from the various components of the chainsaw. This is a very important task because the sawdust from the chainsaw would quickly build up on the moving parts and prevent them performing their functions. On the casing there is an on/off switch. This switch determines whether the chainsaw will run at all. It determines whether electricity from the alternator travels to the spark plug or not. Having a switch like this is a great safety feature both for emergency stops and for making sure the engine is not accidentally started. It serves another purpose along with protecting the chainsaw. It also protects the user from the moving parts of the chainsaw. The crankshaft is moving at very high RPM's and if it wasn't secluded from the user it could easily break a finger. The primary environment that the casing operates in is the outside environment. It protects the engine of the chainsaw by absorbing the brunt of the external elements and hazards.

Component Form:The component's primary shape could be called a shell. The casing is largely three-dimensional because its basic shape is a cube that only has four sides on it, a top, bottom, and two sides. The rough overall dimension are as follows: the length is 5", the height transitions from 5" down to 3", and the width is 5". The general shape is said to be a shell because its basic shape is a cube but it is hollow as opposed to solid. It is hollow because practically all of the other chainsaw's components are enclosed inside the casing. It is missing two sides because the components need to be able to be placed inside the casing somehow, and having two open sides allows for the engine and other components to be placed in easily. The two open sides are eventually covered by two other outer casing pieces. The approximate of the weight of this component is about one pound. The weight is very light because the component is hollow, and the chainsaw's overall weight must be light so each component is designed to be light. The component's material appears to be cast iron. This material is used for a number of reasons. Cast iron is a fairly strong metal yet lightweight. It needs to be strong to protect the components on the inside, but lightweight because its a handheld device and if it weighed too much it would be difficult to use. Cast iron is also able to be melted and become fluid which is important because it was manufactured using investment casting. Furthermore, cast iron is a relatively cheap metal, which shows that economic considerations were used when selecting the material. There are lighter, stronger metals than cast iron, but those metal are very expensive. Cast iron fulfills the functional goal of the component without being too expensive. Societal factors were considered as well because their are stronger metals but they are not as light, so the engineers selected a metal that would be light enough for use by a large amount of people. The casing is one of the only components that the user sees during typical use. With that being said, the casing has no particular aesthetic features. The color is black like all cast iron, and it is textured like cast iron. But it appears that their were no aesthetic considerations when making this component.

Manufacturing Method:Cast iron products are generally cast, this component being no different. It is manufactured using a number of methods. The overall shape of the casing was obtained using investment casting techniques; however, the geometry is so complex that is would have to be machined afterwards as well. There is a large amount of evidence to suggest that the manufacturing methods stated were used. For example there appears to be no parting line at all on the component, which suggests that it would have been investment cast and not die cast. There is no riser marks on the component, but they may have been removed when one of the various holes were cut in the casing. The casting only created the general shape of the component; it must be machined afterwards to create all of the holes. The majority of holes in the casing were drilled and the more complex shapes were milled out. Along with subtractive machining processes, there is also some additive manufacturing. A part of the component was welded on after it was cast. This was done because the part that was welded on was very complex itself and needed to be cast itself. The material, cast iron, suggests that the component was cast as well because cast iron can become fluid and be poured into a mold. The component could have started as a sold block of cast iron and then only subtractive processing could have been used to create the component. This process would have created a lot of waste because the component is so large and hollow, and it would have been very time consuming and expensive. This suggests that both environmental and economical factors were considered in the manufacturing of the casing. Cast iron is a very common metal and is recyclable by being melted down again. These two facts shows even more environmental considerations were thought about.

Component Complexity:

• Function Complexity: 1
• Geometry Complexity: 4
• Manufacturing Complexity: 3

Solid Model Assembly

When solid modeling we wanted a program at which we could make the parts interact and move. Autodesk Inventor was a program that can do that. This program can also slide parts in half and still allow the parts to move. This would help in showing how parts interact more clearly. Another reason that we chose this program is that it is a program that we are fairly familiar with. This program can individually model each part, create detailed renderings, and make videos of the system in action. These three things are located below in that order.

Components

We chose to solid model the drive train which includes: the crankshaft, connecting rod, piston head, bearings, piston rings, piston pin and connecting rod screws. This system is the most essential part of the chainsaw and is a cause for many different engineering decisions. This system contains different design options that would severely change the power and efficiency of the chainsaw. This system also has a complex motion that is not seen from the outside of the chainsaw. Below is a table of each part rendered and a description of what the part does, including some notes about its creation.

Number	Component	Description	Model
1	Crankshaft	The crankshaft acts as a cam, converting translational work from the piston into rotational work. The radius of the cam on the crankshaft changes the stroke length which is an important factor in engine power and efficiency. The crankshaft's center of mass is not located along this rotational axis. This is because when the piston provides torque from the power stroke, it needs to return to its original state. A counter weight provides the necessary torque and must be tuned to provide the right return rate. When modeling this, it became apparent that the two chamfers located on the counterweight side are essential to provide clearance from the piston head. The left side of the crankshaft (as shown in picture) has right hand threads along with a key to keep the fly wheel rotating at the same angular speed as the crankshaft. The other side of the crankshaft has left hand threads to keep the chain-side of the drive train from falling off.	CAD Rendering of crankshaft
2	Connecting Rod Assembly	The connecting rod assembly consists of two pieces plus the screws that connect the piston head and the crankshaft. The length of the rod is dependent of the stroke length and the cylinder diameter. It must be long enough to provide clearance between the crankshaft and the piston head. This is best shown in Rendering 2	CAD Rendering of rod assembly
3	Piston Head	Provides a boundary which the exploding gas can do work against. The radius of the piston head should be large enough so that the connecting rod does not interact with the side of the piston head.	Cut-away CAD Rendering of piston head
4	Bearings	The 20 cylindrical bearings significantly reduce the friction caused from the connecting rod rotating around the crankshaft and inside the piston head. To reduce friction, the bearings must be made of a hard material with high tolerances.	CAD Rendering of bearing
5	Piston Rings	The 2 piston rings are located on the piston head and must keep the piston head from hitting the walls of the combustion chamber. The Piston rings must also seal the piston head so that no gas escapes past the piston. To do this, they must be made of a material that expands at the engine run temperature. This provides a good seal.	CAD Rendering of piston ring
6	Piston Pin, Piston Bearing	These fasteners are important in keeping the drive train together. The piston pin must be highly constrained with the hole in the piston to prevent the pin from falling out of the piston head. The piston pin is a force fit to achieve minimal movement from the piston head. The piston bearing provides a medium for the piston pin and the connecting rod to be better constrained. This assembly is better shown in render 3	CAD Rendering of Piston Bearing(left) and Piston Pin (right)
7	Ring Snap	These 2 rings act as fasteners to keep the piston key in place, keeping the piston head on the connecting rod. To place one of these snaps in place one must use a tool to clamp the two holes together place it and then release it. It is made from a metal that can bend for initial installment. Their placement is easily show in the cut-away rendering.	CAD Rendering of Ring Clip

Assembly Renderings

Below are renderings that are referenced in the component chart. It also includes an assembly cut-away and an exploded view of the assembly.

Rendering 1. CAD rendering of drivetrain assembly with counterweight away from piston head.

Rendering 2. CAD rendering of drivetrain assembly with counterweight near piston head.

Cut-away rendering. CAD rendering of drivetrain assembly inside piston head.

Exploded view of crank assembly. Numbers labeled in component table.

Video Renderings
Piston Video 1 is a video showing the piston head reciprocating back and forth while the crankshaft is rotated from the piston's movement.
Piston Video 2 is a video of the same setup but cutting the system in half. This easily shows how the connector rod and the counterweight from the crankshaft come close to the piston head's walls. It also provides a simplification of the system from a system in three dimensions to a system of two dimensions.
Both videos go through three cycles.

Engineering Analysis

In the design of a chainsaw, as with any design there is intensive analysis of components. One of the most essential systems contained within a chainsaw is the engine, which is powered by combustion within the combustion chamber. The explosion creates a high-pressure system that moves the piston out. The flow of high and low pressure within the combustion chamber, along with mechanics of the pistons motion is the driving force behind the functionality of the chainsaw.

In designing the chainsaw there are certain expected qualities such as torque supplied by the engine, as well as an expected horsepower. That is to say, the engine was designed with a numerical range of torque and horsepower as necessary constraints. The main contribution to these values comes from the happenings found within the combustion chamber. During analysis of these happenings one should ask the questions, What determines the torque output of the engine? What determines the horsepower of the engine?

Problem Description

Determine the torque and horsepower in the Eager Beaver Chainsaw

Diagram

Force applied by piston

Assumptions

Engine combustion chamber relative pressure ranges from 0 to 25 psi

Force is constant from 0 to pi (see diagram)

Inertia is negligible

Governing Equations

EQ.1) Pressure = Force * Area

EQ.2) Area of circle = PI R^2

EQ.3) Torque = Force * Distance (perpendicular)

EQ.4) Horse Power = (2*PI*Torque*rpm)/(33000)

Calculations

Measurements yielded that the diameter of the circle at the bottom of the piston was 1 and 7/16 inches. Dividing that number by two and plugging it into equation 2 we find that the area of the circle

Area = 1.622 square inches.

Next, we plug in this area and the 25 psi as described in the assumptions to equation 1. This will find the force that the piston exerts upward. Note that 25 was used as it is the maximum psi the allotted amount of fuel is able to produce. Therefore, this is assuming that the chainsaw is at full throttle so results from here on out will be maximum values for this engine.

Force= 40.55 lb

Measurements showed that the distance from the piston connecting rod to the center of the shaft was 1/2 inch. Plugging this value as well as the force value into equation 3 finds us the maximum torque applied to the shaft during the cycle. Note that answer is divided by 12 to convert inches to feet.

Torque = 1.69 ft*lb

Using the torque, and the maximum rpm located in the instructions manual, plugged into equation 4 we find the horse power of the engine inside the chainsaw. Note max rpm is 4200

Power = 1.35 hp

Solution Check

Units-

Area= inches * inches = square inches

Force = lb / square inches * square inches = lb

Torque = ft * lb = ft*lb

Deduction- 1.35 is a seemingly reasonable horse power for a chainsaw engine so it is most likely correct

Discussion and Interpretation

After completing the calculations and fully analyzing the engine cycle, it is clear that engineers must be very familiar with all of these concepts when designing and testing the product. A product like a chainsaw is expected to be able to supply enough power to the chain that it is able to cut through wood with a certain degree of ease. With this in mind the engineers would have a set range of torques that the motor must be able to reach. Using a simple gear ratio the motor is attached to the chain so it is very important to know and understand what kind of torque your motor will be outputting to create a competitive product.

If engineers wanted to increase power they could do so by increasing the area of the piston, the distance between the piston connection rod and the shaft, or the pressure in the combustion chamber i.e. more fuel air mixture. As displayed by the governing equations, any one of these changes would increase torque, and therefore, horsepower of the engine.

This being said we are aware that there are more detailed ways of analyzing this information. A set max psi was established in the assumptions. However, this can be broken down into smaller components. This pressure is caused by compression and combustion of an air fuel mixture of approximately 14:1 ratio. Though it is possible to determine the increase in pressure once this mixture is combusted, no member of our group is an expert in deflagration and calculations would take an extremely long time. 25 psi was determined as an appropriate assumption based on previous knowledge of engines.

Design Revisions

Change #1

Electric Start

Why

Electric start is a rare feature to find on a product such as a chainsaw. Most chainsaws have a pull start system which requires users to place the device on the ground and stabilize it with their foot or hand as they pull on a starter chord several times until it starts. This can be particularly difficult if the engine has not been started in a while which is normally the first time a chainsaw is used after winter. An electric start system would simplify this process to simply plugging in the device to a power supply for a few seconds as the user pushes a button. An electric motor would turn over the engine and start the chainsaw in a much less strenuous manner than the pull start method.

GSEE Considerations

Global-

For this design to be implemented worldwide, there would need to be a plug-in power system that considered various types of outlets as well as varying current or voltages that might be found in different countries.

Societal-

This design would expand the number of people who could work in fields that required chainsaw use as it lowers the physical demand that most chainsaws require. Pull start systems are not necessarily able to be started by smaller, less physically fit people. With an electric start chainsaw, smaller people such as young adults, and less fit men and women would be able to either do more yard work themselves or even be able to work for a yard work company.

Economic-

The electric start system would be much more convenient however it would most certainly increase the cost of ownership. Maintenance on a pull start system is very simple. The most common issue is that the string is pulled too hard and is severed. This is a relatively low cost in comparison to the cost of replacing an electric motor. This being said, the likelihood that the electric start motor will malfunction is much lower than the possibility that the pull string will break.

Effect on Target Audience and Price

As stated earlier, the electric start chainsaw would be much more accessible to smaller, less physically fit people. However, those who have worked with chainsaws a lot might not want to pay the extra money to have the luxury of electric start, or may even prefer pull start to electric start. Therefore, when making this change we are completely shifting the target audience from physically fit workers to smaller, less fit workers. This product might be appealing to a house wife, or smaller individual who is relatively inexperienced with chainsaws and wants something that is more straightforward than a conventional heavy duty chainsaw. A push to start system comes off as a lot less scary than a pull start. This being said, they would need to pay a bit more money seeing as a pull start system is quite a bit cheaper than an electric motor. The target audience would mostly be less experienced middle class homeowners.

Change #2

Longer Stroke

Why

The loudness of any internal combustion engine is due largely to excess pressure being released from the combustion chamber into the environment. This is evidence that the piston is not absorbing all of the energy that can be obtained from the pressure in the chamber. If engineers made the engine have a longer stroke, then the air would have a larger distance to decompress. This would allow the pressure to do more work on the piston as well as decrease the excess pressure exiting the chainsaw. This would not only make the engine more efficient, but would also make it much quieter.

GSEE Considerations

Societal-

With a quieter engine, chainsaws would be much more pleasant to work with, not only for those who are using the device but also for those around them. It is a generally accepted rule that you don't use a chainsaw in the middle of the night since the neighbors would be disturbed by the loud noise, but with this revision to the engine this might no longer be the case.

Economical-

With longer strokes, the engine would be able to use more energy per cycle and therefore be more gas efficient. This would lower the cost of operation of the chainsaw. This could be a major advantage with the raising cost of fuel.

Environmental-

Similarly to the example posed previously, longer strokes would be more efficient on fuel. This would mean that less octane would be burned and therefore less CO2 would be emitted to the environment. With the ever growing concern of greenhouse emissions in mind, this chainsaw would have a much smaller carbon footprint than previous models.

Effect on Target Audience and Price

This price of this chainsaw would be a bit more seeing as it would require more materials. The longer stroke requires the entire engine to be larger as the circular radius of the path that the piston rod travel would have to be larger in order to move the piston a further distance. The longer the stroke is, the larger the radius of the circular path that the piston rod is traveling. Looking back at the group's engineering analysis section, it is noted that an increased radius would result in a higher torque and therefore higher horsepower. So the engine would not only be quieter and more efficient, but also have higher torque. The target audience for a product like this would be almost everyone who would buy a normal chainsaw; however, this model of chainsaw would necessarily have a larger engine and therefore be a bit heavier than a normal chainsaw. This being said, it is more likely to target those who are more physically fit and who are looking to boost performance. This product would largely target yard work companies that wouldn't mind paying a little extra to have a much higher quality chainsaw.

Change #3

Ergonomic Rubber Grip Handle

Why

The current handle system attached to the Eager Beaver chainsaw is simply an aluminum handle screwed into the chainsaw by 2 screws on either side. If the handle were to be altered to fit the shape of a hand and coated with a rubber exterior, there would be several positive effects. Seeing as the chainsaw is often used for an extended period of time, it would increase comfort of the user immensely. Holding a heavy chainsaw by a metal handle given that the vibrations of the chainsaw would travel up the users arm and cause discomfort. Rubber would act as a shock absorbent material that would fit into the users fingers and spread out the surface area. This would result in the most comfortable user experience by the user. The new handle would no longer be removable as it would be a part of the body, so serviceability of the engine would have to be slightly altered so the body could still come apart.

GSEE Considerations

Societal-

People who work for yard work companies would be using this device for several hours at a time. With a metal handle this would cause much discomfort and in some cases medical damage may be caused by extended exposure to vibrations up the users arm. This new ergonomic handle would help prevent this from happening.

Environmental-

Although little rubber is needed to make this handle, it is noteworthy to keep in mind that rubber is made in part from oil which is a limited resource. It is possible that rubber may become an impractical resource to use on this handle over time.

Effect on Target Audience and Price

The shift in target audience would not be very significant since almost anyone who uses a chainsaw would prefer a more comfortable handle but it would particularly target those who use chainsaws for many hours a day and do not want to have sore arms. This being said, the price tag of this chainsaw would be slightly higher than it would have been previously since there would be a necessary raise in cost of production given more supplies used.