Gate 3.

Project Management: Coordination Review

Our group has communicated and gotten along very well with one another. However there are a few conflicts that we have to resolve. Our schedules are all quite different. There is always a time when a group member has somewhere to be or something to attend. The only other issue that we faced while doing this gate was a technical problem where we could not get access to any solid modeling program.

Communication is a key value to a successful group. Each of us have different qualities and knowledge to bring to the group. We work best when we all work together to utilize everyone's strengths, since everyone has their own expertise and knowledge to bring to the team. We have had issues with all of us to get together at one place at one time. Tyler works and lives off campus, Garret and Timothy lives off campus, and Dylan has class after the MAE course when we are most likely to meet. For this reason it is not always easy to get us all on campus during lab hours. We usually take much work home as possible and do different parts of the project individually. But despite all of the scheduling issues, we work together well when we are able to get together.

The other issue that we had in finishing gate three was getting access to a 3D CAD program. We tried on multiple occasions, multiple computers, and multiple log-ins to get Engineering Pro Wildfire to work. After trying on different computers and asking classmates for help with no success, we still did not find a solution to our problem. When asking the instructors, they told us to email nodehelp or attempt to get access to Furnas 1019 CAD lab by emailing Betty Brown. Nodehelp said that there no CAD program is currently working on campus except in Furnas 1019. They said they didn't know what the problem was or when it would be fixed, and to email Betty Brown to get access to Furnas 1019 (which we had already done). We have still received no response from Betty Brown. We resolved this problem by finding a free modeling program offered to students, Autodesk Inventor Professional 2012, and installing it on one of our personal computers. Our computer struggled to handle the program but with our individual knowledge of SolidWorks and AutoCad we were able to finish our three dimensional solid modeling.We did experience some difficulty completing Gate 3 at times, but we ended up splitting up the work and meeting to put it all together, and to add any missing components.

Product Archaeology: Product Evaluation

All the major components of the Tecumseh TNT100 engine were analyzed based on the following criteria which can be seen in the Component Summary

Specifications - The basic size and shape of the component, as well as model number.

Component Function - What the component is intended for and what is it associated with.

Component Form - The material the component is made up of and why, as well as aesthetic properties.

Manufacturing Methods - How the component was manufactured and what influenced the methods used.

Complexity

The Complexity of each part was assessed based on 3 factors

• The number of component functions
• The number of manufacturing processes used
• How intricate the geometry is.
  • Components with more intricate geometries cost more money and time to manufacture. The component will be scaled from 1, being not complex at all, to 3, being very complex.

The 3 numbers for each of the factors will be added together to get an overall rating for component complexity. The complexity scales from least complexity to most complex components and ranges from 2 to 8. The key is intended to give an idea of how the complex a component is. If a rating between 2,5 or 8 is giving, interpolate between.

• 2 – These components are very simple. One process was used to manufacture it and therefore has a simple geometry. These components have only one function.
• 5 – These components are relatively complex compared to a rating of 2 but not nearly as complex as a component with a complexity rating of 8. Usually only have 1 function and are manufactured in a couple of steps. Geometry doesn’t seem overly complex.
• 8 – These components are very complex. It took multiple steps and processes to manufacture it which has a correlation to how complex its geometry is. These complex components usually have multiple functions. If there is only one function, the shape is very intricate and the component’s function is a main function in making the engine run.

Component Summary

Component	Specifications	Component Function	Component Form	Manufacturing Methods	Complexity	Image
Oil Pan	Model #: 34831A Quantity: 1 Approx. Weight: 1-2lbs General Shape: shelled plate Dimensions (cm): 22x22x4	Function: Contain Oil, House and protect engine components. Multiple Functions: Yes Associated Flows: Oil in Function Environment: Filled with oil to lubricate and prevent overheating.	Material: Aluminum Influencing Factors Economical: Aluminum is cheeper then many other metals. It is light and can help increase the engines efficiency and running costs. Environmental: Aluminum is highly and easily recyclable and reusable after the engines disposal or from machining waste. Aesthetic Properties: Rough cast interior and black painted exterior to prevent rust and improve looks.	Methods Used:Die Casting, Drilling, Grinding Evidence:The geometric complexity of the engine block including fins had to be die-cast because any other method could not achieve this complexity and machining would be too expensive and time consuming. The visible holes can be achieved by drilling. The smooth flat surfaces show that grinding has been used. Why method was used: Die casting is the cheapest and easiest way to create a complex shape such as the oil pan. Drilling is also the easiest way to create precise holes. The parts have to be ground in order for all the parts to fit perfectly. Influencing Factors: Economical: Casting is a cheep way to make a complex shaped part. This part could have been milled but it would have been costly, and still may have needed ground to achieve tolerances. Environmental: Casting uses less waist material to depose of or reuse then milling or turning.	Complexity:8 Functions:2 Manufacturing processes:3 Geometry:3
Camshaft	Model #: 35992 Quantity: 1 Approx. Weight: 2-3lbs General Shape: rod with gear and tear-drop shaped lobes Dimensions (cm): 7.3x7.3x12.6	Function: Rotates to open and close valves simultaneously which bring in air and gas while expelling exhaust. Multiple Functions: Yes Associated Flows: Importation of air and gas as well as getting rid of exhaust Function Environment: Rotates withing the engine block lubricated by oil to avoid abrasive damage because it is in a hot environment and is constantly moving.	Material: Steel Steel was chosen because its strength and high melting temperature is needed due to it being under constant heat and movement. Cast iron would have been to brittle. Influencing Factors: Societal:Steel is strong. It improves the appeal of the component knowing that it will be strong, safe and should last. Economical: Steel is expensive compared to iron or aluminum, using this increases the component cost, but its strength makes it the best material choice. Environmental: Steel is recyclable, and reusable after the engine is disposed. Aesthetic Properties: Rough cast surface on shaft. The lobes that push the valves have a smooth, polished surface to ensure as little friction as possible on the pushrods for decreased wear and tear.	Methods Used: Die Casting, Turning, Grinding, Welding Evidence: The rod was first die-cast, some parts of the rod were never touched after the casting and can be seen. The ends of the rod were then shaped to the desired diameter using turning, shown by the axial symmetry on the ends and the cut marks. The lobes were grinded which can be seen by the clean finish. The gear was welded into place, seen by weld marks. Why method was used:Die casting was used to achieve the overall complex shape which is unachievable or too expensive with other methods. Influencing Factors: Economical: Casting is a cheep way to make a complex shaped part, but still needed to be ground and turned to achieve shape and tolerances.	Complexity:8 Functions:2 Manufacturing processes:4 Geometry:3
Oil Pump Assembly	Model #: 29914 Quantity: 1 Approx. Weight: 10-15oz General Shape: tube and ring Dimensions (cm): 5.9x2.7x1.4	Function: Uses motion of non-concentrically rotating shaft to move. This motion moves the stationary oil pump in and out pushing oil through the hole in the pump ring and up the camshaft to lubricate components. The pump pulls oil from one hole and then pushes the oil through another hole. Multiple Functions: Yes Associated Flows: oil flow Function Environment: The oil pump ring rotates off-axis around the camshaft. The oil pump piston is held in place by a groove in the oil pan. It has to withstand the force created by the torque of the camshaft and internally withstand the pressure of the oil.	Material: Plastic and steel Axial symmetry and cut marks around rod show turning was used. Influencing Factors Economic: Plastic is significantly cheaper than metal. Societal: plastic could negatively effect the parts appeal and perceived strength. Aesthetic Properties: Smooth plastic (oil ring), Polished metal (oil pump piston). These smooth surfaces allow a proper seal between the moving parts in the pump. This allows the oil pump to produce pressure and push oil throughout the engine.	Methods Used: Injection Molding, Drilling, turning Evidence: Parting lines can be seen where mold was. Axial symmetry and cut marks around rod show turning was used on the steel part. Why method was used: The cylindrical shape of the metal rod was fast and easily achieved by turning. Plastic made it easier and less time consuming to mold and drill out holes. The cylindrical shapes led to injection molding being the main method. Influencing Factors: Environmental: Injection molding is cheep and has little waste. It also requirers little processing after completion.	Complexity:5 Functions:1 Manufacturing processes:3 Geometry:1
Engine Block and Cylinder	Model #: 33883 Quantity: 1 Approx. Weight: 5-7lbs General Shape: rectangular Dimensions (cm): 25x17x10	Function: Engine block houses gears preventing damage and holding them in place. The cylinder holds piston and allows for combustion energy to move piston. Multiple Functions: Yes Associated Flows: Holds entire assembly that transfers the combustion energy to translational energy to rotation energy. This is also where gas enters and leaves as exhaust. Function Environment: The engine block has moving parts inside generating heat from friction. Oil must be held inside used to eliminate damage. Combustion generates a heat inside cylinder and must hold up to a constant heat and pressure force.	Material: Aluminum Influencing Factors: Reduced weight of the biggest part of the engine. Societal:The light weight of the engine makes it easier for user to push it around their lawn Aesthetic Properties: Smooth metal, black painted exterior to prevent rust and improve looks.	Methods Used: Die Casting, Grinding, Drilling Evidence: The geometric complexity of the engine block including fins had to be die-cast because any other method could not achieve this complexity and machining would be too expensive and time consuming. There are also part lines visible. Grinding was used to make sure the oil pan would be flush with the engine block, the smooth finish indicates this. Why method was used: Intricate shape led to die casting. Influencing Factors: Economic: This part was not machined but die-cast, saving time, money and labor.	Complexity:8 Functions:2 Manufacturing processes:3 Geometry:3
Heat Sink/Cylinder Head	Model #: 36476 Quantity: 1 Approx. Weight: 1-1.5lbs General Shape: square Dimensions (cm): 13x12x3.5	Function: To dissipate the heat given off by the engine. This prevents over-heating and protects other components from being damaged. Acts as a combustion chamber head. Multiple Functions: Yes Associated Flows: exporting heat energy Function Environment: located on the outside of the engine to allow the heat to dissipate easily to the air outside. It is also located directly above the piston chamber where combustion occurs to move heat from the source.	Material: Aluminum Influencing Factors: Aluminum was chosen for it's heat conductivity Aesthetic Properties: Partially rough from casting, partially smooth from machining. Was painted black, but a lot of the paint blistered and flaked off over time.	Methods Used: die casting, drilling Evidence: rough finish, complex geometry and parting lines indicate die casting. holes where drilled to create places for blots to hold heat sink in place Why method was used: To achieve complex geometry of fins. Influencing Factors: Economic: This part was not machined but die-cast, saving time, money and labor.	Complexity:5 Functions:1 Manufacturing processes:2 Geometry:2
Pull Start Gear	Model #: 590519 Quantity: 1 Approx. Weight: 10-15oz General Shape: round Dimensions (cm): 9.5x9.5x0.8	Function: To Start the engine by pulling a cord that spins the pull gear which spins the flywheel creating the initial spark needed to start the engine. The pull start gear is reset after each pull due to the coil that attaches to it. Multiple Functions: No Associated Flows: Converts human energy to rotational energy	Material: Plastic Influencing Factors: This gear deals with minimal force compared to other metal gears in the engine and does not need to be metal Aesthetic Properties: Smooth white plastic from manufacturing processes. Part was not aesthetically changed after manufacturing.	Methods Used: Injection Molding Evidence: The gear shows parting lines indicating injection molding was used. The intricate parts of the gear, such as the teeth indicate injection molding. Why method was used: Any other process would be to expensive and time consuming to make such an intricate geometry. Influencing Factors: Environmental: Injection molding is cheep and has little waste. It also requires little processing after completion.	Complexity:4 Functions:1 Manufacturing processes:1 Geometry:2
Pull-Start Mount	Model #: 590520 Quantity: 1 Approx. Weight: 0.5lbs General Shape: bent sheet Dimensions (cm): 12x9x5	Function: Mounts pull start to the side of the engine. Allows access for the pull start to be removed. Multiple Functions: Yes Function Environment: Located between the pull start and the engine block. Has to be able to withstand the force created by the torque applied to turn over the engine.	Material: Steel Influencing Factors:steel was used to handle the force from using the pull start Aesthetic Properties: Smooth finish, painted black for improved looks because it can be seen on the outside of the engine.	Methods Used: Forging, Turning, Riveted. Evidence: Forging was used to bend the sheet metal into the proper shape using a die, indicated by the fact that the metal is thin. The rod was turned the axial symmetry shows this. It was the riveted to the sheet metal part of the component. Why method was used: Forging allows one to bend the sheet metal to the shape of a die. In order for the rod to stick on the sheet metal it has to be riveted on. Influencing Factors: Economic Factor: Cold rolling increases the strength of the material, thus using less material, which leads to saving money.	Complexity:5 Functions:1 Manufacturing processes:3 Geometry:1
Metal Coil	*Model #: 590433 Quantity: 1 Approx. Weight: 2-5oz General Shape: spiral Dimensions (cm): 9.5x9.5x0.4	Function: Used as a spring to reset the pull-start after it has been pulled. Allows user to try and pull-start the engine multiple times in a row making it easier to start. Multiple Functions: Yes Associated Flows: human energy from the pull cord to rotational energy Function Environment: held under a cap to prevent coil from unraveling.	Material: steel Influencing Factors: The modulus of elasticity of steel allows it to be used as a spring because it takes a lot of force to plasticly deform. Aesthetic Properties: Smooth, unpainted metal. coil spring cannot be seen when the pull start system is assembled so it was not painted	Methods Used: rolling, milling Evidence: rolling was used to make the steel thin enough to bend into a coil. milling was used to get the required coil thickness. Why method was used: To get metal as thin as this coil is it had to be rolled since it is flat, not round like a wire which is manufactured by drawing. Influencing Factors: Economic Factor: Cold rolling increases the strength of the material, thus using less material, which leads to saving money.	Complexity:4 Functions:1 Manufacturing processes:2 Geometry:1
Head Gasket	Model #: 33015A Quantity: 1 Approx. Weight: <2oz General Shape: 2-D rectangular with cutout Dimensions (cm): 13x9.5	Function: Allows a tight seal so that there is no intake or exhaust leaks. Multiple Functions: No= Associated Flows: N/A Function Environment: It is located between the heat sink and engine block. It has to be able to with stand heat and pressure.	Material: Aluminum with epoxy center Influencing Factors: To make a tight seal. Aesthetic Properties: Shiny Metal surface with pits. Little Aesthetic design, mostly a result of manufacturing processes.	Methods Used: Rolling, Forging, Adhered, Drilling Evidence: Rolling was used to obtain the sheet metal. Multiple sheets of metal was adhered then forged to stick together. When forged it also cuts out the irregular shapes. Drilling was used to obtain the circular holes. Why method was used: Rolling is the easiest way to obtain multiple sheets of metal. Forging allowed multiple sheet metals to combine while also cutting out the irregular shapes. Drilling is the easiest way to obtain circular holes. Influencing Factors: Economic Factor: Cold rolling increases the strength of the material, thus using less material, which leads to saving money.	Complexity:4 Functions:1 Manufacturing processes:2 Geometry:1
Gas Tank	*Model #: 33904B Quantity: 1 Approx. Weight: 1-2lbs General Shape: rectangular prism Dimensions (cm): 28x15x8	Function: To hold gas that has yet to be used by the engine. The gas tank is where the user inputs the gas into the system. The gas is transferred from the tank to the piston chamber. Multiple Functions: Yes Associated Flows: importation of gasoline Function Environment: the outside of the tank is exposed to the natural environment and can become wet. The inside of the tank is exposed to gasoline and its fumes, the plastic must be able to contain the chemical.	Material: plastic Influencing Factors Economic:A plastic gas tank is much cheaper than a metal tank especially because of the size of the component. Aesthetic Properties: Rough to texture. Black plastic which goes along with the black painted metal housing.	Methods Used: injection molding, adhering Evidence: Injection molding was used to shape two halves of the tank. This is indicated by the rough pattern on the outside of the tank, only achievable through injection molding. The two halves were put together using some type of adhesive. Why method was used: Complex shape only achievable with these methods. Since its hollow two halves had to be adhered. Influencing Factors: Environmental: Injection molding is cheep and has little waste. It also requires little processing after completion.	Complexity:5 Functions:1 Manufacturing processes:2 Geometry:2
Metal Housing	*Model #: 33891B Quantity: 1 Approx. Weight: 10-12lb General Shape: circle with protrusion Dimensions (cm): 28x20x7	Function: To protect the inside components of the engine from damage. Multiple Functions: no Associated Flows: none Function Environment: Subjected to outside environment, needs to withstand the elements.	Material: Steel Influencing Factors: Steel best protects against physical and environmental damage that the engine goes through Societal: The color black as well as other available colors appeal to buyers. Steel makes the product look sturdier and more expensive which people see as a good thing. Aesthetic Properties: painted black with rusted underside from lack of paint. Painted to look nice from the exterior.	Methods Used: Rolling, Forging, Sawing, Drilling Evidence: Rolling was used to get the flat surface. Forging was used to bend the sheet metal to the desired shape. Sawing was used to cut the irregular hole shapes. Drilling was used to create holes for the screws. Why method was used: Rolling is the easiest way to obtain sheet metal. Forging allow one to manipulate the shape. Sawing is the easiest way to create irregular holes. Drilling is the easiest way to create circular holes. Influencing Factors: Economic Factor: Cold rolling increases the strength of the material, thus using less material, which leads to saving money.	Complexity:8 Functions:1 Manufacturing processes:4 Geometry:1
Piston	Model #: 35546 Quantity: 1 Approx. Weight: 4-5oz General Shape: Cylinder Dimensions (cm): 6.5x6.5x5	Function: To convert Pneumatic energy from combustion to the the crankshaft through translational energy. Multiple Functions: No Associated Flows: Combustion to pneumatic to translational energy Function Environment: Is under constant high heat and pressure due to combustion.	Material: Aluminum Influencing Factors: This is a moving part. Since aluminum is light less force is required to move it, resulting in saving energy within the system. Aesthetic Properties: Smooth gray surface. Smooth to allow easy movement, little aesthetic design.	Methods Used: Die Casting, Turning, Grinding Evidence: The piston seems to be die-caste because of its complex geometry, this is visible on the inside. The outside, however looks more finished and polished. The notches for the gaskets were cut using turning as it needs to be precise for them to work correctly. The piston was finished using a grinder to get the exact diameter needed, even a thousandth of an inch may have been taken off for the piston to fit perfectly in the cylinder chamber Why method was used: Die casting was required to get complex shape. Grinding used to get exact shape. Influencing Factors: Economic: This part was not machined but die-cast, saving time, money and labor.	Complexity:6 Functions:1 Manufacturing processes:3 Geometry:2
Connecting Rod	Model #: 30963B Quantity: 1 Approx. Weight: 8 oz General Shape: Flat Bar Dimensions (cm): 11x1.8x2	Function: To convert translation energy from the piston to the the crankshaft to get rotational energy. Connects the piston to the crankshaft. Multiple Functions: No Associated Flows: Translational to rotational energy Function Environment: Under constant heat and motion and needs to be well lubricated.	Material: Aluminum Influencing Factors: This is a moving part. Since aluminum is light less force is required to move it, resulting in saving energy within the system. Aesthetic Properties: Semi rough gray surface, mostly as a result of manufacturing processes. Little Aesthetic design.	Methods Used: Die Casting, Drilling Evidence: The connecting rod was clearly made by die casting. This is indicated by parting lines being visible and the rough finish of the part. Drilling was used to make a precise hole for where the piston is attached. Why method was used: Die casting was required to get complex shape. Influencing Factors: Economic: This part was not machined but die-cast, saving time, money and labor.	Complexity:5 Functions:1 Manufacturing processes:2 Geometry:2
Crankshaft	*Model #: 34233A Quantity: 1 Approx. Weight: 4-6lbs General Shape: Rod Dimensions (cm):	Function: To convert translation energy from the connecting rod to rotational energy which is what the ultimate function of the engine is. Connects to the magneto and main spinning component for the blades. Multiple Functions: Yes Associated Flows: Translational to rotational energy Function Environment: Under constant heat and motion and needs to be well lubricated.	Material: Steel Influencing Factors: Steel was chosen because its strength and high melting temperature is needed due to it being under constant heat and movement. Cast iron would have been to brittle. Societal:Steel is strong. It improves the appeal of the component knowing that it will be strong, safe and should last. Economical: Steel is expensive compared to iron or aluminum, using this increases the component cost, but its strength makes it the best material choice. Environmental: Steel is recyclable, and reusable after the engine is disposed. Aesthetic Properties: Smooth where connecting rod contacts it so that it has low friction. Other parts have rough surface as a result from casting.	Methods Used: Die Casting, Turning, Milling Evidence: The crankshaft's center was clearly made by die casting seen by parting lines and the rough finish of the section. Turning was used to get a precise diameter of both ends of the shaft. Milling was also used to carve notches in the shaft ends because the notches are not axially symmetric like the rest of the shaft. Why method was used: Die casting was required to get complex shape. Turning was used to get precise measurements. Influencing Factors: Economic: This part was not machined but die-cast, saving time, money and labor.	Complexity:7 Functions:1 Manufacturing processes:3 Geometry:3
Dip Stick	Model #:36879 Quantity: 1 Approx. Weight: 1-2oz General Shape: rod with cap Dimensions (cm): 18.5x1	Function: To allow the user to determine if enough oil is in the system. Multiple Functions: No	Material: plastic and aluminum Influencing Factors: Societal:oil sticks to the aluminum allowing the user to easily read the level. Aesthetic Properties: there is an indicator on the stick for the user to easily determine if the correct amount of oil is in the engine.	Methods Used: injection molding, forging Evidence: The plastic part of the dipstick shows parting lines and excess flash on the inside, these are indications of injection molding. Forging used to stamp out the aluminum part of the dip stick. Why method was used: injection molding was used to create the complex shape, referring to a hollow tube, which is easily achievable by injection molding. Influencing Factors: Environmental: Injection molding is cheep and has little waste. It also requires little processing after completion.	Complexity:5 Functions:1 Manufacturing processes:2 Geometry:3
Dip Stick Housing	Model #: 34380 Quantity: 1 Approx. Weight: 1-2oz General Shape: cylindrical Dimensions (cm): 17x2x2	Function: Where the oil is imported by the user into the engine. Protects the dipstick from debris and other harm. Multiple Functions: Yes Associated Flows: importation of oil Function Environment: has oil flowing through it.	Material: plastic Influencing Factors: plastic must not interact with oil. Economic: plastic is cheaper than metal. If the part doesn't need any structural rigidity so plastic is a better choice. Aesthetic Properties: Black and White Plastic. The Exposed Parts are black to match the gas tank while the unexposed parts are mixed color.	Methods Used: injection molding Evidence: The plastic part of the dipstick shows parting lines. Why method was used: Any other process would be to expensive and time consuming to make such an intricate geometry. Influencing Factors: Environmental: Injection molding is cheep and has little waste. It also requires little processing after completion.	Complexity:4 Functions:1 Manufacturing processes:1 Geometry:2
Flywheel	Model #: not found Quantity: 1 Approx. Weight: 2-3lbs General Shape: cylindrical Dimensions (cm): 17x17x4	Function: The flywheel has a magnet inside of it. When the flywheel spins it generates electricity by creating a magnetic field with the magneto which is used to start the engine. It also serves to function as a momentum carrying device to keep the engine spinning and drive the piston up during the compression stroke when no energy is being generated. Multiple Functions: Yes Associated Flows: Electrical energy to combustion Function Environment: Spins freely just under metal housing. Subjected to outside air.	Material: Aluminum Influencing Factors: A lighter flywheel allows for the user to use less force when pulling the pull start Aesthetic Properties: Gray unpolished metal. Little aesthetic design, most of its qualities come from its material and manufacturing processes.	Methods Used: Die Casting Evidence: The intricate geometry of the fly wheel, which includes many fins and teeth, as well as the rough finish are characteristics of die casting. Why method was used: Intricate shape led to die casting. Influencing Factors: Economic: This part was not machined but die-cast, saving time, money and labor.	Complexity:5 Functions:1 Manufacturing processes:1 Geometry:3
Magneto	Model #: 730207 Quantity: 1 Approx. Weight: 6-9oz General Shape: Dimensions (cm): 10x10x2	Function: Creates a magnetic field with the flywheel to generate electricity used to start the engine. Multiple Functions: No Associated Flows: rotational energy from the flywheel to electrical energy. Function Environment: Located under the flywheel. when the engine is on a magnetic field is created around the magneto. the magneto is not exposed to the outside environment as water may cause it to malfunction.	Material: Steel, plastic and aluminum Influencing Factors: different materials are used in this assembly to allow it to perform its multiple functions. Aesthetic Properties: Rough gray surface with black wiring. Little Aesthetic design, mostly a result of manufacturing. The wire insulation is colored back to match the other plastic parts.	Methods Used: die casting, drawing, injection molding, riveting Evidence: parting lines are evidence of die casting of the steel part and injection molding of the plastic part. Drawing was used to make the wires. riveting to attach parts together. Why method was used: complex geometry of steel and plastic part require die casting/injection molding Influencing Factors: Environmental: Injection molding is cheep and has little waste. It also requires little processing after completion.	Complexity:8 Functions:1 Manufacturing Processes:4 Geometry:3
Spark Plug	Model #: 33636 Quantity: 1 Approx. Weight: 2-4oz General Shape: cylinder Dimensions (cm): 7x2.5x2.5	Function: To provide spark at proper time intervals. The spark is delivered at the top of the combustion chamber to ignite the air/fuel mixture. The spark plus is responsible for starting the chemical reaction in the combustion chamber. Multiple Functions: Yes Associated Flows: Rotational energy is converted to voltage at the magneto, the electric energy is delivered to the spark plug via a wire, the spark initiated the transition from chemical energy to mechanical energy. Function Environment: The spark plus is threaded into the engine's head. The spark plus must withstand extreme heat and repeated creation of spark.	Material: aluminum, steel, an insulating ceramic, and (copper, nickel-iron, or noble metal for the tip) Influencing Factors: Functionality Aesthetic Properties: cylindrical shape, smoothed plastic, most likely a result of manufacturing with little aesthetic design.	Methods Used: machining Evidence: precise threads were cut, as well as a strong, precise tip Why method was used: precision is necessary for a spark plug to function properly, consistently, and reliably.	Complexity:4 Functions:1 Manufacturing processes:1 Geometry:2
Carburetor	Model #: 632795A Quantity: 1 Approx. Weight: 1-2oz General Shape: Cylindrical components Dimensions (cm): 14.5x6x5	Function: The carburetor allows air and fuel to enter the engine. It also controls the air-to-fuel mixture to ensure that the same ratio of air and fuel is used with every cycle of the engine. The carburetor also has a rubber "priming bubble" that allows the user to push fuel into the carburetor to ease the starting procedure. Multiple Functions: Yes Associated Flows: Transfer of chemical energy into combustion chamber. Function Environment: Attached to engine block, must maintain seal under slight pressure changes.	Material: plastic and aluminum Influencing Factors: different materials are used in this assembly to allow it to perform its multiple functions. Aesthetic Properties: Smooth and black. Designed to look smooth since it can be seen on the exterior of the engine.	Methods Used: Injection molding, machining, casting Evidence: Parts have slight seams, Metal parts are precise Why method was used: Cheap and easy to mass produce when using injection molding, machining is a precise method to manufacture parts	Complexity:8 Functions:2 Manufacturing processes:3 Geometry:3
Valve Cover	Model #: 32755 Quantity: 1 Approx. Weight: 1-2oz General Shape: Flat sheet of metal. Two bolt holes on opposite sides. Dimensions (cm): 8.5x4x0.5	Function: Prevent debris from entering the the valves and to allow access for valve repairs. Allows for easy access to the valves. Multiple Functions: Yes Associated Flows: none Function Environment: Attached to engine block. Must withstand heat and seal out debris.	Material: Steel Influencing Factors:Must be made with a material strong enough to protect the valves and valve springs. Aesthetic Properties: semi-smooth steel. Most likely ground smooth because it can be seen from the outside of the engine	Methods Used: Drilling, Forging Evidence: Drilling was used for the 2 holes on the side. Forging was used to get the indent in the center of the plate. Why method was used: Drilling allows one to create a precise hole. Rolling was used to get the object to be flat, while forging allows the object to have the indent shape.	Complexity:4 Functions:1 Manufacturing processes:2 Geometry:1

Solid Model Assembly

The following are solid CAD models of parts of the piston cylinder system of our one cylinder lawn mower engine. We modeled these parts in Autodesk Inventor Professional 2012. We wanted to model components that would not be too difficult to achieve an accurate model but still were part of a main subsystem of the engine that had a vital function. It was for this reason that we chose to model the piston from the piston-cylinder as well as the piston rings, connecting rod and all their connecting components.

Figure 1	Piston-The main component used to capture the explosive pneumatic energy in the combustion chamber
Figure 2	Add connecting rod pin- connects the piston to the connecting rod and allows rotation of the connecting rod.
Figure 3	Add small piston rings- Used to help seal off the combustion chamber.
Figure 4	Add large piston ring- Used to help seal the combustion chamber but allow in oil to lubricate cylinder walls.
Figure 5	Add connecting rod- converts the translational energy from the piston to rotational.
Figure 6	Add connecting rod cap- used to hold the connecting rod to the crankshaft and still allow rotation.

Engineering Analysis

The analysis process can be used in many ways, including in the design process. The analysis process can be used for multiple reasons including the design of things such as the piston and piston rings or a heat sink. The engineering analysis helps people develop a step by step model to accomplish the necessary task or problem. An example of using the analysis process to help determine how a particular design is as follows:

This is an example problem of examining a basic design of a heat sink and how it would function.

Problem Statement:

An engines cylinder is surround by many heat sinks that serve to help increase the rate of heat transfer out of the engine to prevent heat damage. A basic model of a heat sink is metal base with extended metal plates protruding from it. These plates increase the engines exposed surface area and therefore increase the rate of heat dissipation by convection. Find the rate of heat dissipation by the heat sink on our internal combustion engine.

Diagram:

Figure 1: Heat loss of heat sink

Assumptions:

Assume standard temperature and pressure (STP). Standard Temp Tf=15 degrees Celsius. Standard Pressure P= 1 atm.

Assume convection is the main source of heat loss and therfore that the heat loss from conduction and radiation is insignificant. Assume constant surface temperature. Assume steady heat flow in. Assume that the engine is running at a constant operating temperature Ts=150 degrees Celsius.

Governing Equations:

Qconv = (h)(A)(Ts-Tf) where Qconv is the rate of convection heat loss, h is the

convection heat transfer coefficient, A is the surface area, Ts is the surface temperature, and Tf is the air Temperature.

Calculations:

In this step one would change variables and calculate the modeled heat loss rate Qconv for different heat sink designs using the given assumptions. One would need to make sure that all calculations were using correct units and that all units were in the same unit system (i.e. SI or English)

Solution Check:

In this step one would need to confirm if the solution from the calculation steps. One could compare the Qconv found to known values of other heat sinks from other similar engines. One could also do unit analysis to check that all of the units used were correct.

Discussion:

If it is found that the heat sink is not efficient enough after testing at getting rid of excess heat. The following solutions could solve the problem.

• Increase surface area by lengthening the fins, because surface area, A, is directly related to the heat loss, Qconv.
• Using a different material with a higher heat transfer coefficient will increase efficiency, as it is also directly related to heat loss, Qconv.

Design Revisions

Redesign 1:

The basic design of our lawn mower engine is relatively simple, compared to larger more powerful engines, and yet a functional design. We did notice, however, when you rotated the engine, before its full disassembly, that many of the components’ tolerances were not highly accurate. As a result as the engine ‘turned’ many of the parts fit loosely enough that the individual motion of the components was sometimes not steady and many components rattled or wobbled slightly as they interacted. This would make the engine run very loudly and cause much vibration throughout the device. This rattling not only would cause slight discomfort for the user but also could increase the speed at which the engine wears and increase the chance of component fatigue as well as increase stress and heat damage over time. One of our redesigns for this engine would not necessarily be redesigning its parts, but redesigning each its manufacturing processes to decrease the components individual tolerances so the parts fit together with more precision. Increasing the components' accuracy should decrease the noise and vibrations as well as increase the life expectancy of the engine, and decrease energy loss due to heat and vibrations. Doing this would most likely increase the cost of the engine, but if it last longer it could save the owner in replacement costs, which affects its economical design factors. These changes could improve the engines appeal and marketability affecting societal design factors. It also could affect environmental design factors by increasing its efficiency and decrease the amount of engine waste from disposal if the owner replaces them less, but could increase production waste as a result of more detailed grinding and energy use during production. Overall I feel decreasing the tolerances on each component would improve the engine.

Redesign 2:

In addition to decreasing the tolerances of our parts, changing the material of some of our parts could increase the engine's life span. There are several components within the engine that are plastic. Our oil pump ring as well as a few gears are made of plastic. These components show evidence of fatigue more then the steel and aluminum parts do. As plastic ages it becomes more brittle and it is inferior to metal in many ways (i.e. strength, toughness, fatigue resistance, melting resistance, hardness) except manufacturability. Changing these components’ material from plastic to aluminum would increase the engine’s wear resistance and could increase its lifespan and decrease replacement costs for the owner. When considering economical design factors and engineer would see that this would increase production costs but could help improve societal design factors by increasing appeal and marketability knowing that all components were made out of superior materials and the engine could last longer. An example metal oil pump is shown in figure 2 below.

Figure 2: An Example of a Metal Oil Pump

Redesign 3:

In our engine there is a single piston that combustion drives down and rotates the crankshaft. The piston is driven down by pneumatic energy but is carried back to its starting position simply by rotational momentum of the rotating parts (much of which is supplied by the flywheel). This means the engine does not run perfectly smooth and that the torque output changes as the piston goes up and down. Another option for redesign is to replace the single cylinder with two smaller ones. If the connecting rods were connected 180 degrees apart from one another on the crankshaft, as piston one is pushing down and rotating the crankshaft, piston two would be moving upward. This would help make the engine run more smoothly and have a more consistent energy output with the exception of the instant that the two pistons are changing direction, the engines movement is never fully dependent on only momentum but is always being driven by one of the pistons. This change would affect economic factors as it would increase the cost, but since the engine would run more smoothly it may last longer and save on replacement costs. This also would have an affect on societal factors as you could now call the engine a 2 cylinder engine which sounds more advanced even though it may have the same torque output. This change may also help improve the engines efficiency which would effect environmental and economical factors. Overall the cost of the engine may go up, but it would improve its performance and reduce vibrations to improve handling comfort. An example of a basic in-line 2 cylinder engine can be seen in figure 3 below.

Figure 3: An Example of a basic In-line 2 Cylinder Engine