Gate 3: Product Analysis

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Group 22 - Tecumseh Engine Disassembly Process 2011


Project Management: Coordination Review

Cause for Corrective Action

    Each member of our group, like everyone else, has their strengths and their weaknesses. It is important to utilize each member’s strengths while improving upon each member’s weaknesses. Our group has started to get a feel for each member’s strengths and weaknesses and is now working well together to take advantage of each person’s talent.

    Our group has made many changes since the beginning of the project. For example, our group had a very tough time communicating with one another. The majority of the group was able to attend most meetings and make up the work and research they missed if they could not attend. The other two members seemed to have other priorities to take care of instead of the tasks assigned for the project. These two members were extremely hard to work with as it became very hard to communicate with them because they seemed to be absent for most meetings and even the dissection process. This lead to confusion in future assignments for the two members and as each assignment related to past parts of the project it became very hard for these members to catch up. A few weeks went by as the majority of the group gradually began to do more work than the other two members on each assignment. The unfair work load and poor communication between group members lead to insufficient work and last minute touch-ups before each deadline. This made it clear that communication would be a huge factor in the success of each assignment because without the use of necessary meetings, emails and text messages our group would not be able to finish each task thoroughly and efficiently.

    The majority of the group decided that it would be beneficial to figure out possible solutions to improve the group’s overall communication. First the group agreed the other two members need to be confronted about their lack of contribution for each assignment. This turned out to be extremely helpful as each member was able to discuss their personal difficulties that have been affecting the group’s progress. Once the problems began to surface the group was then able to resolve each member’s issue.

    of the members seemed to be really stressed with other classes and simply felt they had no time to focus on the project. Conveniently, the member recently dropped one of their classes and told the group that they would now be able to put more effort in each task they are assigned.

    The other member was having trouble balancing the group’s project on top of their work schedule. This group came to an understanding that even though this group member would not be able to make some of the meetings they would still be required to do their share of research and work. This problem was resolved by communicating and coming up with a system to involve this member with the project and each task that was performed. The member would be emailed with a task for each assignment to do on their own to fit their busy schedule while still being able to talk to the group and ask for advice or help on comprehending the material.

    Other improvements our group has added include a recognition system and a record of attendance. To increase the motivation in each member to do their best on each assignment and reward those who do, our group has decided to accredit each member’s work with the use of author labels on the Wikipedia page. It is obvious how significant each group meeting is to the progress of each assignment, in order to improve this attendance at each meeting the group has decided to record attendance to document the trend of each member’s attendance and expectantly encourage each member to be present.

    Author: Ryan Sans

Product Archaeology: Product Evaluation

Component Summary

Part Function *Complexity Material Manufacturing Method Quantity Image
Gas Tank This part is used as a containment and the supply source of gasoline used for the combustion. 1 Plastic Injection Molding 1
Figure 25: Tecumseh Gas Tank
Recoil Starter To Start the engine by pulling a cord that rewinds with every pull. When the cord is pulled it spins the flywheel creating the initial rotational motion and spark. 3 Plastic Injection Casting 1
Figure 26: Tecumseh Recoil Starter with unwind cord
Flywheel The flywheel provides rotational energy to the crankshaft and helps to create a magnetic field with the magneto with embedded magnets on the side of the flywheel. this field will help provide electrical energy to spark a combustion. 6 Aluminum Die Casting, Machining 1
Figure 27:Tecumseh Flywheel
Air Filter Filters the air needed for combustion and helps keep any objects that could harm the engine out. 2 Plastic,Sponge Injection Molding 1
Figure 28: Tecumseh Air Filter disassembled
Carburetor The carburetor is responsible for mixing the air coming in from the filter and the gasoline coming the gas tank. The main job of the carburetor is to provide enough gasoline to make the engine work efficiently. 10 Iron Die Casing, Machining 1
Figure 29: Carburetor
Magneto The magneto, using the magnetic field generated by the rotational motion of the flywheel, generates an electrical current that creates periodic sparks. The spark generated by the magneto creates a combustion with mixture of gas and air coming from the carburetor. 8 Aluminum, Iron Ferrite, Machining Die Casting 1
Figure 30: Tecumseh Magneto
Spark Plug It releases the spark that the magneto produces for the combustion of the mixture of gasoline and air 4 Silver Machining, Investment Casting 1
Figure 31: Spark Plug
Piston The piston converts the pneumatic energy generated by the combustion into transitional motion. When the combustion takes place it creates a force against the piston making a the linear motion .The piston motion transfers energy to the flywheel through the crankshaft which stores it then releases when the piston does not provide force. 5 Cast Aluminum Casting and Machining, Subtractive 1
Figure 32: Tecumseh Piston
Camshaft Opens and closes the valves that import air and gas as well as expel exhaust. A gear is used to rotate the camshaft and which signals the valves to open and shut 3.5 Steel Investment Casting 1
Figure 33: Tecumseh Camshaft and Gear
Crankshaft Converts the transitional motion of the piston into rotational motion.For this specific product the crankshaft is used to spin a blade. 3 Steel Casting and Machining 1
Figure 34: Crankshaft

* Complexity is in a rate from 1 to 10. 10 being the more complex in the context of function, parts, shape, etc.

Authors: Kevin Perez, Matthew Whitman

Component Flow Diagram

    The component flow is illustrated in figure 22 below on the left, it represents the interactions between each component during the operation of our product. For a better understanding of the component interactions relating to energy we can compare this diagram to the energy diagram that was explained in gate one as shown below in figure 23 below on the right:
        Figure 23: Energy Flow
        Figure 22: Component Interactions

        Author: Ryan Sans

      Product Analysis

      Component Summary

      Component Function

        Our product, a 5 HP Tecumseh engine, was designed to power a lawn mower. While mowing the lawn, there is the potential risk of damaging the engine by rocks and debris kicked up by the blades. Also rain and other weather could contribute to some wear and tear the product could experience. In order to counter act that, the designer of the engine used a tough cast iron shell to house the more delicate parts.

      Component Form

        It was necessary to design the product to have a smaller size, making it easier to push the finished product (lawn mower). Primarily a three dimensional product, the engine weighs roughly 5 pounds and is about 12in x 6in in size. There is not much symmetry to the engine due to the many individual subsystems associated with it and its aesthetics and color were not taken too much into account because the final product would hide most of the engine.

      Manufacturing Methods

        Multiple materials were used in the design of our product. For the outer shell of the engine, cast iron was necessary in order to protect the interior of the engine from damage stemming from use of the lawn mower. The interior parts are mainly metallic, such as the alternator, piston, crankshaft, gear box, and cam shaft, in order to ensure long life for the engine. There are some plastic parts such as the gas tank and oil tube as well as some rubber insulation over the wires connecting the magnetron to the piston cylinder. Most of these pieces were made through die casting for quick production with few errors at a low cost. This is evident because of the parting lines that can be seen on many of the parts throughout the engine.

      Component Complexity

        Our product was designed by Tecumseh Power to function as a lawn mower engine. The designer had to take several main factors in to consideration when developing the product such as durability, efficiency, ease of us, and functionality. In order to achieve the necessary standards in each of these areas, the designer had to decide on the proper materials, production process, and overall layout of the engine.
        After the dissection of the product, we were able to apply the knowledge gained through lecture to figure out how each part was produced. Many of the parts including the outer shell, fly wheel, alternator, air filter, and many of the gears appear to have been produced through die casting. Die casting would serve to make the parts of the engine quickly, reliably, as well as inexpensively. One of the major clues that pointed us in this direction was the parting lines that are visible on each part. Investment casting may have also been used on some parts that require more detail, such as the cam shaft where no parting lines were discovered. Many of these parts were made of a sturdy metal, mostly cast iron, in order to ensure the longest possible life of each part. Other parts such as the gas tank and air filter were made from plastic and the alternator and magnetron included magnets. Each part must also have a high melting point to endure the high temperatures that the engine could reach.
        It was necessary to design the product to have a smaller size, making it easier to push the finished product (lawn mower). Primarily a three dimensional product, the engine weighs roughly 5 pounds and is about 12in x 6in in size. There is not much symmetry to the engine as a whole due to the many individual subsystems associated with it; however the individual parts required different geometric design. The fly wheel, alternator, crank shaft and cam shaft, being required to rotate, all possessed lines of symmetry. The piston and carburetor are also symmetric. One logistical design factor that was included was the location of the gas tank. Putting the tank near the surface makes it easier for the user to add gasoline and change the oil without having to disassemble the engine. Its aesthetics, color, and finish were not taken too much into account because the final product would hide most of the engine from sight.

      Product Analysis

      Component Function Form Manufacturing Method Complexity
      Crankshaft The crankshaft is responsible for outputting the work generated by the engine. It utilizes the transitional motion of the piston and converts it into rotational motion. The crankshaft also drives the camshaft while it rotates. The crankshaft is approximately 10in long and weighs about 8 ounces. The shape of the crankshaft is basically a long rod with a gear attached to one side and an indent (journal) in the middle. The gear on the crankshaft is fitted with the gear from the camshaft and the journal attaches to the rocker arm. The crankshaft is made of steel in order to ensure durability. Forging is used to manufacture most crankshafts while some high performance crankshafts are made using billet machining. These processes are needed in order to make later adjustments in the crankshaft to achieve the best efficiency. This component is somewhat complex because the manufacturer needs to achieve the correct timing with the cam shaft and the piston.

      Complexity: 6

      Camshaft Rotates with the crankshaft and is responsible for opening and closing the valves while the engine runs. The Camshaft has a gear on one end that is fitted with the gears on the crankshaft. It also has two bumps on the shaft called cams. The shaft is about 3 in long and the gear has a radius of ½ in. CNC Machining and forging are commonly used to manufacture the camshaft because of the ability to make small changes to increase efficiency. In order to create an efficient engine, the cam timing must be precise. Because of this, a lot of research is done to pinpoint the proper orientation and geometry of the cams. Although our product does not require as high as performance as automobiles, it is still important to have the correct timing.

      Complexity: 5

      Piston Arm The piston arm works to transfer the transitional motion of the piston to the crankshaft. It does this by moving with the piston head as it alternates between strokes and rotating the crankshaft in the same motion. The piston arm is approximately 3in long, 3/4 in wide, 1/4 in thick, and weighs about 4 ounces. There is a slight angle in the neck of the arm which allows the arm to rotate the crankshaft. The arm is made of aluminum because of its light weight and durability. Piston arms are typically made through die casting because of its inexpensive high volume output. This component is not that complex in its design or its interactions with the other components with the exception of the energy transfer between transitional and rotational mechanical energy.

      Complexity: 2

      Piston Ring The piston ring serves to seal the combustion within the combustion chamber as well as properly lubricate the engine with oil. The piston ring is a circular shape with a small horizontal gap that allows the ring to be wrapped around the piston head. There is also a grove in the ring that allows for the dispersion of oil. The ring on our product is about 2in in diameter and weighs less than an ounce.Ring material ranges between cast iron and steel because of the need to withstand high temperatures and have high malleability. Piston rings are typically machined because of the level of detail and the small size of the ring. This component is rather complex because of the small details that are used to disperse the oil and the ease at which the ring can be broken (the group found that out the hard way).

      Complexity: 7

      Spark Plug The spark plug is responsible for beginning combustion by igniting the fuel/air mixture in the combustion chamber. It receives energy from the flywheel as it spins passed the magneto and uses that energy to generate a spark which begins combustion. The spark plug has threads on one side that allow it to be screwed into the engine and a socket on the other end that emits the spark. It is mainly cylindrical in shape, approximately one inch in length, 1.4 in in diameter, and slopes towards the side that emits the spark. The spark plug is composed of several different components such as the shell, insulator and the central conductor. These parts are either made from alumina or ceramic. The spark plug must either be assembled by hand or machine. Welding, injection molding, and machining are all used in the manufacturing process. Because of its many systems, the spark plug is very complex (An entire analysis could be created around the spark plug itself). The transfer of energy that takes place inside the spark plug is also rather complex.

      Complexity: 10

      Flywheel The flywheel is designed to rotate with the crankshaft in order to generate electrical energy through induction. The flywheel has a magnet on the outside of it that passes by a magneto which generates an electrical current that goes to the spark plug. The flywheel is circular with a diameter of 8 inches and a thickness of 3/4 in. It is made from aluminum because it is non-magnetic and lightweight (weighs about 6 ounces). The light weight makes it easier for the user to start and requires less work from the crankshaft to rotate, thereby making it more efficient. The flywheel is made through die casting and machining to ensure geometric symmetry and that it will rotate smoothly. This component is not that complex to manufacture but is somewhat complex in the energy transfer it performs (mechanical to magnetic to electrical)

      Complexity: 6

      CAD Model Assembly

        Three main components of the Tecumseh engine are the Flywheel, Piston and Crankshaft, working together to create the rotational motion. These parts are ideal for the CAD drawing. There are other important factors that help the components achieve their purpose but they are more complex and small which would be more complicated to draw and would crowd the CAD drawing.
        AutoCAD 2010 was used for the drawings, is an easy software and is the only CAD that our group has knowledge of use.

      Authors: Kevin Perez, Darroch Moorhead

      Figure 34: AutoCAD drawings of Piston, Crankshaft and Flywheel
        (flywheel was not included in assembly because it did not connect with the piston or crankshaft, but it is an important part)
        (Assembly shown at bottom of image)

      ****All dimensions are in English unit inches****

      Author: Darroch Moorhead

      Figure 35: 3D Model of Tecumseh 5hp Engine Piston

      Author: Ryan Sans

      Engineering Analysis

        An internal combustion engine has many components and features that work together during the combustion process. The engine utilizes the chemical energy brought into the cylinder from the air/fuel mixture which is ignited by the spark generated by the alternator and magneto. The controlled explosion causes the pressure from the expanding gas to force the piston down the cylinder. This generates the translational energy needed for the piston to rotate the crankshaft. It is easy to see that the piston plays a significant role for the Tecumseh 5hp engine as it is responsible for most of the energy transfers that take place during the combustion process. Engineering analysis would be used in the design process of the piston as it is one of the most important parts of our product and is crucial to the engines performance. First the engineer would identify what tasks the piston is used for, its positions during the use of the piston and the operating environment that would affect the pistons functionality.
        • Convert pneumatic energy from the expanding gas to translational mechanical energy
        • Small range of motion up and down the cylinder
        Operating Environment
        • The average temperature of a piston crown in a gasoline engine during normal operation is typically about 300 °C (570 °F).
        • Friction on the cylinder head from the piston head.
        • Possible material expansion under high temperatures.
        • Size of Cylinder affecting the power output
        Second the engineer has to breakdown what the problem is and determine the process needed for a successful design. This step is crucial to the design of the product as the engineer uses each of the seven steps of analysis to generate a solution. During this process it is important to pay attention to every detail as there is a lot of room for error.

      1. Problem Statemet

        Design a piston for the Tecumseh 5hp engine to work efficiently under the high temperature of 300 °C. The piston must also move freely in the cylinder with as little friction as possible. The material of the piston must also be chosen carefully as some materials expand more rapidly under higher temperatures. The size of the cylinder is taken into account as more air/fuel is allowed into the combustion process producing more power to be generated in the crankshaft.

      2. Diagram:

      Figure 23: Pictorial representation of the piston's two positions and factors involved in the design process
      Figure 24: Illustration of important measurements needed for the dimensional analysis of the piston

      3. Assumptions:

      Assume the piston is designed from six factors
      • Piston to Deck Volume
      • Piston Dome volume
      • Cylinder Displacement
      • Combustion Chamber Volume Efficiency
      • Piston Compression Depth
      • Head gasket volume

      4. Governing Equations:

        Piston to deck volume:

        • PDV = (0.7854*BORE²*DPC)+(VPD-VPB)

        • PDV = Piston deck volume
        • BORE = Length of piston
        • DPC = Distance to piston clearance
        • VPD = Volume of piston depressions
        • VPB = Volume of piston bumps

        Piston dome volume:

        • DV = (HCV + GV + PDV - (CD / (TCR - 1.00)))*(-1)

        • DV = Piston Dome Volume
        • HCV = Head Chamber Volume
        • GV = Gasket Volume
        • PDV = Piston Desk Volume
        • CD = Cylinder Displacement
        • TCR = Target Compression Ratio

        Cylinder Displacement (cc):

        • CD = (BORE)*(ES)*.7854*(ES)*16.387

        • CD = Cylinder Displacement
        • BORE = Length of the piston
        • ES = Stroke of Engine

        Combustion chamber volume efficiency:

        • VE = (3456*CFM)/(CID*RPM)

        • VE = Volume Efficiency
        • CFM = Engine air flow – Cubic feet per minute
        • CID = Engine displacement
        • RPM = Rotations per minute

        Piston Compression Depth:

        • PCH = BL – ((ES/2)+RL) – PDV

        • PCH = Piston Compression Depth
        • BL = Engine Block Length
        • ES = Stroke of Engine
        • RL = Rod Length
        • PDV = Piston to Deck Volume

        Head gasket volume:

        •HGV = (HGCT*0.7854*BORE²)

        • HGV = Head gasket volume

        HGCT = Head gasket compressed thickness
        • BORE = Length of piston

      5. Calculations

        After the necessary equations have been chosen for design of the piston a general solution is generated based on the solutions calculated from these equations.

      6. Solution Check

        Once the solutions have been determined a proper solution check is used to decide if the solution is reasonable as well as to rule out any defective diagrams, bad assumptions, unnecessary aplied equations, improper numerical manipulations and inccorect units.

      7. Discussion

        Once the solutions have been determined they are discussed based on the concepts and feasible considerations with the manufacturing process.
        1. Concepts
        • What is necessary for the piston to operate efficiently?
        • Is the piston going to last for long periods of time and use?
        2. Feasible Considerations
        • What sacrifices can be made to make the piston a low cost while still working efficiently?
        Next the engineer would generate the concluding solutions based on each of the solutions and considerations above to form the final dimensions and material to be used when manufacturing the piston. This is a critical step as it will determine the market price of the piston based on the size, type and amount of material used, and the processes necessary to create the piston.

      The Manufacturing Process:

        • The manufacturing process begins with a 3 meter long aluminum rod that is pushed and cut into slices called slugs by a rotary saw. The factory recycles any excess or non-used aluminum shavings.
        Figure 1: Aluminum Rods
        Figure 2: Rotary saw cutting the Aluminum

        • Next the punch press and die is preheated to 426 °C this is the temperature needed to forge the aluminum. The aluminum parts are then brought to an oven of the same temperature via conveyer belt where they await to start the punching process.
        Figue 3: Punch press being preheated
        Figure 4: Aluminum slugs being transported by conveyer

        • The punch applies two-thousand tons of pressure to form the initial state of the piston. One in ten forgings are dunked in water and checked for defects.
        Figure 5: Punch Press
        Figure 6: Slug being checked after forging

        • The forgings need at least an hour to cool before they are heated twice more. The first time it is heated at a higher temperature to strengthen the metal the second heating is used to maintain its strength
        Figure 7: Second heating process
        Figure 8: First heating process

        • Next the factory uses a lathe to form the necessary shape of the forging for machines that handle it in later processes. Small holes are drilled into the sides of the piston to help lubricate the piston with oil when it is operating.
        Figure 9: Lathe forming the slug
        Figure 10: Oil holes drilled into piston

        • Another lathe reduces the diameter of the piston and cuts three slits in the side, two for compression rings and one for an oil control ring. These slits allow mobility of the piston and enhance the seal during the controlled explosion inside the cylinder. Another hole is drilled for the wrist pin in order to link the piston to the connecting rod.
        Figure 11: Lathe reducing diameter
        Figure 12: Lathe cutting slits
        Figure 13: Wrist pin hole being drilled

        • A milling machine is then used to shave about two millimeters of aluminum off the piston to reduce the overall weight. White lubricant is sprayed on the piston during the milling process to help cool it down while shaving the metal. Another milling machine cuts of the top of the piston to create a dome for the piston to slide easily up and down inside the cylinder.
        Figure 14: Milling machine shaving piston
        Figure 15: Milling machine creating dome on piston

        • Another lathe is then used to shave about one millimeter more of the aluminum off the piston to create clearance when the piston expands under high temperatures. Two intersecting drain holes are then created for lubrication in the wrist pin.
        Figure 16: Lathe shaving piston
        Figure 17: Lubrication holes drilled

        • An engraving machine records data and model numbers on the piston. Workers then remove sharp edges from the piston by hand or belt sander that could be hazardous to the cylinder walls.
        Figure 18: Engraving of the piston
        Figure 19: Workers removing sharp edges on piston

        • A Cutting machine smooth’s the edges inside the piston for a snug fit with the wrist pin.
        Figure 20: Cutting machine smoothing the edges for the wrist pin

        • Finally, high pressure jets are used to spray the pistons with hot deionized water which reduces all traces of lubricant and oil used during the manufacturing process.
        Figure 21: High pressure jets

      Testing and Validating:

        • Before shipment of the product a prototype must be created and tested for performance and safety. If the prototype fails any of the tests, the design of the piston has to be modified to meet all the expectations of each test.

      Sales and Production:

        Once the piston is able to function efficiently and is safe for the consumer to use, the product is then able to be put on the market to be used in small engines or sold separately for repairs.
        Figure 22: Finished product of the piston

      Delivery and Support:

      • Finally the finished, tested approved product is shipped and delivered to the consumers. The manufacturer receives positive and negative feedback from the users which will help to improve upon the future design of the piston.

      Author: Ryan Sans


      Design Revisions

        When it comes to design revisions to improve our Tecumseh 5hp engine there are many factors to consider. Among the most important, it is necessary for the engine to operate at the highest efficiency possible to satisfy its economical desire. Other economic improvements are made to increase the protection and durability leading to a longer life of the engine for consumer. Environmentally speaking, the engine is also designed with the thought of reducing harmful emissions by producing cleaner exhaust as a byproduct. Societal factors include the simplicity of human interaction with the engine and how to improve it. This means that the design modifications of the engine revolve its components and the features of each one. Six of the most significant improvements are illustrated below along with the modifications and benefits involved.

      1. Direct Overhead Valve Design (OHV)

        Feature Modifications
        • Altering the location of the valves from the side of the cylinder to above the combustion chamber for higher intake and exhaust stroke efficiency
        • Changing the position of the camshaft from outside the cylinder head to inside it to rotate faster and reduce the complexity of the engine,br/>
        Component Modifications
        • Additional pushrods are combined with the rocker arms and camshaft of our product to open and close each valve
        Economic Benefits
        • Decreases oil temperature
        • Smaller in size
        • Enhanced wear resistance
        • Enriched oil consumption
        Environmental Benefits
        • Cleaner burning engine
        • Less moving parts leads to a reduced noise output

      2. Automotive Style Piston Ring: (3 Piece Oil Ring with Chrome Plated Rails)

        Feature Modifications
        • Better oil regulation
        • Enhanced sealing from the combustion chamber
        Component Modifications
        • Introduce a more efficient piston ring by replacing the old one
        Economic Benefits
        • Longer life as a result of reduced wear on the piston
        • Concentrated lubricant consumption
        • Improved engine durability

      3. High-Performance Cartridge Style Air Filter: (Dual Seal Design)

        Feature Modifications
        • The dual seal design of the new air filter allows for the air to be passed through two types of filtering mediums providing the best quality air to the engine
        Component Modifications
        • Old filter is eliminated and replaced by the new dual seal design filter
        Economic Benefits
        • Improved life
        • Advances the quality of air imported to the engine

      4. High-Performance Cartridge Style Oil Filter:

        Feature Modifications
        • Introduction of an enhanced oil filter built from more advanced material providing better protection and overall functionality
        Component Modifications
        • More advanced pressure valve for increased oil fluidity
        • High temperature anti-drain back to aid oil detainment
        Economic Benefits
        • Prevents dry starts
        • Permits oil to flow during cold starts
        • Diminishes oil restriction

      5. Ready Start®: (Breakthrough Starting System)

        Feature Modifications
        • Introducing the Ready Start® components designed by Briggs and Stratton determines when and when not to choke the engine by sensing the temperature of the engine based on the temperature it is during the operation
        Component Modifications
        • Additional components such as the air vain, thermostat and choke plate are used to regulate the amount of fuel that enters the engine. As the flywheel is rotated it pushed the air vain which opens the choke plate. The thermostat senses the heat of the engine and keeps the choke plate open as long as the engine is warm.
        Economic Benefits
        • No risk of overflowing the engine or failing the spark plug
        Societal Benefits
        • Eliminates the initial starting step of manually priming or choking the engine

      6. Reduction of weight in each part: (Mainly the piston, rings and wrist pin)

        Feature Modifications
        • Faster, more efficient moving parts as a result of a lighter mass engine
        Component Modifications
        • Less material is used for the piston, rings and wrist pin as a more sleek design can shred a few inches of aluminum from each part
        Economic Benefits
        • Smoother running engine

        Author: Ryan Sans