Group 8 - Lawnmower (Gasoline Powered)

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	| Engine Cover || Prevents debris from entering the engine. || Plastic || Injection Molding || [[File:EngCover2012.jpg|125px|thumb|Mower engine cover.]]		| Engine Cover || Prevents debris from entering the engine. || Plastic || Injection Molding || [[File:EngCover2012.jpg|125px|thumb|Mower engine cover.]]
	|-		|-
−	| Gas Tank || Serves as a reservoir for fuel until it is needed by the engine. || Plastic || Injection Molding	+	| Gas Tank || Serves as a reservoir for fuel until it is needed by the engine. || Plastic || Injection Molding ||[[File:Gas2012.jpg|125px|thumb|Gas tank, outlined in yellow, attached to the engine.]]
	|-		|-
−	| Air Filter Cover || Prevents extra debris from clogging the air filter. || Plastic || Injection Molding	+	| Air Filter Cover || Prevents extra debris from clogging the air filter. || Plastic || Injection Molding || [[File:Filter2012.jpg|125px|thumb|Air filter and cover, outlined in red, attached to the engine.]]
	|-		|-
−	| Spark Plug || Converts electrical energy into thermal energy in order to ignite fuel and air mix in the combustion chamber. || Steel, Ceramic || Steel: Drilling, Die Casting; Ceramic: Molding, Drilling, Machining	+	| Spark Plug || Converts electrical energy into thermal energy in order to ignite fuel and air mix in the combustion chamber. || Steel, Ceramic || Steel: Drilling, Die Casting; Ceramic: Molding, Drilling, Machining || [[File:Spark2012.jpg|125px|thumb|A spark plug similar to what would be in the lawn mower engine]]
	|-		|-
−	| Muffler || Dampens the noise created by the engine. || Steel || Die Casting, Drilling	+	| Muffler || Dampens the noise created by the engine. || Steel || Die Casting, Drilling || [[File:Muffler2012.jpg|125px|thumb|The exhaust muffler from the mower engine.]]
	|-		|-
−	| Carburetor || Mixes fuel with air; sends fuel-air mixture to combustion chamber. || Aluminum || Die Casting, Drilling, Milling	+	| Carburetor || Mixes fuel with air; sends fuel-air mixture to combustion chamber. || Aluminum || Die Casting, Drilling, Milling || [[File:Carb2012.jpg|125px|thumb|The engine's carburetor.]]
	|-		|-
−	| Engine Head || Has a hole where the spark plug is inserted; holds various fins for the purpose of cooling the engine. || Iron || Drilling, Machining	+	| Engine Head || Has a hole where the spark plug is inserted; holds various fins for the purpose of cooling the engine. || Iron || Drilling, Machining || [[File:Head2012.jpg|125px|thumb|The engine head on the fully assembled engine.]]
	|-		|-
−	| Flywheel || Stores kinetic energy, then uses that energy when the engine is not producing power; it also contains a magnet which provides electrical energy to the spark plug. || Iron || Die Casting, Drilling, Milling	+	| Flywheel || Stores kinetic energy, then uses that energy when the engine is not producing power; it also contains a magnet which provides electrical energy to the spark plug. || Iron || Die Casting, Drilling, Milling || [[File:Fly2012.jpg|125px|thumb|The engine flywheel.]]
	|-		|-
−	| Governor || Limits the speed of the camshaft in the engine. || Plastic, Iron || Iron: Drilling, Machining; Plastic: Injection Molding	+	| Governor || Limits the speed of the camshaft in the engine. || Plastic, Iron || Iron: Drilling, Machining; Plastic: Injection Molding || [[File:Gov2012.jpg|125px|thumb|The engine's governor.]]
	|-		|-
−	| Camshaft || Holds piston rod and various cams that push on the push rods, which open the valves in the combustion chamber. || Steel || Drilling, Milling, Grinding	+	| Camshaft || Holds piston rod and various cams that push on the push rods, which open the valves in the combustion chamber. || Steel || Drilling, Milling, Grinding || [[File:Cam2012.jpg|125px|thumb|The camshaft in the opened engine, highlighted in yellow.]]
	|-		|-
−	| Piston Rod || Connected to the crankshaft and rocker arms; when the piston rod pushes the elongated part of a cam, it forces the valves in the combustion chamber to open. || Aluminum/Silicon Alloy || Die Casting	+	| Piston Rod || Connected to the crankshaft and rocker arms; when the piston rod pushes the elongated part of a cam, it forces the valves in the combustion chamber to open. || Aluminum/Silicon Alloy || Die Casting || [[File:Piston2012.jpg|125px|thumb|The piston piston, composed of the piston rod (outlined in red), and the piston head (outlined in green), removed from the engine.]]
	|-		|-
−	| Piston Head || Uses energy from ignited fuel-air mixture to push piston rod, which turns the crankshaft and camshaft. || Aluminum || Drilling, Machining, Die Casting	+	| Piston Head || Uses energy from ignited fuel-air mixture to push piston rod, which turns the crankshaft and camshaft. || Aluminum || Drilling, Machining, Die Casting || (See picture for Piston Rod)
	|-		|-
−	| Valves || The intake valve allows the fuel and air mixture to enter the combustion chamber; the exhaust valve allows the gases formed during the combustion process to exit the chamber. || Steel || Forging, Grinding	+	| Valves || The intake valve allows the fuel and air mixture to enter the combustion chamber; the exhaust valve allows the gases formed during the combustion process to exit the chamber. || Steel || Forging, Grinding || [[File:Valves2012.jpg|125px|thumb|The engine's intake and exhaust valves, highlighted in red.]]
	|-		|-
−	| Crankshaft || Transforms the linear motion of the piston into a rotational motion. || Steel || Milling, Die Casting, Drilling, Grinding	+	| Crankshaft || Transforms the linear motion of the piston into a rotational motion. || Steel || Milling, Die Casting, Drilling, Grinding || [[File:Crank2012.jpg|125px|thumb|The crankshaft, removed from the engine (the offset part near the center is where the piston rod would attach).]]

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Revision as of 01:49, 15 November 2012

Contents 1 Gate 1 - Project Planning 1.1 Project Management 1.1.1 Work Proposal 1.1.2 Management Proposal 1.2 Product Archaeology 2 Gate 2 - Product Dissection 2.1 Project Management 2.1.1 Preliminary Project Review 2.2 Product Archaeology 2.2.1 Disassembly 2.2.2 Subsystem Connections 3 Gate 3 - Product Analysis 3.1 Project Management 3.1.1 Coordination Review 3.2 Product Archaeology 3.2.1 Product Evaluation

Gate 1 - Project Planning

Project Management

Work Proposal

The plan to reverse engineer the lawnmower is to meet as a whole group at Evan’s house off campus. He has all of the necessary tools and equipment to disassemble the mower. We plan on going step-by-step taking apart each component of the lawnmower. From initial inspection, the tools that are required to disassemble each part of the lawn mower include, but will not be limited to:

• 3/8 and ½ drive socket set with multiple length extensions, many different metric sizes
• Multiple length, and size, Philips head and regular (flat head) screwdrivers
• Torx screwdrivers
• Needle nose pliers
• Rubber mallet
• Penetrating oil/lubricant (PB Blaster)

The estimated time that it will take to fully disassemble the lawnmower is 3-5 hours, depending on what complications we run in to. Some challenges we may encounter as we go are frozen and/or stripped bolts, and sheared bolts. We do not plan on removing any parts that are riveted together because we won’t be able to reassemble those parts correctly, so removing rivets will not be a challenge.

Our group, as a whole, has at least a basic competency necessary to work with the mower, and specifically the engine; this includes skills with technical aspects such as disassembling the machine and identifying the functions of parts, as well as a grasp of the concept associated, i.e. how a gasoline engine works.

Management Proposal

Project work is to be split up as evenly as possible between the five members of our group. Specific tasks will be assigned based on each member's title within the group:

• Project Manager , Kevin Bartosiewicz (kbartosi@buffalo.edu): Responsible for the successful planning, execution, oversight, and completion of a project. This includes coordinating information across the group, setting up team meetings, ensuring Gates are completed in a timely manner, and regularly assessing the collective productivity of the group. Strengths include consistent punctuality, effective written and oral communication, and strong organizational skills; hands-on skills and knowledge of combustion engines are limited.
• Technical Expert , Evan Farino (evanfari@buffalo.edu): Responsible for overseeing of disassembly of lawnmower, as well as analysis of the different components and access to necessary tools. Strengths include several years' experience working with mechanical systems and good group collaboration; skill with computers (solid modeling, Wiki, etc.) are basic.
• Communication Liason , Anibal Martinez (anibalma@buffalo.edu): Responsible for coordination of communication between our group and the professors, will take note of any question that the group has and address it to the professors and/or TA’s, and make sure that everyone in the group is aware of their tasks. Strengths are hands-on experience with combustion engines and good organizational skills; public speaking and time management are not strong points.
• Solid Modeler/Factotum , Jordan Pytlak (jordanpy@buffalo.edu): Responsible for computer-generated models of machine components, as well as helping any group member if they are having trouble and performing general work necessary for the project, but not covered specifically by any other person. Strengths include familiarity with Solidworks, good teamwork, and strong problem-solving; writing skills and combustion engine knowledge are limited.
• Group Collaborator/Reporter , Andrew Serwon (agserwon@buffalo.edu): Responsible for editing and combining different pieces of each Gate from each member and posting them to the group Wiki page, as well as any additional work necessary. Strengths include strong writing skills and ability to learn quickly; time-management and hands-on skills are somewhat lacking.

Group meetings will be held weekly or bi-weekly (depending on availability) at 3:30 p.m. on Thursdays in the Silverman Library (Capen Hall). Any meetings that require work with the lawnmower will be held at Evan's house, and dates and times will be decided at the preceding Thursday meeting based on the availability of the group as a whole.

Note: Conflicts will be handled through group communication.

Product Archaeology

Based on pre-dissection observation, there are many bolts, all metric sizes, that are the majority of the “fasteners” holding each part together. As long as those come out, there should be no problem disassembling the lawnmower. There is nothing more difficult than just unscrewing pieces from other pieces.

Development Profile : The “Recycler” series of mowers was introduced in 1990. Since then, the product has seen routine updates. In 1999, for example, „Toro introduced the Personal Pace® self propel drive system on walk mowers that enables users to mow at their own “personal pace” The Toro Company History. A majority of Toro corporate offices are located the United States. In the 1990s, the U.S economy was very strong under President Clinton’s time in office. In addition, the North American Free Trade Agreement was implemented in 1994. This resulted in the immediate reduction of export tariffs between the U.S and Mexico. In general, this was a prosperous time for manufacturers in America. As shown in the chart, Toro lawnmowers are sold in the United States, Europe, Australia, Asian, Canada, and Latin America.

This lawn mower is intended to be accessible to consumers in both operation and price, many of whom use the product for residential use. Of course, the simple goal of a lawn mower is to effectively cut grass.

Usage Profile : The intended use for the lawn mower is essentially to cut the grass and make it look presentable to the people who look at the owner’s house. This particular model is made for home use because of its small size and low price, but Toro also makes larger models that are specifically designed for commercial use. The lawn mower cuts the grass, and it can also be used to blow debris from a driveway or sidewalk.

Energy Profile : There is chemical, thermal, kinetic and electrical energy being used by the lawn mower. The engine has a container where the user gasoline is stored until it is ready to be used. The engine that our lawn mower has uses the four stroke cycle. This means that chemical energy from gasoline is the main source of energy for the engine. But in order for the engine to start up in the first place it needs input from the user.

1. The user has to pull on a cord which in turn causes the crankshaft to rotate. The rotation of the crankshaft then makes the pistons in the cylinders to move.
2. The intake valve opens in the cylinder. This allows a gasoline and air mixture to enter into the cylinder. The piston is moving towards the bottom of the cylinder at this point (Intake Stroke).
3. The rotation of the crankshaft causes the piston to move to the top of the cylinder, compressing the fuel and air mix (Compression Stroke).
4. When the piston reaches the top of the cylinder, there will be a spark plug firing. The spark plug receives its energy from an electrical source such as a battery or magneto. This spark will cause the chemical energy in the gasoline to turn into thermal energy. A controlled explosion will happen at this point which will force the piston to move downward. This linear motion is the converted to rotational energy by the crankshaft (Power Stroke).
5. The energy that the crankshaft received from the piston in the previous step is then used to rotate the blades that will cut the grass, achieving the goal of the lawn mower.
6. Finally, the piston will move back towards the top of the cylinder, where the exhaust valve will open. The piston will force the gases that were created during the explosion out of the engine, clearing the way for more fuel to enter the cylinder and restarting the cycle from step 2 (Exhaust).

Complexity Profile : The lawnmower is a combination of many different parts that work together. There are many small components such as bolts and screws that keep the lawnmower together as well as springs. The major components consist of:

• Self-propelled system: A plastic handle is pushed down by the user while the safety lever is against the handle, which allows a transmission to engage on the axle connecting the rear wheels. The transmission runs off of a belt that is connected to the main shaft of the engine under the deck. It uses gears to turn the horizontal circular motion of the shaft to vertical motion to move the wheels forward along the ground. As the user pushes the handle farther, the faster the mower moves.

• Engine: The engine is the most complex part of the lawnmower. It is started by a pull start. This means that the user pulls a string that is connected to the flywheel on top of the engine. As it spins from the outward pull, the internals of the motor are in synchronized motion. As long as the pull start is pulled hard enough, the spark plug will spark and ignite the fuel and air mixture, then the engine runs on its own without the user constantly pulling on the string. The internals are extremely complicated, and have to run in sync with each other perfectly or the engine will encounter major failure.
• Other, less complex systems: Included: adjustable height, the blade and the chute. The adjustable height works by adjusting the angles of the four wheels. The user pulls a tab out and lifts or lowers the deck and then pushes the tab into the desired height level “notch”. The blade is bolted to the bottom of the engine’s shaft and turns with the revolutions of the motor. There are two chutes on this lawnmower. One on the side opens when the user pulls it up. There is a spring holding it down against the side of the deck until the user lifts it. There is a hole in the deck behind that plastic piece. When it is lifted, grass can exit the hole. The second shoot is on the back of the deck. This one works the same way as the one on the side, and the user can attach a bag behind it to catch the grass, unlike the side chute.

The adjustable height and chutes are not very important in the overall working condition of the mower. On the other hand, the self-propelled system with the safety lever, and the engine, have to work together in order for the lawnmower to cut the grass and move forward at the same time. Also, the blades have to be attached to cut grass. Once the motor is started, the blades are spinning under the deck. Then, the user holds down the safety lever as they push down on the plastic handle, which gives the mower forward motion while cutting the grass. This is a necessity for the lawnmower to function as it was designed to.

Material Profile : Materials that are clearly visible include steel, cast iron, plastic and rubber. The handle is made of steel tubing; the individual components of the motor and transmission are made of steel plate. The throttle and safety cable is made of steel cable. The motor and deck are made from cast iron due to the complex contours and shapes. There are various hardness’ of plastic throughout the lawnmower. The wheels are made of a very hard, thick plastic for strength. The chute covers, gas tank, and propelling handle are made of a similar plastic, and the engine cover is made of a thinner, flexible plastic. The gas line and belt is made of rubber. What cannot be seen from the outside observance of the mower are gaskets in the engine and transmission, which should be made of rubber. Other internal parts should be made of steel as well.

User Interaction Profile : The user starts the mower by priming the engine, and then pulls the pull-rope while keeping the lever pressed down against the handle. Once started, just stand behind and push it wherever the grass needs to be trimmed. The user must at least know rudimentary engine parts like the throttle and choke, these can also be looked up in the owners manual if not familiar with gasoline engines at all. The mower is very easy to use, however it does take a little bit of brute strength to start. It is self-propelled so you don’t have to push it the whole time and tire yourself out, just walk behind it and point where you want to go. Some maintenance is required, that comes with all gasoline engines. Regular oil fills, keep the filter clean, make sure spark plugs are working, and keep it topped off with gas. Not too difficult for the everyday person. On the mower you have to keep the blades sharpened, you can either do it yourself or take it to pretty much anyplace the sells mowers to do for you. I would recommend taking the blade in to get sharpened professionally because it has to perfectly balanced and if you mess up, you could destroy the mower or get hurt.

Product Alternative Profile : There are very few alternatives to this product:

1. Gasoline/Electric Manual Push Mowers: Lawnmowers, either powered by combustion or electricity, that have no form of self-propulsion and must be pushed by the user.

• Advantages: These models are generally less expensive than self-propelled mowers.
• Disadvantages: User-propelled models create require the user to propel the machine forward as well as to turn it, causing more effort to be needed.

2. Completely Manual Lawnmower: These models have no engines, and are propelled and powered solely by manual work by the user.

A manual lawnmower from the American Lawn Mower Co.

• Advantages: Much less expensive than any gasoline- or electric-power models; gives off no emissions.
• Disadvantages: User must put in large amounts of work to propel the machine, and mowing time is generally longer than with a powered model.

3. Ride-on Lawnmowers/Tractors: Riding mowers are ideal for large plots of land, such as parks, fields, and farms. They are generally gas-powered.

• Advantages: Allow grass to be cut much quicker and easier, as the user needn't put more effort in than pushing a pedal and steering; models with seats and only a spot to stand can be found; some models include cup holders.
• Disadvantages: Generally much more expensive than push models, and the size of residential grassy areas generally don't rationalize the extra money necessary to purchase a riding model rather than a push model.

4. Leaving the grass to grow without cutting it

• Advantages: User doesn't have to put in any work; no gasoline/electricity necessary.
• Disadvantages: Extremely long grass is unsightly; may warrant rodents and other pests to live among the grass; owner could face fines from local government.

5. Livestock: Animals such as goats, cows, rabbits, and other grass-eating animals could be set on their own to maintain the lawn.

• Advantages: Animals require no gas or electricity; potentially sustainable due to reproduction; feces can be used as fertilizer.
• Disadvantages: Require a constant source of food, may not be viable if grass growth is erratic; owner may face fines from local government.

Overall, the model we have chosen is the best choice for residential use; it is within the middle range of pricing, requires less fuel and maintenance than some alternatives, and can perform its task with a small amount of work from the user, all while performing its intended job consistently. Self-propelled mowers similar to the one we chose generally average around $400; user-propelled combustion/electric mowers generally average about $250; completely manual models average around $150; riding mowers generally cost between $1,000 and $2,000; uncut grass fines are usually about $150.

Gate 2 - Product Dissection

Project Management

Preliminary Project Review

The goals that were initially set forth in the Work Proposal have been met with general success. While the plan that had been outlined was not entirely descript, it left room for our group to assess our needs and goals as we went along. Ideally, it would have been best to create an all-encompassing, detailed dissection plan/proposal from the very start, but this is the first group project of such a magnitude that most members have dealt with. As such, group members may have felt hesitant to take the lead since a strong team dynamic and level of comfort had yet to be established in the early stages of the project. At the time of writing, we have collectively developed a better sense of what is expected from by the professors, as well as what we can expect from each other. In the following two sections, we will look at each facet of our original work and project proposals to discuss what pertinent information may have been absent and how, or if, this affected our group’s performance.

1. Work Proposal Review:

• As outlined, the lawnmower was dissected at our Technical Expert’s residence. The proposal did not set forth an exact date or time, but these details were easily agreed upon through consideration of each member’s availability. Luckily, all members were available at the same time, on fairly short notice (2-3 days ahead of time). To avoid the possibility of a schedule conflict in the future, our timetables will be discussed at the early stage of each project gate.
• A dissection plan was not explicitly provided in Gate 1. This is likely the result of two circumstances. Firstly, the majority of the group has not done a complete mower (and engine) teardown in the past. Secondly, our Technical Expert was trusted to have intimate knowledge of this process. At the expense our Gate 1 score, we did not take the initiative to research the specifics or elaborate on our knowledge. This could have turned out to be very problematic, but our Technical Expert did, in fact, competently lead and help the other group members through the dissection process. In the remaining gates, it will be necessary to have a more structured approach in order to avoid a possible roadblock if our group collectively lacks a particular skill or skillset.
• While we did not allude to the specific tasks of each member for the dissection process, our roles were established as we went along, rather naturally. For example, the Project Manager and Group Collaborator had the least experience in breaking down an engine, so they were charged with documenting a photographing the steps taken during dissection. In addition, it was a good chance to broaden their knowledge of 4 stroke engines as the other members explained the inner-workings of our project as we progressed. This builds confidence in technical knowledge for future gates. The Technical Expert was in charge of leading the teardown. Since the remaining two members also were comfortable in a hands-on setting, they jumped in when it was possible to work on two or more components at a time.

2. Management Proposal Review:

• From the start of the project, it was understood that the workload for each assignment was to be split as evenly as possible by each group member. In general, this has been accomplished. When delegating tasks needed to complete each gate, a group discussion is held to determine which member has the skills to handle the job, and the time required to complete said job is considered. When possible, or necessary, tasks are completed collectively. For example, the dissection process was completed as a group, as described above. After this collaborative effort, the written portion of Gate 2 was discussed and divided between members based on their title.
• Project work is split up as evenly as possible between the five members of our group. Specific tasks are assigned based on each member's area of expertise. Upon dissection on the lawnmower, it was determined that each member had the knowledge required to complete any area of the written assignment. As such, these tasks were delegated based on the time required and personal interest. The only exception was found in the “How To” portion of this gate. We found our Technical Expert to have the most intimate knowledge of the mower breakdown. In addition, completion of the final draft and wiki upload was to be performed by our Group Collaborator. Out of fairness, and in order to leave time for error checking, each written task must be submitted roughly three days prior to the due date.
• The group meetings have been held often and successfully. In our initial proposal, we did not outline a meeting schedule, but we had agreed to make ourselves available every Tuesday and Thursday at 3:30pm, as needed. Via email and our interactions preceding every MAE277 lecture, we assess what has been accomplished, and decide whether or not a deeper discussion needs to take place. Generally, we end up meeting at least once a week, sometimes twice a week. The Project Manager mediates these sessions, and we have gravitated to a regular itinerary. We normally begin by reviewing what we are expected to determine, both individually and as a group, and then move on to finding solutions to any roadblocks. For example, if a member is unsure of the best way to present a collection of data and information, a friendly argument regarding which type of graph would most easily aid the reader ensues. Or, if a task requires the research of additional information, this data is obtained as soon as possible during the meeting.
• Thus far, we have not had any member conflicts. As it was described earlier, the workload is divided as fairly and evenly as possible through member discussion. Tasks are determined collectively, not dictated by a sole member. In the future, if a member falls behind in their assignment, we will collectively step in and help finish the workload. However, this is a situation that we have yet to encounter.

Product Archaeology

Disassembly

Listed below is the step-by-step process we took in disassembling the lawnmower. The steps are numbered in the order in which each part was removed. Listed with each part is whether or not the part is intended to be disassembled, the tools used to disassemble it, and the difficulty of its removal (on a scale from 0 to 10, where 0 is no work necessary, and 10 is extremely difficult to remove. The scale is based on the amount of energy spent removing a part, and how accessible each bolt or screw holding the part on was; also, the factor of needing more than 2 hands is considered in the rating.)

1. Handle (Safety lever and self-propulsion engagement)

Handle

• Intended to be removed due to the use of a nut that requires only a hand. The cables are not intended to be removed.
• Tools Used:
  • Hand - Unscrew two “nuts”
  • Needle nose pliers - Pull off cable mount from bracket next to carburetor and the other from bracket on rear axle; pull each side of the handle outward off of the bolts
• Difficulty: 3

2. Wheels (front and rear)

Wheels

• Not intended to be removed because the bolts are hard to access between the wheel and mower deck.
• Tools Used:
  • ½ inch wrench and ½ inch regular socket - Each wheel is connected to mower deck with two bolts
• Difficulty: 7

3. Blades

Blades

• Intended for removal because they need to be changed or sharpened in order to cut grass well.
• Tools Used:
  • 5/8 in. regular socket - Hold blade with heavy gloves and turn bolt
• Difficulty: 2

4. Rear chute

Rear Chute

• Not intended to be removed because you must take other parts off to access the screws holding it onto the deck.
• Tools Used:
  • 3/8 in. socket - Remove the 4 bolts and pull off
• Difficulty: 3

5. Rubber flap behind chute and plastic shield

Rubber flap and plastic shield

• Not intended to be removed, but can be easily if the user does not like it.
• Tools used:
  • Phillips head screwdriver - Unscrew 1 screw on each side and pull off
• Difficulty: 2

6. Transmission (Gear box)

Transmission

• Not intended for removal because it is sealed with an RTV-like substance and the gears have to be lined up correctly.
• Tools Used:
  • T20 Torx - Remove the 8 torx screws
  • Putty Knife - wedge between the two piece case and pry the case off, breaking the seal
• Difficulty: 2

7. Gears

Gears

• Not intended for removal because they are in a sealed case.
• Tools Used:
  • Hand - Pull wheels outward and the gears will separate and come off
• Difficulty: 1

8. Belt

Belt

• Not intended for removal because the user cannot remove it without removing the gear box in order to take it off of the pulley on the worm gear.
• Tools Used:
  • Hand - Pry belt off of pulley on the engine output shaft and the pulley underneath gear box
• Difficulty: 3

9. Engine

Engine

• Not intended for removal due to the fact that multiple parts are connected to the motor that have to be taken off before the motor is removed.
• Tools Used:
  • ½ inch regular socket - Unscrew 3 bolts holding motor on deck
• Difficulty: 4

10. Engine cover

Engine cover

• Intended for removal due to the fact that it is only held on by easily accessible Phillips head screws and can be taken off for normal inspection of engine parts.
• Tools Used:
  • Phillips head screwdriver - Unscrew 3 screws and pull both pieces off
• Difficulty: 2

11. Gas tank

Gas tank

• Not intended for removal because other parts have to be removed before the user can access the screws holding it on.
• Tools Used:
  • 8mm socket
  • Pliers - Unscrew bolts surrounding the pull start; pinch hose clamp on bottom of tank and slide down the rubber hose
• Difficulty: 3

12. Air cleaner and cover

Air cleaner and cover

• Intended for removal since it is only held on by 1 accessible screw and cleaning or changing of air cleaner is recommended for proper maintenance.
• Tools Used:
  • Regular screwdriver - Unscrew 1 screw and use hand to unscrew knob in center of cover, pull off, air cleaner will fall out, or pull out
• Difficulty: 2

13. "Shell" with pull-start riveted on

"Shell" and spark plug

• Not intended to be taken off because it is bolted on in various places.
• Tools Used:
  • 3/8 in. socket with extension - Remove all bolts on all sides of the shell, lift off engine
• Difficulty: 4

14. Spark Plug

• Intended for removal because it may need to be replaced after a lot of use to maintain engine health.
• Tools Used:
  • 20mm deep socket - Unscrew and lift out of hole
• Difficulty: 1

15. Muffler cage protector

Muffler cage protector

• Not intended for removal because there is no need to remove it.
• Tools Used:
  • 8mm regular socket - Remove the screws on both ends of cage and pull off
• Difficulty: 3

16. Carburetor

Carburetor

• Not intended for removal because bolts are hard to access and is a delicate, necessary, part to the functionality of the engine.
• Tools Used:
  • 3/8 in. regular socket with extension - Remove bolts holding carburetor onto engine block and pull off throttle return spring
• Difficulty: 5

Note: The following parts (muffler excluded) are not intended for removal because they are extremely important for proper functionality of the engine and are difficult to access.

17. Head

Engine head

• Tools Used:
  • ½ inch regular socket - Remove the 8 bolts while engine is in vice or held by another person, pull off
• Difficulty: 4

18. Lower engine case cover

Lower engine case cover

• Tools Used:
  • 3/8 in. regular socket - Remove bolts holding case onto engine block
  • Rubber mallet - Turn engine downward and tap around the edges of the case until it frees from gasket and engine block, slide off output shaft
  • Challenge - The case would not separate from gasket and block, had to use force with mallet to break it free
• Difficulty: 7

19. Flywheel

Flywheel

• Tools Used:
  • 15/16 in. regular socket - Unscrew Bolt while holding output shaft in place, pull off input shaft
• Difficulty: 3

20. Muffler

Muffler

• Not intended for removal because you must take off cage and small cover before the user can access the 2 bolts holding it onto the engine.
• Tools Used:
  • 8mm regular socket - remove the 4 bolts holding on small cover to access 3/8 bolts underneath
  • 3/8 in. socket - Remove 2 bolts holding muffle to engine, pull off
• Difficulty: 3

21. Governor

Governor

• Tools Used:
  • Gravity - Governor will fall off if it is face-down. If not, lift off with hand.
• Difficulty: 0

22. Camshaft

Camshaft

• Tools Used:
  • Hands - Pull out
• Difficulty: 3

23. Piston rod and piston

Piston rod and piston

• Tools Used:
  • 8mm socket - Unscrew 2 bolts and remove bottom piece of piston rod. Turn crankshaft so that the piston rod and piston can slide out next to crankshaft
• Difficulty: 5

24. Crankshaft (input and output shaft)

Crankshaft

• Tools Used:
  • Hand - Pull out
• Difficulty: 2

25. Breather assembly

Breather assembly, valve, and valve springs

• Tools Used:
  • 8mm socket - Unscrew 2 bolts and lift off
• Difficulty: 3

26. Valves and valve springs

• Tools Used:
  • Hand - Lift out valves from top of engine block and pull out springs through space that was covered by the breather assembly
• Difficulty: 2

Subsystem Connections

The subsystems involved:

• Carburetor
• Pull cord
• Blades
• Engine
• Handle
• Wheels
• Blade Housing
• Air Filter
• Muffler

These subsystems are connected as follows:

1. Carburetor to Engine: The purpose of the carburetor is to deliver a fuel and air mixture to the cylinder, so the carburetor and engine need to be connected together. Since the carburetor is gravity fed it needs to be located somewhere below the fuel tank. The carburetor is connected to engine by two bolts.
2. Air Filter to Carburetor: The air filter get rid of any debris in the air going into the intake before that air is sent to the carburetor. This is to ensure that no damage is caused to the insides of the engine by foreign material and to help make the combustion process more efficient. The air filter is connected to the engine by one screw.
3. Pull Cord to Engine: The Pull cord is connected to the flywheel. When the user pulls on the cord, it transfers kinetic energy to the flywheel, which in turn causes the piston and crankshaft to start moving. There is a magnetic strip that is part of the flywheel. This strip induces an electrical current into two copper wires stationed next to the flywheel. This electrical energy is transferred to the spark plug. This creates the spark that ignites the fuel and air mixture inside of the piston cylinder. The pull cord is wrapped around a spool. This spool engages the flywheel when it is pulled. This transfers the energy from the user to the engine, which allows the engine to start its four stroke cycle.
4. Engine to Blades: The lawnmower engine is connected to the blades via a drive shaft. The drive shaft transfers the kinetic energy created from the combustion of the fuel and air mixture to the blades. This allows the blades to cut the grass and fulfill the purpose of the lawnmower. The blades are connected to the engine by a single bolt.
5. Handle to Blade Housing: When the user pushes on the handle, it transfers kinetic energy to the wheels, which cause the whole lawnmower structure to move. The handle is connected to the rest of the lawnmower by two bolts. One on each side of the handle.
6. Engine to Blade Housing: The engine is connected to the blade housing with bolts. The blades are located just below the engine. This is also the area where the drive shaft connects to the blades. The engine is connected to the blade housing with 3 bolts.
7. Wheels to Blade Housing: The wheels are connected to blade housing with some bolts. The wheels transform the kinetic energy provided by the user into rotational energy, which allows the lawnmower to move. Each of the four wheels are connected to the blade housing with two pairs of bolts and nuts.
8. Muffler to Engine: The muffler is connected to the engine with three bolts. The purpose of the muffler is to dampen the noise created by the operation of the engine. The muffler is connected to the engine by two bolts.

How the connections are implemented: All of the subsystems are implemented automatically when the engine is started except the wheels and handle. After the pull cord is pulled and the engine starts, the blades start to spin due to the force applied by the piston onto the driveshaft. The piston is powered by the combustion of the air that that comes through the air filter and mixes with gasoline in the carburetor. After combustion the exhaust gasses are forced through the muffler. This all happens without any human interference. However, in order to get the mower to move, the user must push on the handle and transfer that energy to the wheels.

• GSEE influences: The designers wanted the mower to be as easy as possible to operate (societal) and able to be operated in all climates (global) so they would not have to build different variants, which cost more money (economical). They wanted the average homeowner to be able to operate it without problems (societal) or much maintenance (economical). The product is designed to be mass-produced on an assembly line to minimize cost and maximize production (economic) so all of the subsystems are built separately and then put together at the end. The engine is not built buy the lawnmower company TORO. They contract out the engine production to Briggs & Stratton, which is a very good engine builder and has all the tools, machines, and know-how to produce engines for the TORO company. TORO researched the cost difference of designing and building their own engines and saw that is was cheaper to contract out instead of building their own plant (economical/ environmental). As with any gasoline engine, you will have exhaust fumes that pollute the environment but the engine tries to maximize output energy without wasting any gasoline or losing it to friction (environmental).

• The mower is built to maximize performance so all of the connections are physical so the energy is transferred between subsystems is instantaneous. The physical connections also help to keep the cost down.

Subsystem arrangement:

• Reasons for subsystem placement: The subsystems are placed so that the whole mower will be balanced and safe. The engine is place directly in the middle of the blade housing, the wheels are evenly spaced and are holding up the blade housing which is holding up everything else. The air filter is mounted to the carburetor so is can mix clean air with the fuel. The muffler is not facing at the user so fumes won’t be blowing towards him and the handle is at a certain distance away so that with an average step, the users feet will be a safe distance away from the blades. The pull rope extends up the handle and is held there by an eyelet so the user can start the mower from the same place he will operate it from.
• Placement restrictions: You cannot put the blades next to the handle, which is not practical or safe. The muffler and air filter should be separated so the engine isn’t taking in exhaust fumes. The pull rope shouldn’t be near the blades to ensure safety upon starting.

Gate 3 - Product Analysis

Project Management

Coordination Review

In Gate 2 of this project, there was one unresolved challenge facing the group:

• Clearly-Outlined Roles: In the past we had not decided upon each member’s task in the early stages of each assignment. This resulted in members having undefined tasks until the due date was realized to be quickly approaching.

Solution: In preparation of this gate, the group met shortly after Gate 2 was completed and created a detailed plan of which members were responsible for each portion of the assignment. This allowed members to gain extra benefit from lecture material that was relevant to their task in this gate. In addition, this was helpful to the member responsible for the solid-modeling portion of Gate 3. Since it had been a fair amount of time since any of us have done any modeling (if ever), this allowed for an ample period to get reacquainted with the process.

While working on this gate, we also encountered a new temporary setback:

• For a short time, we did not schedule any group meetings or discussions. However, this is purely due to the fact that each member had at least 4 exams scheduled in a period of 3 days. The weight of exam grades on one’s GPA required a lot of extra study effort and little work on this project during that period of time.

Future Solution: Look ahead to upcoming exams and start working on project assignments before the heavy studying sessions begin.

Product Archaeology

Product Evaluation

Component Summary

Component	Function	Materials	Manufacturing Process	Picture
Handle	Allows the user to push and steer the lawnmower.	Plastic, Steel	Plastic: Injection molding; Steel: Forming, Drilling	Our lawn mower's handle.
Wheels	Convert the kinetic energy input by the user into rotational energy, which allows the lawnmower to move.	Plastic	Injection Molding, Drilling	One of the mower's four wheels.
Blades	Cut grass by spinning, using energy from driveshaft.	Steel	Drilling, Grinding, Die Casting	The mower's blade.
Transmission Housing	Holds the gears in the rear axle together.	Plastic	Injection Molding, Drilling	The mower's transmission and housing.
Engine Cover	Prevents debris from entering the engine.	Plastic	Injection Molding	Mower engine cover.
Gas Tank	Serves as a reservoir for fuel until it is needed by the engine.	Plastic	Injection Molding	Gas tank, outlined in yellow, attached to the engine.
Air Filter Cover	Prevents extra debris from clogging the air filter.	Plastic	Injection Molding	Air filter and cover, outlined in red, attached to the engine.
Spark Plug	Converts electrical energy into thermal energy in order to ignite fuel and air mix in the combustion chamber.	Steel, Ceramic	Steel: Drilling, Die Casting; Ceramic: Molding, Drilling, Machining	A spark plug similar to what would be in the lawn mower engine
Muffler	Dampens the noise created by the engine.	Steel	Die Casting, Drilling	The exhaust muffler from the mower engine.
Carburetor	Mixes fuel with air; sends fuel-air mixture to combustion chamber.	Aluminum	Die Casting, Drilling, Milling	The engine's carburetor.
Engine Head	Has a hole where the spark plug is inserted; holds various fins for the purpose of cooling the engine.	Iron	Drilling, Machining	The engine head on the fully assembled engine.
Flywheel	Stores kinetic energy, then uses that energy when the engine is not producing power; it also contains a magnet which provides electrical energy to the spark plug.	Iron	Die Casting, Drilling, Milling	The engine flywheel.
Governor	Limits the speed of the camshaft in the engine.	Plastic, Iron	Iron: Drilling, Machining; Plastic: Injection Molding	The engine's governor.
Camshaft	Holds piston rod and various cams that push on the push rods, which open the valves in the combustion chamber.	Steel	Drilling, Milling, Grinding	The camshaft in the opened engine, highlighted in yellow.
Piston Rod	Connected to the crankshaft and rocker arms; when the piston rod pushes the elongated part of a cam, it forces the valves in the combustion chamber to open.	Aluminum/Silicon Alloy	Die Casting	The piston piston, composed of the piston rod (outlined in red), and the piston head (outlined in green), removed from the engine.
Piston Head	Uses energy from ignited fuel-air mixture to push piston rod, which turns the crankshaft and camshaft.	Aluminum	Drilling, Machining, Die Casting	(See picture for Piston Rod)
Valves	The intake valve allows the fuel and air mixture to enter the combustion chamber; the exhaust valve allows the gases formed during the combustion process to exit the chamber.	Steel	Forging, Grinding	The engine's intake and exhaust valves, highlighted in red.
Crankshaft	Transforms the linear motion of the piston into a rotational motion.	Steel	Milling, Die Casting, Drilling, Grinding	The crankshaft, removed from the engine (the offset part near the center is where the piston rod would attach).