Group 2 Gate 2
This section includes more analysis of both the group and the chainsaw. The group's management and work conditions are analyzed first, including this sections work and management and looking forward to the section and any future problems. Chainsaw analysis includes a dissection of the product, a parts catalog, and an analysis of the connections within the chainsaw. The dissection includes the tools used and step by step instructions of the process. The connections sections incorporates flow charts the represent the connections and the related flows.
Cause For Corrective Action
Along with an analysis of the chainsaw, an analysis of our group needed to be completed in order to make our group better. The following two sections include an analysis of both our work proposal and management proposal from Gate 1.
Management Proposal Analysis
With regards to management, the group has not yielded many issues. As shown in the Google calendar link, we planned to meet every Monday and Wednesday right after class and work in the dissection lab. The report writing would be done on Saturday or Sunday. We followed this plan very well. After the dissection was complete we continued to meet on Monday and Wednesday to write the report as opposed to weekends. One negative to this meeting schedule is that one of the members did have a scheduling conflict that caused him to miss most of the meetings on Mondays. This conflict was overcome by having other members step up their duties on these occasions. The roles of our group, although very specific in Gate 1, were more lenient as we worked. Each member of the group did a bit of each role. There was never just one person writing down all the observations or one person working on the wiki. Granted, people were responsible for their duties and roles, but we helped each other complete the work in a timely manner. There were no serious conflicts between group members, and everyone worked well together. As stated in Gate 1 all members of the group are familiar with each other. This familiarity made collaboration quite natural and did not result in much conflict. The first week of dissections went smoothly as the lab was very low traffic. This being said, the next week on Monday when we went to the dissection lab it was unmanageable to work in due to the number of people in the lab at the same time. We knew that if we stayed in the lab we would not be as productive as possible. To solve this problem, we decided to take our chainsaw out of the lab and do the dissection in our room. A few of the members together had enough tools to be successful in dissecting the remainder of the chainsaw. The meeting dates that we established worked very well and we were able to finish the dissection of the chainsaw quickly and begin on the report and wiki aspect of the gate. As stated in the work proposal analysis, in Gate 1, we started working on the wiki too late and consequently, it was lacking in professionalism. To fix this problem we started working on the wiki a week before it was due and were able to finish the wiki with time to get feedback.
Work Proposal Analysis
The work proposal in gate 1 was intended to explain the group’s plan to dissect the product. It explained a basic plan for dissection. These plans were developed without knowing anything about the internal components of the chainsaw and were strictly based on observation of visible external components coupled with the groups assumptions of how a chainsaw functions. As stated in our work proposal “One of the largest challenges we will face is not knowing exactly what we will find inside of the chainsaw”. Given this lack of information the group devised a plan that took the approach of expecting the unexpected. Not knowing exactly what tools would be necessary to take the product apart, the group decided to disassemble it in the dissection lab where a multitude of tools would be available. Proper documentation of this disassembly was also a major factor mentioned in the groups work proposal. “It is necessary to take extraordinary caution to make sure we are able to put all components of the device back in their original working locations. For this purpose there will be 2 people documenting how the product is being taken apart.” In execution of the dissection, the plans outlined in the work proposal were very helpful. Unlike we had originally assumed, many of the fasteners were not matching, there were several fasteners holding the chainsaw together so being in the lab was crucial in dissection.
Documentation was by far the slowest aspect of dissection. This was done by taking pictures with an iPad and using an app to draw quick notes to ourselves on how everything was taken apart. These same pictures can be seen in the steps below after they have been edited with photoshop. Every time a screw was unscrewed or component was removed, the group would have to stop working while photos were taken and documented. Although this took a long time the results were worth the time. Every step of the dissection has an in depth visual and written documentation which is necessary for the gate. Overall there is not much that can be said that went wrong during dissection. Except that there was one component that we were unable to take apart. Consequently we went to the machine shop to acquire some help.
Potential future problems are inevitable, but if they are expected they can be solved quickly. One of the problems that we will face in the future is Thanksgiving. During that break the group will not be able to meet because we will all be home. This problem will be discussed and solved as the date approaches. Time management will be another problem because each member of the group has test and other assignments that need to be completed as well.
In order to better understand our Eager Beaver Chainsaw, it must be dissected for further analysis. The sections that follow represent our directions for dissecting the machine and our consequential analysis of the machine as dissection took place.
Step by Step Disassembly
- Flathead Screwdriver
- 7/16" Socket Wrench
- 5/16" Socket Wrench
- 1/2" Socket Wrench
- Long 5/8" Socket Wrench
- 5/32" Allen Key
- T20 Torx Head Screwdriver
- T15 Torx Head Screwdriver
- Needle Nose Pliers
The difficulty scale ranges in values between 1 and 5 with 1 being the easiest and 5 being the hardest. The scale is based on the number of tools used, the forced required to complete the step, time it takes to complete step, the number of hands/people needed, and difficulty of completing step. Some of the step difficulty may be more based on one factor than another.
1. The step requires no tools and is very easy to accomplish. The time required and required coordination is minimal.
2. The step requires one tool at a time but is still fairly easy to accomplish. The time and required coordination is still minimal.
3. The step requires more than one tool or hand and is fairly time consuming. The component is accessible but the requires coordination.
4. The step requires more than one tool or hand and is moderately time consuming. It is hard to access the component but easy to accomplish the step once it is accessed.
5. The step requires more than one tool or hand and is very time consuming. requires intensive coordination and the component is not easily accessible.
Step by Step Dissection
Table 1 shows a step by step dissection of the chainsaw. It includes detailed descriptions of the instructions, tools required to complete each step, any notes that we have discovered during our disection, a difficult scale, and a picture or any important or ambiguous part in the step.
|Product Dissection By Steps|
|Step||Description||Tool Required||Difficulty of step (1-5)||Important/Ambiguous Part Locations|
|1||To remove the brake assembly which is located on the chain side of the chainsaw, remove the 7/16" nut, and 7/16" bolt using a socket wrench. Then remove the two flathead screws using a screwdriver highlighted in red. When removing this assembly watch for a small metal nipple which might be easily lost. Turn the brake handle 180 degrees so that it can be pulled off. From the brake assembly, use pliers remove pivot lever. This dislodges the spring and the black lever.||7/16" Socket Wrench,
|2||Remove blade, chain and aluminum handle. First, remove the chain by wedging it out from around the blade and the drive wheel. Taking off the chain takes a little work but twisting the chain a little can help ease the step. Once the chain is off, the blade can be easily slid off horizontal. To remove the aluminum handle, remove the 5/16" bolt with a socket wrench,located on the top, and the flathead screw with a screwdriver, located on the underside. The bolt is highlighted in red.||5/16" Socket Wrench
|3||Working from the opposite side as before, (left side) remove the starter housing. To do this, remove four flathead screws. These screws are highlighted in red. The housing is still connected by the pull cord. Cut the cord towards the top to minimize the cord loss. Remove the filter that covers the air intake.||Flathead Screwdriver
|4||Before taking the tank off, be sure to drain the chainsaw of all of its fluids including the oil and the gas/oil mixture. Also, be sure to do this step on some sort of paper to catch the gas and oil. To remove the tanks, the front casing must first be removed. To remove the front casing, remove the two 5/16" bolts located on the front of the chainsaw. Remove the metal pump wire-handle. After removing the front casing, it will reveal the fuel tanks which has a black hose connecting it. Remove that hose. Push the white tab with some force. This tab is located on the bottom of the chainsaw this tab is highlighted in red in the picture. After the tab is pushed in, pull out the tanks horizontally. Use some force to disconnect the tanks from the gas-line. Dislodging the tank can be difficult but if you use a little force it can be dislodged.||Table Cover
5/16" Socket Wrench
|5||Next detach the exhaust. To do this, remove the outer screws with a 5/32" Allen key. These screws are highlighted in red in the picture. This holds on the exhaust cover plate on. Removing the cover plate reveals two more 5/32" screws. Remove them with the Allen key and remove the exhaust.||5/32" Allen Key||2|
|6||Take off the choke lever by removing the flathead screw that it holds it in place. The screws are highlighted in red. The lever is a small black lever located on the left side near the red engine switch and shown in the picture. Also disassemble the plastic handle by removing two flathead screws with a screw driver. Taking the plastic handle also removes a metal plate along with two plastic spacers. Next, remove the spark plug wire then unscrew the spark plug with a long 5/8" socket wrench. This needs to be a long socket so that it can reach the nut portion of the spark plug. A wrench of the same size can be used but it is harder to maneuver in this situation.||Flathead Screwdriver,
Long 5/8" Socket Wrench
|7||Removing the trigger is a tricky step so it is broken into two steps. The trigger is connected at the top of the wrap around casing by a spring. Use needle nose pliers to bend the spring and remove it. This spring is highlighted in gold in the image to the right.||Needle Nose Pliers||3|
|8||Now that the top-side of the trigger is disconnected, remove the metal wire connecting the trigger and the throttle. The wire is highlighted in red in the picture to the right. Use needle nose pliers bend the cable and remove it. This step is especially difficult because bending the metal wire requires some force applied with the pliers. The wire is located in a tight space which also makes the process harder.||Needle Nose Pliers||5|
|9||Remove the three remaining flathead screws holding the wrap around casing to the drivetrain system. One is located on the top of the chainsaw to the right of the red engine switch. The second one is located under the chainsaw and the last one is located on the left near the air intake. After removing these screws separate the casing from the drivetrain as depicted in the image to the right. When removing the drivetrain, pull the carburetor gasket through the casing.||Flathead Screwdriver||2|
|10||Unscrew the four flathead screws, highlighted in red, holding the casing of the crankshaft to the combustion chamber. Remove the piston/crankshaft assembly from combustion chamber.||Flathead Screwdriver||2|
|11||To disconnect carburetor and alternator by unscrewing 3 torx head screws with a T20 torx screwdriver. The assembly should be in three parts. From the alternator, disconnect the grounding wire, and the on/off switch wire. From the carburetor, remove three plastic tubes and the gasket separating the carburetor and the combustion chamber. Use needle nose pliers to remove the throttle cable bending the wire at to fit through the hole.||T20 Torx Screwdriver,
Needle Nose Pliers
|12||Unbolt the crankshaft by holding the crankshaft in a vise while removing the 7/16" nut, on the brake side, with a socket wrench. The nut is threaded the opposite way so turn it clockwise to remove. This may take some force to remove. Unbolt the other 1/2" nut from the other side of the crankshaft. Remove brake assembly and magnet head. The magnet will need to be hammered out of place.||7/16" 1/2" Socket Wrench
|13||Unscrew the two T15 torx screws holding the rod to the crankshaft. Taking this apart will dislodge 20 roller pins. Be sure not to lose these as they are very small. Next, take the two big and two small spacers off of the crankshaft.||T15 Torx Screwdriver||2|
|14||From the carburetor, unscrew the four screws that have washers on them shown in red. Be sure to note the order in which the gaskets, plastic reservoirs, and metal pieces go. This is shown in the picture to the right.||Flathead Screwdriver||2|
|15||Unscrew the black tuning screws labeled "hi" and "lo." Remove the black gasket. Then unscrew and remove both cylindrical gates noting which gate goes in which side. Also, unscrew the lever assembly (in red). This metal assembly is very small and contains a pin, a lever and a spring.||Flathead Screwdriver||3|
Table 1: Step by step dissection of chainsaw.
Notes About Non-Removable Parts
Our chainsaw was assembled in a factory with heavy machinery making some of the parts permanently assembled. Removing these parts would result in breaking the part so we did not disassemble them. Examples include:
- During step one the brake assembly has parts that are riveted together. Removing this rivet would break the part.
- The alternator referenced in step 11 is encased in rubber. Taking this apart would result in destroying the inner workings.
- The carburetor referenced in contains many non-removeable parts. This includes the brass shafts which are riveted in place. There is a plastic C-ring holding an air screen which, if removed, would break. There are also two brass plug welshes that are pressed in.
When researching about our product, an Owner's Manual was found in PDF format. In the manual there was a parts list, which we used to make sure we had all the components during the dissection. Below in, Table 2, are all of the components we found when dissecting our product. (Note: Not all parts in the Owner's Manual are listed below due to the fact that the Owner's Manual displayed dissections of every subsystem in the chainsaw. We could not physically dissect every single subsystem built in the chainsaw due to the consequential inevitable, and irreversible part damage of certain subsystems.)
|Part #||Part Name||Count||Part #||Part Name||Count||Part #||Part Name||Count|
|1||Nipple (Yellow Casing)||1||2||Flat Head Screw (Yellow Casing)||2||3||7/16 Bolt (Yellow Casing)||1|
|4||7/16 Nut (Yellow Casing)||1||5||Chain||1||6||5/32 Screw (Side of Filter)||2|
|7||Filter||1||8||Filter Cover||1||9||5/32 Bolt (Filter)||2|
|10||5/16 Screw (Handle Top)||1||11||Flat Head Screw (Bottom Handle)||1||12||Screw (Intake Casing)||1|
|13||Intake Filter||1||14||Screw (Starter Chord)||2||15||Screw (Handle by Spark Plug Area)||2|
|16||Rip-Cord Handle||1||17||Filter Casing||1||18||Spacer (Handle by Spark Plug Area)||2|
|19||Plate (Near Spark Plug)||1||20||Pull Chord Reel||1||21||Metal Handle||1|
|22||Blade||1||23||Big Yellow Casing||1||24||Plastic Handle||1|
|25||Front Casing||1||26||Brake Handle||1||27||Gas Tank||1|
|28||Spark Plug||1||29||Screw (Black Casing)||2||30||Pump Handle For Oil||1|
|31||Choke Handle||1||32||Screw (For Choke Handle)||1||33||Screw (Next to Red Switch)||1|
|34||Screw (For Bottom Back Casing)||1||35||Screw (For Top Back Casing)||1||36||Screw (Side of Back Casing)||1|
|37||Throttle Trigger||1||38||Throttle Spring||1||39||Trigger Throttle Screw||1|
|40||Motor||1||41||Main Casing||1||42||7/16 Reversed Thread Nut||1|
|46||Fly Wheel||1||47||Large Spacer||2||48||Small Spacer||2|
|49||Rod Assembly||1||50||T15 Screw (Crankshaft)||2||51||Rollers||20|
|52||Drum (Sprocket/Bearing Assembly)||1||53||Flathead Screw with Washer (Carburetor)||4||54||Metal Carburetor Cover||1|
|55||Black Diaphragm with Holes||1||56||Black Diaphragm (No Holes)||1||57||Plastic Body||1|
|58||Brass Philips Screw||2||59||Carburetor Gasket||1||60||Steel Choke gate||1|
|61||Brass Throttle Gate||1||62||Screw With Spring Hi||1||63||Screw With Spring Low||1|
|64||Philips Screw Lever||1||65||Small Rod||1||66||Small Lever||1|
|67||Small Spring||1||68||Small Pin||1|
Table 2: A list of all the parts we found in dissecting the chainsaw.
Most of the subsystems are connected by a combination of different screw, nuts and bolts. For example, the alternator and carburetor are attached to the combustion chamber by a set of three screws. The brake and the starter are connected to the crankshaft by nuts. The spark plug has threads on it and is simply screwed into the combustion chamber. Another physical connection is the chain to the crankshaft. The crankshaft has teeth that connect to the chain to rotate it.
There are a few ways of transporting signals. The kill switch, when engaged stops the alternator from supplying electricity to the spark plug, making it impossible for the chainsaw to work. The trigger is a variable switch that affords human input and uses a wire, electrical signal, to control the amount of fuel/air mixture that is allowed into the combustion chamber. This controls the speed of the chainsaw. The final signal is a user input to the brake. The brake then disengages the chain.
Most of the mass transported in this system is a mixture of fuel, air and oil. The tank has two chambers, one of which holds oil that is transported through a fuel line to a pump which lubricates the chain. The other chamber holds a 40:1 mixture of gasoline and oil. The oil in this mixture lubricates the piston within the combustion chamber. This mixture goes through another fuel line to the carburetor. The carburetor then mixes this with air and vaporizes it. The vapor is then released into the combustion chamber. After the explosion, the waste gases are expelled through the exhaust.
The subsystems work together to produce the rotational energy that drives the chain to cut through wood. The starter takes the human energy of pulling the ripcord and converts that to rotational energy. This gives the crankshaft its initial rotational energy. The alternator converts this rotational energy into electrical energy which is then transported through a wire to the spark plug which transports the electrical energy into the combustion chamber. The fuel is a source of chemical energy and combines with the electrical energy in the combustion chamber. This is converted into thermal energy which drives the piston to create linear mechanical energy. The crankshaft then converts the linear mechanical energy into rotational energy which drives the rotation of the chain.
Below is a flowchart of the functions of the product. Figure 1 shows the overall function of the chainsaw and its inputs and outputs. Figure 2 is a much more detailed view of the functions. The blue functions consist of the choke, throttle, and carburetor. The red functions are the tank. The yellow functions are the starter, alternator, and spark plug. The green functions consist of the engine, crankshaft, clutch, and chain.
The engine is in the middle of the chainsaw for better balance of the machine. It is surrounded by an outer casing and other parts to keep the heat away from the user. The tank is adjacent to the engine, yet separated by a small gap to prevent excess heat transfer. The tank contains both the fuel tank and the oil tank and is adjacent to the engine with nothing in between them so the oil line can be connected straight to the pump, which distributes it onto the chain. The carburetor is located directly to one side of the engine, which is on the same side as the fuel tank so that the fuel line from the tank can go straight to the carburetor with little obstruction. The choke and air intake is located on the carburetor because that is where the fuel and air is mixed. The alternator is next to the carburetor and directly adjacent to the starter. The alternator and the starter have to be touching because the starter has rotating magnets and the alternator creates an electric current. The electricity from the alternator travels to the spark plug, which is located on the engine. There is a hole in the outer housing so the spark plug can be changed without taking the whole engine out. On the opposite side of the engine is the exhaust and the braking system. The exhaust is intuitively on the opposite side as the air intake. The brake system and chain are connected to the crankshaft and drive train along with the starter. The braking system is operator with a lever that is on the front of the chain saw. The chain is connected to the drive train on the same side as the brake so that when it is activated it can engage and disengage the drive train which allows the chain to spin or not. The chain is extended out with a chain blade that is located in the same location as the chain.
Connection of Subsystems
Why Are They Connected?
- The air intake is connected to the carburetor to allow proper air/ fuel mixture to facilitate combustion
- The fuel tank is connected to the carburetor to allow proper air/fuel mixture to facilitate combustion
- The carburetor is connected to the combustion chamber to allow mass flow into the combustion chamber where the air and fuel mixture will combust
- The spark plug is connected to the combustion chamber to transfer electrical energy into the chamber, which will ignite the combustion
- The alternator is connected to the ignition system in order to supply it with mechanical energy to convert to electrical energy
- The alternator is connected to the spark plug in order to supply it with electrical energy for combustion
- The throttle is connected to the carburetor in order to regulate the amount of air flow and therefore fuel/air mixture entering the engine
- The choke is connected to the carburetor in order to regulate the amount of air flow and therefore the fuel/air mixture entering the engine
- The starter is connected to the ignition system in order to supply initiating mechanical energy necessary to start continual operation
- Brake is attached to the chain in order to prevent mechanical energy from getting to the chain when brake is initiated
How Are Their Connections Implemented?
- The air intake is connected directly to the carburetor by screws
- The fuel tank is connected to the carburetor by a small connector at the bottom of the fuel tank that snaps into the carburetor
- The carburetor is directly screwed into the combustion chamber
- The spark plug is attached to the combustion chamber by a small wire that runs from the plug itself into the chamber
- The alternator is not physically connected to the ignition system however it is influenced by magnetic pulsations that occur when the rotation of the system occurs
- The throttle is connected to the carburetor by a throttle cable attached to a small rotating component that directly moves a valve controlling air flow
- The choke is directly screwed into a valve control on the carburetor which controls air flow
- The starter is connected to the ignition system by a string that is attached to a ratcheting wheel that allows only rotation when the user pulls the string
- The brake is connected to the chain by small teeth that are also used to drive the chain as well as stop it
- Global- Due to global considerations, the connections have to be strong enough to withstand a wide range of weather conditions such as heat, humidity and cold. Also, this chainsaw was designed, made and intended for use in the United States of America. As a result, all of the nuts and bolts use English units.
- Societal- The chainsaw is a potentially dangerous tool and therefore needs certain safety precautions. All of the moving parts except for the chain itself are enclosed to increase safety. Also, all of the electrical wires are encased in rubber to prevent unwanted electrical discharge. The inclusion of a brake system allows the user to quickly disengage the chain if anything goes wrong. Also the dual trigger system increases safety by not allowing the user to use the throttle accidentally. The length of the blade can be adjusted by a screw making it easy to do.
- Economical- The use of screws, nuts, and bolts as fasteners which is much cheaper than welding, soldering or using other means to connect parts. Also, this allows the parts to be easily replaced if one breaks instead of having to buy a whole new chainsaw.
- Environmental- The carburetor has screws so it can be tuned. This can be used to limit the amount of fuel used, thus limiting the amount of environmental damage. Additionally, the chainsaw is made using largely recyclable materials.
Performance Influences for Connections
Mass flow through the system is comprised of high pressure air and fuel. This is necessary for powerful combustion within the combustion chamber but also results in a need for very powerful fasteners and near perfect seals between components. Combustion is a basic requirement for this chainsaw to function as it is responsible for the power driving the system. For this reason, almost all of the components in the chain saw are connected by several screws. There are a few connections that are not made by screws. For example, the connection of the alternator to the spark plug. This is simply connected by a wire as it is the most effective way to channel current to supply the spark. Another connection type would be the snap in nozzle that connects the fuel tank to the carburetor. Since the fuel tank is not pressurized, there is no need for a powerful seal between it and any component. One of the most unique connections lies between the chain and the drive system. The chain is driven by a lubricated gear that lays within the chain allowing a low friction, high torque capable connection that is very useful for allowing the chain to spin at very fast speeds to cut wood.