Group 32 - Chainsaw
Cam Borowiec - Group Leader
Andrew Koonce - Wiki Expert
Scott Chown - Communications Liason
Matt Lang - Solid Modeling Expert
Gagan Reddy - Dissection Leader
Group Member Pros/Cons
|Matt Lang||-5 Years of CAD Experience
-Works Well in Groups
|-Little Understanding of Engines
-Poor Public Speaking
|Andrew Koonce||-Knowledge of Engines
-Good With Computers
|-Poor Public Speaking
|Cam Borowiec||-Good Public Speaking
-Natural Leadership Skills
|Scott Chown||-Good Communication Skills
-Good With Computers
|-Lacks Dissection Knowledge|
|Gagan Reddy||-Prior Dissection Experience
-Knowledge of Engines
Gate 1: Request for a Proposal
For this project we have to disassemble, analyze and reassemble a product. Our group was given a chainsaw. By looking over the chainsaw we can tell that the complete disassembly, including engine, should take a couple hours. The initial steps for disassembly include the removal of the handles and plastic casing. This is done with the use of a #3 flat head screwdriver. Next, various parts will be removed from around the engine including the pull-cord mechanism and fuel tank. Doing this will require two adjustable wrenches and a #3 flat-head screwdriver. All that’s left is a basic two-stroke engine. This will require hex-wrenches and possibly Phillips head screwdrivers of various sizes. Along with the disassembly a report is due October 30th. In this report we will discuss how our management proposal is going. Also, we need to discuss how the disassembly went compared to what we were expecting. The next part of the project, due November 23rd, is the analysis of the chainsaw. Solid models of components of the chainsaw will be created and reviews on the parts must be made. When the chainsaw is finally reassembled a final review is written. This includes the reassembly plan. This is due December 7th, and the final delivery is due December 11. There will be a few challenges in disassembling our chainsaw. One of the challenges of disassembly is that we are working on a chainsaw that is roughly 25 years old. This is a factor because there is not too much information on the exact model. One very important piece of info is the gas to oil ratio needed. The gas-oil mixture results from the use of a two-stroke engine. If this mixture is not right the engine will be at risk of seizing due to a lack of oil, or produce excess smoke, and fill the muffler with oil sludge. Also, the age might create issues with removing screws or bolts that have rusted. Working in a group has advantages by allowing a diverse knowledge and experience in different fields. Two of our group members have experience with CAD. One member has been working with CAD for 5 years. He has worked with 3 different programs and is currently working with a fourth. Most of the members have basic knowledge on how a chainsaw works. A couple of the members have knowledge about two-stroke engines and experience repairing them, one specifically has in depth knowledge of two-stroke engines and is very familiar and comfortable with disassembling and reassembling them. This still results in some shortcomings, as nobody has worked on a wiki before. A couple members have not disassembled complex object before, so extra care should be given to the organization of the disassembly and parts.
Time and work management are an important factor in the success of this project. We will try to use our time efficiently, but some time will be left at the end of the project to finish if we get behind. For the workload we have decided to split the work on the wiki, report, research and disassembly in a way that maximizes project unity. Everyone will contribute to most major processes to allow for a better understanding of the project and a smooth flow of communication. Also, group meetings will ensure we stay on task. Our main point of contact will be Cameron Borowiec. His phone number is (716)-515-8028, and his e-mail is firstname.lastname@example.org. He can be reached by phone at just about anytime of the day and any day of the week except for Mondays, Wednesdays, and Fridays between 3:00P.M. - 5:00P.M. due to lack of service in Knox Hall. During those times he can be contacted by e-mail. E-mail will most likely prove to be the best way of contact though due to his involvement in various clubs and activities. Our back-up point of contact will be Andrew Koonce whose phone number is (518)-694-6695 and his e-mail is email@example.com. Andrew can be contacted almost as easily as Cameron. However, due to the involvement in multiple clubs, email is the best way to get a hold of him. Our meetings places and times will vary, but seeing as our product can be taken from our lab it is safe to say that we won’t be meeting there most of the time. Cameron or Scott will retrieve our product from the lab and keep it with them. They have an easy way of transporting the product to a convenient location. Tuesdays, Thursdays, and weekends will tend to be the best days to collaborate on our assignments, and Cameron’s south campus apartment shall prove to be an excellent environment to meet in and work at. Minimally we plan to meet two times a week, increasing our meetings if we fall behind. We plan, as a whole, to meet together during times that are convenient for all of us, so as a group we can disassemble the product together. By splitting up the work evenly amongst us, we can ensure that no one is under worked. This will also help make sure the work will get done. We will assign three people to mainly work on the Wiki and keep it up to date with our information. Relocation of the chainsaw will occur only if we can find a convenient location for it where everyone can work on it.
The roles and responsibilities of each member will be somewhat equally divided. Because we are working in a group situation with members who have different schedules, it will be tough to say who’s doing what until we start really working together and figure out each other’s strengths and weaknesses. We plan to fall into a pattern, and strengthen are plan of action as we figure these things out. As each new task is presented to us we will decide as a group who has the right strengths and abilities to overcome the challenges of that specific obstacle.
Initial Product Assessment
- What is the intended use of the product?
The intended use of our product is quite obviously to cut through wood, specifically trees, logs, and branches that are too thick to but cut down by use of a bow saw. As do most power tools and other tools, our chainsaw has a very specific purpose and it strongly recommended to not use it for any purpose other than that. A chainsaw does not cut through materials other than wood. As for cutting through boards or plywood, there are much more accurate types of saws depending on the type of cut you are trying to make. A chainsaw is only intended for inaccurate cuts of lumber. Then, if a more accurate cut is desired one would use one of the many other types of cutting devices.
- How do you think the product works?
A chainsaw in the simplest form is a two-stroke engine geared with a chain that extends out of the main body. The two stroke engine, allows for two parts of the Otto cycle to occur simultaneously for a more consistent output of energy. The four steps in the Otto cycle are intake, compression, combustion, expansion (exhaust). The two stroke engine allows for the intake and exhaust steps to occur together. This allows power to be delivered every rotation.
The piston moves in relation to the expanding and contracting gas, but only creating a positive force after ignition. This occurs when electrical energy is transferred from the spark plug to ignite the fuel mixture, resulting in chemical energy. This energy forces the piston to move towards the crankshaft, producing mechanical energy. The rotation of the crankshaft is then applied to the chain from the sprocket, resulting in a fast moving blade to chop down trees.
- Is the product currently functioning?
Our product is currently not functioning, because there is no fuel or chain. Chainsaws require a certain gas/oil mixture that still needs to be researched or the engine will not work properly. This mixture is different for various chainsaws. Once we obtain the correct fuel mixture we might have more problems, resulting from the age. However, we will not be able to use the chainsaw for it's intended use because the chain has been removed. Our guess is that it was removed for safety issues, so we aren't worried about it. The chainsaw will still run normally without it.
- How complex is it?
The product, compared to other new and improved models is slightly less complex. If a new chainsaw with a fuel injected engine (a somewhat ridiculously unnecessary attribute for a chainsaw to have) as well as variable speed capability is about a 6 on a scale of complexity compared other similar products that utilize a similar type of small engine, then our 25 year old carbureted chainsaw is a solid 2.5. The most complex part about our chainsaw is the 2-stroke engine, which is not very complex at all, again when compared to other similar products.
- What materials are used in the project?
The main material used on the outside of the chainsaw is plastic. It is used for the casing of the bulk of the components and a pull handle. There is some type of metal visible which is used for the handle and also the bar of the chainsaw. There is also a rope visible which is pulled to start the engine and rubber used to cover the spark plug.
Inside of the chainsaw, it can be assumed that there are more metals used for the engine and for the gears to drive the chain. There may also be plastic used for the gas tank and other small components to hold the chainsaw together.
- If you had to use this product, would you be happy with it?
This chainsaw looks to be quite old so we are not sure we would be pleased using this product. Holding the chainsaw, the location of the grips makes it quite comfortable to use. There are basic labels on the body of it that an average person would be able to understand. If we were to use the product, we think it would be quite easy to do so.
The product does require some maintenance. The chainsaw needs regular replacements of gas, oil, and lubrication for the chain. There are labeled areas on the body of the chainsaw which make it fast and easy to service it.
- What other alternatives to your product are there? How do these alternatives compare?
As stated before, this is an older model chainsaw. Today, there are many different alternatives to this product. This chainsaw is not produced anymore, but present day chainsaws range in price from $50 upwards of $400. The more expensive the chainsaw, the bigger and more powerful it is. There is no real advantage to this product over any modern day comparison. This chainsaw is rusted and is not as powerful as anything used today. If any spare parts were needed to fix the chainsaw, it would be incredibly difficult to find a retailer with the needed parts. While with modern chainsaws, all it usually takes is a call to the manufacturer to find the part you need.
Gate 2: Preliminary Project Review
Our work and management proposals were successful with a couple conflicts along the way. The challenges in the disassembly were limited to removing the centrifugal clutch. This required an enormous amount torque. To do this we used a vice grip to lock up the crankshaft. Also, we had to use a metal rod to extend our moment arm. This challenge in disassembly was not predicted and caught us off guard.
Following our management proposal we had left time in our disassembly process to handle any situations like the clutch removal. However, our initial plan to meet twice a week was found to be unnecessary. The full disassembly was done in two meetings, and a trip to the lab to remove the clutch. After the Request for the Proposal was due, Andrew went to the lab and signed out the chainsaw. He then took it with him and did a quick analysis disassembly. By removing the three outer covers over the flywheel, clutch and intake, a secondary analysis for tools and challenges was done. This took him 25 minutes at most. This is where we found the clutch removal problem. Our list of tools required was confirmed.
Our next meeting was at Cam’s apartment, where everyone gathered on October 15th at 5pm. For two hours we worked on the disassembly. During the disassembly we took photos of the whole step process and recorded our progress in an Excel document (see attached). At the end of the two hours we had removed everything from the main component up to the intake (see Chart 1 for details). Next we met October 20th at the same place and time (Cam’s apartment @ 5pm). During this time we finished our disassembly. The next day we went to the lab to remove the clutch. Overall, we have to say our disassembly was a success and we plan on continuing our management proposal into the next gates.
|Step||Tool Used||Part Removed||Location on Product||Time it Took||Ease Rating 1-5||Directions|
|1||Straight Blade Screw Driver||Intake Cover||Exterior||5 sec||2||Turn the bolt 90 degrees and pull plastic cover off.|
|2||Straight Blade Screw Driver||Intake Cover Locking||Underneath the intake cover||5 sec||2||Remove the bolt.|
|3||14 mm Socket & 1/4" Drive||Clutch Cover||Exterior||30 sec||2||Remove both nuts and washers, and slide the cover off of the protruding bolts.|
|4||None||Chain Bar||In between clutch and body||1 sec||1||Slide it off of protruding bolts that hold it in place.|
|5||Straight Blade Screw Driver||Handle||Exterior||1 min||2||Remove all four bolts holding it in place.|
|6||Straight Blade Screw Driver||Flywheel Cover||Exterior||1 min||2||Remove all 3 bolts.|
|7||Straight Blade Screw Driver||Bottom Exterior Cover||Bottom||1 min||2||Remove all 4 bolts.|
|8||crescent wrench||On/Off Switch||Attached to the bottom cover||5 sec||2||Remove the thin nut holding it in place.|
|9||Straight Blade Screw Driver||Muffler/Exhaust Cover||On the side, next to the clutch||30 sec||2||Remove all 3 bolts attaching it.|
|10||Straight Blade Screw Driver||Exhaust Header||Under the muffler/exhaust Cover||30 sec||2||Remove all 3 bolts holding it in place.|
|11||Spark Plug Wrench||Spark Plug||At the top of the cylinder||30 sec||4||Remove the spark plug by twisting it.|
|12||14 mm Socket & 1/4" Drive||Fly Wheel||Under the flywheel cover||30 sec||3||Remove the bolt holding it onto the shaft protruding through the center of it.|
|13||Straight Blade Screw Driver||Magneto and Spark Plug Wire||Beside the flywheel||15 sec||2||Remove the 2 bolts holding it in place.|
|14||Straight Blade Screw Driver||Spark Plug Timing Mechanism||Above the timing mechanism||3 sec||2||Remove the clip/lock and pull plastic cover off.|
|15||Straight Blade Screw Driver||Choke||Connected to the intake||15 sec||3||Slide the choke out from intake.|
|16||Straight Blade Screw Driver||Intake||On the top under the intake cover||10 sec||2||Remove the bolt holding it in place and slide out.|
|17||14 mm Crescent Wrench||Cylinder||Surrounding the piston and connecting rod, beneath the intake||5 min||3||Remove all 4 of bolts and nuts.Then slide it off.|
|18||Straight Blade Screw Driver||Battery||Next to the crankshaft, under the flywheel||10 sec||2||Remove the 2 bolts holding it in place.|
|19||None||Plastic Holder||Next to the crankshaft||.5 sec||1||Pull it out.|
|20||Straight Blade Screw Driver||Timing Mechanism||Surrounding the crankshaft outside of the crankcase.||5 sec||2||Remove the bolt.|
|21||Straight Blade Screw Driver||Left Half of Casing||Exterior||5 min||2||Remove all 7 bolts attaching it to the other half of the body casing.|
|22||None||Throttle and Cable||Inside the handle part of the external casing||1 sec||1||Lift it out of place.|
|23||Vice Grips, 15/16" Crescent Wrench, and Leverage Bar||Clutch Assembly||Attached to the crankshaft on the opposite side of the casing from the piston and connecting rod.||5 min||5||Clamp the vice grips to the crank case in a position that will prevent the counter balance to pass it therefore keeping the crank shaft from spinning freely. Put the open end of the crescent wrench in the slots on the clutch and using a leverage bar in the other end of the wrench, twist in the direction of the arrow (reverse threaded) and pry it off.|
|24||None||Crank Shaft, Piston, and Rod||Inside the crankcase and protruding from both sides||30 sec||3||Twist and pull it out of place.|
The Difficulty Scale is rated accordingly:
- 1 = No tool required
- 2 = One tool required with little force required
- 3 = One tool required with a large force required or an awkward positioning
- 4 = Multiple or specialized tools required with little force required
- 5 = Multiple or specialized tools required with a large force required
Gate 3: Coordination Review
The complexity scale is rated as listed below.
- 1 = One or two parts that easily fit together
- 2 = Three to seven parts that require some knowledge to assemble
- 3 = Seven to twelve parts that require accuracy, and full knowledge of the products use, to assemble.
- 4 = More than twelve parts that require full knowledge of the mechanical system.
- 5 = It has many parts that require machines and careful examination to assemble.
|Length||Thread Width||Head Size||Quantity|
|1 3/16"||1/4"||7/16"||4 with lock washers|
|Square||7/16" x 7/16"||2/8"||3/16"||4|
|Square||3/8" x 3/8"||3/16"||1/8"||2|
|Hex||1/2" x 1/2"||5/16"||5/16"||2|
|Hex||9/16" x 9/16"||5/8"||3/16"||1|
|Hex||9/16" x 9/16"||7/16"||1/16"||1|
|Hex||3/8" x 3/8"||1/8"||1/8"||1|
The design of the chainsaw is relatively obsolete because of its age. With it being 29 years old, there have been many advances in technology that we have today that could make the chainsaw significantly better.
- One of these new design methods would be to put 2 piston rings around the piston head instead of the single one that is on our chainsaw now. This is not a very technologically advanced design but, it is very cheap to do and will help the consumer greatly. This ensures that if the primary piston ring breaks or wears down and releases the seal to the cylinder wall, there is a back up that will keep the chainsaw working properly without the need of emergency repair.
- Another simple add on to the chainsaw would be a temperature gauge that reads the heat inside the cylinder. This is a simple way of making the consumer aware of lack of oil in the gas/oil mixture which is needed for the piston to work properly. This would be a much more expensive addition than the piston ring but it could save the chainsaw from complete uselessness. If a user knew that the chainsaw was becoming over heated, he could let it cool before the engine seized or fix the ratio of oil and gas.
- One thing that is common with chainsaws today, which would be a great improvement on the chainsaw we have is an external fuel tank made of plastic. This tank would be cheaper to produce than its aluminum counterpart in our chainsaw. The disadvantages of the aluminum fuel tank is that the aluminum is heavier than the plastic the external tank would be made out of and that the fuel tank could have a larger volume if it was placed outside the body of the chainsaw instead of being crammed into the body. This would greatly benefit the consumer while also benefitting the company. The company would save a great amount of money switching from aluminum or an aluminum alloy to a cheaply mass produced plastic tank while the customer enjoys a lighter and longer lasting, in terms of refueling, chainsaw.
Solid Model Assembly
We chose Autodesk Inventor 2010 for our solid modeling program. We did this because our solid modeling expert has been working with this program for 5 years and would not have to learn another programs mechanics. We chose to model the piston assembly because it provides the main power for our system to work.
- Named link: Chainsaw_Piston_Assembly
What is the frictional force needed for a 2-stroke engine to cease?
- Friction is constant around the entire cylinder
- Coefficient of friction between the piston and cylinder is .03
- The normal force at cease is 110N
- Temperature is constant
- Piston and cylinder made of Aluminum
Ff = .03*110N= 3.3N
The values for the coefficient of friction and the normal force were obtained from VTT research notes on the friction inside of a 2-stroke engine. This helps to confirm that the force I obtained is close to the actual force.
* Note: no pictures are up yet because of technical difficulty. (This includes the parts of the product, parts of the CAD assembly, and the diagram for the Engineering Analysis.)
Gate 4: Critical Design Review
|Step||Tool Used||Part Removed||Location on Product||Time it Took||Ease Rating 1-5||Picture (Y/N)||Directions|
|1||None||Crank Shaft, Piston, and Rod||Inside Crank Casing and Protruding from Both Sides||30 sec||2||Y||Insert the parts back into the crankcase.|
|2||Vice Grips, 15/16" Crescent Wrench, and Leverage Bar||Clutch Assembly||Attached to Crank Shaft on Opposite Side of Casing From Piston and Rod||5 min||5||Y||Clamp the vice grips to the crank case in a position that will prevent the counter balance to pass it therefore keeping the crank shaft from spinning freely. Put the open end of the crescent wrench in the slots on the clutch and using a leverage bar in the other end of the wrench,twist in the direction opposite of the arrow (reverse threaded) and tighten the clutch on.|
|3||None||Throttle and "Cable"||Inside the handle part of the casing||1 sec||1||Y||Set the trigger onto shaft according to the picture.|
|4||Straight Blade Screw Driver||Left Half of the Casing||Exterior||5 min||1||Y||Screw in all 7 bolts holding the two sides of the casing together.|
|5||Straight Blade Screw Driver||Timing Mechanism||Under the timing mechanism cover||5 sec||1||Y||Bolt the timing mechanism back on. (*Make sure the contact trigger barely makes contact with the sensor to result in the right timing.)|
|6||None||Plastic Holder||Next to Crank Shaft||.5 sec||1||Y||Insert the plastic holder back in it's slot.|
|7||Straight Blade Screw Driver||Battery||Next to Crank Shaft, Under Flywheel||10 sec||1||Y||Screw the battery back in with the two bolts.|
|8||14 mm Crescent Wrench||Cylinder||Surrounding Piston and Rod, Beneath Intake||5 min||3||Y||Bolt the cylinder back on. Make sure the piston ring is compressed and the piston goes in straight. Also, check to make sure the intake port lines up with the casing.|
|9||Straight Blade Screw Driver||Intake||Top, Under Intake Cover||10 sec||2||y||Slide the intake in, bolt it on, and connect the fuel line.|
|10||Straight Blade Screw Driver||Choke||Connected to Intake||15 sec||2||Y||Insert the tab on the end of the choke onto the intake.|
|11||Straight Blade Screw Driver||Spark Plug Timing Mechanism Cover||Above Timing Mechanism||3 sec||1||Y||Place the cover back on and insert the clip onto the copper shaft.|
|12||14 mm Socket & 1/4" Drive||Fly Wheel||Under Fly Wheel Cover||30 sec||2||Y||Bolt the flywheel back on to the crankshaft.|
|13||Straight Blade Screw Driver||Magneto and Spark Plug Wire||Beside the Fly Wheel||15 sec||2||Y||Bolt the magneto back on. Make sure the magneto is as close to the flywheel as possible, but not touching it. Spin the flywheel a couple times to test the clearance.|
|14||Straight Blade Screw Driver||Exhaust Header||Under Muffler/Exhaust Cover||30 sec||1||Y||Screw the three bolts back on.|
|15||Straight Blade Screw Driver||Muffler/Exhaust Cover||Side, Next to Clutch||30 sec||1||Y||Reattach the exhaust using the three bolts removed.|
|16||crescent wrench||On/Off Switch||Attached to Bottom Cover||5 sec||1||Y||Slide the switch back into the bottom casing, and screw the thin hex nut back on.|
|17||Straight Blade Screw Driver||Bottom Exterior Cover||Bottom||1 min||2||Y||Bolt the cover back on using the four bolts. Leave the lower left (looking at the chainsaw from the user's view) bolt off.|
|18||Straight Blade Screw Driver||Flywheel Cover||Exterior||1 min||2||Y||Bolt the cover back on using 3 bolts.|
|19||Straight Blade Screw Driver||Handle||Exterior||1 min||2||Y||Bolt the handle back on using the four bolts, nuts and washers.|
|20||None||Chain Bar||In between Clutch and Body||1 sec||1||Y||Slide the bar back onto the bolts and the bolt that adjusts the chain tension.|
|21||14 mm Socket & 1/4" Drive||Clutch Cover||Exterior||30 sec||1||Y||Bolt the cover back on with the two washers and nuts.|
|22||Straight Blade Screw Driver||Intake Cover Locking||Underneath Intake Cover||5 sec||1||Y||Attach it using a single bolt.|
|23||Straight Blade Screw Driver||Intake Cover||Exterior||5 sec||1||Y||Place the cover over the intake, push the screw in and turn it 90 degrees.|
Does your product run the same as it did before you disassembled it?
The product still does not work. The pull start still gets jammed and slowly recoils, and the engine needs replacement parts in order to be repaired. Also, there is a hole in the crankcase preventing the chainsaw from ever working.
What were the differences between the disassembly and the reassembly processes?
During reassembly the same tools were used, however there is more detailed work required to make the chainsaw work. This includes a miniscule distance between the magneto and the flywheel, The timing of the spark plug must be accurately positioned, and the carberator must be tuned according to the manual. Overall we were able to reassembly the chainsaw with no problems.