Gate 4 - Group 12 - 2012
In the previous gate the group extensively analyzed the subsystems of the Weed Eater Variable Speed Handheld Blower. The GSEE (global, societal, economic, an environmental) factors were considered and specific design revisions were proposed. Gate 4 allows the group the consolidate all of it's research on the product. Concluding all of the extensive analysis, the product has been reassembled and the mechanisms of it's motion and energy transfer have been recorded. Furthermore, specific design revisions of a wider scope have been proposed for the overall function of the product.
Critical Project Review
Cause for Corrective Action
Gate 3 was the most time consuming and extensive part of the project for the group as a whole and individually. Coupled with numerous substantive exams in other classes, as well as the large amount of work that went into Gate 3, this was a trying section of the project for the group. However, building on our previous pitfalls and using the momentum of our regular meetings and communication, the work was divided fairly and time consciously.
For this gate, we experienced similar issues of handing in quality work on time. Each individual member is not working at an equal level, and increased revisions and communication have been implemented to support these issues. Communication is yet another issue the group continues to experience. When there is an issue with individual group members work, it is not communicated in a timely manner, and all group members are not keeping in touch enough. To solve this issue, an increased amount of group communication is being implemented on the file-sharing Facebook group and in person to make sure each member is up to par with their work.
The recent break and quickly approaching due date for Gate 4 acted as a catalyst for these issues. However, the proper precautions are being implemented to minimize these setbacks and the group is still moving ahead with work.
Scale of difficulty is from (1) to (3).
Step 1: Choose where to start from. We decided that this was the engine block itself, the core of the leaf blower.
Step 2: Assembly of the Piston and cylinder. The parts involved are the Piston and rod, the cylinder and the main block.
Step 3: Insert the piston into the cylinder. This is a very difficult thing to do without the right tool, a piston ring compressor. Without this tool we hand to get the ring into the cylinder by compressing it with our hands and then using a screwdriver to pry the rest of the ring in.
Difficulty: With tool (2); Without tool (3)
Step 4: Attach the cylinder to the main block, but do not screw it in yet.
Step 5: While the piston cylinder is loosely attached to the main block, attach the bearing in the piston rod onto the crankshaft. Then after it is attached, tighten the piston cylinder to the block as tight as possible to make sure there is no future compression leaks. It may also be a good idea to add a tiny amount of oil into this area as lubricant.
Step 6: Attach the crank shaft cover to the main block.
Step 7: Attach the carburetor spacer to the main block and make sure that it is as tight as possible with 4mm allen key
Step 8: Attach the air filter housing to the carburetor making sure that the blue switch is in the “CHOKE” slot of the air filter housing.
Step 9: Screw the carburetor and air filter housing into the carburetor spacer and make sure it is at tight as possible with 4mm allen key.
Step 10: attach the air filter into the air filter housing.
Step 11: Attach the air filter cover to the air filter housing.
Step 12: Attach the generator to the main block.
Step 13: Attach the muffler to the main block with 4mm allen key.
Step 14: Attach the pull chord housing to the main block with 4mm allen key, making sure that the spacer is put onto the crankshaft before the housing is attached. Make sure the you are able to pull the chord and it seems to be functioning properly before continuing on to the next step.
Step 15: Attach the handle and the engine cover to the main block with a 4mm allen key. Make sure that the springs to the handle are under the screws as shown in the picture and the next one as well.
Step 16: Attach the exhaust cover to the engine cover and pull chord housing with a 3mm allen key.
Step 17: Attach the turbine housing to the pull chord housing with a 4mm allen key.
Step 18: Attach the turbine to the crankshaft in the turbine housing with a ½ inch socket and make sure that the screw is tightened as much as possible.
Step 19: Attach the turbine housing cover with a 4mm allen key.
Step 20: Attach the tube and the turbine housing cover to the turbine housing (as shown in picture).
Mechanism: The mechanism that we decided to analyze for this gate is the piston, piston rod, and crankshaft assembly. This assembly is the most important part of the entire device; it’s what drives it and allows it to function. The assembly is located within the engine and is, in some way, linked to every other subsystem in the leaf blower. Most of the subsystems work because of the energy supplied by the assembly.
Technical Name: Crank-Slider
Purpose: It converts the linear energy created by the upward and downward motion of the piston into the rotational energy of the crankshaft which is then used to create the constant rotation of the turbine blade.
How it Works: At the mechanism level, the crank-slider works very simply. The piston or as the model shown below calls it, the slider, is attached to the crankshaft via a connecting rod and pin. When the crank is turned the rod pushes the slider back and forth, or up or down, depending on how the crank-slider mechanism is orientated.
When applied to the Weed Eater 25cc Gas Variable Speed Handheld Blower: The engine used in the blower is a two-stroke engine, which means that the cycle is completed in two up and down movements with only one revolution of the crankshaft. The piston is pushed upwards from the air/fuel mixture, which also collects on top of the piston. As it moves upwards, the fuel is compressed. The spark plug then ignites, burning the fuel, and forcing the piston downward. The burned gas is then released through the exhaust outlet. And finally the fuel being fed in through the carburetor is pushed once again to the top of the piston, ready to be compressed again.
Pressure = Force*Area
Force = mass*acceleration
Torque = Inertia*angular acceleration
Inertia (circular solid shaft) = (pi*Radius^4)/2
Angular Acceleration = dw/dt
Power = Torque*2pi*Rotational Speed
The addition of an external fuel level indicator would improve the usability of this product significantly, this coupled with a small chart with an estimated run time at each of the fuel level indications would allow the user you save time and money by allowing them to have easy access to this information. This change would be a global factor as this would make the product more usable to anyone trying to use it across the world.
The addition of plastic loops on the product for the easy assembly and remove of a strap or harness would help with the distribution of the leaf blower’s weight and this would assist the user in handling and operating the product. This simple addition would increase the product audience and cause those who many have found the leaf blower uncomfortable or too heavy to hold to now be able to use the product with more easily. This addition would be a societal factor as the product has become more diverse in the product audience.
The third system revision to the product would be an electric motor and electric user interface. This electricity dependent system might be slightly more costly in the end, but it may benefit the design in terms of serviceability, less environmental degradation, improved performance or efficiency, and ease of use. Whether it is decided to pass the slightly higher production costs to the consumer or not, these benefits could favor the design change. Being of electrical components, there are less parts to maintain and service regularly. This would also prove to increase the ease of use in the interface as starting the engine or regulating air intake or blower power would be easier to manage. A system that runs on electricity also uses no fuel other than the electricity needed to start and run the product, minimizing effects on the environment during usage. Lastly, an electric motor accelerates faster than a physical motor and may provide more power for the energy being used.