Difference between revisions of "Alligator Lopper: Gate2"
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[http://gicl.cs.drexel.edu/wiki/Group_22_-_Black_%26_Decker_Alligator_Lopper Alligator Lopper Homepage]
Revision as of 10:23, 14 November 2012
The Alligator Lopper has a fairly straightforward which effectively ties in three main subsystems which are the Chainsaw Subsystem, the Trigger Assembly subsystem, and the Scissor Action Subsystem. Both the Scissor and the Trigger Assembly Subsystems were relatively easy to deconstruct. This assessment is based on the locations of bolts that need to be removed and also the types of tools required by the bolts in order to dissect the subsystem.
Below this are a number of different subsections regarding the dissection of the Alligator Lopper and its component and subsystem interactions. They appear in the following order:
Difficulty Rating System: A three point system was implemented in order to rate and understand the difficulty involved with dissecting the product. Each step is rated based on this scale and an overall rating of difficulty will be assigned to each of the three groupings of components.
Dissection: Outer Cover/Handles: Provided are step by step instructions with visual aides in order to facilitate the diss-assembly process of the Alligator Lopper by a different user. The Outer Cover/Handles are the first thing that that must be taken apart in order to reach the motor mount, motor, and chain system.
Ease of Dissection Analysis: Outer Cover/Handles: This section will address how the difficulty for the Outer Cover/Handles was determined and the factors which determined what the intended difficulty was supposed to be.
Dissection: Chain Guard and Chain Guard Cover: Provided are step by step instructions with visual aides in order to facilitate the diss-assembly process of the Alligator Lopper by a different user. The Chain Guard and Chain Guard Cover may be removed first if the goal of the user is to just gain access to the chain. However it is placed as the second general group of components to be removed since our overall goal was to completely dissect the Alligator Lopper, not to just gain access to the chain.
Ease of Dissection Analysis: Chain Guard and Chain Guard Cover: This section will address how the difficulty for the Chain Guard and Chain Guard Cover was determined and the factors which determined what the intended difficulty was supposed to be.
Dissection: Internal Motor Mount and Motor: Provided are step by step instructions with visual aides in order to facilitate the diss-assembly process of the Alligator Lopper by a different user. This last group of components in the dissection process can be disassembled as far as separating the magnet and coil of the motor. This yields the smallest components our dissection can produce without causing permanent damage to those components.
Ease of Dissection Analysis: Internal Motor Mount and Motor: This section will address how the difficulty for the Outer Cover/Handles was determined and the factors which determined what the intended difficulty was supposed to be.
Difficulty Rating System
1 - Parts or components can be removed from their housings or corresponding components without further use of tools not included with the Alligator Lopper. The user only needs the provided tool to preform the step or requires no tool to preform the step.
2 - Some components must be removed in order to access the desired component. Common tools such as a Flat or Philips head screwdrivers or an Allen wrenches are required to complete the step.
3 - The desired component is located below multiple parts or subsystems. It cannot be accessed or removed without first removing the parts or subsystems obstructing it. Less common tools, such as a Torque screwdriver, are required to complete the step.
Dissection: Outer Cover/Handles
|Step Number||Step||Difficulty Rating||Image|
|1||Start by orienting the Alligator lopper so that it lies on its side with the motor sticking up. This will allow for access to the screws holding the cover together and also to the motor and its housing||1|
|2||Remove two Allen head bolts in the orange cover surrounding the motor’s base. Once removed, this small, half circle shaped cover will easily slide off, revealing the spring that keeps tension on the handles so that they remain closed.||2|
|3||Remove the four Philips bolts from the very top of the motor cover. Remove the top motor cover from the motor.||2|
|4||With the Alligator positioned so that the missing cover is facing the user, remove the 6 Philips heads screws from the far sided handle.||2|
|5||Once removed, lift the outer cover of the handle upwards. Once free of its top half, the trigger system is revealed within the handle. It is composed of a black trigger, two small springs positioned above each end of the trigger, and a switch above the middle of the trigger||1|
|6||Gently pull upwards on the trigger. This will free the springs from compression, so make sure they do not become airborne and lost. Store the springs and the trigger in a safe place where it will not become lost||1|
|7||Pull upwards on the switch so that it will become freed from the two orange plastic pegs it is anchored with.||1|
|8||With the trigger assembly removed from the handle, pull up on the last half of the shell. This completely removes it from the Alligator Lopper, revealing a gear which interlocks with teeth on the cover used to open and close the jaw.||1|
|9||Remove the spring in its trench besides the motor cover and store in a safe location.||2|
|10||On the second handle, there is a small panel held in place by a single Philips head bolt. Remove this bolt along with the small panel it holds.||2|
|11||Next, remove the remaining 10 Philips screws from the orange cover that makes up both the handle and the cover around the motor mount.||2|
|12||Pulling upwards on the cover will separate it from its bottom half revealing the second trigger assembly.||1|
|13||Gently pull upwards on the trigger. This will free the springs from compression, so make sure they do not become airborne and lost. Store the springs and the trigger in a safe place where it will not become lost||1|
|14||Located next to the trigger is the cord which supplies the motor with electricity. It is held in place by two Philips head bolts. Remove the bolts so that the cord can come free from the lower half of the handles.||2|
|15||Two wires lead from the large black cord: a small white one and a small black one. They enter a small white contact box which connects it with the wires that run within the lopper and they are held by two small Flathead screws within the contact box. Loosen these flathead screws until the wires are able to slip free. Store the black cord in a safe location.||2|
|16||Pull upwards on the switch so that it will become freed from the two orange plastic pegs it is anchored with. This will allow the switch to become separated from the lower half of the handles.||1|
Ease of Dissection Analysis: Outer Cover/Handles
Average Difficulty Rating of Dis-assembly: 1.5
Based on the both the difficulty ratings we assigned to each step and also the replacement parts available online, this part of the dis-assembly was intended to occur by the designers. All of the screws and bolts that were removed were removed by common Philips head screwdrivers and Allen wrenches. These types of tools are usually in the possession of the target consumer for the Alligator Lopper. In addition these screws and bolts were easily accessible either outright or with the removal of one additional component.
The following parts may be purchased as replacements for the Outer Cover/Handles:
Gear for the Rotating Jaw
In order to gain access to the parts provided online as replacements, the outer handles of the Alligator Lopper must be removed. All of the screws used to hold the cover in place were located right on the surface of the handles and were accessible without removing multiple components. The ease with which they can be accessed is a sign that it was designed with possible part maintenance or replacement in mind further along in the product life cycle. Furthermore, the tools required to remove these screws were a standard Philips head screwdriver, a standard Flat head screw driver, and and Allen wrench.
|Required Tool||Steps Requiring Tool||Total Screws Removed with tool|
|Philips Head Screwdriver||3,4,10,11,14||22|
These three tools are most likely to be in the possession of the intended consumer. If they are using the Alligator Lopper to do yard work, chances are very high they also own common screwdrivers and Allen wrenches.
Based on the replacement components available and also the ease with which this section may be disassembled, the assumption is that the designers of this product did intend their consumer to take apart this portion of the product to preform maintenance on the Alligator Lopper
Dissection: Chain Guard and Chain Guard Cover
|Step Number||Step||Difficulty Rating||Image|
|1||Flip the Alligator Lopper over so that it rests on the motor||1|
|2||Using the wrench provided with the tool, loosen the two bolts located in the center of the black cover at the beginning of the jaw. When removed, pull off the black cover exposing the chain, sprocket, jaw, and the chain guide.||1|
|3||Locate the rotating jaw with the teeth. It is held together with three Allen headed bolts. Once removed, lift the half side of the jaw up and separate it from the lower half.||2|
|4||The bottom half pivots on a bolt held together by a nut recessed into the lower half of the jaw. Using an Allen wrench, remove the bolt. Pull the lower part of the jaw off the bottom cover.||2|
|5||Located at the bottom of the chain guide is a small plastic clip. This is used to hold the chain guide close to the frame when the two major bolts are removed. Pushing the plastic clip away from the guide towards the sprocket allows the operator to remove the chain, chain guide and sprocket.||2|
|6||Once that is removed, the operator can lift the last plastic cover off of the motor, motor mount, and gear mount.||1|
|7||Underneath this cover is the plastic clip that holds the chain guide in place. With it are two tensions springs that keep the clip compressed against the chain guide resisting slip.||1|
|8||Remove the clip and two springs being careful not to lose them||1|
Ease of Dissection Analysis: Chain Guard and Chain Guide Cover
Average Difficulty Rating of Dis-assembly: 1.38
This overall difficulty rating reflects the type of tools that were required to dissect this section, the location of the screws and nuts required to take it apart, and also how intuitive the whole dissection process was. Based on these factors the only conclusion that is drawn is that the design process was intended to make these the easiest components to remove.
The following is a list of replacement parts sold online for the Chain Guard and Chain Guide Cover:
Chain Bar/Chain Guide
These components are sought after the most since the chain and chain guard area experience the most stress during the product life cycle. Replacement chains are very easy to come by and relatively inexpensive ($23.89) since the lifetime of the chain is much shorter than the lifetime of the whole tool. It thus seems fitting to grant easy access to these parts in the inevitable event that the operator is required to replace it.
The tools required to remove this part of the product are as simply and common as the tools required in he Outer Handles/Cover disassembly. The only required tools are two different Allen wrenches and the wrench that was provided with the Alligator Lopper. This again is a testament to the intentions of the designers to make this part of the product as easy to take apart as possible. The fact that a wrench was included in the box the product came in means that even if the user had no access to any other tools, they still could gain access tot he chain assembly area. The number of bolts required to remove the outer cover also shows the cover was meant to be removed. Only two nuts secured to bolts holds the cover over the chain. By using the provided wrench, the user can have to cover off very quickly in order to service a worn out or faulty component.
|Required Tool||Steps Requiring Tool||Total Screws/Nuts Removed with tool|
|Allen Wrench #1||3||3|
|Allen Wrench #2||4||1|
Once again the Allen wrenches are most likely going to be in the possession of the consumer at the time of purchasing the Alligator Lopper and maintenance.
Averaging the difficulty rating of all the steps together gave an over difficulty rating of 1.38. This value is comparable to the average difficulty of the Outer Cover/Handles which was 1.5. This is reflected by what dissecting these groups of components reveal. Taking apart the Chain Guard and Chain Guide Cover gives the user access to the chain, sprocket, and chain guide. It makes sense that the Alligator Lopper would be designed so that the user can quickly and easily access the chain since this is the area that would experience the most wear and tear.
Dissection: Internal Motor Mount and Motor
|Step Number||Step||Difficulty Rating|
|1||Using a Philips screw driver and a torque screw driver, remove the two torque headed bolts and the one Philips head bolt.||3|
|2||Pull the metal internal motor mount to apart into two pieces.||2|
|3||Within the motor mount is a large gear with a drive shaft connected to a small gear on the drive shaft of the motor. In addition, the two main bolts that hold the chain guides, jaws, and outer covers together are sandwiched between the two sides of the internal motor mount. Remove these bolts and place in a safe place||2|
|4||Pulling on the drive shaft of the larger gear, remove the large gear from its housing||1|
|5||Unscrew the four Philips head screws located on the side of the motor cover. The screws were difficult to remove which leads us to believe they were with an adhesive to prevent removal and access to the internal workings of the motor.||3|
|6||Remove the long plastic motor wire retainer.||2|
|7||Once removed, pull apart the sides of the motor cover.||2|
|8||Inside is the coil and magnet. The magnet can be pulled out of the center of the coil.||3|
Ease of Dissection Analysis: Internal Motor Mount and Motor
Average Difficulty Rating of Dis-assembly: 2.25
With a difficulty Rating of 2.25, this is the hardest portion of the Alligator Lopper to dissect. This is due in part to the tools required to preform the dissection, the strength it took to actually separate some of the components, and the relative complexity of the components that were revealed.
Once opened fully, we discovered there was a gear exchange within the Internal Motor Mount. The drive shaft of the motor was fitted with a gear with a very small radius. this spun a larger gear which had a very large radius. The explanation for this gear exchange is explained with the following equation:
Torque = Radius x Force
Since the force translated from the small gear is going to equal the force translated to the big gear, and the radius of the gears increases, the overall torque produced by the motor is increased by the gear exchange. This gear was smothered in a green lubricant within its housing to make sure that it spins freely while the motor is operating. One of the risks taken by taking apart the motor mount is that dirt can clog the gear housing making the gear difficult to spin.
By taking apart the motor, there is the risk that damage could be done to its internal components. This would cut short the lifetime of the product since the motor is powerhouse in this product. It was discovered however that one can purchase a replacement brush assembly for the motor. The work required to get to the brush assembly seems more costly and timely to the average consumer than just buying a new product. This is partly due to the preventative measure put in place to discourage the dissection of this part.
The measures we noticed that were put in place were the introduction of torque screws and the possible use of adhesive in assembling the motor cover. When taking apart the Internal Motor Mount, there were two torque screws used to keep the mount together. Torque head screwdrivers are not normally included in the collection of tools an average homeowner has at their disposal. This measure is trying to deter the user from dissecting the mount and thereby gain access to the gear housing. Furthermore, the screws used to hold the two halves of the motor cover together were extremely tight. It took a lot of force to unscrew them in comparison to the force required by other screws in the dissection process. This may due to two different things; either the screws were tightened very hard in assembly or they were installed in addition to some sort of adhesive.
|Required Tool||Steps Requiring Tool||Total Screws Removed with tool|
|Philips Head Screwdriver||1,5||6|
|Torque Head Screwdriver||1||2|
Giving the user the option to replace a brush assembly seems to be only useful to those who have the proper amount of time and tools required to fully dissect the Alligator Lopper. The difficulties encountered taking apart the internal motor mount and motor seem to provide evidence that it was not meant to be opened on a regular basis for servicing or maintenance. Due to the complexity of the tools required to dissect it in conjunction with the methods used to install the motor cover around the motor the conclusion is made that the average user is not meant to open this part of the Alligator Lopper up.
Subsystem Interaction Diagram
Subsystem Interaction Analysis
• The first level diagram depict that the trigger requires human input in order to engage the motor of the chainsaw. In the second level diagram, it is detailed that the dual trigger system allows the machine to function when both triggers are simultaneously pressed. The triggers trip a switch , which allows the electricity to flow from the source to the motor itself.
• After the trigger is pressed, electrical energy is transferred from the electrical source, which is provided through the cord, into the motor allowing it to spin in order to produce rotational mechanical energy. The energy produced by the motor is then transferred to the drive assembly (which consists of the clutch and sprocket) increasing the torque due to the internal gear exchange. In turn, the mechanical energy from the sprocket's teeth interaction with chain is engages the rotational motion of the chainsaw producing electrical work out.
Note: The First Level Subsystems diagram shows that the trigger and the motor work in parallel ensuring the two must operate simultaneously in order to proceed to the final step of the overall performance procedure.
3) Human Interaction The final piece to the system is the chainsaws interaction with the cutting material. In order for this to occur, there is a need for pressure to be applied to the handles of the chainsaw as well as mechanical energy from the chain. The mechanical energy is then turned into energy used to shear the material. In the end, it is visibly clear that the material is being cut.
Note: The First Level Subsystems diagram shows that the trigger and the motor work in series with the point at which the material and chainsaw make contact.
The subsystems for the lopper have been arranged in a manner that seems fitting and logical based on user interaction. Initially, the user applies the pulling force to expose the cutting surface, while simultaneously bringing the cutting object into contact with the surface. It is important that these two subsystems are together because of the safety precautions. The user must apply a force to expose the blade, and any mishap from the user would result in the cutting edge to be immediately covered up by the guard. The user input for the triggers is important as well because it is a dual switch that requires both triggers to be pressed at the same time. This is yet another safety feature that aids the user. What is equally as important, is how the electrical signal that is sent from the triggers to the motor is almost instantaneous. The need for consistency with the motor enables user satisfaction and security. It would be detrimental for the user to have unexpected problems in mid cut.
There are methods as to how the subsystems are implemented within the final product. There are imposing factors that give reason to how and why the subsystems are set up and designed the way they are. Globally, the overall use of the electric motor is dependent on the ease of access to a source of household or public power. Clearly, the environmental factors that influence the subsystem of the motor is the use of electricity as a zero emission source of power as opposed to a gasoline powered engine. Socially, it is more logical, knowing the product will be used in residential areas, to use the distinctly quieter motor (a full 15 dB). There is the noticeable economic trade off where the combination of electrical and human subsystems adds the benefits of simplicity and low maintenance, but gives up the power and strength of a gasoline powered chainsaw.
These subsystems all contribute to the overall performance of the lopper. The primary focus being user safety, is addressed by the dual motor triggers located on the handles. This requires the user to have full control over the tool before operating the motor. The connection between the power-drive and the revolving chain is crucial to the performance of the product as well. The motor must be able to supply enough torque through the intermediate clutch and transfer it through to the chain. The use of a successful gear ratio is the driving component behind this process.
Understanding the placement of each subsystem allows us to gather knowledge about how production methods and demand have influenced the final product. Beginning with the simplest, the triggers on the handles simply allows for safety, comfort, and functionality. The wiring from these triggers can add to the diversity of location for the rest of the systems. Having the motor, sprocket, and chain track all in the same arm gives added simplicity to the scissor pivot motion that construction of the product suggests.
Certain Factors Influencing the Subsystem Connections
- Unlike traditional chainsaws, it is clear that the Black and Decker Alligator Lopper was designed to be used by both men and women rather than just by men. The electric switch triggers used to signal the electric motor are very easy to depress. The small electric motor is also a lot lighter than a traditional gas powered motor, which allows the Lopper to lower its weight considerably in comparison with a normal chainsaw.
- The electric motor and smaller chain/bar assembly also allows the Lopper to cut material much more quietly than a traditional chainsaw. Between the loud gas motor and large cutting edge for a normal chainsaw, they often emit sound levels that are comparable to most heavy commercial power tools. All together interacting subsystems only add up to 98 decibels in the Alligator Lopper due to lowering the output power of the system by using electricity rather than gas power.
- The start up time of the Lopper is almost instantaneous due to the connection between an electric power source and the chainsaw subsystem. Once the power cord is plugged in, all it takes is the squeeze of two triggers and power is instantly transferred to the motor, and in turn mechanically to the chain. This was obviously designed to reduce pre-use leg and arm work such as required in the start up process of a gas powered chainsaw.
- While using an electric motor to transfer the trigger signal and power source into mechanical energy instead of a traditional gas motor, the Lopper cuts back on possible pollutants that other similar tools release into the environment. Black and Decker could easily market this as a way to “think green”.
- The plug in electric power supply and electric motor allow the lopper to be stored easily without much preparation. There is no need to drain any fuel before storing it long term. This differs from the storage process of a gas powered saw. Improper storage could result in a large mess along with possible flooding the engine and ruining it.
- The majority of the component replacement parts are very cheap, most of which can be purchased from the Black and Decker website for under $32. All of the functions between the sub-systems are fairly straight forward to the point where untrained consumers can fix most problems that would arise with the Lopper.
- With the price of gasoline rising with no end in sight, the use of electricity as the main power source for the Lopper greatly reduces costs for the consumer to use the product.
- Each of the components is made up mostly of the same materials including heavy duty plastic and thin steel. This allows the manufacturer to buy these materials in bulk, and therefore at a cheaper rate. This tool was also assembled using a large number of the same screws and fasteners. This allowed the manufacturer to either buy or produce in bulk as well, which would in turn save them production costs. These saving are then passed down to the consumer in the form of a cheap product.
- The lighter-duty nature of this tool allows it to be produced in a much cheaper manner than most other chain saws. While only having to design the Lopper to handle the lighter duties of the average homeowner, the manufacturer can use cheaper components that don’t have to meet commercial/heavy duty specs. Although the electric motor and 4 inch bar on this “saw” can’t match the capabilities of a two-stoke gas powered 16 inch bar saw, this product is considerably less expensive to build/manufacture. The manufacturer can then pass these savings down to the consumer in the form of a cheaper end product.
- When looking at tools designed for the average suburban homeowner, safety is always a huge concern. This can easily be seen in the double-trigger safety system within the trigger sub-system. This forces the operator to keep two hands on the lopper at all times when it is in use, therefore minimizing the risk of injury.
- The handle-jaw subsystem also minimizes risk of injury by only exposing the cutting edge/bar of the lopper only when the operator wants it to be open. The subsystem is also spring loaded to keep the jaws closed.
- The risk of kick-back with this “saw” is greatly reduced due to the lack of power associated with the small electric motor providing power to the chain/bar. The average homeowner, women included, using this tool usually would not be prepared to face or even be strong enough to handle the kick back associated with the average chain saw and this eliminates that need.
- The smaller bar and less powerful electric motor makes the lopper a lot less intimidating to the average consumer than a full-sized chain saw. The smaller cutting edge and the fact that is covered by the jaws of the handle-jaw subsystem makes this tool look a lot safer to use than a normal saw, and in turn most people are a lot less hesitant to use it.