Alligator Lopper: Gate4

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Gate Four

Management Proposal

Managing is the process of getting work accomplished with and through the efforts of other people. As a group we have understood the importance of management in the overall completion of the project. It is important to have a clear vision of what is needed to be accomplished and to separate the responsibilities according to each persons unique skill set. As a group we organized the team by assigning responsibilities and reducing potential problems caused through effective communication.

Alicia- Communication is key when managing a project effectively and Alicia has taken responsibility of this task by emailing everyone according to the time available to complete the project. She was also assigned to complete one of the mechanism's which she has done successfully.

Keerthi -

Alex- One of the members who was involved in the reassembly of the chainsaw, Alex specified each instruction and made note of all the steps as well as the equipment used during reassembly. He was given the task of organizing the steps into a table. Each picture that was taken was annotated and each step was explained in detail.

Spencer and Zach - Reassembly of the product as well as the revisions were done by them. They effectively stated the pros and cons as well as all the GSEE Factors involved when formulating the new design.

Product Reassembly

The product was assembled in three main stages: the Motor and Motor Mount Assembly stage, the Chain Guard and Chain Guard Cover Assembly stage, and the Outer Cover/Handles Assembly stage. Each Stage is followed by a short discussion regarding difficulties encountered, tools required, and assembly process.

Difficulty Rating System

1 - Parts or components can be attached to 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 assembled in order to access the desired component. Common tools such as a Flat or Philips head screwdrivers or an Allen wrench are required to complete the step.

3 - The desired assembly is based on multiple parts or subsystems. It cannot be put together without first building the parts or subsystems it is based on. Less common tools, such as a Torque screwdriver, are required to complete the step. The step may also involve manipulating an ungainly part into position and require some time devoted to assembling the product correctly.

Assembly: Motor and Motor Mount

Step Number Step Difficulty Rating Image
1 Place the two parts of the motor together so that the coiled part fits within the magnet. 1
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2 Place the two sides of the motor cover together around the motor and secure in place with the corresponding 4 Philips head screws. The motor cover should cover part of the motor mount. 3
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3 Take the large gear and place it in the motor mount housing so that its teeth interlock with the teeth of the drive shaft coming out of the motor. 1
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4 Place the two large hex bolts into the outlines of the bottom side of the motor mount cover. Fasten the motor mount cover to the motor mount, covering the large gear so that all that shows of it is its drive shaft. Both bolt threads are exposed along with the driveshaft. 1
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5 Fasten the motor mount cover to the motor mount using one Philips head screw and two Torque head screws. A size T15 Torque head driver is used to screw in the Torque head screws. 3
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Average Difficulty: 1.8

The toughest part about assembling the Motor and Motor Mount was in fact attaching the motor cover. The orientation of the two sides of the motor cover in relation to the motor mount is confusing and required about 10 minutes of attempts in order to finally get the cover together. In terms of ease of assembly for the rest of the Motor Mount, the required effort was minimal.

Two tools were used to complete this assembly: a Philips Head screw driver and a T15 Torque head driver. While the philips screw driver is easy to come by in most homes, most of those homeowners do not have a collection of Torque head drivers. This would make it difficult for a homeowner to either disassemble or assemble the motor mount. We also used the same steps in reverse that we used during the disassembly process. The steps did not change radically since these components were easy to assemble.

The motor cover was most likely assembled with the use of a robot since it would be difficult for a human to immediately attach the cover successfully without some trial and error. The gear and the motor mount cover was most likely assembled by a human since it requires lubrication which looked like it was applied sloppily.

Assembly: Chain Guard and Chain Guard Cover

Step Number Step Difficulty Rating Image
1 Holding the outside cover, attach the black clip to the two pieces of plastic so that the round ends of the springs are around the plastic anchors. While installing place the bar on the outside of the cover and allow the black clip to lock over the jaw and keep it compressed against the cover. 3
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2 Being careful not to dislodge the bar and the bar clip, place the motor mount with its bolts and driveshaft oriented downwards onto the inside of the cover. The bottom of the motor mount should rest above the black clip and hold its springs in place. 3
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3 Using two Philips head screws intended for this step, secure the motor mount to the bottom cover. 2
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4 Place the black quarter gear over the hole next the motor mount. The hex shaped hole should be face up which will contain a nut. 1
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5 On the opposite side of the cover, the bottom half of the jaw is fitted into the hole on the cover. Tightening the bolt inside the hole in the jaw will lock onto the nut in the gear. Make sure the gear lines up with the square extension from the jaw, tightening it with a 7/32 inch Allen Wrench. 2
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6 Place the sprocket onto the drive shaft so that it sits on the outer cover. Hold the chain bar underneath the black clip so that the two bolts extending through the cover pass through the slit in the bar. Place the chain around the sprocket and bar. 2
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7 Take the lower side of the moving jaw and secure the upper side of the jaw to it using three nuts and bolts. A 5/32 inch Allen wrench is required. 2
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8 Place the black cover over the chain bar and sprocket. Secure the nuts to the two bolts extending through the cover using the tool provided with the Lopper 1
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9 The chainsaw portion of the Lopper is fully assembled. The handles and switches must now be assembled. -
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Average Difficulty: 2.0

The most difficult part to assembling the Chain Guard and Chain Guard cover was successfully installing the small black bar clip. It was difficult to hold the springs in place around their anchors while also trying to install the motor mount above it. We had no way of actually holding the clip in place while its springs were anchored and the clip would simply fall out of place. Our solution was to actually install the bar prematurely and hold it in place so that the clip would have a stable surface to latch onto. When that had been done, the springs stayed around their anchors and the motor mount was easily dropped into place over the clip and secured in place using two Philips head screws.

The other relatively difficult component to install was the rotating jaw and the gear it is fixed to. The gear lined up perfectly with the jaw, however one of the nuts which was required to install the other half of the jaw was inaccessible after bolting the jaw to the gear. Our solution was to lay the nut in the hole in the jaw before connect the jaw to the gear so that when the second half of the jaw was to be installed, the nut was already there and could be threaded onto the bolt.

In terms of tools, a 5/32 Allen key, a 7/32 Allen key, the hex wrench provided with the Lopper, and a Philips head screw driver were required to assemble this section of the Lopper. Other than the initial problem of installing the black clip and the second problem regarding the jaw, the rest of the assembly was easy to follow and intuitive. We did alter the steps used in the disassembly process when we attached the bar when installing the clip. When taking it apart, we took the bar off before we even had access to the clip. In the assembly, we had to attach the bar at the same time as the clip.

For the assembly process, it would make sense for a robot to fasten the motor mount to the cover since it is a straightforward task. The installation of the bar and chain however was probably done by hand since it is task intended to be completed by the user. Finally the outer cover was probably attached by hand since the nuts were not overly tightened and were meant to be removed by the user.

Assembly: Outer Cover/Handles

Step Number Step Difficulty Rating Image
1 Attach the wires from the external black cord to the white wire connector. Secure the wires using the small Flathead screws located in the connector. 2
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2 Secure the black cord to the inside of the handle by fastening the cord clip with two Philips head screws. 2
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3 Attach the wires to the switch and push the switch down on the two plastic pins. 1
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4 Place the springs for the trigger on the two plastic pegs on the back of the trigger. Being careful to control the springs, force the trigger into its plastic housing compressing the springs against two plastic backstops. The trigger should be held in place by the force of the springs. 1
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5 Being careful not to knock the springs and the trigger loose, lower the second half of the handle cover over the motor. Secure with 10 Philips head screws. 2
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6 Lower the bottom half of the handle into place so that its teeth fit into the trench around the motor in the lower handle. 1
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7 Using a screwdriver to compress the large spring in the trench, fit the spring into the trench so that it pushes against the teeth in the top handle. 2
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8 Attach the wires to the switch and push the switch down on the two plastic pins. Place the springs for the trigger on the two plastic pegs on the back of the trigger. Being careful to control the springs, force the trigger into its plastic housing compressing the springs against two plastic backstops. The trigger should be held in place by the force of the springs. 1
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9 Lower the top half of the handle onto the lower half being careful not to knock out the springs or trigger. Secure in place with 8 Philips head screws. 2
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10 Slide the semicircular orange plastic clamp around the other side of the motor and secure it to the top handle using two Allen headed bolts. A 5/32 Allen key was required. 2
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11 Finally place the outer motor cover over the top of the motor and secure it to the inner motor cover using four Philips head screws. 2
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12 The Alligator Lopper is now fully assembled. -
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Average Difficulty: 1.6

The only major difficulty we encountered was trying to get the compression spring into the trench with the teeth of the top handle. We attempted for perhaps 10 minutes to force it in by hand but each time the spring came loose. It was finally installed when we used a flat head screwdriver to compress the spring within the trench and then installed the second handle.

The product was most likely assembled by hand for these steps since they require wiring switches to the outer cord and the motor. Most wiring jobs are done by hand since a worker can decide how much wire to use, where to store the extra wiring within the cover and can also wire it quickly. It would also be cost ineffective to build machinery to automatically attach the last few covers to the product when it can easily be done by hand.

The tools required to finish the assembly were a 5/32 inch Allen key, a Philips head screw driver and a small flat head screwdriver used in the installation of the spring. This was by far the easiest part of the assembly. The covers were only held together by Philips head screws therefore putting them together was a breeze. We did run into some trouble when installing the spring but it was quickly overcome with the application of a small flat head screwdriver. With the exception of the spring and installing the triggers, we roughly followed the same steps in reverse which we used for the disassembly process.


Drive Chain Mechanism

Technical Name: Gear train

Components:Sprocket, Large Gear and Chain

Purpose: The purpose of this mechanism is rotating the chain of the chainsaw.

How it works: The sprocket located on the shaft of the large gear spins simultaneously with rotation of the large gear. The teeth of the sprocket interlace with the chain to prevent slipping. When the gear increases the torque produced by the motor and transfers it to the sprocket, the chain begins rotate. As the sprocket is turned, it moves the chain by pulling a link towards it. Tension in the chain, which is circular, is being pulled towards the sprocket while the opposite side is being pulled away from the sprocket.



Switch Linkage

Technical Name: Linkage

Components: Spring, Trigger, Switch

Purpose: The switch linkage mechanism allows the user to press the trigger, which ultimately starts the chainsaw.

How it works: When the user presses the trigger the spring compresses which turns on the chainsaw. If this system was not there the triggers within the chainsaw would not return to its original state because the springs would not be present. When the user compresses the springs the trigger contacts the respective switches allowing the motor to run. The trigger is located in between the two sides of each handle. The springs are located beneath the trigger and are held in place by plastic anchors proved the necessary force to keep the trigger pressed against its housing and away from the switch below it. When the user depresses the trigger, they must counteract the force of the springs. The trigger makes contact with the switch. When both triggers are compressed so that they make contact with their respective switches, the motor is allowed to run and the chain to move. There are two triggers used within the product, each trigger being held by two springs. Unless the two triggers are pressed simultaneously the chainsaw will not work which is key to gaurantee safety and make sure accidents do not occur.

Formulas: Fs=kx

Jaw Mechanism

Technical Name: Reverse Motion Linkage

Components: Gear, Jaw, Handles

Purpose: The purpose of this mechanism enabling the user with the ability to open and close the mouth of the Alligator Lopper via the handles of the product.

How it works: The gear is held in place to the free moving aluminum jaw of the Lopper by a bolt and a lock nut. The teeth located on the handle, which provide rotation for that component, interlocks with the teeth of this gear. As user pulls the handles apart, the teeth of the handle rotates, which causes the turning of the gear. The gear that is attached to the jaw rotates and this causes jaw to rotationally open.


Refer to the diagram in the Gear Mechanism.

Design Revision

Portable Gasoline Power Plant


The suggested design revision is to substitute the current electrical rotary motor with a compact gasoline powered internal combustion engine. The current motor has its benefits and drawbacks as with any other piece of equipment, but the improvements of the gasoline engine would outweigh the added negative effects. The gas engine would enable users to achieve a wider radius of movement that is not restricted by the length of the extension cord plugged into the house. This addition also provides a much larger torque force that the axle of the drive shaft creates. This empowers the tool with the ability to cut through denser wood and larger diameter pieces.

In order to obtain this feature, there would have to be a few adjustments to surrounding components to accommodate the engine. First and foremost, a small gas tank would need to rest in a spot that is easily accessible for the user when they need to refill it. The dimensions of the product, as a whole, would be subject to change to allow for a pull cord starter that would kick the engine on with sufficient user input. To properly withstand the added weight of the components, it would be strongly considered to construct the housing out of durable metal casting or stamping. This allows the product to take on larger forces acting against it and gives it a higher tolerance for stress. The four main factors of engineering play a significant portion in the analysis of the decision to potentially change from electrical motor to gasoline engine.

Factors Governing the Design Revision


One of the global factors that go into the product revision is that it enables users that are unable to receive electrical supply the ability to perform jobs. The user has a longer range to go away from his home now that he/she is not restricted to the length of the extension cord. Another global factor being the product may be used in a location that would otherwise possess an electrical supply, but for some reason is unable to deliver the electricity. Take the affected areas of the recent Hurricane Sandy devastation for example where this tool had the possibility to vastly facilitate the cleanup process.


The social factors that contribute to the analysis are those that affect the living areas of communities. The electrical motor would certainly run quieter than the gasoline engine, which could cause concerns for those who do not want to listen to a noisy engine in their previously quaint neighborhood. Almost identical are the issues relating to the public’s concern with the gas emissions that are expelled into the atmosphere for the residents to inhale and have to deal with; a negative attribute that is associated with the gasoline engine.


There are tradeoffs when it comes to the economic factors involved with revising towards a gasoline engine. On one hand, the user saves money by not drawing electrical power from his utility supply. However, the money spent on gasoline can prove to be costly in the long run. The improvement economically is that the long distance wear and tear is reduced by the heavier duty materials as opposed to the weaker electrical materials


The environmental factor that benefits the revision for gas engines is the widespread debate over where our nonrenewable resources are being allocated. By transitioning from electricity to gasoline, coal and other power generation sources are preserved for better use while refined gasoline takes over. However the negative effect is that the gas powered engine is another source for harmful environmental emissions.

Increase Bar Size


The proposed design revision is lengthening the bar and chain assembly. Such a revision would not greatly reconfigure the makeup of the saw, but would merely require some increased dimension changes of the existing components. One of the limiting factors of the Lopper’s function is the size of the bar/chain assembly and the limited cutting edge of the saw. These factors greatly limit the size of the wood/debris that the operator can tackle with this tool, and increasing the length of such would greatly increase the range of the Lopper. Making such a revision to the Lopper would be fairly simple and straight forward. The most noticeable and most obvious change to the current design would be an increase in the length of the bar. The bar does not need to be over anything over a foot long like most other traditional chain saws, but a six or eight inch bar would work well for this application.

As a direct result of the increased bar length, the chain would also need to be increased in length. The chain needs to fit snug along the guide track of the bar to cut efficiency, and a longer chain would need to be designed/included with this Lopper to ensure this would not change with a longer bar. The chain guards would also need to be redesigned so as the new bar with the increased length could still fit inside them. One of the main selling points behind this saw is its safety features and keeping the entire bar encased within the guards is a large part of that. The Lopper would also need a longer set of handles, as the longer and heavier bar/chain assembly would require a greater amount of leverage to open and close the jaws with the same amount of force. A design revision of such simple nature could easily be coupled with other proposed design revisions to create an even more versatile and improved final model.

Factors Governing the Design Revision


Such a design revision to the Alligator Lopper would dramatically help increase the range of debris the tool can cut through. By increasing the bar of the chainsaw assembly from four inches in length to eight inches in length, the Lopper is now able the cut through debris twice the size of what it could before the design revision. This would open the Lopper up to large markets of consumers that would have previously believed the Lopper to be too small to handle the tasks they demand of their cutting tools. Combining the versatility of a chainsaw with an eight inch bar with the safety features originally included on the Lopper could give the tool a marketing niche that has not been previously utilized. Suddenly the Lopper is no long confined to just the suburban American doing light residential yard work, but it suddenly is capable of handling large enough debris to be considered for light commercial duty’s, and starts appearing in the country side accomplishing slightly more heavy duty work. Such a revision opens this product up to a barge of different markets in which the Lopper was not previously suitable.


By keeping the bar and chain completely enclosed within the jaws/chain guards of the product through the design revision, the Lopper still keeps its distinguishable safety features, but now has an increased range of function. Previously the operator of the Lopper was forced to sacrifice performance and versatility in the name of safety but with the enhanced bar/chain assembly that compromise has been limited. The ceiling of what debris size the average homeowner can tackle before having to either call a professional or renting/buying a larger saw would be significantly raised.

The increased bar length could also have a sentimental value to some operators that feel emasculated when using the comparatively little saw. The longer bar would give the Lopper a more powerful, tough and commanding figure. The larger bar would give the operator that tough, authoritative feeling that operator of most other traditional chainsaws experience. This would be a hit among men would otherwise see the Lopper as a woman’s tools when featuring the smaller bar current four inch bar.


Since this revision is solely based upon increasing the size of the Lopper, it will undoubtedly require more material to material during manufacturing. The bar is fabricated out of aluminum, the chain out of steel, and the chain guards and handles are both composed of a commercial grade plastic. Since all of these components are being expanded in one way or another, more of these materials would be needed to be purchased during manufacturing, undoubtedly raising the manufacturing price of the Lopper. These increased costs would most likely be passed on to the consumer in the form of an increase in retail price of the product. This increased cost could be offset by the increased sales in otherwise untapped markets.


As stated before, the components that would be expanded in the wake of the lengthened bar design revision are mainly composed of aluminum, steel, and commercial grade plastic. All three of these materials, more of which will be required after the design revision, are derived from non-renewable resources. Using more of these materials would help increase the ravishing of our planet’s ecosystems for more petroleum and metal ores to produce these extra materials. But the environmental impacts from producing the excess materials should be the extent of the environmental impact of the lengthened bar. The Lopper should not require any extra torque from the motor, which has negligible emissions anyway.

Motor Assisted Opening Jaw


This proposed design revision would completely alter both the trigger system and the jaw system. Instead of using two handles to manipulate the jaw into place around a branch, a small DC motor can be employed to do the same action as the user’s arms. Using such a motor would eliminate the need for two pivoting handles. As a result there would be one main handle extending out of the machine towards the user. A second horseshoe handle would be placed on the chain motor’s housing. A small secondary motor would be placed directly opposite the larger chain motor. This small motor would most likely contain a gear exchange to increase its torque. It would then drive a gear directly attached to the moving jaw, much like the current gear attached to the jaw on the product now. The motor would then be used to manipulate the jaw at the control of the user.

A new trigger system would thus need to be employed to insure a factor of safety is present in the product. The proposed trigger system would rely on two main triggers and two jaw control buttons. The trigger would be placed on the underside of the handle extending out of the product. It would most likely be surround by a trigger guard which would protect it from accidentally being depressed. On the opposite side of the handle from the trigger there would be two buttons: an open jaw button and a close jaw button. Pressing and holding either of these buttons would employ the motor into opening or closing the jaw. The orientation of the trigger and the jaw buttons allows the user to use his right hand to manipulate all three. When gripping the handle, the fingers would close around the trigger and squeezing the handle would depress it. The thumb of the right hand would then be able to use the two buttons controlling the jaw, much like how a user may interact with buttons on a TV remote. The second trigger would be placed on the horseshoe handle now attached to the chain motor housing.

Factors Governing the Design Revision


This design revision allows for less strenuous human interaction required to operate the product. By changing the jaw opening mechanism to a motor, more people which previously may have been limited in using the product by muscle limitations may now use the product. This semi-automation of the product makes it friendlier to woman and older homeowners, something which this product has strived to accomplish since its creation. Since this product is still intended for home owner usage and not commercial usage, its market does not change drastically when compared to the current product. This design revision only affects the different type of homeowners that can comfortably operate it.


By changing the location of the handles along with the motor assisted jaw, the ergonomics of the product are improved in three major ways.

  1. The support handle is placed directly on the chain motor’s housing. This allows the user to more comfortably lift and support the product. The heaviest part of the Lopper is easily its motor which is used to spin the sprocket and chain. By placing a handle directly on this heavy component instead of having the user support it by handles located farther away from the motor, the user can more comfortably hold it. It essentially places a handle much closer to the product’s center of gravity making it easier to manipulate.
  2. By changing the jaw opening mechanism to motor control, the Lopper relies much less upon the user’s muscular force capacity. The current design requires the user to compress the handles with enough strength so that it forces the chain to cut the branch. This means the user must be able to exert this force for the length of time required by each cut. In addition to holding the product itself, this action can tire the user. The motor allows the user to use all of his strength to support and the position the product instead of dividing it between that and clamping the jaw. The lack of parts required to move by the user’s strength also allows the user to get a better grip on the Lopper. Since they are not closing or opening handles, their grip remains stationary on the product. This firm stationary grip gives the user more control when manipulating the product.
  3. The one trigger may be operated passively with the left hand and the other trigger and jaw control buttons may be operated by the right hand. The current product requires a squeezing action with both hands to operate the triggers. This design revision allows the user to engage the trigger on the handle located on the chain motor’s housing passively. Simply holding the product by this handle forces the trigger to be depressed against the user’s hand by gravity. This means only the right hand must squeeze the handle to engage the trigger. In addition the right thumb is used to operate the jaw instead of both arms and chest muscles. The actions required to open and close the jaw are minimal in comparison to the actions required by the current product.

In addition to improving ergonomics, the factor of safety already present in the current Lopper is increased with this design revision. Both triggers are left in place since this system for engaging the motor is effective. In addition to the triggers, the addition of jaw manipulation buttons forces the user to only manipulate the jaw when the product is plugged in. This decreases the chance that an awkwardly placed Lopper could spring open unintentionally exposing the chain. It also decreases the chance that the jaw could slip open in the middle of a cut since the motor controls the jaw, not the muscles of the user. Anything which takes the dependence of the product out of the muscular ability of the user and places instead in control of a motor increases the safety of the product.


The price of the product would undoubtedly increase. An additional motor for the jaw system would cost somewhere between $5 to 15$, while the gears and housings would be about an additional $10 and the additional switches and wiring about another $5 to $10. Conservatively speaking, this design change would cost $35 dollars. At optimal costs, it could only cost an additional $20. Manufacturing costs would not change too much. The addition of the second motor and two new switches would be offset by eliminating a second major handle extending out of the product. Material requirements would not change radically since the new system can be built using the same materials as the rest of the Lopper.


Since the power system does not change on the Lopper, its emissions and impact on the environment does not change drastically. However since the system is less cumbersome to operate and easier to support, the amount of branches the user can cut from a stationary position increases. It is now easier to lift higher and cut branches at or above the user’s chest level. The operation of the product now depends on how far the user can comfortably support the product. The previous design relies on how comfortably the user can both hold the product and still be able to effectively provide force to operate the jaws. The design revision thus allows the user to operate the product farther from their body and also at a large height relative to the user’s chest. This means a large portion of the environment can be cut using the new Lopper. It is also more likely to be used in more awkward situations, like atop a ladder. This allows the user to trim higher branches and thick shrubs since the product is easier to manipulate.

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