Difference between revisions of "Alligator Lopper: Gate3"

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(Gate 3)
(Gate 3)
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The lopper’s success is determined by its output, abilities, and dependence on the job. Breaking the product down into its many components allowed us to isolate each one and determine its significance to the success of the overall function. We chose the drive gears and sprocket component as our subject for engineering analysis. We felt it was necessary to put this component through its paces and derive more data and information about the component and its service to the overall product. The gears integrate nearby components that make up the composition of the entire power drive of the product. Rotational energy from the motor is translated into cutting power in the outdoors. These gears must stand up to the rigor of heavy duty workloads, which means high RPMs and torques applied to the teeth of the gears and sprocket. Through analysis, we intend to discover just how much of an impact that the gear ratios have on the power and velocity output of the motor and its translation into the chain’s abilities. The gears must combine to produce the proper output of power and velocity in order for the chain to perform sufficiently. Engineering analysis gives us a clear idea of the methods of study to help us determine the ratio that is present, as well as an optimal one.
 
The lopper’s success is determined by its output, abilities, and dependence on the job. Breaking the product down into its many components allowed us to isolate each one and determine its significance to the success of the overall function. We chose the drive gears and sprocket component as our subject for engineering analysis. We felt it was necessary to put this component through its paces and derive more data and information about the component and its service to the overall product. The gears integrate nearby components that make up the composition of the entire power drive of the product. Rotational energy from the motor is translated into cutting power in the outdoors. These gears must stand up to the rigor of heavy duty workloads, which means high RPMs and torques applied to the teeth of the gears and sprocket. Through analysis, we intend to discover just how much of an impact that the gear ratios have on the power and velocity output of the motor and its translation into the chain’s abilities. The gears must combine to produce the proper output of power and velocity in order for the chain to perform sufficiently. Engineering analysis gives us a clear idea of the methods of study to help us determine the ratio that is present, as well as an optimal one.
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PROBLEM STATEMENT
 
PROBLEM STATEMENT
  
 
Determine the proper gear ratio between the motor output shaft and the larger gear such that the sprocket will turn with sufficient angular velocity and rotational force to propel the chain saw in a linear direction suitable for effective cutting ability.  
 
Determine the proper gear ratio between the motor output shaft and the larger gear such that the sprocket will turn with sufficient angular velocity and rotational force to propel the chain saw in a linear direction suitable for effective cutting ability.  
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DIAGRAM
 
DIAGRAM
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[[File:Gear_Ratio.png]]
 
[[File:Gear_Ratio.png]]
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 +
What values are necessary?
 +
 +
To approach this problem the following values would be needed:
 +
The possible rotational velocity (rpm’s) of the electric motor
 +
The possible torque the electric motor could produce
 +
The needed force on the chain for optimum cutting performance
 +
The needed speed of the chain for optimum cutting performance
 +
The size of the sprocket required by the chain.
 +
Whether there is a predetermined gear radius for the gear on the electric motor, and if so what is that radius?
 +
 +
 +
ASSUMPTIONS
 +
 +
 +
For such calculations to be made, the following assumptions would need to be made:
 +
The force required by the chain is constant.
 +
The angular velocity and torque from the electric motor’s small gear is constant.
 +
The bearings in which the shaft of the large gear and sprocket are mounted are frictionless.
 +
The bearing in which the drive shaft of the motor sits is frictionless.
 +
The interaction of the teeth of the two interlocking gears is frictionless.
 +
 +
 +
GOVERNING EQUATIONS
 +
 +
When approaching such a problem the following governing equations will come into play:
 +
Τ1 ⁄r1  =  T2 ⁄ r2
 +
ω1 *r1 = ω2 *r2
 +
F3 = τ2 /r3
 +
V3 =ω2 *r3
 +
 +
These variables represent:
 +
τ1= The torque from the electric motor
 +
r1= The radius of the gear on the electric motor’s drive shaft
 +
ω1 =The rotational velocity of the electric motor gear
 +
τ2= The resulting torque produced by the large gear
 +
r2= The radius of the large gear
 +
ω2=The rotational velocity of both the large gear and sprocket
 +
r3= The radius of the sprocket
 +
F3= The force of the sprocket on the chain
 +
V3=The linear velocity of the outside of the sprocket/linear velocity of the chain.
 +
 +
 +
SOLUTION CHECK / INTERPRETATION
 +
 +
Using the equations above one could easily find the gear ratio between the large gear of the gear exchange and the small gear of the electric motor output.  Checking the solution for solution would require checking calculations, as well as comparing to the ration found to other simial gearing situtions and making sure the values determined are reasonable.  There is real defined unit to the ratio determined as it is a ratio, the ratio is merely a fraction of two values.  Unless the size of one of those two gears is predetermined, we only find the ratio between the two gears radii.  As long as this ratio is kept between whichever gear sizes the designers decide to use, the output from the sprocket to the chain should stay the same.  This allows for significant flexibility through the design process regarding the drive train of the chain saw.  The actual gear sizes would need to be determined by the available space within the product, weight/cost restraints on the gears, the power needed to overcome the rotational inertia of the gears, the efficiency of different sized gears.  The final size of the gears would require much more research and calculations than what is displayed in this problem analysis, but it does solve for the very critical gear ratio.
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Revision as of 15:20, 16 November 2012

Contents

Gate 3

Project Management

As a group, we have learned to manage our time as to dedicating the required amount to the work of this project.

Alex has grown as a project manager in that he has learned the strengths and weaknesses of the group members, and has taken charge of assigning tasks to the group based on such knowledge. We also used this project as a means of learning new skills or improving upon already learned skill.

Work:

  • Alex - Because he has previous experience with the SolidWorks software, Alex is in charge of designing the three dimensional modeling, as well as the component summary.
  • Keer and Allicia - To gain a better knowledge of the different components, the manufacturing processes, and the mechanical origin of the material, they are responsible for the product analysis.
  • Spencer - He is in charge of the engineering analysis. It is beneficial to him considering he is a sophomore, it will broaden the knowledge of engineering applications.
  • Zachery - His responsibility revolved around the design revision. Being a sophomore as well, this task will broaden the knowledge of engineering applications.


By in general, we did not experience many problems with regard to the overall gate.

Component Summary

Component Name Function Material Forming Process Part Number Image
Gear This gear is fixed to the free moving jaw of the Lopper. The teeth located on the handle which is allowed to rotate interlocks with the teeth of this gear. When the handles are pulled apart, the teeth on the handle move turning this gear. The gear, which is attached to the jaw, rotates which rotates the jaw open. The gear is held in place to the jaw by a bolt and a lock nut. Only one such gear is used within the product. High density plastic Injection Molding 588088-00
Gear 22.jpg
Wire Housing Cover This small housing cover is located on the outside of the actual handles. It is held in place by a Philips head screw. Once removed, the user is given access to the connection where the wires running from external cord are joined with the wires used internally within the Alligator Lopper. There is only one wire housing cover used within the entire product High density plastic Injection Molding -
Cover 22.jpg
Trigger The trigger is located in between the two sides of each handle. The springs located beneath the trigger and 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. Trigger:High density plastic, Spring:Steel Alloy Trigger:Injection Molding, Spring:Drawing and curling -
Trigger 22.jpg
Power Cord with Male Electrical Socket The cord protector is made of high density plastic which serves to protect the male electrical socket. This socket is used to connect the product to its power source through the use of an extension cord. From the Cord Protect runs the Cord Set which is comprised of a copper wire insulated with rubber. The cord set enters the product at the end of a one of the handles and is connected to the internal wiring of the Lopper. Cord Protector:High density plastic, Cord Set:Copper Wire, Rubber Insulator Cord Protector:Injection Molding, Cord Set:Drawing of Copper into wire, coating the wire with rubber Cord Protector:770235-00, Cord Set:588370-00
Power Cord 22.jpg
Large Gear This gear connects the driveshaft of the motor to the sprocket. The gear located on the drive shaft of the motor is very small in comparison with this gear. This gear exchange increases the torque produced by the motor and transfers it to the sprocket which moves the chain. The large gear has its own driveshaft which the sprocket slides onto. Therefore the rotation of the gear causes the rotation of the sprocket and as a result the movement of the chain. This gear sits within the motor mount/gear housing. There is only one of these gears in the product. Steel Die Casting -
Large Gear 22.jpg
Sprocket The sprocket slides onto the shaft which is connected to the large gear. When the large gear spins, the sprocket spins. The teeth of the sprocket make contact with the chain in a fashion that does not permit slipping. When the sprocket is turned, it moves the chain by pulling a link towards it. Tension in the chain, which is circular, means that when one side of the chain is being pulled towards the sprocket, the opposite side is being pulled away from the sprocket. There is only one sprocket in the product. Steel Die Casting 587580-00
Sprocket 22.jpg
Bar Holding Latch The two springs are connected to two anchors which sit underneath the outside cover of the Lopper nearest to the chain assembly. This is where the bar sits on the Lopper. The clip portion of the plastic component extended through the cover and over the edge of the bar. The tension springs keep the latch firmly over the bar, holding it snugly against the outside cover. There is only one of these clip/spring components holding the bar against the cover. Latch: High Density Plastic, Springs:Steel Alloy Latch: Injection Molding, Springs: Drawing, Coiling of the Wire -
Bar Latch 22.jpg
Handle Compression Spring Located around the motor within the cover of the second handle is a small trench. Within this small trench sit both the teeth of the top handle and this compression spring. When the handles are together, the spring is at its largest allowable length in the trench. It creates a force which pushes the handles together. When the handles are separated, the force of the spring is overcome. As the teeth of the handle rotates into the trench, it makes contact with the teeth of the gear opening the jaw. Meanwhile the spring is fully compressed. Letting go of the handles allows the force of the compressed spring to overcome the force of friction between both the teeth in the handle and the gear, and also the teeth of the handle and the walls of the trench. This forces the handles together and the jaw to close, which is its resting position. Steel Alloy Coiling of the Wire -
Comp Spring 22.jpg
Chain The chain is arguably the most important component since it is the cutting surface. It is composed of many small steel links which are joined by rivets. The pattern repeats every three links. The first link has a long flat cutting surface followed by a link with a small pointed cutting surface. The third link in the pattern has no cutting surface and serves as a connection between the two cutting surface links as the pattern repeats. Each link has flat driving links on their bottom so that they can latch onto the sprocket without slipping. Thus the sprocket can move the chain without risk that the chain will slip off. Steel Stamped, cutting surfaces bent and filed 587579-00
Chain 22.jpg
Motor Mount This component has two circular spaces in which sit the large gear and the small driveshaft from the motor. The inside is coated with a lubricant so that the gears can spin with as little friction as possible. It contains a number of holes, both threaded and unthread, with which the outside covers of the Lopper are attached. It is the center most component within the machine which everything is attached to and built around. Aluminum Injection Molding -
Motor Mount 22.jpg
Motor Mount Cover The motor mount cover is bolted into the motor mount. It contains the gear exchange between the motor drive shaft and the sprocket drive shaft. In addition, it also anchors two bolts which are threaded through the cover out of the exterior of the product where they are used to anchor the bar and chain covers. Aluminum Injection Molding -
Motor Mount Cover 22.jpg
Jaws These two components are bolted together and allow for the operator to clamp onto the target branch or limb. When bolted together, these two are fastened directly to the gear which is operated when the operator works the handles. When this occurs, the jaw is opened allowing for the operator to clamp onto the target. It also protects the operator from the blade when it is not being used to cut. Aluminum Injection Molding Jaw: 587587-00, Cover: 590089-00
Jaws 22.jpg
Bar The bar is the guide around which the chain rotates. It has a slot along its edges in which the driving links of the chain slide while not in contact with the sprocket. Aluminum Stamped 587578-00
Bar 22.jpg
Top Cover The top cover surrounds half of the chain at all times. It is stationary and is attached to the orange plastic cover and handle. This safety feature keeps the operator from unintentionally coming into contact with the side of the chain not in use while cutting. Aluminum Injection Molding 587577-00
Top Cover 22.jpg
Switch The switch is used to control the flow of electricity to the motor which runs the chain. There are two such switches located beneath the two triggers. There is one switch and trigger in each handle, requiring the operator to depress both switches in order to run the blade further increasing the safety of the product. High Density Plastic, Copper Injection Molded plastic, Stamped Copper leads and Connectors -
Switch 22.jpg
Terminal Block This unit connects the two wires from the external cord to the internal wiring of the product. It can be accessed in the handle beneath the wire housing cover. Used once in the product to connect the cord attached to the power source to the internal wires. High Density Plastic, Copper Injection Molded plastic, Stamped Copper leads and Connectors 373883-00
Terminal Block 22.jpg
Wire Clamp This clamp fastens one end of the external cord on the inside of the handle before its wires are inserted into the connector. This insures that the operator will not accidentally rip the wire out of the project and provides stability to the wires entering the connector. Sheet Metal Stamped 821070-00
Wire Clamp 22.jpg
Outside Cover The outside cover is connected to the product through the use of two bolts anchored between the two sides of the motor mount. It covers up the sprocket and some part of the bar and chain assembly. This cover prevents foreign materials from being lodged between the sprocket and the chain which could unhook the chain, making it useless. High density plastic, aluminum Both Injection Molded and joined with Adhesive 588087-00
Outside Cover 22.jpg
Motor Housing Two sides make up the motor housing. They join together around the motor, protecting it from dirt and foreign objects. In addition, the housing provides anchors for the wiring that leads into the motor making sure that it does not become separated from its leads. High Density Plastic Injection Molding -
Motor Housing 22.jpg
Bottom Handle 1 This part of the handle is the one which the sprocket sits on, the bar is fastened to, and to which the top cover is fastened to. It provides not only the form for half of the bottom handle, but it also protects the motor mount and the bottom of the motor. The bar is fastened to the cover and the drive shaft for the sprocket passes through it from the motor mount located below. The handle portion of the cover also provides an anchor for the switch along with an area to mount a trigger. High Density Plastic Injection Molding -
Bottom Handle 1 22.jpg
Bottom Handle 2 The second part of the bottom handle completes the shape of the handle which contains the trigger. In addition it provides a top cover for the motor mount and actually surrounds the motor itself keeping it in position. High Density Plastic Injection Molding -
Bottom Handle 2 22.jpg
Top handle The top handle is comprised of two sides. When connected together they house the second trigger and its wiring. The end of the handle is unique in that is semi-circular in shape and has a number of teeth that extend below it. These teeth sit in a trench located on the Bottom Handle 2. Held in place by a compression spring, when the handles are opened, the semi-circular part of the handle slides through the trench located around the motor. This makes contact with the gear which then then opens the jaw it is connected to. High Density Plastic Injection Molding -
Top Handle 22.jpg
Outer Handle Fastener This semi-circular piece of plastic fits around half of the motor, resting on the Bottom handle. It is screwed into anchors located in the top handle, creating a snug ring around the motor and its outer cover. This piece keeps the top handle connected to the motor so that it does not slip of during the operation of the product. High Density Plastic Injection Molding -
Outer Handle Fastener 22.jpg
Motor Cover The motor cover is the cup shaped plastic cover which goes over the two sides of the motor housing. When fastened in place with screws, the motor cover keeps the Top Handle and the Outer Handle Fastener in place so that it cannot move vertically in relation to the motor and be pulled off. In addition to holding the Top Handle and Outer Handle Fastener in place, it also keeps foreign objects from becoming introduced into the motor. High Density Plastic Injection Molding -
Motor Cover 22.jpg
Brush Assembly Spring loaded connectors which are wired into the motor. When the triggers are depressed, electricity flows through the brush assembly into the motor and out through the other brush assembly. The charge that is introduced to the coil causes it to spin within the magnet of the motor. Steel Injection Molding (housing) Metal Connectors 588878-00
Brush Assembly 22.jpg
Motor Coil The coil of the motor is made up of bunched copper coils. It spins within the magnet when an electric charge is introduced. This is done with two Brush Assemblies which introduce a charge to the coil. When this happens, the coil unit spins. This coil is attached to a drive shaft so that when it does spin, it powers the gear and in turn the sprocket and chain. Drawn Copper wire, steel, epoxy Die Casting, Drawing, Assembly -
Motor Coil 22.jpg
Motor Magnet The magnet is circular and surrounds the coil. When charged, the magnetic field caused by the magnets forces the copper coil to spin creating mechanical, rotational energy. Iron Alloy Die casting -
Motor Magnet 22.jpg


Product Analysis

In this product analysis, we consider the major components of the Alligator Lopper such as the Jaw, Motor, and such; and we chose to neglect other minor components such as the screws, gears, and internal wiring of the system.

Grading

Upon analyzing the Lopper's components, we created difficultly scale to rate the complexity of each major component.

Scale Meaning
1
  • Component has no significant functionality within the overall system.
  • Component form is common in all product families.
  • Component is simple to manufacture.
  • Component cost is low.
2
  • Component has minimal functionality within the overall system.
  • Component form is common in most product families.
  • Component is simple to manufacture.
  • Component cost is low.
3
  • Component has a significant functionality within the overall system.
  • Component form is common in some product families.
  • Component is simple to manufacture.
  • Component cost is affordable.
4
  • Component has a significant functionality within the overall system.
  • Component form is common in few product families.
  • Component is moderately simple to manufacture.
  • Component cost is affordable.
5
  • Component has a highly significant functionality within the overall system.
  • Component form is common in this product family only.
  • Component is moderately complex to manufacture.
  • Component cost is affordable.

Component Table

Component Component Function Component Form Manufacturing Component Complexity
Cover (Top)
Top Cover.png
The purpose of this component is to cover the top half of the exposed chainsaw in the Alligator Lopper, which prohibits the user from any form of risks for injuries. This components is stationary with regards to its position on the chain and bar components, however it does act as a clamp with its bottom counter part, the jaw, to provide a firm grip of the material during the cutting process. This promotes a clean and steady cut to the material. The body of the top cover has an a smooth filleted outer edge and a symmetrically similar hollow inner gap because its position requires the component to take a shape to that of the chain and bar components. The inner edge of the cover is a smooth fillet and covers rough an inch of the blade. Weighs approximately 0.25 lbs. The cover is made of aluminum, and has been processed through injection molding. Aluminum is a metal that is easy to mold and inexpensive to manufacture, which is highly beneficial with regards to production time and consistent designing; it is economically inclined toward the customers and producers. Although aluminum does not have the same specific strength as steel or titanium, it is lightweight and durable enough to provide the protection for the user, and has long lasting resistance to wear and tear. This makes it easier for any user to handle. The cover also provides the chain with protection from rusting, breakage and exposure to other material interactions besides that of the material being cut. 3
Jaw
Jaw and Cover.png
The jaw, while it may limit the size of the material that can be operated on, acts as a clamp, opposite to its Top Cover counterpart, providing the user with a firm grip of the material during its cutting process. Because it is an outdoor tool, this component is prone to exposure of hard material and year round weather. It also serves as a protection for the user from the chainsaw during times of storage because the Top Cover and Jaw complete cover the exposed teeth of the chainsaw. The properties of the Jaw are ultimately the same as the opposing Cover component; however the design of the Jaw is a bit complex due to the added teeth on the inner edge of the rigid . It is also made from aluminum, and has been processed through injection molding. Similarly to the Cover component, the injection molding process is for the benefits of production cost and consistent quality, especially for a product with such rigid details in the design. 4
Bar
Bar.png
The bar is a fixed, stationary component that acts as a guide for the chain, which wraps around the entire outer edge of the bar. The component is controlled with respect to the upper handle; while the chain is spinning, the user applies pressure to both of the the handles allow them to compress and make contact with the material to perform the cutting action. The bar is an elongated round edged part. Weighs approximately 0.45 lbs. The component that is made from aluminum is a simple shape with a rounded edge, however it is a bit price to replace. The bar's thin and elongated shape suggests that is has been stamped into it current form. 4
Switch
Switches.png
The purpose of this component is to basically start the chainsaw, compared to the traditional pull cord. Within the system, there are two switches, one located under each of the triggers. In order to activate the chainsaw, the user must simultaneously press the trigger, which will activated the switch, and compress the handle to begin the cutting process. These switches are made from high density plastic and copper wiring. They are not exposed hidden within the handles, which protect the wiring from the environment. These switches appear to have been processed through injection molded plastic, and stamped copper leads and connectors. 3
Top and Bottom Handles
Top and Bottom Handles.png
The main functions of the handles are to control the chainsaw and cutting the material. They are the component that must be compressed in order to perform the overall function of the Lopper. The material of the handles is high density plastic. This is an especially beneficial material to use because it is durable; its properties include good impact resistance, light weight, very low moisture absorption, and high tensile strength. The method in which the handles were created is injection mold. Because plastic can melt and form easily, this reduces the time needed to meet the demand of the consumers. Added to that, it ensure that the product can be easily maintained, and the price for maintenance is affordable. 4
Trigger
TriggerAll.png
The function of the trigger is to set off the engine throttle and get the system up and running. There are two identical triggers and they need to be pressed simultaneously for it to work. The human input which is put into this component when pressed is then converted into mechanical energy flow which results in the rest of the subsystems functioning appropriately. The pressed trigger trips a switch which allows electricity to flow to the motor. The component is almost like a cap that is hollow and set up with springs under it. This material is made out of plastic and is relatively light weight. This component is black which sets it apart from the other orange parts. It is a different color because it performs one of the main functions. It does not really have an aesthetic finish. The component is approximately 4 X 1 X 1 inches. The components shape is appropriate to how it is meant to perform. Since the inside is empty it has the ability to fit the springs which will be pushing against the switch when needed. Injection Molding. Some evidence that supports this is that it is made out of plastic which is the material generally used in injection molding. Riser marks and parting lines are also seen on the material which further proves that it was made in this way. The shape of the trigger definitely influenced the way that it was made because there are two identical triggers on each chainsaw and injection molding is one of the best ways to speed up production if a mold is being reused. 3
Chain
ChainAll.jpg
The ultimate function of the chain is to cut the wood or material of the users choice. When the triggers are engaged, the clutch make contact with the motor drive shaft and the sprocket. This in turn spins the sprocket which drives the chain around the chain guide. The chain does not work alone but instead is triggered by these various different subsystems. This component best functions in areas with branches and wood that needs to be cut and/or shaped. It is easier to hold and carry compared to a heavy duty chainsaw which is meant for large scale agricultural work. The component helps cut the wood. It consists of steel links held together by rivets, and really resembles the chain on a bicycle. It's key differences are sharp cutting teeth on the outside of the chain loop, and flat drive links on the inside, to retain the chain on the saw's bar and allow propulsion by the engine or motor. This component is used primarily for cutting down trees and clearing land of plant and bush growth quickly and effectively. It is generally 2 dimensional. The component is almost like a miniature version of a bicycle chain. It does not have an aesthetic finish and it is generally made out of steel or another type of metal. This component is used for functional reasons and plays a major roll in the overall function of the chainsaw. The individual links which make up a chain have to be made separately and then assembled later. The highest-quality chain links are made by pouring molten metal into individual molds and then allowing it to cool and solidify. Average chain links are made from a large press machine that stamps them out of sheets of stainless steel. In order to make the chain saw links the links are placed in a tool and die. Hollows are present, which is where the backs of the rivets are placed, then a guide link, then a cutting link, then a guide link, and so on. Once the links are in place the tops of the rivets are placed over all the joints. A button is pressed, activating a stamp which presses down and seals the rivets together, finishing the chain. The material that the saw was made of definitely supported this because otherwise one would be unable to use the manipulative process in order to produce multiple chain links. 5
Power Cord
Power Cord.png
The basic and sole purpose of a power cable is to transport electrical energy from the source of the electricity to the device. The cord protector is made of high density plastic which serves to protect the male electrical socket. This socket is used to connect the product to its power source through the use of an extension cord. From the Cord Protect runs the Cord Set which is comprised of a copper wire insulated with rubber. The cord set enters the product at the end of a one of the handles and is connected to the internal wiring of the Lopper. The cord protector is made through injection molding. This can be proved because it is made out of rubber which is one of the common materials used during injection molding. The Cord Set is done through drawing of copper into wire and coating the wire with rubber. The shape is like a tube which is easily made through injection molding for a rubber cover. 5
Wire Housing Center
Wire Housing.png
The wire housing center is intended to keep the wires away from exposure and maintain the safety of the product. This small housing cover is located on the outside of the actual handles. It is held in place by a Philips head screw. Once removed, the user is given access to the connection where the wires running from external cord are joined with the wires used internally within the Alligator Lopper. There is only one wire housing cover used within the entire product The small housing cover is made through injection molding. This can be proved with the parting lines and riser marks on the component. 3
Motor Coil
Motor Coil.png
The rotating coil generates a magnetic field that alternates N and S depending on which brushes are connected to it. There has to be an external magnetic field for the rotating coil to act against. This powers the gear which turns the sprocket and fuels the chain to start rotating. The coil of the motor is made up of bunched copper coils. It spins within the magnet when an electric charge is introduced. This is done with two Brush Assemblies which introduce a charge to the coil. When this happens, the coil unit spins. This coil is attached to a drive shaft so that when it does spin, it powers the gear and in turn the sprocket and chain. The motor coil is made through die casting, drawing and assembly. Drawing is generally used for wires. It is done by pulling the material through a diet to obtain the desired shape. 5

Solid Modeling

The most important components of the Alligator Lopper are the ones that comprise the drive shaft, gear exchange, second drive shaft, and sprocket. These components translate the rotational energy produce by the motor, increase its torque, and then transfers that energy to the chain through the sprocket. This is what gives the chain its energy and motion. In addition the motor mount itself is extremely important as a component to the rest of the product because almost everything is built around it. It has a number of holes, both threaded and smooth, which allows other parts to be screwed or bolted to it. So in terms of not only the mechanics of the Lopper but also the overall structure, the components we chose are integral to the successful operation of the product.

Alex modeled the components using Solidworks, which is a three dimensional modeling software program. The interface is very user friendly and intuitive and its rendering of the model provides a very aesthetically pleasing depiction. Not only does it render shadows, it also can show glare off of rounded parts resulting from artificial light sources. In addition, Alex has had experience using Solidworks since he used it over the summer during his internship.

Motor Mount

This is a model of the Motor Mount which encloses the large gear.

Motor Mount Cover

This is a model of the Motor Mount Cover which is fastened to the Motor Mount. The driveshaft of the large gear extends through this piece so that the sprocket can be fixed to the shaft outside of the mount.

Motor Drive Shaft

This is a model of the Motor Drive Shaft which is fastened to the motor's coil. When the motor is engaged, it spins the drive shaft which makes contact with the Large Gear through the teeth located at the end of the shaft.

Large Gear

This is a model of the Large Gear whose drive shaft connects to the sprocket. The purpose of this large gear is to increase the torque of the motor.

Sprocket

This is a model of the Sprocket which makes contact with the chain. It is fastened to the drive shaft of the large gear. When spun, it spins the chain around the bar.

Assembly

This is the total assembly with all the mates unsuppressed. This is what this group of components looks like when fully assembled
This is the total assembly viewed from an angle.

Exploded Assembly

This is the total assembly with some of the mates suppressed. This is what this group of components looks like when exploded in a vertical manner
This is the total exploded assembly viewed from a different angle.
This is the total exploded assembly viewed from a different angle.



Engineering Analysis

INTRODUCTION

The lopper’s success is determined by its output, abilities, and dependence on the job. Breaking the product down into its many components allowed us to isolate each one and determine its significance to the success of the overall function. We chose the drive gears and sprocket component as our subject for engineering analysis. We felt it was necessary to put this component through its paces and derive more data and information about the component and its service to the overall product. The gears integrate nearby components that make up the composition of the entire power drive of the product. Rotational energy from the motor is translated into cutting power in the outdoors. These gears must stand up to the rigor of heavy duty workloads, which means high RPMs and torques applied to the teeth of the gears and sprocket. Through analysis, we intend to discover just how much of an impact that the gear ratios have on the power and velocity output of the motor and its translation into the chain’s abilities. The gears must combine to produce the proper output of power and velocity in order for the chain to perform sufficiently. Engineering analysis gives us a clear idea of the methods of study to help us determine the ratio that is present, as well as an optimal one.


PROBLEM STATEMENT

Determine the proper gear ratio between the motor output shaft and the larger gear such that the sprocket will turn with sufficient angular velocity and rotational force to propel the chain saw in a linear direction suitable for effective cutting ability.


DIAGRAM


Gear Ratio.png

What values are necessary?

To approach this problem the following values would be needed: The possible rotational velocity (rpm’s) of the electric motor The possible torque the electric motor could produce The needed force on the chain for optimum cutting performance The needed speed of the chain for optimum cutting performance The size of the sprocket required by the chain. Whether there is a predetermined gear radius for the gear on the electric motor, and if so what is that radius?


ASSUMPTIONS


For such calculations to be made, the following assumptions would need to be made: The force required by the chain is constant. The angular velocity and torque from the electric motor’s small gear is constant. The bearings in which the shaft of the large gear and sprocket are mounted are frictionless. The bearing in which the drive shaft of the motor sits is frictionless. The interaction of the teeth of the two interlocking gears is frictionless.


GOVERNING EQUATIONS

When approaching such a problem the following governing equations will come into play: Τ1 ⁄r1 = T2 ⁄ r2 ω1 *r1 = ω2 *r2 F3 = τ2 /r3 V3 =ω2 *r3

These variables represent: τ1= The torque from the electric motor r1= The radius of the gear on the electric motor’s drive shaft ω1 =The rotational velocity of the electric motor gear τ2= The resulting torque produced by the large gear r2= The radius of the large gear ω2=The rotational velocity of both the large gear and sprocket r3= The radius of the sprocket F3= The force of the sprocket on the chain V3=The linear velocity of the outside of the sprocket/linear velocity of the chain.


SOLUTION CHECK / INTERPRETATION

Using the equations above one could easily find the gear ratio between the large gear of the gear exchange and the small gear of the electric motor output. Checking the solution for solution would require checking calculations, as well as comparing to the ration found to other simial gearing situtions and making sure the values determined are reasonable. There is real defined unit to the ratio determined as it is a ratio, the ratio is merely a fraction of two values. Unless the size of one of those two gears is predetermined, we only find the ratio between the two gears radii. As long as this ratio is kept between whichever gear sizes the designers decide to use, the output from the sprocket to the chain should stay the same. This allows for significant flexibility through the design process regarding the drive train of the chain saw. The actual gear sizes would need to be determined by the available space within the product, weight/cost restraints on the gears, the power needed to overcome the rotational inertia of the gears, the efficiency of different sized gears. The final size of the gears would require much more research and calculations than what is displayed in this problem analysis, but it does solve for the very critical gear ratio.



Design Revisions

Jaw Operation Revision

Have the opening jaw be operated on a single pivot point so that the action of opening the handles directly translates to the opening of the jaw, without the gear system intermediary. This system could improve the grasp of the operator on the target material being cut since his force applied to the handles is not translated through plastic gear teeth. This interaction which is present now could result in the slipping of gears or the shearing of some teeth based on the force applied. By allowing the jaw and handle to remain a single moveable entity, it removes the chance for there to be slippage while the handles are engaged. It is fully under the control of the operator.

Factors Influencing Design Change:

Economic: This system is simpler to put together. It is based on the concept of scissors in that pulling the handles apart will result in the jaws being pulled apart too. As a result, a simpler handle is required instead of the current handle with gear teeth. This added simplicity makes it easier to manufacture. In addition the elimination of the gear system removes the need for multiple parts currently in use. The gear required now to make contact with the teeth on the handle is not required, cutting down production costs. Furthermore, the jaw itself can be created in one part rather than two. It then can be directly attached to the handle. In this simple change, four parts have been combined into two parts: a plastic handle which is directly attached to a single aluminum jaw. This simplification drives down production and material costs even further.

Societal: The safety of the product increases because another cause of slippage in the jaws is eliminated. With the gear teeth system, there is a chance that the teeth will slip resulting in the loss of grip in the handles and quite possibly loss of control of the product itself. By having the jaw directly coupled with the handle, the chance that the grip will slip is lessened. Furthermore, this design change places more control directly in the operator. By eliminating the gear system, it eliminates the small differences in production tolerances in the teeth of the connection. With the current design, the user could apply a force to the handles and it would not be entirely translated into the jaws. With this change, the user can be assured his applied force is felt in the jaws. The idea of putting more control in the hands of the user is certainly appealing to a consumer since the mindset is usually one of “the more control, the better.”

Handle Elimination with a Different Jaw Operation Revision

Instead of having two handles which are used by pulling them apart, one handle is used instead with a large spring operated trigger and two small trigger switches midway up the handle. The concept behind this design is that much like the current design, the jaw is operated by the use of a gear system. Instead of providing the rotation for one of the gears by pushing two handles apart, the gear is operated by a pulling action in the horizontal direction by depressing a large switch. The action required to operate the switch is a clenching motion with the user’s hand. To deal with the safety factor, two switches would be placed midway down the handle where the user would comfortably support the product with his other hand. The switches would be located on opposite sides of the handle so that one could be depressed with the thumb while the other would be depressed by the fingers.

Factors Influencing Design Change:

Economic: The system would us a modification of the current system in place to open and close the jaw. It would still rely upon the same concept of using gears and teeth. However now it would eliminate the need for two handles and would require only one simplistic handle instead. The elimination of an entire second handle would decrease materials cost and production cost. This design change would be able to facilitate selling the product at a cheaper price since Black and Decker’s overhead cost would decrease.

Environmental: This change in design also results in a change of environmental usage. Instead of being used primarily below the user’s chest and close to the user’s body, the chainsaw can be extended further away from the body. This directly effects what the user can access in terms of material and objects to be cut. Branches that are harder to reach or two high to reach comfortably with the current design can be cut using this design. The environment this tool shapes is directly controller by where it can be used and with this change, it creates a larger environment that can be altered.

Societal: By changing the layout of the handles, the design improves the user’s comfort while operating the project. It is more comfortable to hold, similar to holding a long pain roller or even a rifle. By creating a subsystem that relies upon the force in the user’s forearm, and not his chest, the subsystem can be operated farther from the body. The strength in one’s forearm is impacted little by how close their arm is to their body, unlike the chest muscles needed to operate the current design. The safety of a two switch system is still maintained in this new design. Instead of having two hands operate two switches, one hand can now operate two switches. By placing a thumb switch and finger switch in the middle of the handle where the supporting hand is intended to be placed, the design change maintains safety while still eliminating an entire handle.

Debris Bagging Feature

An extra feature which can be added to this existing system is a debris collection intake located within the chain cover. While the motor is in operation it creates air currents which vent excess heat outside the product. By using this airflow to create a vacuum, a small aperture can he placed in the chain cover than can suck up small bits of debris caused by using the chainsaw. This debris would be collected in a small cloth bag next to the motor which would be removable to allow for it to be emptied. It would allow the user a cleaner working environment since the debris created from the saw would not fall on the ground but rather be collected in the bag. This concept is similar to a bagger on a lawn mower, except scaled down to the size of the Alligator Lopper.

Factors Influencing Design:

Global: This system could be used more readily in areas that are prone to wildfires. By reducing the amount of debris and saw dust that is spread around the environment, the amount of material in the environment readily available to catch fire would decrease. This would be an ideal feature to have if storms or natural disasters are relatively frequent causing people to clean up after them. This product could also be used indoors if desired. The less mess it leaves means that it is easier to use in confined spaces. This feature would be perfect if the operator was using it as a tool in the demolition of a room as part of a remodeling process.

Economic: Unfortunately adding this feature would increase the production cost and material cost. Since there are only a couple additional components required, production cost would not see a drastic increase. However the introduction of a debris bag introduces a material not yet used in the current Lopper design: Cloth. Although relatively cheap, introducing it into the manufacturing and assembly process would require an initial investment on the part of Black and Decker.

Environmental: The debris collection system would have an impact on the environment since it would leave it cleaner after working with the Lopper than using the current design. This would result in less effort placed on cleanup of the environment and the debris created from using the Lopper and more focus placed on actually doing the job.

Societal: Any extra feature that can be advertised over a competitor’s product is always welcome in marketing that product. Consumers love small extra features placed in a new product because it makes it more convenient to use that product. A feature that reduces mess and clean up time would certainly be welcome by consumers. Plus if Black and Decker offered the Lopper with this feature close to or at its current price, a consumer would surely be enticed to purchase it over a competitor that lacks this feature.

External Black Cord Removal

By eliminating the black cord with the male electrical socket and instead placing that socket directly in the handle surround by a plastic housing, the product would become safer to user, store, and handle. The cord is not long enough to provide any real length to an extension cord when using it far from its power source. Furthermore an extension cord is already required to connect the product to the power source since the black plastic housing around the male electrical socket prevents it from being plugged directly into an outlet. The cord also makes it slightly more cumbersome to handle since it is swinging freely when not plugged in. By providing a housing around a male socket located at the end of the handle and also a small plastic tether for an extension cord, the Lopper would be safer to use. Many electrically driven yard machines have this feature already, such as weed whackers. It makes sense to add this feature to the lopper.

Factors Influencing Design:

Economic: By eliminating the need for the cord and the plastic housing located on the cord, production costs and material costs would decrease by a little bit. Although the cost difference is not drastic, any savings that can be passed onto the customer or turned into profit are most assuredly welcome. In addition the elimination of the cord eliminates the possibility for another component failure. Since replacement cords are sold by Black and Decker, removing the cord removes a replacement part a consumer might have to purchase.

Societal: The safety of the wiring from the power source to the product will increase. Pulling on the cord by accident will result in the portion of the extension cord looped around the tether to take the force, not the cord clamp currently holding the black cord in the handle of the Lopper. There is no risk that the cord will fray over time at the point where it enters the handle since there will be no external wiring at all. The possibility that the user can come into contact with the frayed cord near the handle is removed since no such cord would exist. This drastically reduces the risk of the user being shocked by the external wiring of the Lopper increasing its overall safety effectiveness.


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