Gate 3 - Group 4

Latest revision as of 16:12, 16 November 2012

Gate 3: Product Analysis

Purpose

With our hammerdrill now fully dissected, we can now complete a detailed analysis of it. Here in Gate 3 we will examine the product at the component and subsystem level, while gathering detailed information of its form and functionality. Specifically, in the section of the project, we will document a parts list, analyze several individual components, provide solid-modeled assembly drawing of a few of our parts, analyze a function/mechanism present in out product, and also recommend a few design changes.

Project Management: Coordination Review

Cause for Corrective Action

Our goup management has not been confronted with any new, unexpected problems, in addition to those mentioned in previous gates. We have concluded how extremely difficult it is for all four members to meet together outside of class time, due to personal schedules, yet we have still succeeded in combining our efforts to complete project work. While keeping in close contact via email and text messaging, we have found it most beneficial to evenly distribute the work amongst the group members, by collectively determining who is best suited to complete certain tasks. While each member has had their schedules filled with other homework, exams, and working several days a week, careful planning and time management has proven beneficial for the completetion of gates thus far.

Product Archaeology: Product Evaluation

Parts List/Component Summary

Component #	Component Name	Amount Required	Component Function	Material	Manufacturing Process	Image Guide
1	Torx Screw	3	Fastens handle cover to field case.	Steel, Black Oxide Finish	Cold Forging, Thread Rolling, Chemical Conversion Coating
2	Torx Screw	2	Fastens Brush Assemblies to Field Case.	Steel, Black Oxide Finish	Cold Forging, Thread Rolling, Chemical Conversion Coating
3	Torx Screw	2	Fastens chuck assembly to field case.	Steel, Black Oxide Finish	Cold Forging, Thread Rolling, Chemical Conversion Coating
4	Torx Screw	1	Fastens chuck assembly to field case.	Steel, Black Oxide Finish	Cold Forging, Thread Rolling, Chemical Conversion Coating
5	Torx Screw	2	Fastens baffle to field case.	Steel, Zinc Finish	Cold Forging, Thread Rolling, Chemical Conversion Coating
6	Lag Bolt, Hex Head, 3/8" X 4 1/2"	1	Fastens handle to handle clamp.	Steel, Zinc Finish	Cold Forging, Thread Rolling, Chemical Conversion Coating
7	Side Handle	1	Provides stability for user while drill is in operation.	Plastic, Black	Injection Molding, Drilling
8	Handle Clamp	1	Locks Handle in desired position on Chuck Assembly.	Aluminum	Metal Casting, Sand Blasting
9	Chuck Assembly	1	Delivers rotational motion to the drill/ fastener from the gear assembly	Plastic, Stainless Steel	Injection Molding, Extrusion, Milling, Drilling
10	Gear Assembly	1	Gears down rotation from motor to chuck assembly and increases torque output.	Steel	Drawing, Drilling, Cold Forging, Broaching
11	Bearing, Ball	2	Reduce friction between gear assembly, chuck assembly and armature.	Stainless Steel	Cold Forging
12	Baffle	1	Holds field secure inside of field case.	Plastic, Black	Injection Molding
13	Selector Assembly	1	Engages and disengages hammering action.	Plastic, Black	Injection Molding
14	Plug	2	Dampens vibrations from armature and field case	Rubber, White	Extrusion
15	O Ring Seal	1	Forms a water tight seal inbetween chuck assembly and armature. Retains lubricant inside of gear assembly.	Rubber, Black	Vulcanizing
16	Brush Assembly, Right	1	Disharges armature and returns power back to trigger assembly.	Plastic Black, Copper, Steel	Injection Molding, Rolling, Extrusion, Soldering, Vulcanizing
17	Brush Assembly, Left	1	Charges armature from trigger assembly.	Plastic White, Copper, Steel	Injection Molding, Rolling, Extrusion, Soldering, Vulcanizing
18	Armature	1	Armature experiences a charge and discharge causing an armature reaction. This reaction moves paralel to the magnetic field producing a rotational action which turns the worm screw and fan on armature.	Steel, Copper, Ceramic	Metal Casting, Injection Molding, Drawing, Cold Forging, Annealing
19	Field	1	Produces a magnetic field for armature to react with.	Steel Copper	Injection Molding, Drawing, Cold Forging, Stamping, Annealing
20	Trigger Assembly, Variable Speed, Reversable	1	Allows user to control rotational speed of drill and reverse.	Plastic Black, Steel, Copper	Injection Molding, Stamping, Soldering
21	Field Case	1	Houses and protects all electrical components.	Plastic, Yellow	Injection Molding, Pad Printing
22	Handle Cover	1	Provides a stable comfortable grip for user and houses/ protects trigger assembly and bursh assemblies.	Plastic Yellow, Rubber Black	Injection Molding, Vulcanizing, Co-Injection (sandwich) Molding
23	Power Cord, 18 Gauge, 2-Wire	1	Delivers power to the trigger assembly.	Rubber Black, Copper	Drawing, Vulcanizing, Soldering
24	Chuck Key	1	Allows the user to tighten/ loosen the chuck.	Black Oxide Waxed Steel	Drawing, Forging, Welding
25	Key Holder	1	Holds key in place on power cord.	Rubber, Yellow	Vulcanizing

Product Analysis

1st Component: Field Casing

• Component Function
  

The predominant function of the field casing is to protect the inner components of the drill and provide a solid outer shell for the drill. The field casing is comprised of two identical halves fastened together by several screws. The inner parts and components of the drill such as the armature,field and gear assembly are all contained within the upper part of the field casing. The lower handle portion of the field casing houses the trigger assembly. The handle provides the user with the ability to use the drill. Without this ergonomically designed handle, the user would not be able to easily grip and use the drill. Human energy is inputted into this component. This form of energy is responsible for keeping the drill in position to best complete the task designated by the user. The drill housing operates in a standard atmosphere, up to a certain temperature to prevent deformation. The field casing can operate and perform well in any practical environment. Obviously the drill would not be used somewhere that was hot enough to melt the plastic the field casing is made of.

• Component Form
  

Field Casing

The field casing is in the shape of an L with many different contours. The right and left sides of the casing are similar in shape, but are not completely identical due to the way the components on the inside are arranged. The field casing is primarily three dimensional in order to house the internal components. The shape of the field casing is also influenced by the assembly of the internal components. The components are arranged on the inside of the drill to minimize the internal volume. The handle provides ergonomic grooves for fingers. The drills field casing is the largest component of the drill. However, it is very light compared to its size. It is about a pound. The housing is made out of plastic. The manufacturing process used to make the field casing is injection molding. The material often used in injection molding is plastic. The field casing must be strong enough to protect the inner components from drops and falls and normal use of the drill. Plastic is pretty durable and cheap so it is well suited to protect the inner components of the drill and it will not effect the overall price of the drill to much. Injection molding is very cheap to use to create mass quantities of parts. The plastic used to make the field casing can be recycled at the end of the drills life cycle. Aesthetically, the drill housing has a very basic appearance. It is yellow in color with a black patch and yellow lettering. The drill casing has a dull and slightly rough finish. The functional purpose of this finish is to help prevent slippage of the users hand.

• Manufacturing Methods
  

The field case is produced by using injection molding. This is evident through the flow marks of the plastic found on the inside of the casing along with the gate and runner marks found on the edges of the casing. The choice to use plastic as a cheaper, lighter weight material and the intricate design is the exact reason injection molding was used as the manufacturing process. If metal was chosen as the material this part would be manufactured using casting and then have to be machined to refine and clean up the cast.

• Component Complexity:
  

Level: 1

The single manufacturing process used is injection molding. Two injection molds are used in the production. One for the left and right sides. The single material used is plastic. The number of materials used to create the component is also very important in determining the complexity of the component.

• Interaction Complexity:
  

Level: 1

• The field casing of the drill holds all the inner components of the drill in place by fitting them into the slots defined by the molding of the casing. The right and left sides of field casing are fastened together by screws.

2nd Component: Power Cord

• Component Function
  

The predominant function of the power cord on the hammer drill is to bring electrical energy into the drill. All the components inside the drill need electrical energy provided by the power cord. The electrical energy is imported to the system through the power cord and is converted to rotational energy by the motor. The power cord is plugged into the wall using human energy. The power cord can only operate in an environment where there is an electrical power outlet. Part of the electrical cord is also housed inside the field casing. This is where the wires are connected to the trigger. This is how the human controls the input of electrical energy to the system.

• Component Form
  

Chuck key

The power cord is made of a flexible and durable rubber allowing it to be bent and folded into any shape. The cord is primarily cylindrical in shape. The cord is about one centimeter thick. At the end of the cord is a 3 prong wall adapter. Due to the flexibility of the cord, the drill can be used around any obstacle. The metal prongs on the wall adapter transfer electrical energy from the power outlet to the drill. The cord is very light. It weighs about a pound. The outer layer of the cord is made of rubber. This rubber protects the copper wire inside that transfers the electrical energy to the drill.The rubber outer layer acts as an insulater on the copper wire making it safe to touch the power cord while it is plugged into the wall.The inner wire had to be made of something conductive. Copper is an electrical conductor and is a relatively cheap metal. The plastic plug portion of the cord is made through injection molding which is cheap and very efficient. The plastic used can be recycled at the end of the drills life cycle. Aesthetically, the power cord is thin and black making it as unnoticeable as possible. The surface finish of the power cord is smooth and shiny making it able to slide against surfaces without damaging them.

• Manufacturing Methods
  

Several methods are used to produce the power cord including drawing, vulcanizing and soldering. The copper is first drawn to its desired thickness. After drawing, the copper is somewhat brittle so the copper wired is put through an annealing process. THe annealing process allows for the copper wire to bend without breaking. The copper is then soldered to the prongs for the plug. All of this is then loaded into an autoclave with black rubber and vulcanized to its final desired shape. Vulcanizing is used to "set" raw rubber into a desired shape. It heats the rubber to a specific temperature and pressure. When the rubber cools it retains the shape it was heated in. The rubber provides a protective casing around the copper. Evidence of vulcanizing can be seen in a cross section of the power cord. The rubber has completely filled all voids between the copper wiring showing that it had been heated to a melting point under pressure. The shape of the cord needed to be flexible so the copper needed to go through an annealing process and rubber was needed as a protective casing due to its flexibility.

• Component Complexity:
  

Level: 2

More than one manufacturing process is used. Three different materials are used: plastic, rubber, copper. The number of manufacturing processes used is the biggest factor in determining the components complexity. The number of materials used to create the component is also very important in determining the complexity of the component.

• Interaction Complexity:
  

Level: 2

• The power cord provides electrical energy to the system. Without this electrical energy, the system is useless.

3rd Component: Side Handle

• Component Function
  

The predominant function of the side handle is to give the user a place to hold on to the drill. This will in turn give the user more control over the drill and make the operation of the drill much safer. The side handle connects to the handle clamp which is connected to the drill. Human energy is imported from the users hand. The human energy provides stability to the drill when it is in use. The handle can operate in any practical environment. The drill would not be used in an environment hot enough to melt the plastic it is made out of.

• Component Form
  

Handle

The side handle is made of a durable non flexible plastic. The handle is three dimensional, cylindrically shaped and it flares out at both ends. The handle is 6 inches long and an inch wide at the ends. The handles shape is ergonomically designed so it easily fits into a wide variety of hand sizes. The handle is solid plastic and weighs about a half pound. Economically, the manufacturers choose to make the handle out of plastic because it is very durable, cheap and recyclable. Also, not all drills include an extra removable handle. The manufacturers included it to improve the safety of the user and bystanders. Aesthetically, the handle is very basic. It is black and has grooves in it to help provide the user with more grip and less slippage. The handle also bears the DeWALT name on it. The handles finish is shiny, smooth and has the grooves to provide more grip.

• Manufacturing Methods
  

The handle is produced using injection molding and drilling. Black plastic is forced into a mold producing the cylindrical shape and texture. It is then drilled through the center to produce a hole running the length of the handle. Evidence of the injection molding can be seen in the gate and runner marks on the side of the handle. Evidence of the drilling can be seen in the tooling marks on the inside of the handle. The choice to use a plastic allowed for a detailed texture to be manufactured on the handle. If this handle was made out of metal a lathe would be used to produce the cylindrical shape and then the texture would also be applied through turning. The handle would then be drilled out while still on the lathe. Plastic allows the part to be produced in fewer manufacturing processes.

• Component Complexity:
  

Level: 1

• One single manufacturing process is used. The single material used is plastic. The number of manufacturing processes used is the biggest factor in determining the components complexity. The number of materials used to create the component is also very important in determining the complexity of the component.

• Interaction Complexity:
  

Level: 1

• Human energy is imported onto the handle by the user to provide drill with more stability. The handle connects to the handle clamp and the handle clamp is attached to the drill.

4th Component: Handle Clamp

• Component Function
  

The predominant function of the handle clamp is to attach the handle to the drill. This in turn will give the user a place to hold onto the drill. Human energy flows from the user to the handle and through the clamp onto the drill which in turn provides extra stability to the drill. The handle clamp can be used in any practical environment. The user would not be able to operate a the hammer drill in an environment that would be hot enough to melt the metal the clamp is made of.

• Component Form
  

Handle Clamp

The clamp is primarily circular and has a cylindrical part that attaches to the handle. The circular part wraps around the drill and is clamped on. The handle clamp is three dimensional. The circular part is about 4 inches wide and the cylindrical part is about an inch wide. The clamp is made of a very durable, light and strong metal, aluminum. The clamp itself weighs about a half a pound. Metal was used to make the clamp as strong as it could be. Economically, the fact that it's made of metal makes it more expensive than if it was made of plastic. Also a global concern would be the availability of aluminum in the area where the clamp is being manufactured. Aesthetically, the clamp is not very appealing. The clamp is bright sliver in color. The handle clamp has a brushed aluminum finish. This is used instead of a shiny smooth finish so the clamp doesn't slip when its in use.

• Manufacturing Methods
  

The handle clamp is produced though casting and sand blasting. Molten aluminum is poured into a cast of the handle clamp and allowed to cool. The casting is then removed from the cast and sand blasted to produce the desired finish. Due to the intricate design of the handle clamp the only other reasonable way to produce this part would be to use CNC machining, this however would raise the cost of production.

• Component Complexity:
  

Level: 1

• One single manufacturing process is used. The single material used is aluminum. The number of manufacturing processes used is the biggest factor in determining the components complexity. The number of materials used to create the component is also very important in determining the complexity of the component.

• Interaction Complexity:
  

Level: 1

• The human energy flows from the handle, which is connected to the clamp. The clamp connects the handle to the drill providing extra stability.

5th Component: Chuck Assembly

• Component Function
  

The predominant function of the chuck assembly is to rotate the drill bit. The electrical energy imported into the system is converted to rotational energy in the armature which spins the gears and the gears spin the chuck. The drill bit is attached to the chuck. Also, using the chuck key, drill bits can be removed and replaced by other bits. This is done using human energy to turn the key inside the chuck. The chuck can operate in any environment that provides enough space for it to spin. Also the chuck can work in any practical environment. The user would not be using the drill in an environment hot enough to melt the metal it is made of.

• Component Form
  

Chuck Assembly

The chuck assembly is primarily cylindrical with a tip at the end. There is also a shaft inside which connects the chuck to the gear assembly. The chuck assembly is symmetrical along this shaft. It is a three dimensional part. the whole chuck assembly is about 4 inches long. The end opposite of the tip is about 3 inches in diameter and connects to the field casing. The tip of the drill is conical in shape. It is about a half inch in diameter and connects to another cylindrical piece that is an inch in diameter. The whole chuck assembly weighs 2 pounds. This is mainly due to the materials it is comprised of. The whole chuck assembly is made of steel except the part that connects to the field casing. The tip is made of stainless steel. Stainless steel was chosen for this part of the chuck assembly because it is going to come into contact with a variety of different surfaces that could potentially damage it. Globally, the chuck assembly could only be manufactured in a region where the steel is available to be mined. Economically, the chuck assembly adds a bit to the price tag due to the price of steel and the manufacturing processes it must go through to be shaped into the chuck assembly. The chuck assembly must however created with a high grade of precision due to the fact that it will be exposed on the outside of the drill and spinning at high speed. It must be safe for the user and bystanders to be around it. Aesthetically, the chuck assembly does not add much to the drill. The plastic part of the assembly that connects to the field casing is black and has a matte finish. The middle cylindrical part of the assembly is the color of steel and has a smooth grooved finish. The tip of the chuck assembly is made of stainless steel and has a shiny finish.

• Manufacturing Methods
  

Due to the many components of the chuck assembly several manufacturing methods have been used to produce all of its parts. The black gear housing is produced through injection molding. Evidence of this can be seen in the gate marks left on the inside of it. The Chuck is produced though turning, machining, broaching, vulcanizing and adhesion joining. Metal rod is cut to length and put in a lathe. The rod is then turned down to the desired diameter and the end of the barrel is cut at an angle to make a chamfer. Evidence of this can be seen in the tool markings left on the barrel of the chuck. After turning the end of the rod is drilled out while still on the lathe. The rod is then removed and placed on a drill press where the 3 key holes are drilled into the side of the barrel. The end of the barrel is given its edging with a broaching machine. The textured rubber grip around the barrel is produced through vulcanization and attached to the barrel with an adhesive such as an epoxy. Due to the chuck assemblies intricate design and several materials, different manufacturing methods were needed.

• Component Complexity:
  

Level: 2

• More than one manufacturing process is used. Three different materials are used: plastic, steel, stainless steel. The number of manufacturing processes used is the biggest factor in determining the components complexity. The number of materials used to create the component is also very important in determining the complexity of the component.

• Interaction Complexity:
  

Level: 2

• Rotational energy is imported from the gear assembly to the chuck assembly making the chuck spin and in turn making the drill bit spin. Human energy can be imported using the chuck key to remove drill bits.

6th Component: Armature

• Component Function
  

The predominant function of the armature is to convert magnetic energy from the field to mechanical rotational energy. The armature creates a magnetic field opposite to that of the field which results in the creation of rotational energy. The armature is essential to the flow of energy throughout the hammer drill. The flow of magnetic and rotational energy are present in the armature. Due to the heat energy released from the armature creating rotational energy, the armature operates in a very hot environment. The armature must remain on its axis. any movement could cause the armature to malfunction. Since the armature is housed inside the drill, it can be operated in any outside environment the rest of the drill can function in.

• Component Form
  

Armature

The Armature is primarily cylindrical in shape. It is 3 dimensional and is axially symmetric along along the shaft that connects it to other components. The Armature is quite large and takes up a lot of space inside the field casing. The main cylinder in the middle of the armature is made of steel. The copper wire on both sides of this cylinder sticks out as it is quite bright. At the left end of the armature is a large steel gear and a ceramic circular piece which connects to the field casing. The shape of the armature is impacted by the space it must fit in and its over all function to convert magnetic energy into rotational energy. The whole armature is about six inches in length. Also due to the materials used to create it, ceramic, copper and steel, it is quite heavy. The whole Armature weighs about two and a half pounds. The manufacturing processes definitely impacted the materials that would be used to craft it. Globally, the armature would have to be manufactured in a location where steel and copper were available. Also due to the materials it is made of, the armature adds quite a bit to the price of the drill. The armature must also be manufactured with a great deal of precision due to the fact that it must operate correctly to ensure the safety of the user and bystanders. The armature has no aesthetic purpose. It is housed inside the field casing of the drill. The armature is designed for functionality rather than aesthetics. The coloring of the armature is simply the natural colors of the materials from which it is made. The copper wires are not finished and neither is the steel. This prevents any extra and unnecessary cost.

• Manufacturing Methods
  

The armature has several different components and subsequently required several different manufacturing methods including metal casting, injection molding, turning, stamping, adhesion and annealing. The main shaft of the armature is produced through turning, reducing its diameter till desired diameter is reached. Metal plates are stamped out and adhered together using a high temperature resistant epoxy. Copper wire is then drawn to a desired thickness and put through an annealing process to reduce brittleness and increase the flexibility of the wire. This wire is then wrapped around the metal plates producing an electric motor armature. A plastic fan is then produced through injection molding and added to the end of the shaft of the armature to help maintain cool temperatures inside of motor. The armature assembly is then attached to the rear of the gear box housing. The gear box housing was produced through metal casting. Evidence of the metal casting can be seen in the rough edges left where the two dies came together.

• Component Complexity:
  

Level: 4

• 4 manufacturing processes are used. The materials used are steel, copper and ceramic. The number of manufacturing processes used is the biggest factor in determining the components complexity. The number of materials used to create the component is also very important in determining the complexity of the component.

• Interaction Complexity:
  

Level: 3

• The armature takes the magnetic energy in the field and converts it to rotational energy. This process is essential to the overall function of the drill.

7th Component: Gears Assembly

• Component Function
  

The main function of the gear assembly is to act as a gear reduction and from the armature to the chuck. It takes the rotational energy and changes it by decreasing the velocity and increasing the torque at the chuck. The gear assembly connects the armature to the chuck which in turn makes the chuck rotate. The gear assembly is housed inside the field casing. The gear assembly operates in a high speed and friction environment inside the casing because of the gear reduction process that is occurring. The gears are very tightly joined by their teeth.

• Component Form
  

Gear Assembly

The gear assembly is circular and contains 2 of differing diameters. The gear assembly is symmetrical along the axis of its length. It is three-dimensional along the entire portion of the component. The gears in this part of the gear assembly are shaped to interact with the other gears inside the drill. The gears in the gear assembly connect the armature to the chuck. There are 2 different gears on the shaft. The larger gear has a diameter of a half inch and has angular teeth. The smaller gear is a quarter inch thick and has normal straight teeth. All the gears are made of steel. Steel is very strong and not very expensive. The whole gear assembly weights about a quarter of a pound. Globally, the gears can only be produced in an area where steel is readily available. Environmentally, steel becomes a big concern because it takes a long time to decompose in the environment. However, steel gears are very durable and can be reliably used for years. Since the gear assembly is housed on the inside of the drill, aesthetics was not really considered. The gears are dark gray, the color of steel. There is no reason to put any finish on to them since they are inside the drill. Any paint or finish may interfere with the gears function.

• Manufacturing Methods
  

The gear assembly consists of two gears and a shaft. The cylindrical shape of the gears is formed through cold forging. This technique is often chosen because it strengthens the material by aligning it on a molecular level. The teeth of the gears are then machined out by using a broaching machine. Evidence of this can be seen in the tool marking left behind on the inside wall of each gear tooth. Finally the gears are drilled out though the middle to create a hole for the shaft. The shaft is produce through turning and cut to length on a metal lathe. The ends of the shaft are then drilled out while still on the lathe to produce a pocket to hold the ball bearing. Tooling marks are left on the shaft but it also has produced a semi smooth finish. The gears are then forced onto the shaft by using a press. The gears are the most critical part of the drill. They are going to be put through a lot of stress and need to be durable. The cold forging produces a strong metal resistant to wear.

• Component Complexity:
  

Level: 2

• Three manufacturing processes used. One material used, steel. The number of manufacturing processes used is the biggest factor in determining the components complexity. The number of materials used to create the component is also very important in determining the complexity of the component.

• Interaction Complexity:
  

Level: 2

• Rotational energy is imported from the armature and transferred through the gears to the chuck assembly.

Solid Modeled Assembly

• For our solid modeled components and assembly, we decided it would be best to show the interactions between the shafts and gears which allow for the product to work correctly. The assembly we formed consists of the motor shaft, the helical gear, the gear shaft, and it's ball bearing, the shaft gear, the chuck gear, the chuck shaft, and it's ball bearing. The ball bearings are what lie in between the connections of the shafts to the drill base and chuck base. Since the motor powers the drill, it was important to show the motor shaft interacting with the gear assembly. The gear assembly connects to the chuck shaft and therefore the drill bit. The motor shaft extends underneath the helical gear on the gear shaft, which also has a shaft gear on the other end. This shaft gear connects to the chuck gear above it which is held in place by the chuck shaft extending to the drill bit. The overall rotational motion in the drill bit is transferred from the motor through the shaft and gear components thus our reasoning to reveal this assembly; it is the most bare-bone assembly which allows for the hammer drill to function.

• In order to draw up the described assembly in a 3D program, we chose to use Creo Parametric as our CAD package. This was a result of one of our members having previous experience with this program. This member is currently taking a course which requires assignments done in Creo Parametric so due to their familiarity with it, Creo (Pro/ENGINEER) was chosen.

Individual Part Drawings

Individual Part Drawings

Assembly Drawings

Assembly Drawings

Engineering Analysis

We selected the gear system for analysis, because it is an important mechanism that plays a major role in the function of this drill. Its purpose is to transfer the rotational energy of the motor to the rotational energy of the chuck/bit, by changing the RPM. In the original design process, engineers had to design a sufficient and efficient gear train to produce a desired drill bit RPM, from a given motor RPM. While disassembling and playing around with the parts, we rotated the drill chuck to see the relationship between the output and input RPM's. We discovered that the chuck actually rotates much slower than the motor shaft, and therefore expected the following calculations to agree with this observation. The designers most likely would have created an analysis similar to the following.

Problem Statement

• Given the speed of the motor (in revolutions per minute) and the sizes of gears, determine the final output speed (in RPM) of the drill bit.

Diagram of the System

n = number of teeth on gear

Assumptions

• 100% efficiency, no speed lost by friction
• Constant rotational velocity (neglecting accelerations to simplify calculations)
• Drill bit/chuck rotate at same velocity as final gear
• The first gear has the same rotational velocity as the motor
• Motor is running at full power
• Neglect the resistance force on drill bit from different drilled surfaces
• Gear teeth mesh perfectly (neglecting any speed loss from gaps between gears)
• (For the calculations): neglect direction of shaft/gear rotation
• Input speed from motor is 30,530 RPM
• Motor shaft and Gear #1 have same RPM
• Gear #2 and Gear #3 have same RPM
• Gear #3 and drill bit have same RPM

Governing Equations

• (w2)/(w1) = (n1)/(n2)
• Overall Gear Ratio = (Output Rate)/(Input Rate)

Calculations

(w = rotational speed; n = number of teeth on gear)

• Determine RPM of Gear #2

(w2)/(w1) = (n1)/(n2)

(w2)/(30,530 RPM) = (5 teeth)/(31 teeth)

w2 = 4924 RPM

• Determine RPM of Gear #4

w2 = w3 = 4924 RPM

(w4)/(w3) = (n3)/(n4)

(w4)/(4924) = (17)/(31)

w4 = 2700 RPM = Output Speed

• Determine overall gear ratio

Overall Gear Ratio = (Output Rate)/(Input Rate)

Overall Gear Ratio = (2700 RPM)/(30,530 RPM)

Overall Gear Ratio = 0.088

Solution Check

• All units correctly carried through
• Assumptions were appropriate and reasonable
• Resulting answer seems quite logical
• No errors were made in our calculations

Interpretation/Discussion

• The typical drill bit speed of a hammerdrill ranges from 1100 to 3000 RPM (http://www.ehow.com/facts_7707316_can-drills-used-regular-drilling.html). Our calculated output speed came to 2700 RPM, which is an acceptable value according to the given range of average values mentioned at ehow.com. We also discovered that the overall Gear Ratio is 0.088, which makes sense because we knew through intuition that the design of gear teeth ratios in this gear train would step down the motor RPM to a much lower drill bit RPM. If we calculated a much lower RPM, such as under 100, we could conclude the gear system to be unbeneficial. Such low RPM's could be achieved by basic human-powered hand tools. A much higher RPM such as 10,000 would be too much, lowering the control the user has over the drilling process. Listed below are the effects we would see if certain assumptions weren't made:

-If the drill bit/chuck did not rotate at the same speed as Gear #4, then we could not conclude the final output speed

-If the gear teeth did not mesh perfectly, then some speed would be lost, lowering the final output speed

-If we didn't ignore resistance forces, the calculations would have been much more complex, and would have lowered the final output speed

-If the motor wasn't running at full power, then the output speed would be much lower

For the sake of our calculations however, all the assumptions were very reasonable, and therefore allowed us to successfully produce a logical answer.

Design Revisions

Throughout the dissection and analysis of our hammer drill, we have decided to recommend these design revisions which would improve all aspects of the drill.

A cordless hammerdrill

• Revision 1:

Remove cord

Removing the electrical cord and replacing it with a lithium ion battery would make the drill much more convenient for the user. Also, making the hammer drill cordless makes it much safer to operate. It eliminates the risk of the user or bystanders tripping over the electrical wire. Also, by making the drill cordless, the user unbounded as far as where they can operate the drill. The user wouldn't have to be within a few feet of an electrical outlet. Economically, cordless drills on average cost 40-50 dollars more than corded drills. The concern that cordless drills output less power than corded drills wouldn't be a concern to everyone. Many consumers may find the convenience of the drill being cordless to outweigh the power loss.

A hammerdrill with an LED

• Revision 2:

Add LED Light

Adding an LED light to the hammer drill would make the drill much more convenient to use. It would give the user the ability to operate the drill in an environment with little or no lighting. Also it would increase the precision of the drill by being able to see exactly what your drilling, which would in turn increase the users safety. Economically, adding an LED light would not add much to the overall price of the drill. LED's are very cheap.

Current handle without knuckle guard

• Revision 3:

Add Knuckle Guard

Adding a knuckle guard to the removable handle that clamps to the drill would significantly increase the safety of the user. While the user is operating the hammer drill, shard of debris may be shot up toward the drill and the user. Adding the guard would protect the users hand on the handle while they are operating the drill. In order to address economic concerns, the guard would be made of plastic so it would be cheap and easily made. Also, since it is made of plastic, it can be recycled at the end of the drills life cycle.

Current system for storing chuck key

• Revision 4:

Add Internal Chuck Key Storage

Adding a slot on the bottom or top back of the drill where the user could store the chuck key would be much more convenient than the current system for chuck key storage. Currently, the chuck key is attached to the drill with the rubber key holder. This is a huge design flaw. Not only is the key dangling off the side of the drill annoying to the user, it is unsafe. The chuck key would be designed to slide into the drill and lock in until the user decided they needed it. This would eliminate the need for the rubber key holder and reduce the price of the drill. Also, if the user decided they didn't want to hang the key on with the rubber holder, they may remove it and accidentally lose it causing them to have to pay to replace it. Having convenient storage for the key would eliminate this from happening.