Bike lock

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Revision as of 07:52, 3 February 2014

Left: Serfas Puck Lock  Right: OnGuard U-Lock
Left: Serfas Puck Lock Right: OnGuard U-Lock

Contents

Executive Summary

Product Stakeholder Analysis

Product Usage Study

U-Lock

First, the user will place their bike next to a locking structure. The user will unlock the U-Lock, place the U around the locking structure and the bike frame, then they will return the base to the U-Bar and remove the key. The bike frame is now secured to the locking structure.

Place bike next to locking structure
Place bike next to locking structure
Unlock base from U-Bar with key
Unlock base from U-Bar with key
Place U-Bar around locking structure and bike frame
Place U-Bar around locking structure and bike frame
Attach base to U-Bar and turn the key to secure the lock
Attach base to U-Bar and turn the key to secure the lock

Possible User Issues

Lock can only secure one part of the bike, most commonly the frame. The wheels are still unprotected with this. This constraint is due to the geometry of the U-Bar. It must be small enough to not be a burden to carry around, but must also be large enough to easily fit around most structures and the bike frame. Some users do not use the included clamp, as it may not fit around every bike. They must find some other method of securing the lock to the bike. It sometimes can be difficult to get the notches in the U-Bar to line up properly with the locking bars. If they are misaligned, the key will not turn back, causing frustration.

Puck Lock

First, the user will place their bike next to a locking structure. The user will then unravel the chain around the puck lock. User will wrap the chain around the locking structure and as many parts of the bike as possible. (eg. frame and wheel) The user will then resecure the chain to the central lock cylinder and lock the lock.


Use key to unlock the tubular tumbler lock and disengage the locking pin.
Use key to unlock the tubular tumbler lock and disengage the locking pin.
Free the end of the last link from this plastic retainer and unravel the lock.
Free the end of the last link from this plastic retainer and unravel the lock.
Secure the last link to the main cylinder and depress the pin to lock
Secure the last link to the main cylinder and depress the pin to lock

Possible User Issues

Small chain makes it hard to connect multiple bike components. May leave some parts unsecured. The links can rotate around each other in the wrong way, which makes it difficult to wrap the lock. The long chain, when fully extended, can act as a lever arm and bend the links.


Product Function Study

U Lock

Two bars are moved into place while the key is in the locked position, as indicated by the arrows in the image below. These bars are attached to small nubs on top of the lock assembly. When the key is turned, these nubs turn, which translates to the bars sliding. Only the correct key will match up with the pins in the correct location in order to move the bolts. This locking assembly runs through the center of the base. These bars fit into the notches indicated out in the below figure. Two bars adds a layer of redundancy and makes the lock less prone to being broken compared to single bolt U-Locks.

U-Bar notches
U-Bar notches
Locked and Unlocked
Locked and Unlocked

Puck Lock

This lock consists of a central housing with tubular tumbler locking mechanism and a series of plastic covered metal linkages. The linkage chain stays coiled around the center cylinder of the lock via a plastic retainer at the bottom of the lock, keeping the chain securely and neatly stowed when not in use. This plastic retainer on the bottom of the housing has a circular bump that fits into the free end of the last link holding it tightly in place until the clip is depressed. This releases the chain end allowing it to be unraveled from the center cylinder. Once fully unraveled, the main lock pin can be disengaged via the tubular tumbler lock mechanism located in the center of the housing. The key is used to open the tumbler lock and disengage a pin that runs through the center of the lock housing allowing the free end of the chain to be inserted into a slot at the bottom of the housing. The pin can then be depressed fitting into the open joint on the free end of the last link thereby locking the whole system. The pinned together metal plates act as the chain while the housing functions both as the storage device and lock for the system. To unlock the mechanism, the key is once again used to unlock the central pin freeing the chain to be unraveled from the bike and rewound around the central cylinder where it can be neatly stored until its next use.

Bill of Materials

U-Lock

Exploded View of U-Lock
Exploded View of U-Lock


The following table contains information about each part labled in the above image.

Part # Name Quantity Subassembly Mass [g] Function Material Manufacturing Process Image
1 Rubber Shielding 1 N/A 68 Provides weatherproofing for the U-Bar. It keeps dirt and grime out and prevents scratches. In comparison to the U-Bar it is plush and nice to the touch. Rubber Extrusion
2 U-Bar 1 N/A 330 Can be placed around the chosen locking surface and the bike frame. This is then inserted into the base of the U-Lock and secures the bike to the locking surface. Steel Extruded, Bent, Cut
3 U-Bar Clamp Attachment 1 Bike Frame Clamp 15 Provides nice mating surface for U-Bar and bike frame bracket. Plastic Injection Molding
4 Frame Attachment Screws and Nuts 4 Bike Frame Clamp 1 Screws and nuts used to press clamp edges together around the U-Bar. Steel Off the Shelf
5 U-Bar Frame Attachment Clasp 1 Bike Frame Clamp 13 Nicely holds onto the U-Bar and connects to a base piece that can be attached to a bike frame. Plastic Injection Molding
6 U-Bar Frame Attachment Locking Tab 1 Bike Frame Clamp 4 Tab presses over edge of Clamp attachment on the U-Bar to secure it to the bike frame. Plastic Injection Molding
7 U-Bar Frame Attachment Spring 1 Bike Frame Clamp <1 Spring sits under clasp and provides force on clasp to keep Lock attached to frame attachment. Steel Off the SHelf
8 Frame Attachment Joining Screw 1 Bike Frame Clamp <1 Fastens the two major parts of the frame bracket together Steel Off the Shelf
9 Frame Bracket Base 1 Bike Frame Clamp 17 Holds clasp. Has specific points of rotation so one can change the orientation of the clasp as it connects to the bike. Represents half of the frame bracket clamp. Plastic Injection Molding
10 Mating Pad 2 Bike Frame Clamp 2 Snap in part is smooth and offers a nice mating surface between the clamp and the bike frame (Not Pictured), and the U-Lock and clamp. Plastic Injection Molding
11 Bike Frame Bracket Clamp 1 Bike Frame Clamp 18 Part is placed around bike frame and fastened to the rest of the bracket via screws. Second half of frame bracket clamp. Plastic Injection Molding
12 Locking Bars 2 Locking Mechanism 26 Bars fit into notches cut into the U-Bar. When they are in place they secure the U-Bar in place and prevent its removal. The hooks on either edge sit on nubs that rotate when the key is turned, sliding the locking bars back and forth. Typically coating is used on parts that slide around. Steel Forged and Coated with Titanium Nitrate
13 Lock Component Housing Cylinder 1 Lock Mechanism 28 Neatly holds all the parts necessary to actually lock the lock. It has slots cut such that one cannot insert the lock upside down, tracks for the lock bars to slide on, and is designed such that all force imparted to the lock in an attempt to shock it open are directed around the lock bars. Plastic Injection Molding
14 Lock Housing 1 Lock Mechanism 15 Housing is made to nicely keep the lock in place inside of the component housing cylinder. It has a tab to prevent incorrect insertion of lock. Brass Off the Shelf
15 Rubber Grommet 2 N/A <1 Acts as both a seal to prevent dirt or water from entering the lock component housing cylinder, as well as a cushion to protect the cylinder from rubbing directly against the U-Bar Rubber Stamping
16 Lock Stopper Pin 2 Lock Mechanism <1 Grooves in the lock housing fit around these spring loaded pins. When the key is concerned, These pins are compressed and allow the lock to turn. Brass Stamping
17 Pin Housing 1 Lock Mechanism 8 Housing has space for spring and pins as well as the stopper pins and springs. Has a slot for a key to be inserted. Pin Housing will rotate around inside the lock housing. Brass Off the Shelf
18 Pin Springs 12 Lock Mechanism <1 Pins sit on top of these springs. When the key is inserted and turned, these springs will compress or extend to get all the pins to the same height so the pin housing can rotate. They will return to their natural length after the key is removed. Steel Off the Shelf
19 Pins 8 Lock Mechanism <1 These pins are each individually made with notches at a different height. The height of the notch corresponds to the pattern on the key. The correct key will line up with the notches, allowing the pins to be moved out of the way, allowing the pin housing. Brass Off the Shelf
20 Plastic Endcap 2 N\A 13 Acts as a weatherproofing seal for the outer casing of the lock base. It also seals off the ends of the lock base via a tight fit, discouraging the user from tampering with the internals of the lock. Adds a stylistic element to the lock. Soft Plastic Molding
21 Rubber Shock Absorber 2 N\A 4 Part acts as a weatherproofing seal as well as a shock absorber. Cushions any force that is applied to the ends of the lock. This prevents the lock from being bumped open. Rubber Stamping
22 Lock Bar Actuator 1 Lock Mechanism 3 Slides into grove on back of pin housing. When pin housing rotates, this part rotates as well. The Lock Bars are attached to the nubs on top and turning the pin housing causes the lock bars to slide from unlocked to locked. Brass Off the Shelf
23 Outer Housing 1 Lock Housing 127 A powder coated outer case that neatly houses the entire lock assembly. Has holes in it to accomodate the U-Bar ans well as a small hole in it, presumably for assembly alignment purposes. Coating adds plesant feel in comparison to unfinished steel. Steel Stamping and Welding
24 Key 5 N\A 6 Key is specially made to line up with each of the pins in a specific lock. The track pulls the pins into the correct position, which allows the lock to rotate. Steel and Plastic Row 1, column 8

Puck Lock

Exploded View of Puck Lock
Exploded View of Puck Lock
Frame Clamp
Frame Clamp

The following table contains information about each part labled in the above image.

Part # Name Quantity Subassembly Mass Function Material Manufacturing Process Image
1 Chain Link 14 Chain 20 Multiple links connected by pins allow for folding and extending of chain. Chain can be put around a locking structure and the bike frame in order to secure the bike to that structure. Steel Stamping
2 Protective Plastic Cover 14 Chain <1 Provides weatherproofing for the links to reduce the likelihood of rust for each chain link. Plastic Injection Molding in 2 halves
3 Pins and Washers 13 Chain 3 Connects chain links. Allows for smooth rotation of the links about the axis of the pin. Steel Off the Shelf
4 Outer Plastic Cover 2 N\A 5 Covers outside of lock. Provides weatherproofing for the inner lock components. Provides a nice surface to the touch in comparison to the metal underneath. Plastic Two halves injection molded
5 Upper Lock Housing 1 Lock Housing 68 Provides a place for the chain to lock to the lock body in a compact manner. This part is powder coated to prevent rust and wear. It protects the inner lock mechanisms from the elements. Steel Injection Molding
6 Lock Actuator 1 Lock Housing 8 Spans the lock cylinder and holds everything together. This part is moved when the key is turned. Steel Off the Shelf
7 Lock Housing 1 Lock Housing 11 Holds the two parts of the lock in a nice case. Its hard to break into, to prevent tampering. Steel Off the Self
8 Pins 8 Lock Housing <1 Pins slide into the second pin housing. When they intersect the second pin housing, its impossible to rotate the pin housings. This is how the lock locks. Brass Off the Shelf
9 Upper Pin Housing 1 Lock Housing 4 Second part of pin housing. Does not rotate. When the pins are extended into this piece, the housing cannot rotate. Steel Injection Molding
10 Roll Pin 2 Lock Housing <1 Pins hold the two sides of the Metal lock housing together. These are very difficult to remove without advanced tools to prevent tampering. Steel Off the Shelf
11 Lower Pin Housing 1 Lock Housing 11 Houses the pins and contains keyhole for the locking mechanism. When the pins are extended, they intersect the second part of the housing and prevent the housing from rotating. Steel Off the Shelf
12 Lower Lock Housing 1 Lock Housing 64 Secures the lock parts and prevents tampering. Steel Injection Molding
13 Lower Outer Plastic Cover 1 N\A 7 Provides weatherproofing and a nice surface to the touch for the lock Plastic Injection Molded
14 Worm Gear 2 Bike Frame Attachment 7 Gears move the ridged straps tighten around the bike frame. Locks the straps in place. Plastic Injection Molded
15 Bike Attachment Strap 1 Bike Frame Attachment 7 Wraps around the bike and lets you store the lock on the bike Plastic Injection Molded

DFMA

U-Lock

Design for Manufacture Guidelines
Design Objective Comments
Minimize Part Count Strengths:
  • Most parts fit together without the use of fasteners

Weaknesses:

  • The U-bar clamp assembly is not needed for the U-Lock to function properly as a bike lock and it is unnecessary if the attachment assembly is not used to attach the U-Lock to the bike
Standardize Components Weaknesses:
  • Most of the plastic components are unique and require separate molds
Commonize Product Line Strengths:
  • All of the plastic parts are manufactured through injection molding, minimizing job training
Standardize Design Features Weaknesses:
  • Plastic components are unique and would each require their own molds
Keep Designs Simple Strengths:
  • Design is composed of two main parts: the locking assembly and the U-bar assembly

Weaknesses:

  • Attachment assembly, which increases the complexity, is not necessary for the U-Lock to function as a lock
Multifunctional Parts Strengths:
  • Outer metal casing acts as housing, weatherproofing, and protection for the locking assembly
Ease of Fabrication Strengths:
  • Components are mainly comprised of plastic and steel
Avoid Tight Tolerances Strengths:
  • Tolerances are not too tight because there is some slop between the U-bar and the locking mechanism

Weaknesses:

  • If tolerances are too tight, the U-bar/locking assemblies do not fit together rendering the lock useless
  • Snap and slip fit components require tighter tolerances
Minimize Secondary and Finishing Operations Strengths:
  • Injection molded plastic parts do not require any secondary operations

Weaknesses:

  • Locking bars are coated with Titanium Nitrate after being forged
Take Advantage of Special Process Properties Strengths:
  • Plastic components are colored during the injection molding process


Design for Assembly Guidelines
Design Objective Comments
Minimize Part Count Strengths:
  • A heavy reliance on press fit minimizes the number of fasteners used

Weaknesses:

  • Fairly complicated mounting mechanism has multiple parts to add additional functionality
  • Multiple unique parts are not paired with sub assemblies, requiring additional steps for final assemblies
Minimize Assembly Surfaces Strengths:
  • Main lock and latch sub assemblies are assembled from one direction, main assembly can be easily assembled with minimal reorientation of the assembled parts
Use Sub Assemblies Strengths:
  • The most complex assembly steps are offloaded to sub assemblies that allow for greater visibility and access before being placed into the final assembly

Weaknesses:

  • Multiple unique parts are not paired with sub assemblies, require additional steps for final assemblies
Mistake-Proof Strengths:
  • Single orientation for proper lock tube sub assembly into the housing and additional holes and features to check for and secure it in its proper orientation
  • Symmetric bar design allows for functioning in multiple orientations

Weaknesses:

  • Lock sub assembly can be inserted incorrectly and with adequate force, can be damaged during insertion or removal
Minimize Fasteners Strengths:
  • No fasteners are used for the lock itself and a minimal number of screws are used for the holder assembly

Weaknesses:

  • Extensive use of pins and press fits are used to securely hold the lock together
Minimize Handling Strengths:
  • Lock assembly and part attachment can be done sequentially from either side to minimize lock motion during assembly

Weaknesses:

  • Many pieces need to be supplied disassembled to be used properly by the end user
Minimize Assembly Direction Strengths:
  • Most of the lock can be assembled from either end and sequentially, requiring no repositioning to the finished assembly

Weaknesses:

  • Insertion of the U-bar into the lock for packaging and shipping may require additional manufacturing considerations of orientation of the lock during assembly and positioning of various assembly equipment
Provide Unobstructed Access Strengths:
  • By assembling the lock and latch mechanism on the inner plastic frame, more access is allowed when necessary

Weaknesses:

  • After the final assembly is completed, parts are hidden away to protect against unwanted access and environmental damage
Maximize Assembly Compliance Strengths:
  • U-bar has tapered ends and rounded edges on its grooves to allow for easier insertion into the lock and easier locking during operation

Weaknesses:

  • Lock housing and plastic frame have minimal features to aid in the combination of the two sub assemblies

Puck Lock

Design for Manufacture Guidelines
Design Objective Comments
Minimize Part Count Strengths:
  • There are very few unique parts in the total assembly

Weaknesses:

  • There are fasteners and spacers between every link
  • There are a lot of custom links, not a standard chain or cable
Standardize Components Strengths:
  • Uses a standard roll pin size to hold the main housing together

Weaknesses:

  • Contains highly specialized lock body components
  • Internal locking mechanism requires special production techniques and tooling
Commonize Product Line Strengths:
  • Parts have features that prevents it from being assembled incorrectly which eliminates specialized training

Weaknesses:

  • The complex shape of the housing may require additional complex steps to produce essential features
Standardize Design Features Strengths:
  • Many parts used in the design are repeated in the same dimensions (chain links, chain pins, chain spacers)
Keep Designs Simple Strengths:
  • Repeated chain features and multiples of components within the lock are repeated

Weaknesses:

  • Complicated molds for multifunctional parts may result in higher initial production costs
Multifunctional Parts Strengths:
  • The outer casing acts as protection for the locking assembly, storage for the chain, and housing for the locking mechanism
  • Multiple parts have sub assemblies have multiple functions within the overall design
Ease of Fabrication Strengths:
  • The chain links are stamped

Weaknesses:

  • Highly complex lock housing may be difficult to fabricate due to its high strength requirements and complex overall shape
Avoid Tight Tolerances Strengths:
  • Spacers on the chain links help stiffen lateral motions in the chain, allowing for much looser tolerances when attaching the links

Weaknesses:

  • A lot of press fit components in the lock requires tighter tolerances and additional features to simplify assembly
Minimize Secondary and Finishing Operations Weaknesses:
  • Multiple parts require coatings, insertion into plastic parts, or complex secondary operations
Take Advantage of Special Process Properties Strengths:
  • Powder coating for coloring metals
  • Coloring added during injection molding for plastics
  • Metal inserts are used in injection molded parts


Design for Assembly Guidelines
Design Objective Comments
Minimize Part Count Strengths:
  • Complex housing shapes and interlocking pieces allow for very few fasteners holding the lock housing together

Weaknesses:

  • Redundant worms gears in the bike attachment may function better and reduce overall part cost if replaces with a ratcheting feature in the mount itself
Minimize Assembly Surfaces Strengths:
  • Most of the lock sub assemblies can be sequentially placed from one direction into the final assembly

Weaknesses:

  • Permanent fasteners and individual sub assemblies require multiple directions and side operations for assembly or permanent attachment to the final assembly
Use Sub Assemblies Strengths:
  • Much of the lock can be broken down into a number of sub assemblies that are stacked upon each other for final assembly
  • The chain links are a repeated four piece pattern for easier wrapping about the final lock body
Mistake-Proof Strengths:
  • Many parts, including the lock, have features the prevent assembly in an incorrect orientation

Weaknesses;

  • Not following the proper pattern for the chain links will prevent the lock from being wrapped around the central housing
Minimize Fasteners Strengths:
  • Simple roll pins, a number of snap fit components, and a heavy reliance on press fit components are used to reduce the number of fasteners
  • A number of bumps and depressible plastic extensions are used to fix removable parts in place
Minimize Handling Strengths:
  • Multiple tongue and groove features are used to easily align the lock pieces and sub assemblies

Weaknesses:

  • Additional tooling is necessary to line up the individual chain links for pinning and swaging operations
Minimize Assembly Direction Strengths:
  • Most sub assemblies can be placed into the final assembly from the top allowing for a base to top assembling method

Weaknesses:

  • Some steps in assembling sub assemblies require operations to occur on multiple sides of the sub assemblies and may require operations on multiple sides of a part
Provide Unobstructed Access Strengths:
  • Initial assembly allows for ease of access to features for alignment and attachment, as well as easy access to attachment points such as the two roll pin holes on the side of the housing

Weaknesses:

  • After final assembly the lock is very difficult/near impossible to disassemble or service in a non-destructive fashion
Maximize Assembly Compliance Strengths:
  • Tapered interfaces on the plastic top and bottom covers allow for easier alignment
  • Rounded edges on the casted housing allow for less accuracy when inserting the lock sub assembly and assembling the two lock housing halves

FMEA

Rating for Severity of Failure
Rating Severity Description
1 The effect is not noticed by the customer.
2 Very slight effect noticed by customer; does not annoy or inconvenience customer.
3 Slight effect that causes customers annoyance, but they do not seek service.
4 Slight effect, customer may return product for service.
5 Moderate effect, customer requires immediate service.
6 Significant effect, causes customer dissatisfaction; may violate a regulation or design code.
7 Major effect, system may not be operable; elicits customer complaint; may cause injury.
8 Extreme effect, system is inoperable and a safety problem. May cause severe injury.
9 Critical effect, complete system shutdown; safety risk.
10 Hazardous; failure occurs without warning; life-threatening.
Source: Dieter and Schmidt, Engineering Design


Rating for Occurrence of Failure
Rating Approximate Probability of Failure Description of Occurrence
1 <0.000001 Extremely remote.
2 0.00001 Remote, very unlikely.
3 0.00001 Very slight chance of occurrence.
4 0.0004 Slight chance of occurrence.
5 0.002 Occasional occurrence.
6 0.01 Moderate occurrence.
7 0.04 Frequent occurrence.
8 0.2 High occurrence.
9 0.33 Very high occurrence.
10 >0.5 Extremely high occurrence.
Source: Dieter and Schmidt, Engineering Design


Rating for Detection of Failure
Rating Description of Detection
1 Almost certain to detect.
2 Very high chance of detection.
3 High chance of detection.
4 Moderately high chance of detection.
5 Medium chance of detection.
6 Low chance of detection.
7 Slight chance of detection.
8 Remote chance of detection.
9 Very remote chance of detection.
10 No chance of detection; no inspection.
Source: Dieter and Schmidt, Engineering Design


U-Lock

Failure Mode and Effects Analysis
Item Function Failure Mode Effects of Failure S Causes of Failure O Design Controls D RPN Recommended Actions
Key
  • unlocking and locking U-Lock
  • deformation and/or breaking due to bending stress and/or torsional shear stress
  • can no longer unlock or lock bike
  • need to replace key
6
  • improper use
2
  • multiple keys provided
1 12 None
Lock Mechanism
  • takes input from key and engages or disengages the lock
  • lock mechanism gets jammed or becomes difficult to turn
  • unlocking and locking bike is more difficult
5
  • dirt and grim get into the lock mechanism via keyhole or connection to U-Bar
  • water gets into mechanism and causes corrosion
4
  • system is well sealed against environment with exception of keyhole
  • aside from housing, lock system is composed of brass, plastic, and titanium nitride coated steel, which all resist rust
3 60
  • incorporate a plastic/rubber cover for keyhole
U-Bar
  • connects bike to locking structure
  • bending
  • can no longer use lock
7
  • impact/improper use
2 None 1 14
  • use a stronger material
Lock Housing
  • contains all the elements for the lock mechanism and creates a closed loop with the U-Bar
  • metal pipe housing corrodes
  • difficulty using lock since moving components could be affected by corrosion
3
  • excess water getting into lock housing due to rain or other reasons
4
  • coating on outer surface helps prevent corrosion
  • system is well sealed with exception of keyhole
5 60
  • incorporate a plastic/rubber cover for keyhole
  • metal pipe housing cracks
  • security of lock compromised
  • can no longer use lock
8
  • cold temperatures during winter months cause the metal to become more brittle and impacts could cause cracking
1 None 8 64
  • incorporate an insulated covering for lock housing
Bike Frame Clamp
  • carries lock on bike when lock not in use
  • plastic components crack
  • attachment clip can no longer be used
  • bike lock could come loose during riding and cause injury to the rider and/or bike
7
  • impact/improper use
3 None 8 168
  • look at other attachment options that use softer plastics
  • screws come loose
  • attachment clip can no longer be used
  • bike lock could come loose during riding and cause injury to the rider and/or bike
7
  • wear over time causing threads to get stripped
4
  • initial check to make sure all screws and corresponding components work
5 140
  • use self-locking nuts to secure the screws


Puck Lock

Failure Mode and Effects Analysis
Item Function Failure Mode Effects of Failure S Causes of Failure O Design Controls D RPN Recommended Actions
Key
  • unlocking and locking U-Lock
  • deformation and/or breaking due to bending stress and/or torsional shear stress
  • can no longer unlock or lock bike
  • need to replace key
6
  • improper use
2
  • multiple keys provided
  • key is for a tubular lock, so the shape is more resistant to bending and torsion
1 12 None
Lock Mechanism
  • takes input from key and engages or disengages the lock
  • lock mechanism gets jammed or becomes difficult to turn
  • unlocking and locking bike is more difficult
5
  • dirt and grim get into the lock mechanism via keyhole
  • water gets into mechanism and causes corrosion
4
  • lock mechanism is made of stainless steel and resists corrosion
3 60
  • incorporate a plastic/rubber cover for keyhole
Chain
  • wraps around locking structure and bike to secure the bike
  • bending
  • chain can no longer be wrapped up for storage
4
  • improper use
2 None 1 8
  • use a stronger material
Lower Outer Plastic Cover
  • for aesthetics
  • has a "retaining" bump that holds the chain in place when it is wrapped around the lock housing for storage
  • entire component or part of component snaps off
  • not as aesthetically pleasing
  • chain can no longer be wrapped up for storage
4
  • impact/improper use
4 None 1 16
  • lock should come with replacement parts
  • "retaining" bump wears down
  • not as aesthetically pleasing
  • chain can no longer be wrapped up for storage
4
  • wear/fatigue over time
4 None 3 48
  • lock should come with replacement parts
  • locking mechanism should also be used to lock the chain in place when it is stored instead of using a "retaining" bump
Outer Plastic Cover
  • for aesthetics
  • entire component or part of component snaps off
  • not as aesthetically pleasing
3
  • impact/improper use
4 None 1 12
  • lock should come with replacement parts
Lock Housing
  • contains all the elements for the lock mechanism and creates a closed loop with the free end of the Chain
  • corrosion
  • difficulty using lock since moving components could be affected by corrosion
3
  • excess water getting into lock housing due to rain or other reasons
2
  • coating on outer surface helps prevent corrosion
  • material is stainless steel, which resists corrosion
5 30
  • incorporate a plastic/rubber cover for keyhole
  • cracks/fractures
  • security of lock compromised
  • can no longer use lock
8
  • cold temperatures during winter months cause the metal to become more brittle and impacts could cause cracking
1 None 8 64
  • incorporate an insulated covering for lock housing
Bike Frame Attachment
  • carries lock on bike when lock not in use
  • worm gears securing attachment to bike come loose
  • bike lock could come loose during riding and fall off causing injury to the rider and/or bike
7
  • plastic worm gears and grooves experience wear since system is relying upon tension to hold everything in place
4 None 5 140
  • employ screws and self-locking nuts to secure the Bike Frame Attachment to the bike

DFE

This product has very minimal GHC emissions already due to the lack of energy or material consumption during product use. The primary contributer during the manufacturing to this is the production of steel followed closely by the energy consumption during manufacturing. While these are hard to reduce, considering lower energy machining processes or considering replacing some or all of the steel within the product with recycled aluminum could likely further lower the GHC emissions associated with product production.

A $30 CO2 tax would only effect product price by approximately 58 cents, a fairly insignificant cost change and would therefore be unlikely to effect product sales.

The one downside to these estimates is that they are not the most accurate representation of a bike lock manufacturing. While bike locks are similar in composition to the primary industries represented by Hardware Manufacturing, they are not one of the main representations within the category, dominated by furniture, builders' and motor vehicle hardware. Locks are represented in the second and third of those categories, but not specifically bike locks.


Bike Lock Production
Best Match economic sector number 332500: Hardware Manufacturing
Reference Unit 1 unit
Units consumed per product life 1 unit
Cost per unit (2002 $) $30.89
Lifetime Cost $30.89
Economy-Wide mtCO2e Released per $1M of Output 640
Implied mtCO2 per Product Life $0.0197696
CO2 tax @ $30/mtCO2e $0.593088


Image:mtCO2eGraph.png

Group

Team Leader and FMEA Lead - Jeremy Jiang

Bill of Materials - Ryan Chang

DFMA Leads - Rachel Chow and Alex Munoz

DFE Lead - Melissa Mann

Sources

Carnegie Mellon University Green Design Institute. (2014) Economic Input-Output Life Cycle Assessment (EIO-LCA) US 2002 (428 sectors) Producer model [Internet], Available from: <http://www.eiolca.net/> [Accessed 2 Feb, 2014]


Bureau of Labor Statistics. Inflation Calculator [Internet], Available from:<http://http://www.bls.gov/data/inflation_calculator.htm> Accessed 2 February, 2014.

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