Automatic Two-Speed, Fixed-Drive Hub-

A Baccalaureate thesis submitted to the Department of Mechanical and Materials Engineering College of Engineering and Applied Science University of Cincinnati

in partial fulfillment of the requirements for the degree of

Bachelor of Science

in Mechanical Engineering Technology

by

Kyle Krummert & Roman Zanto

April 2014

Thesis Advisor: Professor Laura Caldwell

ABSTRACT

A fixed-drive bicycle is an excellent and stylish urban bike due its characteristic simplicity. With only one fixed-drive-ratio, the fixed-drive bicycle has no shifters, cassettes, or cables; this requires minimal maintenance and creates a simple aesthetic. Hilly cities, e.g. Cincinnati, OH are difficult for fixed-drive cyclists. The descending of hills is of particular difficulty because the crank cadence increases downhill, and the cadence rpm may surpass the rider’s ability: a crash may result.

The solution to the downhill increased cadence problem is to give the fixed-drive bicycle a second, higher or overdrive gear ratio, while maintaining the bicycle’s characteristic simplicity, i.e. no external mechanisms. One solution to accomplish that is a multiple, internal-gear hub that is fixed-drive and shifts automatically. This Senior Design project report outlines the creation of the hub which happens within twenty-six weeks or two college semesters: from market opportunity to successful prototype.

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TABLE OF CONTENTS ABSTRACT ...... II TABLE OF CONTENTS ...... II LIST OF FIGURES ...... IV LIST OF TABLES ...... IV LIST OF EQUATIONS ...... IV INTRODUCTION ...... 1 BACKGROUND ...... 1 CADENCE ...... 1 ...... 2 EXISTING PRODUCTS AND TECHNOLOGY ...... 4 SRAM AUTOMATIX ...... 4 STURMEY-ARCHER SX3 ...... 5 CUSTOMER FEEDBACK, FEATURES, AND OBJECTIVES ...... 6

SURVEY ANALYSIS ...... 6 PRODUCT FEATURES AND OBJECTIVES ...... 7 ENGINEERING CHARACTERISTICS ...... 8 DESIGN CONCEPTS AND SELECTION ...... 9

UNDERDRIVE DESIGN ...... 9 OVERDRIVE DESIGN ...... 10 CONCEPT SELECTION ...... 11 OVERRUNNING CLUTCH ...... 12 FABRICATION ...... 15 ASSEMBLY OF COMPONENTS ...... 17 ASSEMBLY OF DESIGN ...... 21 TESTING ...... 23 TESTING METHOD ...... 23 TESTING EQUIPMENT ...... 23 TESTING RESULTS ...... 24 RECOMMENDATIONS ...... 25 SCHEDULE AND BUDGET ...... 26 SCHEDULE ...... 26 BUDGET...... 27 WORKS CITED...... 28 APPENDIX A – RESEARCH ...... 29 APPENDIX B – SURVEY ...... 34 APPENDIX C – QUALITY FUNCTION DEPLOYMENT ...... 35

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APPENDIX D – PRODUCT OBJECTIVES...... 36 APPENDIX E – SCHEDULE ...... 37 APPENDIX F – BUDGET ...... 38 APPENDIX G – PURCHASED COMPONENTS ...... 39 APPENDIX H – ASSEMBLY DRAWINGS ...... 40

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LIST OF FIGURES Figure 1 – Epicyclic Gearing Configuration (5) ...... 2 Figure 2 – SRAM Automatix ...... 4 Figure 3 – Sturmey-Archer S3X ...... 5 Figure 4 – Underdrive Design...... 9 Figure 5 – Overdrive Design ...... 10 Figure 6 – Section View of Component Layout ...... 12 Figure 7 – Joining of Hub Body with Ball-ring ...... 13 Figure 8 – Direct Drive Position ...... 13 Figure 9 – Overrunning (Engagement and Disengagement) ...... 14 Figure 10 – S3X Hub Body Fixed End ...... 15 Figure 11 – S3X Planet Carrier Fixed End ...... 15 Figure 12 – S2 Ring Gear after Modification ...... 16 Figure 13 – Post Joining, Newly Modified Ring Gear ...... 16 Figure 14 - Layout of Components to be assembled ...... 17 Figure 15 – Ring Gear Attached to the ...... 17 Figure 16 – Planet Carrier being assembled onto Axle ...... 18 Figure 17 – Complete Uni-assembly ...... 18 Figure 18 – Uni-assembly assembled into Hub Body ...... 18 Figure 19 – Ball Ring ...... 19 Figure 20 - Threading the Ball Ring into the Hub Body ...... 19 Figure 21 – Installing the Driver ...... 19 Figure 22 – Dust Cap Assembly ...... 20 Figure 23 – Full Assembly Built into the Wheel ...... 20 Figure 24 – Assembled Hub ...... 21 Figure 25 – Uni-assembly Removed from Hub Body ...... 21 Figure 26 – Commercial Components ...... 22 Figure 27 – Configuration of Testing Equipment ...... 23 Figure 28 – Crank and Wheel Magnets ...... 24 Figure 29 – Testing Results ...... 24 Figure 30 – Actual Schedule ...... 26

LIST OF TABLES Table 1 – Epicyclic Gearing Gear Ratios ...... 3 Table 2 – Summary of Survey Results ...... 6 Table 3 – Engineering Characteristics ...... 8 Table 4 – Weight Decision Matrix for Concept Selection ...... 11 Table 5 – Budget ...... 27

LIST OF EQUATIONS Equation 1 – MPH to Cadence RPM...... 1 Equation 2 – Planetary Gear Ratio ...... 3

iv Automatic Two-Speed, Fixed-Drive Bicycle Hub-Gear Kyle Krummert - Roman Zanto INTRODUCTION BACKGROUND A Fixed-gear bicycle is a single-speed without a -drive,1 i.e. the crank rotates when the bicycle is in motion. Traditionally, race oriented cyclists ride Fixed-gear as a training tool to improve their cadence, 2 but the fixed has been adopted by urban culture (1). The primary appeal of a Fixed-gear is the following characteristics clean and simple aesthetics. Another appeal of Fixed- is the low-maintenance required as there are minimal moving parts and the components are built to be more durable due to the higher forces generated from the lack of a freewheel (2). Fixed-gears also have appeal because cities limit the viability of multiple gears (9-speed, 18-speed, 21-speed and etc.) as stoplights and traffic are frequent, and thus fewer gears is more practical. Additionally, a rider’s attention may remained focused on the road and surrounding traffic as the Fixed-gear has no gears to shift (3). In summary a Fixed- gear is appealing because of its aesthetics, low-maintenance, durability and increased practicality for city use.

The same appeal as a Fixed-gear is found within a . Hub gear offer increased versatility as they contain multiple gears, but maintain practicality in cities because the gear selection is generally limited (4). Hub gears are also low-maintenance because the gears are within an enclosure protecting them from dirt and potential fall damage. Aesthetically, hub gears offer the same appeal as a Fixed-gear as the gears are internal, but generally cables and shifters are requires for shifting gears (3). In the proceeding sections, existing products are discussed. (See APPENDIX A – RESEARCH for further product information).

CADENCE For this project, cadence is considered for two situations: cadence of bicycle travelling level terrain, and cadence of bicycle travelling downhill and uphill. The first situation of level terrain is considered in order to determine the ideal cadence. The ideal cadence is used as the standard to which the cadence of the second situation, that of hills, is compared; ultimately the standard determines at what velocity the bicycle hub shifts gears.

A major factor in cadence, aside from skill level, is the ratio (SR) (ratio between number of teeth on chainwheel and number of teeth on sprocket). The relationship between cadence and SR is inversely proportional. Cadence can be calculated from a known mile per hour (mph), by the following:

Equation 1 – MPH to Cadence RPM

( ) ( )

where wheel diameter is in inches, and the inverse value of SR is taken in order to put the RPM in terms of the crank. The use of fixed-drive is primarily in areas of flat terrain as they lack the versatility for hills. The major problem with hills and fixed-drives is cadence. Considering a downhill

1 A freewheeling-drive enables a bicycle to “coast,” i.e. to move by cause of momentum or gravity as opposed to propelling power (in the case of bicycle the propelling power is generated via pedaling). 2 Cadence is the revolutions per minute (rpm) of the crank, i.e. the crank. 1

Automatic Two-Speed, Fixed-Drive Bicycle Hub-Gear Kyle Krummert - Roman Zanto descent with a traditional bicycle, the rider is able to “coast” down the grade; however, as a fixed-drive cannot coast the continuously increases. At a particular speed (dependent on the rider), the cadence would require so much of the rider’s attention that the rider losses focus on the road, or the biomechanics of the rider cannot maintain pace with the crank. In this situation the bicycle and rider become unstable which may possibly result in a crash. The cadence at which the rider becomes unstable is based on the individual rider. As recreational riders do not monitor their cadence, the velocity at which the rider achieves an unstable cadence is largely unknown.

It is desirable for the hub design to shift from direct drive (DD) to overdrive (OD) when the cadence reaches the range > 120 rpm. The shift from DD to OD decreases the cadence relative to wheel rpm. In regard to the user travelling downhill, the shift from DD to OD will decrease the cadence allowing the user to descend the hill with a manageable and safe cadence. However, the SR varies between riders and this fact voids the notion of designing the shift to occur at 90rpm; the hub should accommodate as many riders as possible.

In order to accommodate all riders, the hub should shift when the bicycle descends any hill with any SR. Furthermore, the shift should accommodate the needs of the majority of riders. The principle of an overrunning clutch facilitates shifting while descending hills; and the gear ratios are furnished through epicyclic gearing.

EPICYCLIC GEARING Epicyclic gearing is the main mechanism of hub gears. It is responsible for all velocity increases and reductions to the SR. Epicyclic gear trains have three core components: annular gear, planet carrier, and sun gear. The sun gear is the axis about which the planet carrier and annular gear revolve. The planet carrier “carries” at the minimum two planet gears; these planet gears are in mesh with the sun gear and annular gear. The annular gear is a gear with internal teeth, and is often named “ring gear” (for this project, the annular gear is referred to as ring gear). Figure 1 shows the epicyclic gearing configuration.

Figure 1 – Epicyclic Gearing Configuration (5)

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Automatic Two-Speed, Fixed-Drive Bicycle Hub-Gear Kyle Krummert - Roman Zanto By “fixing” one these three core components, simple epicyclic gearing is capable of six gear ratios as seen in Table 1 (6). Moreover, if all three components are fixed, then the gearing rotates at a 1:1 DD gear ratio.

Table 1 – Epicyclic Gearing Gear Ratios CORE COMPONENTS* STATIONARY INPUT OUTPUT VELOCITY RATIO** C S R –VR

C R S

S C R ( ) ( ) S R C

R S C (1+VR) R C S (1+VR) *C, planet carrier; R, ring gear (annulus); S, sun gear.

**VR = Number of teeth in ring gear / Number of teeth in sun gear = ⁄

The highlighted row is the configuration that is particular to this project. This configuration is known as “solar;”3 it generates an OD) gear ratio. Solar configurations are not considered to be epicyclic gearing as tracing the path of the planet gears does not create the epicycloid curve from which epicyclic gearing derives its name. For this project, the is referred to as “planetary gear train.” With the planetary gear train VR known the overall effective gear ratio (GR) is calculated to be:

Equation 2 – Planetary Gear Ratio

( ) ( ) where SR is the sprocket ratio. This determines the GR once the overdrive is active.

3 The solar configuration is recognized to have a sun gear that is fixed and planet carrier and ring gear that are rotatable (15). 3

Automatic Bike Hub Kyle Krummert - Roman Zanto

EXISTING PRODUCTS AND TECHNOLOGY SRAM AUTOMATIX The SRAM Automatix two-speed hub automatically switches gears based on the speed (see Figure 2). The gear ratios are direct drive (1:1) and overdrive (1:1.37) (8). Gear change occurs at a pre-set velocity, depending on wheel size, the hub automatically downshifts when slowing down, stopping, or climbing hills. There is no required (therefore no controlling mechanism) as the centrifugal clutch allows for automatic shifting (7). The centrifugal clutch connects two concentric shafts with the driving shaft nested inside the driven shaft. This is a practical system for varying terrains and city use as the rider’s attention may remain focused on the road and surrounding traffic. The issues with the Automatix are the labor-intensive shift point and the step between speeds.

In order to change the predetermined shift point at which gears change, the entire hub must be disassembled and the spring replaced with an aftermarket spring. This is undesirable because it is not user-friendly for a rider that wants the gear shift to occur at a higher or lower rpm. Second, the low gear ratio is 1:1 and the high gear ratio is 1:1.137. This is undesirable because the majority of the time the planetary gear train is engaged (2), which creates wear on a component that is not easily replaced, i.e. the planetary gear train. (See APPENDIX A – RESEARCH for more information).

Figure 2 – SRAM Automatix

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STURMEY-ARCHER SX3 The Sturmey-Archer S3X, see Figure 3, is a three-speed fixed-gear hub gear (8). Gear ratios for the S3X are 1:1 in first gear, a 25% reduction in second gear and a 37.5% reduction in third (9). Shifting is actuated by a manually operated shift mechanism which allows for rider control when traversing various terrains. The S3X is practical for climbing hills as there are multiple gear ratios. The drawbacks of the S3X are manual shifter and backlash.

The manual shifter requires the bicycle to be outfitted with a shifter and cable. The addition of shifter and cable subtracts from the clean and simple aesthetics that attracts riders to the Fixed-gear (Clark, 2013). Additionally, manual shift detracts the rider’s attention from road and surrounding traffic. (See APPENDIX A – RESEARCH for more information).

Figure 3 – Sturmey-Archer S3X

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CUSTOMER FEEDBACK, FEATURES, AND OBJECTIVES SURVEY ANALYSIS Thirty surveys were returned for data analysis. The surveys were circulated among fixed- drive bicycle enthusiast, bicycle mechanics, experienced riders, bicycle polo players, and the occasional racer to gather an eclectic range of consumer opinion on the proposed product and the products currently available. The survey outlined the major customer features to design into the proposed product (these major customer features are determined from the Interviews (1) (3) (2)) and asked the customer his/her opinion for the importance of the features on the new product and existing products. Importance was rated on a scale of 1-5 for a new product and satisfaction was rated on a scale of 1-5 for existing products, with 5 being the most important or the most satisfied. (See APPENDIX B – SURVEY for complete survey results). The quality function deployment (QFD) summarizes the results of the survey listed in Table 2. (See APPENDIX C – QUALITY FUNCTION DEPLOYMENT for the complete QFD).

Table 2 – Summary of Survey Results

Customer importance Customer Multiplier Designer's Satisfaction Current Satisfaction Planned ratio Improvement Importance Modified weight Relative % weight Relative

Ease of Adjustment 4.50 1.00 2.90 4.50 1.60 7.00 0.18 18% Reliability 4.80 1.10 3.10 4.00 1.30 6.80 0.18 18% Ease of Maintenance 5.00 1.00 3.60 4.50 1.30 6.30 0.16 16% Aesthetics 3.90 1.00 3.10 4.00 1.30 5.00 0.13 13% Range of Adjustment 4.10 1.00 3.40 4.00 1.20 4.90 0.13 13% Cost 4.00 1.00 3.30 4.00 1.10 4.30 0.11 11% Weight 3.80 1.00 3.80 4.00 1.10 4.00 0.10 10%

The customer importance is displayed in Table 2 in the first column and the current satisfaction in the third column. Results illustrate the customer expressed heavy importance on the ease of maintenance and reliability, while ease of adjustment was in a close third. A designer’s multiplier of 1.1 was applied to the customer feature, reliability, because a successful product must perform under all conditions, environments and riding styles. In addition, reliability is correlated to the ease of maintenance and ease of adjustment. Therefore, significant emphasis in the design of this product must focus on the reliability of this product for it to be absolutely satisfying to the customer, reduce overall unnecessary maintenance, and enhance consistency of adjustment.

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Aesthetics is planned to improve 30% although difficult to measure because visual beauty is highly subjective, nevertheless; minimal branding and monochromatic have been described as the preferred design by customers. The cost of current hub gear is within the planned range so there is a projected 10% increase over the existing products. Ease of maintenance will be designed to have a 30% increase in customer satisfaction due to the implementation of external grease fittings, eliminating the need to disassemble the hub for routing greasing. Furthermore, design of an internal uni-assembly will allow the user to easily remove the internals without the need to remove several components. Range of adjustment is proposed to increase satisfaction by 20%. Adjustment is not applicable with the final design. Reliability is projected to increase 30% with utilization of rust resistant materials and sound choice of materials and components based on design factor and stress analysis. Weight is intended to improve 10% with selection of light-weight materials and design simplicity.

PRODUCT FEATURES AND OBJECTIVES The product objectives are generated from the customer features to clarify how these features will be achieved. In accordance with the survey, the list below ranks the product objectives in descending order of customer importance with a percentage of each objective in parenthesis.

1. Reliability (18%) a. Rust Resistant b. Weather resistant comparable to other hubs c. Material selection based on design factor and stress analysis d. Component selection per spec sheet for desired product life e. Protect set from exposure to the elements (weather and debris) 2. Ease of Adjustment (18%) a. Exterior set-screw b. Accessible to adult male hand 3. Ease of Maintenance (16%) a. Internal uni-assembly b. Graphic service manual with steps to guide users c. Annual servicing (internal gear re-lubrication) d. Grease-fittings can be accessed by grease gun e. Metric set, spanner wrench, grease gun f. Lubricant available at local bicycle shops or internet 4. Range of Adjustment (13%) a. Complete range of adjust < four 360º rotations of set screw b. Range will be +/- 2 gear teeth (total range of 4 teeth) 5. Aesthetics (13%) a. One branding < 4in2 b. Monochromatic i. Metal hub body brushed aluminum c. threading pattern 6. Cost (13%) a. Range $100 - $200 (retail) 7. Weight (10%) a. Weight < 3 lbs

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ENGINEERING CHARACTERISTICS The product objectives were then put in a Quality Function Deployment designated as the Engineering Characteristics. The Engineering characteristics were cross-referenced with the product features and weighted to measure the importance of each characteristic to the entire design. These are listed in Table 3 by percentage in descending order of relative importance.

Table 3 – Engineering Characteristics Engineering Characteristics Relative Importance Component Selection 14% Material Selection 10% Exterior Set-Screw 10% Grease Fittings 9% Metal Hub Body 8% Tools 8% Local Bike Shop Lubricant 8% Geometry for accessibility 8% Internal Uni-assembly 6% Adjustment Limited to 4 Turns 5% Threading Pattern 4% One Branding 4% Monochromatic 3% Range of 4 Teeth 3%

The three Engineering Characteristics with the highest relative importance are: component selection, material selection, and exterior set-screw. Component selection entails selection of components for use in the product based on mechanical, physical, and chemical properties gathered from catalogs or other sources with empirical data (i.e., gears, bearings, etc.). Sound selection of components will increase reliability standards desired for the product. Material selection focuses on choosing materials for individual parts, established from stress analysis and materials properties given the particular application. Material selection is imperative to ensure reliability of the product which of the highest importance to the customer. An exterior set-screw is an important design feature, permitted to give the customer easy adjustability. These Engineering Characteristics in conjunction with the others will help achieve the product objectives.

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DESIGN CONCEPTS AND SELECTION UNDERDRIVE DESIGN The first concept is referred to as the underdrive (UD) design (see Figure 4). This concept configuration will shift automatically from an UD state to DD. is supplied to the rear cog from the users input into the drive crank. The rear cog is attached to the driver causing the driver to rotate. Displayed in Figure 4, power flows in from the right moving left through the clutch and ring gear, then out through the planet carrier driving the hub body to power the wheel. The UD is created from the planet, sun, and ring gear configuration. When the sun gear is stationary (in this design the sun gear is fixed to the axle) and the ring gear drives the planet carrier, the output rotation of the planet carrier is less than the input of the ring gear. For example, when the hub gear ratio is 1:0.75, the ring gear will rotate one full turn while the planet carrier will rotate 0.75 or three quarters of a rotation, thus furnishing an UD state. While in UD, the clutch will be disengaged with the driver via a ratchet and pawl design allowing the ring gear to drive the planet carrier. When the clutch is engaged with the driver there will be a direct drive relationship causing the input and output to rotate at the same speed. The clutch disengages and engages via a centrifugal governor (10) (11). Disadvantages of the UD Design are encountered when traveling downhill. A user’s cadence will increase so greatly that his/her legs will not be able to maintain a controlled speed resulting in potential crash.

GOVERNOR WEIGHT CLUTCH REAR COG

DRIVER

POWER FLOW

AXLE

PLANET CARRIER RING GEAR

Figure 4 – Underdrive Design

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OVERDRIVE DESIGN The second concept is referred to as the OD Design (see Figure 5). This concept configuration will shift automatically from DD to OD. Akin to the Underdrive Design, torque is supplied to the rear cog from the input crank. However, the key difference for the OD Design is the configuration with the sun, planet, and ring gear. The OD Design will employ a stationary sun gear fixed to the axle, but the ring gear will be driven by the planet carrier rather than the other way around for the first concept. Therefore, with a 1:1.38 hub gear ratio, the planet carrier will rotate one full rotation while the ring gear rotates one and three eighths turn. Power flow moves from right to left as in the first concept; however, the output is the ring gear. The OD Design configuration is certainly more advantageous for downhill riding. When the user travels down a hill the wheel will start to overrun the input, thus, disengaging the pawls and allowing the hub to shift to OD. This OD gearing will allow the user to safely travel downhill as his/her cadence will remain in a more controlled state.

PLANET CARRIER REAR COG

DRIVER

POWER FLOW

AXLE

RING GEAR PAWL

Figure 5 – Overdrive Design

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CONCEPT SELECTION The two concepts are evaluated via the use of a weighted decision matrix using a five-point scale: see Table 4. Scores range from zero that correlates with an inadequate rating, to four which correlates with an excellent rating. Design criteria of the two concepts are compared using relative weights taken from the QFD (See APPENDIX C – QUALITY FUNCTION DEPLOYMENT).

Table 4 – Weight Decision Matrix for Concept Selection

Design Weight Underdrive Design Overdrive Design Units Criterion Factor Magnitude Score Rating Magnitude Score Rating Ease of 0.18 Experience N/A 0 0 N/A 0 0 Adjustment Reliability 0.18 Experience Decent 2 0.36 Good 3 0.54 Ease of 0.17 Experience Good 3 0.51 Excellent 4 0.68 Maintenance Aesthetics 0.13 Preference Good 3 0.39 Good 3 0.39 Range of 0.13 N/A N/A 0 0 N/A 0 0 Adjustment Cost 0.11 $ 300 2 0.22 200 3 0.33 Weight 0.10 lbs. 3 3 0.3 2.8 4 0.4 Totals 1.0 1.78 2.34

Results from Table 4 below indicate the Overdrive Design is the best concept in regards to the design criterion. The key difference between design concepts isn’t taken from the design criterion but rather the interviews. Experienced riders and fixed-gear enthusiast asserted that the most desired feature with fixed-gear hubs is the ability to safely travel downhill. The underdrive design would benefit uphill riding but sacrifice downhill safety with its inherent inability to reduce cadence. Therefore, the design concept that achieved the highest safety criteria for downhill riding is the overdrive design. Wherein, the overdrive design reduces a rider’s cadence due to shifting to a higher gear, thus increasing downhill safety.

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OVERRUNNING CLUTCH The hub gear is designed to automatically shift based on an overrunning principle. Pawls are utilized as the means of engagement for the clutch (10); wherein the planet carrier is the clutch. A ball-ring threads into the hub body with teeth designed into the inside diameter for the pawls to engage with. Figure 6 displays a section view of the hub to highlight the layout of components and how each component interacts.

Ball-ring Hub Body

Driver

Planet Carrier Pawl Ring Gear

Figure 6 – Section View of Component Layout Designing the ball-ring with the pawl engagement teeth and threading it into the body allows the pawls to directly drive the output of the hub body. Joining of these parts is demonstrated in Figure 7.

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 Ball-ring: Threads into the hub body and engages with pawls allowing direct drive to be achieved.

Figure 7 – Joining of Hub Body with Ball-ring

Starting from rest, the hub will initially be in the D.D. position. The pawls are engaged with the ball-ring (see Figure 8). Thus, the planet carrier is fixed to the hub body and therefore directly drives the hub body giving the 1:1 relationship for the input to output.

 Planet Carrier (red): Receives power from the driver and transfers power to the hub body via the pawl engagement.  Pawls (yellow): Engage with the ball-ring that is fastened to the hub body. Allows power to be transferred directly to the hub body.  Ball-ring (white): Threaded into the hub body. The teeth engage with the pawls to allow power transfer directly to the hub body.

Figure 8 – Direct Drive Position

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Shifting occurs when the output overruns the input. This action takes place during descent. The speed of the will begin increasing due to gravity, causing the wheel to rotate faster than the driver’s input speed. The overrunning action causes the input (i.e. the driver) to be driven by the output (i.e. hub body, and wheel).

Operation of this mechanism works when the ball-ring, which is fastened to the hub body, is rotated past the pawls. When the hub body rotates faster than the input, the pawls will be overrun by the hub body and thus depress the pawls with each rotation. Since the pawls will not provide torque to the ball-ring as descent occurs, the hub body is given the advantage to run past the pawls. The principle of operation is shown in Figure 9.

Figure 9 – Overrunning (Engagement and Disengagement)

Transition to O.D. was initiated by the overrunning of the hub body causing the pawls to disengage, thus allowing power to flow through the gear train.

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FABRICATION Reducing cost is the driving factor for selecting manufacturing/fabrication processes. For this design, utilizing existing products and standard components was the primary means for selecting a fabrication trajectory. High manufacturing cost of custom designed parts proved too costly for the designated budget. Therefore, purchasing existing products that could be adapted for this design was ultimately the direction chosen.

Purchasing existing products such as the Sturmey-Archer S3X and Sturmey-Archer S2 allowed many of the existing internal parts to be fabricated for adaptation to the design concept chosen. Employing the hub body from the Sturmey-Archer S3X was selected because the configuration of this hub is for a fixed-gear. Additionally, selection of an existing hub body guided the parameters for designing internals to be contained within. Figure 10 illustrates the hub body designed for fixed-gear configuration.

Figure 10 – S3X Hub Body Fixed End The planet carrier from the Sturmey Archer S3X was disassembled to be joined with the ring gear from the Sturmey-Archer S2. Disassembly of the planet carrier from the S3X was required for mating with the fixed end of the hub body and joining with the S2 ring gear. The disassembled planet carrier from the S3X is displayed in Figure 11.

Figure 11 – S3X Planet Carrier Fixed End

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Fabrication of the ring gear from the S2 included: grinding, drilling, and bonding. The ring gear from the S2 used for fabrication is displayed in Figure 12 with evidence of modification.

Figure 12 – S2 Ring Gear after Modification The newly modified ring gear from the S2 needed to be formed with the fixed end side of the planet carrier from the S3X to make the hub operate as a fixed-gear. Figure 13 shows bonding of the fixed end side of the planet carrier from the S3X and the modified ring gear from the S2.

Figure 13 – Post Joining, Newly Modified Ring Gear

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ASSEMBLY OF COMPONENTS One of the major characteristics for this design was ease of maintenance which included a uni-assembly of all internals. A layout of all the components to be assembled is shown in Figure 14 (see APPENDIX H – ASSEMBLY DRAWINGS for assembly drawing).

Figure 14 - Layout of Components to be assembled First, the ring gear is attached to the axle by lining up the concentric hole to the axle and simply sliding the axle into the ring gear until the sun gear on the axle mate with the inside face of the ring gear. Figure 15 shows the ring gear attached to the axle.

Figure 15 – Ring Gear Attached to the Axle

The uni-assembly is complete with the inclusion of the planet carrier, ring gear and axle. The planet carrier contains the planet gears and houses the pawls. In addition, the planet carrier mates with the driver which provides power to the internals in either D.D. or O.D. Figure 16 shows the planet carrier being assembled onto the axle. The completed uni-assembly is displayed in Figure 17.

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Figure 16 – Planet Carrier being assembled onto Axle

Figure 17 – Complete Uni-assembly

Once the uni-assembly is mated together, the uni-assembly can be installed into the hub body. The three protrusions on the back of the ring gear mesh and lock into place with the fixed end of the hub body. Figure 18 depicts the uni-assembly assembled into the hub body.

Figure 18 – Uni-assembly assembled into Hub Body After the uni-assembly is locked into position within the hub body the ball ring is threaded into the hub body. Figure 19 shows the ball ring and Figure 20 shows assembly of the ball ring with the hub body.

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Figure 19 – Ball Ring

Figure 20 - Threading the Ball Ring into the Hub Body After the ball ring is tightly fastened to the hub body, the drive can slide into the mating feature of the planet carrier. Figure 21 shows the driver by itself and the driver assembled into the hub body.

Figure 21 – Installing the Driver

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The final step to having a complete hub assembling is threading the dust caps onto the axle to seat with the small cage bearings. Figure 22 demonstrates the dust cap being threaded onto the axle and seating in the driver assembly.

Figure 22 – Dust Cap Assembly

The complete assembly of the hub body built into the wheel can be seen in Figure 23.

Figure 23 – Full Assembly Built into the Wheel

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ASSEMBLY OF DESIGN The components of the assembly are designed to perform in all weather conditions. Internals are completely sealed to prohibit intrusion of any contaminants. Materials are selected for strength, durability, and corrosion resistance to ensure reliability and longevity; more details are found within Figure 24.

• A solid steel axle is selected for strength and rigidity.

• Aluminum 6061 is chosen for the hub body to prevent the effects of corrosion.

• Dust caps and rubber seals are impervious to contaminants for increased longevity of internal

components.

Figure 24 – Assembled Hub Ease of maintenance is a desired characteristic in a hub gear. Therefore, use of a uni- assembly is implemented into this design to provide the user with an easy to maintain hub. All internal components are attached to the hub for further disassembly and adjustment. Removing the uni-assembly, as seen in Figure 25, from the hub body requires standard metric wrench set.

 The complete uni- assembly contains all shifting and gearing components. The uni-assembly is removed from the hub body by pulling the axle away from the hub body.

Figure 25 – Uni-assembly Removed from Hub Body

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Standard and commercially available parts are used wherever applicable. Commercially available parts eliminate the need for design, they are proven to work as intended, and they are typically interchangeable. Implementation of bearings, seals, and gears as shown in Figure 26 are utilized to reduce cost, improve standardization of components, and impose geometric tolerancing of design to standard components.

Figure 26 – Commercial Components

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Auto Bike Hub Kyle Krummert - Roman Zanto

TESTING As the hub gear design is intended to automatically shift at any velocity, i.e. when overrunning occurs, the sprocket ratio is plotted versus cadence. The two gear ratios are approximately 2.2 and 3.0.

TESTING METHOD The two roads that are chosen for testing are Gilbert Avenue and 7th Street in the Central Business District neighborhood of Cincinnati. Gilbert Avenue has a change 230 ft. drop in elevation that occurs in approximately three-fourths of a mile; Gilbert Avenue transitions into E. 7th Street which is flat (only one foot in elevation change). While descending the hill, the hub gear should be in OD, and on the flat the hub gear should be in DD.

TESTING EQUIPMENT Two sensors4 are used in testing: Wahoo Cycling Ant+ Speed/Cadence Sensor and Cateye Strada Cadence Bike Computer. Depicted within Figure 27 is the configuration of the sensors on the bicycle. The Wahoo is a wireless sensor that pairs with the Wahoo Fitness App for iPhone. Of particular importance, the synced iPhone app records all data and enables the user to export the data in spreadsheet form: facilitating data analysis. The Cateye Strada is a wired sensor that has a readout display that attaches to the bicycle’s handlebars. By having a viewable readout of speed and cadence, the user may attempt to maintain a consistent cadence.

Figure 27 – Configuration of Testing Equipment Both sensors use magnets to determine the rpm of the crank and wheel. A magnet is secured5 to the left crank arm, and a magnet is secured to a rear-wheel spoke; there are two sensors, one for crank and one for the wheel as seen in Figure 28.

4 Two sensors are needed because one sensor records data, while the other has a readout display. It is noted that for an additional purchase, the Wahoo’s iPhone readout can be mounted to the bicycle’s handlebars to be viewed while riding. 5 Duct tape is used to firmly secure the Cateye Strada’s wires, which is seen in Figure 27 and Figure 28. 23

Auto Bike Hub Kyle Krummert - Roman Zanto

Figure 28 – Crank and Wheel Magnets As the magnet each rotates through the sensor field, the sensor is activated and records/computes the rpm. The crank and wheel rpms that are recorded are the instantaneous velocities every second.

TESTING RESULTS The testing results indicate that an automatic gear change does occur. In Figure 29 the results are displayed.

4 Cadence versus Sprocket Ratio 3.8

3.6

3.4

3.2

3

2.8 Sprocket Ratio Sprocket 2.6

2.4

2.2

2 0 20 40 60 80 100 120 140 Cadence (rpm)

Figure 29 – Testing Results

24

Auto Bike Hub Kyle Krummert - Roman Zanto

The majority of data points lie between sprocket ratios 2.8 and 3.0, and the minority of data points lie around 2.2. Most of the 2.2 data points correlate with a velocity of three to five mph. These low velocities correlate with the pace of walking; while setting up to test, the bicycle was walked into a starting position. While riding the bicycle nearly all the data points fall around a sprocket ratio of 3.0.

The cause of this is the design of the planetary gear train orientation. It is reversed. The gear train is designed for the crank as the input and wheel as the output. When overrunning occurs, the wheel becomes the drive input and the crank becomes the drive output. Thus, while the crank is supplying the input, the gear ratio is 3.0; while the wheel is the input the gear ratio is 2.2.

RECOMMENDATIONS Despite the gear train being in reverse orientation, the concept of a fixed-drive bicycle automatically shifting gears is proven. For further development of this project it is recommended that the gear train be redesigned for the wheel as the input, and not the output. For that to be feasible, custom parts need to be fabricated which is a substantial cost; therefore it is recommended that further project development has a budget of $5000.

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Auto Bike Hub Kyle Krummert - Roman Zanto

SCHEDULE AND BUDGET SCHEDULE The development and completion of this project occurred within two college semesters, or twenty-four weeks. As part of this project, an “Estimated Schedule” was proposed and accepted. The schedule begins with the Proof of Design agreement on October 16th and ends with displaying project at the University of Cincinnati’s Technical Exposition on April 3rd. Against the Estimated Schedule, the real-time progress is tracked. The “Actual Schedule” is seen in Figure 30. (See APPENDIX E – SCHEDULE for the complete Proposed and Actual Schedules).

ACTUAL SCHEDULE

CONCEPT DESIGN DESIGN MODIFICATION ASSEMBLY TESTING

TECH EXPO

1/3/2014 2/2/2014 3/4/2014 4/3/2014

9/20/2013 10/5/2013 11/4/2013 12/4/2013 1/18/2014 2/17/2014 3/19/2014 4/18/2014

11/19/2013 12/19/2013 10/20/2013 Figure 30 – Actual Schedule

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Auto Bike Hub Kyle Krummert - Roman Zanto

BUDGET The budget is a list of all expenses incurred throughout the design process to project fruition. In Table 5 are the estimated and actual project budgets. Total cost of the project is estimated to be $1660.00; however the actual amount spent is $606.00. (See APPENDIX F – BUDGET for itemized budget).

Table 5 – Budget

CATEGORY ESTIMATED ACTUAL Interview and Consultations $300.00 $70.00 Miscellaneous $200.00 $0.00 Raw Materials $250.00 $9.00 Similar Products $50.00 $190.00 Tools and Hardware $500.00 $137.00 Testing $300.00 $110.00 Wheel, Spokes, $60.00 $90.00 Total: $1660.00 $606.00

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Auto Bike Hub Kyle Krummert - Roman Zanto

WORKS CITED 1. Brannan, Thomas. Bicycle Enthusiast. Cincinnati, September 12, 2013. 2. Hiller, Webster. Bicyle Expert. Cincinnati, September 15, 2013. 3. Clark, Will. Customer. Cincinnati, 09 05, 2013. 4. Beitjahn, Hansen. Startsite. Scheunen Fun. [Online] 06 07, 2011. [Cited: 09 06, 2013.] http://www.scheunenfun.de/shimano-automatic.htm. 5. Droidmakr. Gear Train. Beam-Wiki. [Online] May 10, 2011. [Cited: April 15, 2014.] http://www.beam-wiki.org/wiki/Image:Epicyclical_%28Planetary%29_Gear_Train.GIF. 6. Ferguson, R. J. Short Cuts for Analyzing Planetary Gearing. Machine Design. May 26, 1983, pp. 55-58. 7. Brucey. SRAM A2 Automatix; Introduction to the Internals. CTC Forum. [Online] 04 09, 2012. [Cited: 09 06, 2013.] http://forum.ctc.org.uk/viewtopic.php?f=5&t=62320. 8. SRAM. AUTOMATIX. SRAM USA. [Online] USA. [Cited: 09 02, 2013.] http://www.sram.com/sram/urban/products/automatix. 9. Sturmey-Archer. S3X. Sturmey-Archer. [Online] Sturmey-Archer. [Cited: 09 06, 2013.] http://www.sturmey-archer.com/products/hubs/cid/3/id/47.html. 10. Burkhart, Dan. Sturmey Archer S3X Fixed Gear 3 Speed. How It Works. Youtube. [Online] 10 30, 2013. [Cited: 09 06, 2013.] http://www.youtube.com/watch?v=AJmUds2YQ74&feature=c4-overview- vl&list=PLxn6T6UL2lSrBed0WeIGZxhd1WdyVTi-h. 11. Kimes, John W. and Simon, Bernard J. Ratcheting One-way Clutch Having Rockers Actuated by Centrifugal Force. 7,448,481 United States of America, September 8, 2005. Invention. 12. Segaway, Keizo and Takashi. Bicycle hub having a built-in two stage speed change mechanism. US3494227 A USA, 02 10, 1970. 13. Baker, Evan R., Dunlap, Thomas F. and Walter, Christopher J. Overrunning Pawl Clutch. 5,927,455 United States of America, July 21, 1997. Invention. 14. Allen Gearing Solutions Limited. Epicyclic Gearboxes. Allen Gears. [Online] 2008. http://www.allengears.com/html/epicyclic.php.

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APPENDIX A – RESEARCH

INTERVIEW OF CUSTOMER: Customer Features:  Design Simplicity William Clark  Solid Axel (513) 519-3633  Ease of Travelling 42 W. McMicken St. Downhill Cincinnati, OH 45202

William Clark has rode bicycles for seven years, and Fixed-gear for four years. He has worked as a bicycle mechanic for two years at Performance Bicycle.

Drawbacks of Fixed-gear: . Stopping is hectic, especially downhill. . Destination, distance and traffic are considerable considerations when planning bicycle ride. . Complete concentration on road and surroundings. . Hills are a challenge—uphilll and downhill.

Ideal enhancement of Fixed-gear: . Ease of travelling downhill.

Concerns of Solution: . Sounds expensive. . Design—simplicity is key. . Novelty of the device is an attraction.

Less Concern: . Weight is of little concern. After thoughts: . Hub with solid axel. . Hub that is user-friendly in regard to repairs. . Hub with slightly longer flange to allow for removal of sprocket.

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INTERVIEW OF BICYCLE EXPERT: Customer Features:  Component strength Webster Hiller  Solid Axel (513) 728-1808  Ease of Travelling 4839 U.S. 127 Downhill Cincinnati, OH 45223

Webster Hiller has rode bicycles for twenty-five years of which ten years he raced competitively and Fixed-gear for eight years. He has worked as a bicycle mechanic for four years at Performance Bicycle, and built his own .

Drawbacks of Fixed-gear: Not applicable Ideal enhancement of Fixed-gear: . Ease of travelling downhill.

Concerns of Solution: . Sounds expensive . Component strength

Less Concern: . Weight . Aesthetics After thoughts: . Hub with solid axel . Hub should be easily serviced by local bicycle shops

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INTERVIEW OF BICYCLE ENTHUSIAST: Customer Features:  Component strength Thomas Brannan  Ease of Travelling (513) 550-4702 Downhill 4326 Beech Hill Avenue Cincinnati, OH 45223

Thomas Brannan has rode bicycles for eighteen years, and single-speed for three years. He has worked as a bicycle mechanic for four years at Montgomery Cyclery. Thomas has competitively played bike polo for three years.

Drawbacks of Fixed-gear: . Requires full attention while riding Ideal enhancement of Fixed-gear: . Ease of travelling downhill.

Concerns of Solution: . Reliability . Component strength

Less Concern: . Aesthetics

After thoughts: . Hub that is user-friendly in regard to repairs.

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STURMEY-ARCHER S3X Product: Critiques: http://www.sturmey-  Backlash archer.com/products/hubs/c  Clunky/sudden/ id/3/id/47.html jerky shifting 9/5/2013  Shifting is not automatically Video: actuated http://www.youtube.com/w  Notorious for atch?v=AJmUds2YQ74&fe mechanical failures ature=c4-overview- vl&list=PLxn6T6UL2lSrB Cost: $179.00 USD ed0WeIGZxhd1WdyVTi-h 9/5/2013

The Sturmey-Archer S3X is a three-speed fixed-gear internal hub. Gear ratios for the S3X are 1:1 in first gear, a 25% reduction in second gear and a 37.5% reduction in third. Shifting is actuated by a manually operated shift mechanism which allows for user control when traversing various terrains. The S3X hub gear is especially good for climbing hills due to the designed gear ratios.

Specifications: Weight 120mm OLD 980g, 130mm OLD 990g Gears 3 Transition 160% Colors Black, Silver, Red, Gold, Purple, Turquoise Threaded driver accommodates a single Options speed freewheeler for a non-fixed 3 speed conversion Details 3-Speed, fixed-drive hub gear

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SRAM A2 AUTOMATIX Product: Critiques: http://www.sram.com/sram/  Disassembly urban/products/automatix required for 9/4/2013 adjusting

tensioning spring Forum: for shift point http://forum.ctc.org.uk/view speed. (Our topic.php?f=5&t=62320 design will 9/5/2013 include an Service Manual: external Automatix Service Manual adjustment screw PDF for ease of Date accessed: 9/6/2013 modification to

the shift point)

 Lack of OE The SRAM Automatix two-speed hub automatically switches grease inside the gears based on the speed. The auto 2 provides seamless, thought- unit free shifting from 1:1 to 1:1.37. Gear change occurs at a pre-set Cost: $87.00 USD speed, depending on wheel size, the hub automatically downshifts when slowing down, stopping, or climbing hills. There is no shifter required (therefore no controlling mechanism) as the centrifugal clutch allows for automatic shifting. The centrifugal clutch connects two concentric shafts, with the driving shaft nested inside the driven shaft. This is a fantastic system ideal for urban riding with minimum terrain changes. Advantages of the SRAM Automatix: Smooth shifting, quiet, and relatively light.

Specifications: Coaster brake 980 g, Freewheel 780 g, Disc Weight brake 720 g, SH Rollerbrake comp. 780 g Gears 2 Transition 136% Technology Mechanical centrifugal clutch Highlight(s) Colors Silver, Grey, Silver, Ivory Coaster brake, Freewheel, Disc brake, Options Aluminum hub shell, SH Rollerbrake comp., Gates -drive Details 2-speed automatic shifting

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APPENDIX B – SURVEY

Automatic Two-speed Internal-Geared Bicycle Hub CUSTOMER SURVEY with Results

Our Senior Design project is a two-speed, bicycle hub gear that shifts automatically at a predefined wheel rpm.

How important is each feature to you for the design of an bicycle hub gear? Please circle the appropriate answer. 1 = Low Importance 5 = High Importance . Avg. Aesthetics 1 2 3(3) 4(12) 5 N/A 3.9 Cost 1 2 3 4(15) 5 N/A 4.0 Ease of Adjustment 1 2 3 4 5(15) N/A 4.5 Ease of Maintenance 1 2 3 4(7) 5(8) N/A Range5.0 of Adjustment 1 2 3 4(15) 5 N/A 4.1 Reliability 1 2 3 4 5(15) N/A 4.8 Weight 1 2 3 4(7) 5(8) N/A 3.7

How satisfied are you with the current bicycle hub gear? Please circle the appropriate answer. 1 = Very Dissatisfied 5 = Very Satisfied Avg. Aesthetics 1 2 3(15) 4 5 N/A 3.1 Cost 1 2 3(7) 4(8) 5 N/A 3.3 Ease of Adjustment 1 2(15) 3 4 5 N/A 2.9 Ease of Maintenance 1 2 3(10) 4(5) 5 N/A Range3.6 of Adjustment 1 2 3(15) 4 5 N/A 3.4 Reliability 1 2 3(7) 4(8) 5 N/A 3.1 Weight 1 2 3 4(15) 5 N/A 3.8

How much would you be willing to pay for an bicycle hub gear?

$50-$100 $100-$150 $150-$200 $200-$250

Thank you for your time!

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APPENDIX C – QUALITY FUNCTION DEPLOYMENT

Kyle Krummert

&

Roman Zanto

Auto Bike Hub

9 = Strong Assembly 3 = Moderate -

1 = Weak

ustment limited 4 Turns ustment limited 4

Monochromatic Metal Body Hub Pattern Spoke Threading One Branding Internal Uni FittingsGrease Tools Bike Local Shop Lubricant SetExterior Screw Geometry for Accessibility Adj Material Selection Component Selection Range ofTeeth 4 Customer Importance MultiplierDesigner Current Satisfaction PlannedSatisfaction Improvement Ratio Modified Importance Relative % Weight

Aesthetics 9 9 9 9 1 3 3 3.9 1.0 3.1 4 1.3 5.0 13% Cost 1 9 1 3 1 9 3 9 9 1 4.0 1.0 3.3 3.5 1.1 4.3 11% Ease of 4.5 1.0 2.9 4.5 1.6 7.0 18% 9 9 9 9 3 Adjustment Ease of 5.0 1.0 3.6 4.5 1.3 6.3 16% 9 9 9 9 9 9 Maintenance Range of 4.1 1.0 3.4 4 1.2 4.9 13% 9 3 9 Adjustment Reliability 1 3 9 1 9 9 4.8 1.1 3.1 4 1.3 6.8 18% Weight 9 3 3 1 3 9 9 3.8 1.0 3.8 4 1.1 4.0 10% Abs. Importance Rel. Importance 3 8 4 4 6 9 8 8 10 8 5 10 14 3 (%)

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APPENDIX D – PRODUCT OBJECTIVES

Product Objectives:

Important for this product…

Aesthetics One branding < 4in2 Monochromatic Metal hub body brushed aluminum look…just an idea Spokes threading pattern Ease of Maintenance Graphic service manual with steps to guide users Internal uni-assembly Annual servicing (internal gear re-lubrication) Grease-fittings can be accessed by grease gun…idea Metric wrench set, spanner wrench, grease gun Lubricant accessible to local bicycle shops Ease of Adjustment Exterior set-screw Accessible to adult male hand Weight Weight < 3 lbs Price Range $100 - $200 (retail) Reliability Rust resistant Weather resistant comparably to other hubs Material selection based on design factor and stress analysis Component selection per spec sheet for desired product life Protect set screw from exposure to the elements (weather and debris) Range of adjustment Complete range of adjust < four 360º rotations of set screw Range will be + or – 2 gear teeth (total range of 4 teeth)

36

APPENDIX E – SCHEDULE

37

APPENDIX F – BUDGET

CATEGORY ESTIMATED ACTUAL

Interview and Consultations $300.00 $70.00 Miscellaneous $200.00 $0.00 Raw Materials $250.00 $9.00 Similar Products $50.00 $190.00 Tools and Hardware $500.00 $137.00 Testing $300.00 $110.00 Wheel, Spokes, Tire $60.00 $90.00

Total: $1660.00 $606.00

A38

APPENDIX G – PURCHASED COMPONENTS

CATEGORY ACTUAL Interview and Consultations $70.00 Miscellaneous $0.00 Raw Materials $9.00 JB Weld $9.00 Similar Products $200.00 Sturmey Archer S3X $100.00 Sturmey Archer S2 $60.00 SRAM Automatix $40.00 Tools and Hardware $137.00 Wheeltruing stand $110.00 tool $18.00 Nipple Wrench $9.00 Testing $110.00 Wahoo Sensor $60.00 Cateye Sensor $50.00 Wheel, Spokes, Tire $90.00 Spokes (14g); nipples 36 ct. $40.00 Tire and tube $25.00 service $25.00 Total: $606.00

A39

APPENDIX H – ASSEMBLY DRAWINGS

A40