Automatic Two-Speed, Fixed-Drive Bicycle Hub-Gear 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 wheel 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. ii 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 EPICYCLIC GEARING.............................................................................................................................. 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 ii APPENDIX D – PRODUCT OBJECTIVES........................................................................ 36 APPENDIX E – SCHEDULE ............................................................................................. 37 APPENDIX F – BUDGET .................................................................................................. 38 APPENDIX G – PURCHASED COMPONENTS ............................................................... 39 APPENDIX H – ASSEMBLY DRAWINGS ....................................................................... 40 iii 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 Axle ........................................................................ 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 ...............................................................................................