Bicycle Headset with Adjustable Spring Rate Final Design Report Presented by Drew Drees [email protected] Jonah Masumoto [email protected] Camden Boshart [email protected] Matthew Mounteer [email protected] Prepared for Professor Andrew Kean Mechanical Engineering Department California Polytechnic State University San Luis Obispo June 3, 2021 1 Abstract Fork flop can play an important role in the performance of a mountain bike. This phenomenon of fork flop is known as the tendency that the front wheel of a bike wants to flop over to one side when moving slowly. The fork flop experienced on a bicycle changes with the geometry of the bike, but our team sought to change the fork flop experienced through an adjustable internal spring design that attaches to the bicycle instead. From our research, we decided to utilize torsion springs as the method for mitigating fork flop. We also decided to use load cells and a DAQ to compile and compare the data of our test bicycles. After creating a prototype, we compared the moments experienced on a bicycle with an extremely slack head angle to that of a bicycle with a steep head angle. The bicycle with a slack head angle had our prototype placed on it to provide the fork flop mitigation. Our results show that the bicycle with the slack head angle experienced less moments with our design placed on it, putting it on a comparable level to that of a bicycle with a steep head angle. These results suggest that our internal spring design can mitigate the fork flop experienced on a bicycle without changing the bicycle’s geometry. Our prototype gives an important conclusion that bicycle riders can change the performance of their bicycle without the need for a complete overhaul of their bike. 2 Table of Contents 1.0 Introduction .............................................................................................................................. 7 2.0 Background .............................................................................................................................. 7 2.1 Customer Observation and Research ............................................................................... 7 2.2 Existing Designs and Patents Research ............................................................................ 8 2.3 Technical Literature Research .......................................................................................... 9 2.4 Industry Codes and Standards Research ....................................................................... 10 3.0 Objectives ................................................................................................................................ 11 4.0 Concept Design ...................................................................................................................... 14 4.1 Design Process ................................................................................................................... 14 4.2 Weighted Decision Matrix ................................................................................................ 16 4.3 Final Concept Design ........................................................................................................ 17 4.4 Preliminary Analysis ........................................................................................................ 19 4.5 Design Hazards.................................................................................................................. 20 5.0 Final Design ........................................................................................................................... 20 5.1 Final Design Description .................................................................................................. 20 5.2 Structural Prototype ......................................................................................................... 23 5.3 Design Justification and Material Selection ................................................................... 24 5.4 Cost Analysis Summary and Maintenance Considerations .......................................... 28 6.0 Manufacturing ....................................................................................................................... 29 6.1 Procurement of Materials and Components (already been updated) .......................... 29 6.2 Manufacturing Steps ........................................................................................................ 30 6.3 Top and Bottom Spacers (121000 & 122000) ................................................................. 30 6.4 Housing Assembly (110000) ............................................................................................. 32 6.5 Clamp Assembly (130000) ................................................................................................ 35 6.6 Assembly Process .............................................................................................................. 36 6.7 Outsourcing ....................................................................................................................... 37 7.0 Design Verification ................................................................................................................ 38 7.1 Fork Flop Test ................................................................................................................... 39 7.2 Heat Resistance Test ......................................................................................................... 42 7.3 Weather Resistance Test .................................................................................................. 43 7.4 Adjustment and Installation Test .................................................................................... 45 3 7.5 Aesthetics and Feedback Tests ........................................................................................ 46 7.6 Weight and Volume Tests ................................................................................................ 47 Result Summary ...................................................................................................................... 47 7.7 Future Testing Plans ......................................................................................................... 47 8.0 Project Management .............................................................................................................. 48 9.0 Conclusion and Recommendations ....................................................................................... 49 9.1 Next Steps .......................................................................................................................... 50 Appendices .................................................................................................................................... 53 Appendix A. Stakeholder Needs and Wants......................................................................... 53 Appendix B: QFD House of Quality Table ........................................................................... 54 Appendix C: Project Gantt Chart ......................................................................................... 55 Appendix D: Jamboard Session ............................................................................................. 57 Appendix E: Ideation Design Ideas ....................................................................................... 58 Appendix F: Pugh Matrices for Functions ........................................................................... 62 Appendix G: Design Hazards Checklist ............................................................................... 68 Appendix H: Weighted Decision Matrix............................................................................... 70 Appendix I: Preliminary Analysis ......................................................................................... 71 Appendix J: Failure Modes & Effects Analysis (FMEA) .................................................... 72 Appendix K: Spring Force Analysis Excel Sheets ............................................................... 74 Appendix L: Design Verification Plan & Report ................................................................. 75 Appendix M: Linear Fork Flop Investigation ...................................................................... 77 Appendix N: Spring Fatigue Calculations ............................................................................ 78 Appendix O: Drawing Package ............................................................................................. 79 Appendix P: Experimental Test Procedures ........................................................................ 96 Appendix Q: Uncertainty Calculation ................................................................................ 111 Appendix R: User Manual ................................................................................................... 112 4 List of Figures Figure 2.1 A bicycle headset with damping (a), a motorcycle damper (b) and coil spring (c). ..... 8 Figure 2.2 A handlebar flop stopper (a) and handlebar stabilizer (b) ............................................ 8 Figure 3.1 Boundary diagram isolating a headset on a bicycle frame. ........................................ 11 Figure 4.1: Pugh Matrix for the Subfunction of Returning the Wheel to Center. ....................... 14 Figure 4.2 Function tree for Addressing Fork Flop. ...................................................................