DECEMBER 5, 2018 FREEDOM CONCEPTS DRIVE MODE MECHANISM FINAL REPORT PREPARED FOR: COLIN BOCK, FREEDOM CONCEPTS JIM SYKES, P. ENG., E.I.R., ADVISOR FACULTY OF ENGINEERING MECH 4860 – ENGINEERING DESIGN TEAM 11 JEREMY DRACHUK IAIN FRIESEN JORDAN HOFER JOSH LINSANGAN SCOTT VERCAIGNE Letter of Transmittal December 5th, 2018 Colin Bock Freedom Concepts 2087 Plessis Rd Winnipeg, MB, R3W 1S3 [email protected] MECH 4860 – Team 11 University of Manitoba 66 Chancellors Circle Winnipeg, MB, R3T 2N2 Subject: Letter of Transmittal Dear Colin Bock, Our team is pleased to submit to you our final design report for the Drive Mode Mechanism for Freedom Concepts Inc., marking the completion of phase one of the project. This report will be followed up with the phase two beginning in January 2019, during which our design team will validate the Drive Mode Mechanism through prototyping and testing. If you have any questions, please feel free to contact any of the team members signed below. Sincerely, Team 11 Jeremy Drachuk Joshua Linsangan Scott Vercaigne _ Jordan Hofer Iain Friesen Cc: Jim Sykes ii Executive Summary This report marks the completion of phase one (design) of the Drive Mode Mechanism project submitted by Freedom Concepts Inc. for the MECH 4860 – Engineering Design course at the University of Manitoba. The second phase (prototype) will begin in January 2019 and will be completed in April 2019. Freedom Concepts Inc. is a Winnipeg based company that designs and manufactures adaptive tricycles and mobility devices for people living with disabilities. The company has tasked the student design team with the development of a tool-free mechanism to accomplish two separate drive modes for the rider (freewheel and direct drive) and that is compatible with all current tricycle models. The current mechanism being used on the tricycles relies on frictional contact between four set screws and a standard freewheel sprocket to toggle between the two modes. Although functional, actuation requires the use of a tool and has proven too cumbersome for the average caregiver. The design team conceptualized a two-way ratchet mechanism capable of supporting a freewheel and direct drive mode with a single switch actuation. This concept was developed through research, concept development, and feedback from the client and the course advisor. The mechanism consists almost entirely of laser cut sheet metal and off-the-shelf components from McMaster-Carr® to reduce low-volume production costs and facilitate design changes in the prototyping phase. The estimated cost of the prototype design is $133.99. To meet the requirements set by the client, the design features two spring loaded pawls, one of which can be rotated away or toward an internal gear profile using a switch to support the freewheel or direct drive modes. The sprocket can be easily interchanged with any of the 18, 22 or 26-tooth variations to deliver all three pedaling difficulties that a customer may order. To maximize the lifespan of the device, the design is supported by a full stainless-steel construction, sealed bearings and maintenance plan. Included with the final design is a detailed installation procedure, bill of materials, cost breakdown, preliminary failure modes and effects analysis, and a complete package of preliminary drawings including all three custom sprocket sizes. These deliverables fulfill all requirements of the project as established by Freedom Concepts. An alternative internal tooth profile is also included and will be tested in the prototyping phase. The intuitive and easily actuated toggle switch will improve the user experience and encourage the use of the freewheel and direct drive modes as intended by Freedom Concepts. iii Table of Contents List of Figures .................................................................................................................................. iv List of Tables ................................................................................................................................... iv 1.0 Introduction .............................................................................................................................. 1 1.1 Background ........................................................................................................................... 1 1.2 Objectives .............................................................................................................................. 2 1.3 Project Timeline .................................................................................................................... 3 1.4 Target Specifications ............................................................................................................. 3 1.4.1 Client Needs ................................................................................................................... 3 1.4.2 Technical Specifications ................................................................................................. 4 1.5 Constraints and Limitations .................................................................................................. 4 1.6 Concept Development Summary .......................................................................................... 5 2.0 Detailed Design ......................................................................................................................... 7 2.1 Sprocket Design .................................................................................................................... 9 2.2 Pawl Design ......................................................................................................................... 11 2.3 Toggle Mechanism .............................................................................................................. 12 2.4 Material Considerations ...................................................................................................... 14 3.0 Design Summary ..................................................................................................................... 15 3.1 Preliminary Failure Modes and Effects Analysis ................................................................. 15 3.2 Maintenance ....................................................................................................................... 16 3.3 Assembly Procedure ........................................................................................................... 17 Pawl Disc Assembly: .............................................................................................................. 17 Sprocket Assembly: ............................................................................................................... 19 Installation Procedure: .......................................................................................................... 20 3.4 Cost Summary ..................................................................................................................... 21 4.0 Conclusion ............................................................................................................................... 22 5.0 References .............................................................................................................................. 23 Appendix A – Concept Development ........................................................................................... A-1 Appendix B – Stress Analysis ........................................................................................................ B-1 Appendix C – Preliminary Failure Modes and Effects Analysis .................................................... C-1 Appendix D – Bill of Materials...................................................................................................... D-1 Appendix E – Preliminary Engineering Drawings ......................................................................... E-1 iii List of Figures Figure 1. Present method of operation on tricycle ........................................................................ 2 Figure 2. Project timeline ................................................................................................................ 3 Figure 3. Two-Way Ratchet concept ............................................................................................... 6 Figure 4. Teeth Engagement concept ............................................................................................. 6 Figure 5. Two-Way Ratchet exploded view .................................................................................... 8 Figure 6. Design mechanism - a) freewheel mode b) fixed drive mode ......................................... 9 Figure 7. Interchangeable sprocket designs: a) triangle tooth design b) gear tooth design .......... 9 Figure 8. Sprocket design projected from standard tooth profiles .............................................. 10 Figure 9. 26, 22, 18-tooth sprocket options ................................................................................. 10 Figure 10. Pawl and gear design in a typical ratchet .................................................................... 11 Figure 11. Design mechanism - a) Freewheel mode b) Direct drive mode .................................. 12 Figure 12. Standard freewheel pawl design ................................................................................. 12 Figure 13. Toggle assembly ..........................................................................................................