Professor Brown, Christopher A., ME, Advisor

79 Pages·2013·4.48 MB·English

by  Paolo Masakayan

Project Number: CAB 1205

MANUFACTURING BAMBOO BICYCLE FRAMES WITH MOLDED COMPOSITE JOINTS

A Major Qualifying Project Report

Submitted to the Faculty of the

WORCESTER POLYTECHNIC INSTITUTE

In partial fulfillment of the requirements for the

Degree of Bachelor of Science in Mechanical Engineering

By
_______________________________

Nathaniel Gee

_______________________________

Paolo Masakayan

______________________________

Majd Sbat

______________________________

Mathew Skerritt

______________________________

Robert Winthrop

Date: April 25, 2013

Approved:

_______________________________
Professor Brown, Christopher A., ME, Advisor
Abstract
Inexpensive bicycles promote better development and improve life in third world countries.
One of the easiest ways to produce a cheaper bicycle is to use a cheaper material for the frame.
Bamboo is comparable in strength to aluminum alloy tubes, yet has a much lower cost. Bamboo
bicycles are currently used as a mode of cheap transportation in third world countries. Currently
the most common process used for manufacturing bamboo frames is hand wrapping a composite
layup around each joint. This procedure is labor intensive and results in a slow output of
bamboo bicycles. The objective of this project is to build a less expensive and easier to
manufacture bamboo bicycle frame than ones currently available. Axiomatic design was used
thoroughly in this project. A new joint making procedure was designed to promote easier
manufacturability of the bike. The joints were modeled in SolidWorks. Finite element analyses
with normal static bike loads were performed in ANSYS. The tooling was CNC machined by a
group member on Haas machine tools using ESPRIT CAM software provided by DP
Technology.

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Acknowledgements
We would like to acknowledge our advisor Christopher Brown for his guidance and
assistance throughout the project. We would also like to thank Worcester Polytechnic Institute
(WPI), Adam Sears, Torbjorn S. Bergstrom, Dr. Adriana Hera, and Don Pelligrino. Thanks to
the WPI Manufacturing Laboratory, Haas Automation, Inc., Kennametal Inc., and DP
Technology ESPRIT for their help. Thank you to the Bamboo Bike Studio for their guidance
and assistance in gaining the necessary materials to succeed in this project. Finally, we would
like to thank Axiomatic Design Solutions Incorporated.

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Table of Contents
Abstract ...................................................................................................................................... ii
Acknowledgements ................................................................................................................... iii
Table of Figures ...................................................................................................................... viii
1. Introduction ...................................................................................................................... 1
1.1. Objective ....................................................................................................................... 1
1.2. Rationale ....................................................................................................................... 1
1.3. State of the Art .............................................................................................................. 1
1.4. Approach ...................................................................................................................... 2
1.5. Methods ........................................................................................................................ 3
2. Design Decompositions and Constraints.......................................................................... 4
2.1. Top Level FRs of Main Decomposition ....................................................................... 4
2.1.1. FR1: Sustain up to 300lb Static Loading without Breaking ................................. 5
2.1.2. FR2: Present optimal joint geometry .................................................................... 5
2.1.3. FR3: Use mechanism to hold the bike frame in position ...................................... 5
2.1.4. FR4: Prepare bamboo for manufacturing .............................................................. 5
2.2. Collectively Exhausted and Mutually Exclusive .......................................................... 5
2.3. Additional Conditions................................................................................................... 6
2.4. Top Level FRs for Jig Decomposition ......................................................................... 7
2.4.1. FR1: Steady bike component outline .................................................................... 7
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2.4.2. FR2: Sustain bike tube placements ....................................................................... 7
2.4.3. FR3: Keep tubes in mold ....................................................................................... 7
2.4.4. Maintain mold positions ........................................................................................ 8
2.4.5. Jig core FR/DP Matrix .......................................................................................... 8
2.5. Top level FRs for Wet-layup Decomposition ............................................................... 9
2.5.1. FR1: Form an epoxy casing around joints to provide strength ............................. 9
2.5.2. FR2: Add a layer to the bamboo to provide strength ............................................ 9
2.5.3. FR3: Set mold pieces in place while the epoxy hardens ....................................... 9
2.5.4. FR4: Create a controlled flow for the epoxy when applying .............................. 10
2.5.5. FR5: Holding mechanism to secure the molds ................................................... 10
2.6. Wet-Layup Core FR/DP Matrix.............................................................................. 10
3. Physical Integration ........................................................................................................ 12
3.1 Head Tube ................................................................................................................... 13
3.2 Bottom Bracket ........................................................................................................... 14
3.3 Seat Joint..................................................................................................................... 15
3.4 Dropouts ..................................................................................................................... 15
3.5 Finite Element Analysis.............................................................................................. 16
4. Prototype Production ...................................................................................................... 19
4.1 Prototype Manufacturing ............................................................................................ 19
4.1.1 Mold Making Procedure...................................................................................... 19
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4.1.2 Jig making procedure .......................................................................................... 23
4.1.3 Joint making procedure ....................................................................................... 24
5. Testing and Analysis ...................................................................................................... 26
5.1. Prototype testing ......................................................................................................... 26
5.2. All FRs Satisfied ......................................................................................................... 27
5.3. Improvements of Final Method .................................................................................. 28
6. Iteration .......................................................................................................................... 30
6.1. Plastic mold failure ..................................................................................................... 30
6.2. Aluminum mold .......................................................................................................... 30
6.3. Injection ...................................................................................................................... 30
6.4. Filling molds beforehand ............................................................................................ 31
6.5. Final Method............................................................................................................... 31
7. Discussion ...................................................................................................................... 32
7.1. Evaluation of the Final Design ................................................................................... 32
7.2. Meeting the Original Objective .................................................................................. 33
7.3. Constraints .................................................................................................................. 33
7.3.1. Cost of Materials ................................................................................................. 33
7.3.2. Bamboo strength ................................................................................................. 33
7.4. Potential of a Global Scale ......................................................................................... 34
7.5. Flaws ........................................................................................................................... 34
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8. Recommendations .......................................................................................................... 37
9. Conclusions .................................................................................................................... 39
10. References ...................................................................................................................... 40
Appendix A: Detailed Joint Making Procedure ....................................................................... 42
Appendix B: Axiomatic Design Case Study ............................................................................ 44
Appendix C: SolidWorks Drawings of Molds ......................................................................... 46
Appendix D: Joint Material Property Calculations .................................................................. 48
Appendix E: Full Decomposition............................................................................................. 50
Appendix F: Instron Head tube Results ................................................................................... 57
Appendix G: Molding Process Pictures ................................................................................... 58

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Table of Figures
Figure 1: Core FRs and DPs ...................................................................................................... 4
Figure 2: Main Decomposition Matrix ...................................................................................... 6
Figure 3: Jig Decomposition ...................................................................................................... 7
Figure 4: Jig FR/DP Matrix ....................................................................................................... 8
Figure 5: Wet-Layup Decomposition......................................................................................... 9
Figure 6: Wet-layup FR/DP Matrix ......................................................................................... 11
Figure 7: Solid Model FR Integration ...................................................................................... 13
Figure 8: Head Tube Mold ....................................................................................................... 14
Figure 9: Bottom Bracket Mold ............................................................................................... 14
Figure 10: Seat Joint Mold ....................................................................................................... 15
Figure 11: Dropout Molds ........................................................................................................ 16
Figure 12: ANSYS Frame Test Setup ...................................................................................... 17
Figure 13: Total Deformation .................................................................................................. 17
Figure 14: Von Mises Stress .................................................................................................... 18
Figure 15: CNC Vise ................................................................................................................ 20
Figure 16: ESPRIT Tool Path .................................................................................................. 21
Figure 17: ESPRIT Machine Simulation ................................................................................. 21
Figure 18: Machining of Molds ............................................................................................... 22
Figure 19: Finished molds ........................................................................................................ 22
Figure 20: Mold support brackets ............................................................................................ 23
Figure 21: Dropout Mold Set Up ............................................................................................. 24
Figure 22: Joint Making Procedure .......................................................................................... 25
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Figure 23: Instron Testing ........................................................................................................ 26
Figure 24: Static Loading Test ................................................................................................. 27
Figure 25: Air Bubble Flaw ..................................................................................................... 34
Figure 26: Seat Joint Flaw........................................................................................................ 35
Figure 27: Leaking Flaw .......................................................................................................... 36
Figure 28: Seat Joint Drawing.................................................................................................. 46
Figure 29: Seat Joint Drawing.................................................................................................. 47
Figure 30: Dropout Drawing .................................................................................................... 47
Figure 31: Bicycle Assembly ................................................................................................... 47
Figure 32: Main Decomposition .............................................................................................. 50
Figure 33: Main Decomposition Matrix .................................................................................. 51
Figure 34: Jig Decomposition .................................................................................................. 52
Figure 35: Jig Decomposition Matrix ...................................................................................... 53
Figure 36: Wet-Layup Decomposition..................................................................................... 54
Figure 37: Wet-Layup Decomposition Matrix ......................................................................... 54
Figure 38: Mold Decomposition .............................................................................................. 55
Figure 39: Figure 39: Mold Decomposition Matrix ................................................................. 56
Figure 40: Intron Test 1............................................................................................................ 57
Figure 41: Instron Test 2 .......................................................................................................... 57

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List of Tables
Table 1: Corresponding FRs .................................................................................................... 12
Table 2: Problems and Solutions.............................................................................................. 37
Table 3: Joint Making Procedure ............................................................................................. 42
Table 4: Mold Volume ............................................................................................................. 48

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