16.810 Critical Design ReviewCrossover BicycleIntroduction and Initial DesignVersion 1: Manufactured and TestedVersion 2: Manufactured and TestedAlternative “Boomerang” design16.810 Critical Design ReviewCrossover BicycleTeam 3JoHanna Przybylowski & Laura CondonJanuary 30, 2004Introduction and Initial Design Cross Over Bicycle designed for mass consumer market• Constrain Mass•Optimize Cost• Accept Performance Loading Cases• F1 = 50 lbs• F2 = 75 lbs• F3 = 75 lbs Requirements• Delta 1 < 0.060 mm• Delta 2 < 0.009 mm• Natural Frequency > 505 Hz• Mass < .27 lbs• Cost < $5.20 per part• Cutting Quality = 4F1F2F3Initial CAD Design from Hand SketchVersion 1: Manufactured and Tested Manufactured part slightly different from original design• Bar between bottom holes moved because it was not being stressed• Design freedom used on the “fork” hole: moved diagonally upward• Individual bar widths modified to redistribute mass FEM and Test Results•All displacements were met with FEM•Displacements were ~1/5 and 4/5 less than constraints•Test Delta 1 is factor of 3 greater than FEM•Test Delta 2 is factor of 15 greater than FEMManufactured Version 1 CAD DesignParameter ConstraintFEM Version 1Test Version 1Cost < $5.2 $5.22 $5.22delta 1 (mm) < 0.060 0.052 0.156delta 2 (mm) < 0.009 0.0034 0.051Unrestrained Natural Frequency (Hz)> 505 476 486Mass (lbs) < 0.27 0.246 0.25Version 2: Manufactured and Tested Goal to minimize cost while staying exactly at mass limit• Fillet Radii increased to decrease cutting time• Straight paths joining holes • Altered thickness of bars FEM and Test Results•All displacements were met with FEM•Displacements were ~1/4 less than constraints•Test Delta 1 is factor of 1.5 greater than FEM•Test Delta 2 is factor of 10.9 greater than FEMManufactured Version 2 CAD DesignParameter ConstraintFEM Version 2Test Version 2Cost < $5.2 $5.05 $5.05delta 1 (mm) < 0.060 0.045 0.0685delta 2 (mm) < 0.009 0.0055 0.0598Unrestrained Natural Frequency (Hz)> 505 487 506Mass (lbs) < 0.27 0.27 0.279Alternative “Boomerang” design Goal to eliminate hole in middle to drastically cut cost Optimized mass distribution through iterations to improve performance. FEM and Test Results•All except delta 1 were FEM compliant•Delta 1 is factor of 1.3 greater than FEM•Delta 2 is factor of 3.43 greater than FEMNew Boomerang CAD DesignParameter ConstraintFEM Version 1Test Version 1Cost < $5.2 $4.05 $4.05delta 1 (mm) < 0.060 0.0692 0.090delta 2 (mm) < 0.009 0.0064 0.022Unrestrained Natural Frequency (Hz)> 505 544 563Mass (lbs) < 0.27 0.27
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