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Engineering Analysis

Engineering Analysis. Fantastic Five 8 March 2006 3:00 pm. Overview. Post-Midterm Review Highlights Engineering Analysis Looking Towards Part Drawings. Post-Midterm Review Highlights. Altered Design by: Replaced box with foam pad Keyboard mount to fold 270 o

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Engineering Analysis

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  1. Engineering Analysis Fantastic Five 8 March 2006 3:00 pm

  2. Overview • Post-Midterm Review Highlights • Engineering Analysis • Looking Towards Part Drawings

  3. Post-Midterm Review Highlights • Altered Design by: • Replaced box with foam pad • Keyboard mount to fold 270o • Not to mount on both sides; two sliders on one side • Cams be used to lock height in position

  4. New Changes • Instead of a retrofit, the design will be created for a specific office chair (Dakang Model FY-9926)

  5. Engineering Analysis • Weight based on components: • Wireless keyboard = 5 lbs • Sliders = 9 lbs • Mount, linkage = 15 lbs • Total = 29 lbs • Estimated weight of hands = 30 lbs

  6. Strength Analysis • Using a static analysis of the keyboard and clamp, the forces placed on the load create a moment force around the arm • The analysis is given through the next slides

  7. Loads 30 lbs – Max weight of resting hands 5 lbs – Weight of keyboard and tray apparatus 30 lbs 5 lbs

  8. Dimensions 30 lbs 5 lbs R1 R2 29 in. .75 in. .75 in. 2.5 in. 9.5 in. 3.5 in. 12 in.

  9. Static Analysis 30 lbs 5 lbs R1 R2

  10. F2 = 159 lbs u2 1 L = 7 in. Deflection of Slides • Assume slides are solid Al bars E = 10.4 Mpsi A = (1.0”x .25”) = 0.25 in.2 2 0 0 u2 = - 4.3 e-4 in.

  11. u2 1 2 L = 7 in. Deflection of Slides • Assume slides solid Al beam E = 10.4 Mpsi A = (1.0”x .25”) = 0.25 in.2 F2 = 124 lbs 0 0 u2 = 3.3 e-4 in.

  12. Clamp Force Estimation 30 lbs 5 lbs 7 in. 6 in. Rp Fc

  13. Fatigue Analysis • Fatigue will occur in sliders and hinge • Fatigue in hinge will be negligible; no weight is supported except along with gravity • Fatigue in sliders was unable to be measured. Sliders are rated for 100 lbs in normal use and fatigue is not an issue. For our use, sliders should support the load requirements and fatigue should also not become a factor

  14. Stability During Operation • Stability in operation is based on the strength analysis. • It was found that the moment upon the arm was found to be 41 lbs and the forces upon the sliders were 124 lbs and 159 lbs, respectively • As these forces fall within the limits of the sliders, the stability in operation should be maintained

  15. Dynamic Load • Dynamic force for this design is the fingers depressing keys • Although the moment force changes upon the sliders, the difference is negligible and can be ignored

  16. Material Selection • Keyboard mount – painted wood, plastic • Hinge – brass • Sliders – aluminum • Cam shaft - steel • Protective pad - foam

  17. Safety • Possible Hazards and Solutions • Electrical elements : Spill-proof keyboard • Closing the Hinge : Safety warning sticker • Open Sliders : Slider cover when open

  18. Human Interface • The human interface on this design has 3 features • Distance from user (sliders) • Height from the user (cam system) • Pitch (using keyboard feet)

  19. Tolerances • The tolerance that needs to be specified for the design is the overhang of the keyboard mount on the arm • Overhang must be the same length as the lowest height of the keyboard

  20. Performance Analysis and Prediction • The key points to analyze for the performance are the strength, fatigue, and stability • The analysis shows that all factors are within the limits of rated allowances • This leads to a prediction that the design will perform well after prototyping

  21. Summary • Weight • Strength, Fatigue, and Stability Analysis • Dynamic Load • Material Selection • Safety • Human Interface • Performance Analysis and Prediction

  22. Next Week • Part Drawings – enough information to fabricate the design

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