156B Week 2

1/12/21 Professor Meeting

Weekly Progress Report

What have been done in the past week

• Finalizing designs of past four risk reduction prototypes (2D moment, 3D moments, reaction forces)

• Securing the 3 topics for the design challenges

  • Truss

  • Moment of inertia

  • Center of mass

• Brainstorming ideas for all 3 design challenge ideas

  • Truss bridge

  • Deflection in a cantilever beam with different cross sectional areas for MOI

  • Balancing multiple tiers of a mobile (an arrangement of hanging objects) for COM

Feedback from meeting with sponsor

• Individual feedback given for each demonstration tool

  • 2D moment: Need to make sure that the shaft and acrylic body rotate together, the stand for the peg board needs to be sturdy so that the pegboard does not move during the demonstration

  • 3D moment about an axis: Need to find an appropriate material to show bending moment that is thick enough for the hinge screws to fit in

  • Reaction at various supports: Make demonstration pull out of board, add motion and force arrows

• Truss bridge

  • Need to brainstorm what will be used for the supports (rocker, fixed)

  • Need to brainstorm the pros/cons of limiting the design to only bridges

    • What else would we allow them to do?

    • What more materials would be needed w/ those ideas involved?

  • Can check out Polybridge (online, app store, or google playstore) for design inspiration

    • https://store.steampowered.com/app/367450/Poly_Bridge/

  • Need to replicate pin joints between truss members

    • Reduce friction at joint

    • Binding barrel could be used as a pin joint? https://www.mcmaster.com/binding-barrels/steel-binding-barrels/

  • How do we make this an open-ended design challenge (not everyone doing the same thing)?

    • Students are maximizing a figure of merit that considers cost and strength?

• Moment of inertia

  • Students would be measuring maximum deflection

  • Need to brainstorm more material options for the cantilever beam idea

  • How do we make this an open-ended design challenge (not everyone doing the same thing)?

    • Performance index (FOM) that considers the MOI in 2 axes (subjecting to a load in 2 separate directions)?

  • Need to leave more room for creativity from students

• Center of mass

  • What is the goal of the challenge for the mobiles?

  • Alternative idea: Stacking stones

    • Highest wins

    • Maximize height and width with a small base?

    • Objects would have regular geometries (instead of actual stones) so that the students can calculate the C.O.G.

• When brainstorming ideas, consider how it facilitates learning

List your current concern according to the importance

• Need to reschedule next Monday’s meeting (holiday)

• Having enough time in the quarter to complete all requested demonstrations and design challenges

• We may need to select which models are the most important to complete to prioritize quality over quantity

What is the next step of your project

• Priority: Constructing final prototypes of the demonstration tools (2D moment, 3D moments, reaction forces)

• Report week 1 section draft due on Friday

• Brainstorming more thorough ideas for the design challenges