Instruction Guide: NXT Parts Exploration

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Construction Techniques

This Technic Primer is a resource form Carnegie Mellon Univerisity's Robotics Academy (http://www.education.rec.ri.cmu.edu/)  Robotics Engineering Vol. 1 product (http://www.education.rec.ri.cmu.edu/content/lego/curriculum/rev1_index.htm).

Joining Pieces (examples 1 thru 4)

  • Student can construct 4 assemblies using different friction pegs and beams

Stationary Axles (examples 1 and 2)

  • Students can construct 2 assemblies using axles as structural elements

Optional : Reinforcing Structures and Size Scale

  • Student will not use these techniques soon or often – may be overkill at this point

Optional : Pulleys, Cam Rods and Axis of Rotation

  • Student will not use these techniques soon or often – may be overkill at this point

Gears

  • Assemble Gear Train (steps 1 thru 4 in primer)
    • Add 3 bushings to secure gears (similar to Photo 1_1 )
    • Note ease of motion
  • Alter assembly to use 3 non-friction pegs (tan colored) instead of axles
    • Note ease of motion
  • Alter assembly to use 3 friction pegs (blue colored)
    • Note difficulty of motion

Structural Building Challenge

Use the Building Challenges PPT to give students more insight and practice on techniques for building sturdy and efficient structures with the NXT kit.

Slide 1  

In order to extend a straight beam, a minimum of two pegs must be used

  • The further apart the pegs are, the stronger the connection, but the shorter the resulting extended beam    

Slide 2  

Triangles make very sturdy, strong structures – even when only attached by one peg  

Rectangles (or squares) are not sturdy when only attached by one peg – they readily morph into parallelograms

  • To make rectangles sturdy, at least one corner must be locked at a right-angle – this will inhibit the other corners from moving too
  • The more corners locked, the stronger the rectangle

Slide 3  

To make rectangles sturdy, at least one corner must be locked at a right-angle – this will inhibit the other corners from moving too

  • The more corners locked, the stronger the rectangle
  • Corners can be locked with angled beams and multiple pegs or by creating a triangle in the corner with another beam  

A flat rectangle (or square) presents other challenge

  • Locking these corners will take many pieces unless….
  • This snap-beam part creates a very fast, efficient and effective means of accomplishing this
  • If students try the snap-beam first, have them also try to solve this without using the snap-beam so they appreciate the elegance of this solution  

The mini-bridge challenge gives students a chance to put this new learning into practice

  • Have students build their bridges
  • Encourage then to not simply create a plank bridge (as in the example photo) but also think about how to use triangles to make it stronger
    • Creating triangles on the side of the bridge where one side is two beams on the bridge deck (that will bow together when weight is added) and the other two sides are additional beams connected above the bridge deck, will increase the load capacity of the bridge deck
  • Test the student bridges by incrementally adding weight
  • Discuss why some bridges to better than others
  • Examine the point of failure on bridges that collapse early
  • Discuss ways these could be improved  

Slide 4  

This challenge is all about build long-and-strong (slide 1)

  • The structural building learning (slides 2,3) can be assessed in the Faraday Golf Challenge   in the NXT First Build lesson

As an extended challenge, have students place the brick/battery between the bridge and motor/dude for an additional load on the bridge

Slide 5

Print out this grading sheet for students

Slide 6  

Note: the kit used in this example had 6 straight snap-beam more than the standard 9797 kit