Instruction Guide: EV3 - Parts Exploration

Submitted by Randy Steele on 18 September, 2013 - 08:31

In this Lesson we have 2 Primary Instruction Resources:

1) The Technic Primer

2) The Building Challenges PPT

Construction Techniques

This Technic Primer is a resource from Carnegie Mellon University'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). The Technic Primer uses NXT, but the concepts are mostly the same for the EV3, although the component colors may be different and in some cases not available in the EV3 kit.

Joining Pieces (examples 1 thru 4)

  • Student can construct 4 assemblies using different friction pegs and beams
  • Note: on Step 2, they will need to use beams instead of studded 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
  • Note: on Step 3, they will need to use the 3x5 angular beam instead of the 2x5 arm

Optional : Cam Rods

  • 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
    • Tiny tabs on the rounded blue shaft add friction
    • This same difference is present betrween biege (low friction) and blue (high friction) long pegs and the grey (low friction) and black (high friction) short pegs.
       
  • More exploration of gearing is available in the Introduction to Gears Lesson (later in this Unit) and the Getting in Gear Lesson (in a future Unit).

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 EV3 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 - span the long direction of the box for added challenge.
  • 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 EV3 First Build lesson

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

Slide 5

Print out this grading sheet for students