Make Sense of the Hoberman Sphere / Circle, Linkage

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3D model description

####Make Sense of the Hoberman Sphere/Circle

The Hoberman sphere is a beautiful structure (Hoberman, 1990, 1991), appealing to children and grownups alike. Mathematically, it is an extension of the traditional linkages. Taking two bars of the same length and connecting them in the middle, we get a pair of scissors, the four vertexes of which form a rectangle. Adding more and more, we get a retractable handle (or lift), a long line that never becomes a circle.

However, if we bend the bar a little, say 30 degrees, the math magic happens—a retractable circle. A short analysis shows that one need 360/30 scissors pairs to make a circle. Of course, if you bend it 20 degrees, you would need 360/20=18 pairs.

3D design allows us to build Hoberman circle to help students understand and appreciate the power of mathematics and design. The straight bar is 80mm; the bent one has two 40mm sections.

####Steps

Step One: Make a Line of Scissor Pairs Using the straight bars. It is still fun to play with it.
Step Two: Make a Hoberman circle using 12 pairs of scissors (24 bars) and 36 pins.
Step Three: Play around and ask questions.

• 3D file format: STL
• Publication date: 2019/01/18 at 18:23

Creator

STEAM educator, learning from and working with K-12 STEAM teachers to explore new ideas of teaching and engagement. I firmly believe ART is at the core of STEM learning or all human learning! I owe my ideas and designs to the hundreds of K-12 children and teachers and university professors I have had the pleasure of working with, in multiple disciplines-- math, science,engineering language arts, social studies, early childhood education and more! All mistakes, of course, are mine! There is no warranty or liability whatsoever implied or explicit behind the designs or ideas. They are all posted for their potential educational values.

When working with children, please strictly observe all safety and health procedures! Please refer to the NSTA safety guides: http://www.nsta.org/safety/.

LGBU Contact: LGBU@SIU.EDU