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MatheMUSEments

Spiraling Triangles

By Ivars Peterson

Muse, February 2007, p. 26-27.

Playing with triangles can lead to amazing patterns and three-dimensional structures. That's what Hungarian designer Dániel Erdély (below) found when he created an intriguing geometric form out of two spirals of triangles that get smaller and smaller.

Daniel Erdely

Photo by Regina Márkus

He called the resulting S-shaped object a spidron. Each of its two arms looks a bit like a seahorse's tail.

Spidron arm.

Erdély

The two spiral arms of a spidron consist of alternating sequences of equilateral and isosceles triangles (above).

Drawing a spidron.

Erdély

How to Draw a Spidron's Arm (above): Start with a regular hexagon, which has six corners. Connect every send corner with a straight line to make a six-pointed star. Inside the star is a smaller hexagon. Again connect every second corner. Continue the process until the shape in the center is so small that you can't put in any more lines. The resulting pattern contains six identical copies of a spidron arm.

A spidron tiling.

Erdély, Marc Pelletier, Amina Buhler Allen, Walt van Ballegooijen

Even though spidrons are irregularly shaped, they can fit together without gaps or overlaps to cover a plane (above). For example, you could tile your bathroom floor with this pattern of spidrons.

Sliding-coin puzzle.

Erdély, Marc Pelletier, Amina Buhler Allen, Walt van Ballegooijen

When spidrons are laid down like tiles on a flat surface, then creased in just the right way at the line within each spidron arm, the flat structure can be forced to fold accordion-style into a wavy surface (above). As the folds get steeper, the whole pattern twists and compacts.

Spidron polyhedron.

Erdély, Marc Pelletier, Amina Buhler Allen, Walt van Ballegooijen

Creased and folded spidrons can be assembled into three-dimensional balls (above). This one is made of 120 spidrons.

Are spidrons good for anything besides artwork and maybe bathroom floors? Erdély says spidron surfaces could be used for collapsible solar panels or shock absorbers. And spidron-based blocks might make an interesting toy. But mostly, he admits, they're just interesting for their own sake.


You can learn more about spidrons at www.spidron.hu.

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