USA’s recent work for Math Factory will be featured as a part of their exhibit “The Math Midway” at the World Science Festival Street Fair, which will be held in Washington Square Park on Sunday, June 14, 2009. This fair is intended to inspire and entertain with exhibits based on mathematic principles.

“Wheel Deal”, designed by Ralph Appelbaum Associates, Inc. and built by USA for Math Factory, is one of many exhibits and games featured at the fair. In this exhibit, visitors ride tricycles with square wheels over a large round, flower-shaped platform. The “petals” of the flower are made of a series of inverted catenary curves. The ride is still smooth because the square wheels allow the center of the wheel to always remain level. We’ve seen demonstrations of this principle that travel in a straight line, but never a circle!

This exhibit is an interesting engineering challenge for USA as each tricycle wheel requires unique calculations for its position on the flower’s radius. Material choice is also crucial for the flower surface of the Wheel Deal exhibit. USA is building the flower in layers from 1/8 inch plywood to make the surface precise and durable.

Another mathematical principle is demonstrated at the center of the flower. USA machined a surface to represent the seeds of the sunflower. This seed pattern illustrates phyllotaxis. Phyllotaxis patterns are found in nature and can be seen on pineapples, pinecones, and certain flowers. The number of spirals in each direction is a Fibonacci number.

We hope you have a chance to see the exhibits at the Science Festival. If not, you may catch it as a traveling exhibit at your local science center!

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