Bridges and Wheels, Tricycles and Squares

Dr. Stan Wagon of Macalester College discusses the mathematics
behind rolling a square smoothly. In 1997, inspired by a square
wheel exhibit at The Exploratorium museum in San Francsico, Dr.
Stan Wagon enlisted his neighbor Loren Kellen in building a
square-wheeled tricycle and accompanying catenary track. For years,
you could ride the tricycle at Macalester College in St. Paul,
Minnesota. The National Museum of Mathematics in New York now also
has square-wheeled tricycles that can be ridden around a circular
track. And more recently, the impressive Cody Dock Rolling Bridge
was built using rolling square mathematics by Thomas Randall-Page
in London.