Stan Wagon, a mathematician
at Macalester College in St. Paul, Minnesota, has built a bicycle with square
wheels that actually works! When he rides it on an inverted catenary
“road,” it goes as smoothly as a normal bike. His bicycle
has even been featured in Ripley's Believe It or Not!
Professor Stan Wagon of Macalester College on his square-wheeled bicycle.
From http://stanwagon.com. The bike
“road” is 25 feet long. The whole apparatus is available for
public riding, and resides in the Science Center at Macalester College, Minnesota.