Square Lego wheels
The Troy, NY company that invented a mechanism for powering a vehicle with square wheels has been all over the web lately. Their idea is obvious, but ingenious. The square wheels are turned by a rotating mass mounted atop the vehicle. Everything is angled precisely causing each wheel to successively roll flat as the mass rotates around the vehicle.
Several LEGO maniacs decided to try this on their own. (Video included in the first link.) The results are simple and successful.
