Once you have all of the tools and parts gathered, assembly takes only a few minutes. Instructables member ride_on_toy_dude is only 15, but is already showing promise as an engineer. He used a cordless drill as a motor on an old bike. It was a quick and simple project.
Did I say that it was elegant? No, just quick and simple. Hence the zip ties. He modified a bicycle hand brake to serve as the throttle control. The textured casing of the chuck (if I understand it correctly) rubs against the rear tire, providing locomotion.
Here it is in action!
-via Hack a Day