Sculpturer Eric Peltzer has built his own electric mountain bike using a huge go-kart motor. He writes on his blog: “The reason for this powerful a motor is simple: hills. I live on a steep hill. While a Zap or a US ProDrive rated at 400 watts goes a decent 17 mph on flat land, they slow to 3 to 5 mph on a decent hill. I can pedal that fast. However I wanted to go faster and be able to get up a hill. The simple fact is that you need from 5 to 10 times as much power to go a given speed on a decent grade. This is why a car that only needs 12 hp to go 60 mph on flat roads has an engine that can put out 100 to 200 hp.”

A separate independently created home-made electric bike, found on Flickr (via Makezine). Don’t know much about it, other than it was made by Pete Green and uses a 350W motor.