The Batcycle for the 2008 superhero film The Dark Knight (directed by Christopher Nolan) is called the Batpod and its mock-up was done by Nolan and later designed by Nathan Crowley, who designed the Tumbler for Batman Begins (2005). The bike has 20" front and rear tires (the Tumbler's front wheels), and is powered by a high-performance, water-cooled, single-cylinder engine - geared toward the lower end for faster acceleration and with no exhaust pipes. The exhaust is routed through the hollow steel/aluminum/magnesium tubing used for the frame of the bike. The Batpod is steered by the shoulders instead of hands, and the rider's arms are protected by shields. The two foot pegs are set 3 1/2 feet apart on either side of the tank, which the rider lies on, belly down. The sound effects for the Batpod came, in part, from the sound of the Tesla Roadster's electric motor.