The new incarnation of the Tumbler was proposed by Nolan after he built a proof-of-concept model design out of Play-Doh - a model he admitted looked "very very crude, more like a croissant than a car". Nathan Crowley, one of the production designers for "Batman Begins", then started the process of designing the Tumbler for the film by model bashing based on that shape. One of the parts that Crowley used to create the vehicle was the nose cone of a P-38 Lightning model to serve as the chassis for the car's jet engine. Six models of the Tumbler were built to 1:12 scale in the course of four months. Following the scale model creation, a crew of over 30 people, including Crowley and engineers Chris Culvert and Andy Smith, carved a full-size replica of the vehicle out of a large block of Styrofoam, which was a process that lasted two months.