They are running a CNC Vector Pattern Contest. You can follow the link and rules by clicking on the image below:
Actually, everything 2d on the train has been done with the 1/4", and 1/8" cutters, and the edge quality is second to nothing else I've used............but speaking of trains.......
From that point, I used the vectors to mass out the 3d pieces I actually needed. The barrel was the primary concern. I wanted slits down each side of the barrel for the walkway to slide into. This was for 2 reasons. The first being that it will look so much cleaner at the transition point between the 2 pieces, and the second being the walkways will actually clamp the barrel, preventing it from moving around, essentially making everything structural. A major concern for when the whole thing travels down the highway, at highway speeds.