Reconstructing da Vinci's Armored Vehicle

I. Original Design

The dimensions of this foam-core model is entirely extrapolated from this drawing. It is approximately 3 ft wide, 3 ft long and 4 ft tall. The enclosing conical structure has a porthole on the top. The wheels each have 18 teeth driven by a gear system connected to the side of the wheel closer to the center.

The problem in this system is that turning the crank will result in the gears turning the wheels so that the wheels rotate in opposite directions to each other.

II. Possible Solutions

1. Have the teeth of the wheels facing in opposite directions, while still remaining aligned to each other.
2. Extend the crankshaft so that the gear at one end is moved a wheel-length in front. The gears then rotate the same part of the wheels.