This view shows the construction and thickness of the wheels.  The time train are those wheels on the left next to the black crescent moon.  The bottom wheel is known as the great wheel.  It is 3/8" thick.  It turns the center wheel right above it that is made from 1/4" material.  The center wheel turns the 2nd wheel right above it and made from 1/8" material.  The 2nd wheel turns the escape wheel that is also made from 1/8" material.  The reason for decreasing the size and mass of the wheel is that a larger wheel with more mass will push a smaller wheel with less mass much easier than having all the wheels with the same thickness.  The primary benefit of this design is that the movement will run on less weight.