The flanged centre wheels were attached to a screw, by which the framework of the cart could be raised, so that on level ground the ordinary side wheels were set to be 1-2 inch (25-50 mm) above the surface of the road, and the entire weight of the burden rested on the rail. The side wheels touched the ground only occasionally, but the main weight was borne by the centre wheels, resulting in very low friction. In some experiments, a large log of wood was placed on the ground, over which one of the side wheels would pass without derailing. When a small hole was dug in the line of a side wheel, this could also be passed without an accident.
