Abstract: A tipple comprising a fixed support having two horizontal parallel rails with inboard and outboard ends and a cradle assembly mounted on the rails including two rocker members each with a curved surface engaging the rails. The cradle assembly supports a vehicle on the rocker members with the center of gravity of the vehicle located relative to the curved surfaces such that the cradle assembly with a loaded vehicle thereon freely rolls from a normal, vertical position through an angle of about 135.degree. to a dumping position. Once the contents of the vehicle have been discharged, the cradle assembly automatically and freely rolls back to its vertical position. The curvature of the curved surface can be formed such that the radial distances from the center of gravity of the vehicle to each curved surface decreases along the curvature.