The fifth-wheel coupling of the fifth wheel is a mechanical arrangement that provides the link between an articulated semi-trailer and the towing unit, tractor unit, leading trailer, or dolly. The coupling consists of a kingpin of 50.8-88.9 mm in diameter with a steel pin on the front of the semi-trailer and a horseshoe-shaped coupling equipment called a fifth wheel on the rear end of the towing unit. The surface of the semi-trailer (with ... Read more
