Yaw chains offer a high tensile strength. Two sets of 4 wearing-off Ertalon rails are placed on both sides of the body floor to prevent the moving floor and the body floor from scraping each other (“steel against steel”). This device is also quieter. The two well-protected hydraulic motors driving the moving floor have two gears: the first one to set the moving floor in motion and progressively increase its speed, and the second one for a quick and regular unloading.