A scraper is a construction machine used for smoothing surface, light stock removal of topsoil, excavation and transport of soil very compact, shedding layers of material, cut into thick on the ground, load it, transport it and download it.
Composed of a trailer towed by a tractor and, usually, two axes. The trailer has a movable body, with the lower part equipped with a sharp front edge, which should be replaced periodically for wear. The lowered hopper cuts the soil at the desired height, the inertia of the movement loads the ground in the body, such as a hand planer for wood, where the chip enters the inside and, if the amount is too much, it exits from above. When the hopper is full, it is raised and closed, and the contents carried in the unloading area.
To unload, the hopper must be down in part without affecting the soil. If the exhaust is in front of the rear panel of the hopper or of the ejector, it is hydraulically pushed forward, and the load falls off with a desired thickness, normally between 20 and 30 cm. There are models with one engine and they usually require a crawler dozer, named pusher, with the blade closer than normal, which leads from behind the trailer helping to cut through the toughest grounds. The heavier models have two motors driving one of the front wheels and the other driving the rear wheels, with motors up to 400 kW (536 hp). There are models with an self-loading rotating system that do not require retro thrust.
There are 2 types of scrapers: