A tree chipper or woodchipper is a machine used for reducing wood (generally tree limbs or trunks) into smaller woodchips. They are often portable, being mounted on wheels on frames suitable for towing behind a truck or van. Power is generally provided by an internal combustion engine from 3 horsepower (2.2 kW) to 1, 000 horsepower (750 kW). There are also high power chipper models mounted on trucks and powered by a separate engine. These models usually also have a hydraulic crane.