Woodchipper

A tree chipper or woodchipper^[1] 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 2 to 700 kilowatts (3 to 1,000 horsepower). There are also high power chipper models mounted on trucks and powered by a separate engine. These models usually also have a hydraulic winch.

Tree chippers are typically made of a hopper with a collar, the chipper mechanism itself, and an optional collection bin for the chips. A tree limb is inserted into the hopper (the collar serving as a partial safety mechanism to keep human body parts away from the chipping blades) and started into the chipping mechanism. The chips exit through a chute and can be directed into a truck-mounted container or onto the ground. Typical output is chips on the order of 2.5–5 cm (1–2 in) across in size. The resulting wood chips have various uses such as being spread as a ground cover or being fed into a digester during papermaking.

Most woodchippers rely on energy stored in a heavy flywheel to do their work (although some use drums). The chipping blades are mounted on the face of the flywheel, and the flywheel is accelerated by an electric motor or internal combustion engine.

Large woodchoppers are frequently equipped with grooved rollers in the throat of their feed funnels. Once a branch has been gripped by the rollers, the rollers transport the branch to the chipping blades at a steady rate. These rollers are a safety feature and are generally reversible for situations where a branch gets caught on clothing.

• 
  A Yardbeast 2090, showing a chipper shredder configuration. It is distinguished by two dedicated feed hoppers, for chipping and shredding. This type of machines use a disk rotor with one or more blades and a cluster of hammers and flails to reduce the size of the material.
• 
  This type of machine is used to chip large pieces of wood.
• 
  A portable woodchipper and truck with wood chips collected in the truck bed.
• 
  Wood chips from a small garden chipper.
• 
  Tree chipper mounted by side to tree processing into biomass for energetic burning