As with equipment used in other industries, machines used in the lumber and forestry industry has evolved over the years. Functions that were previously performed manually with chainsaws can now be performed by machines. Examples of this are the feller bunchers, harvesters, etc.
Since logging operations often occur in soft ground conditions the ground pressure that is exerted by the equipment is often a key factor. This ground pressure is expressed in pounds per square inch. This pounds per square inch can be impacted during machine design by controlling the weight of the machine as well as changing the area of the machine that contacts the ground. This can be done by providing wider and/or larger tires on rubber tired equipment, or by providing longer and/or wider track assemblies on tracked equipment.
Delimbers, normally mounted on hydraulic excavators, are used to remove branches from felled trees in the forestry industry. Since their early beginnings, various types have been developed, including chain flail, gate, slideboom, stroke, and pull-through delimbers.
A feller buncher is a type of harvester used in logging. It is a motorized vehicle with an attachment that can rapidly cut and gather several trees before felling them.
A feller buncher consists of a standard heavy equipment base with a tree-grabbing device furnished with a circular saw or a shear. The machine then places the cut tree on a stack suitable for a skidder or forwarder for further processing (e.g., delimbing, bucking, loading, or chipping).
A forwarder is a forestry vehicle that carries felled logs from the stump to a roadside landing. Unlike a skidder, a forwarder carries logs clear of the ground, which can reduce soil impacts but tends to limit the size of the logs it can move. Forwarders are typically employed together with harvesters in cut-to-length logging operations.
A harvester is a type of heavy forestry vehicle employed in cut-to-length logging operations for felling, delimbing and bucking trees. A forest harvester is typically employed together with a forwarder that hauls the logs to a roadside landing.
A skidder is any type of heavy vehicle used in a logging operation for pulling cut trees out of a forest in a process called “skidding”, in which the logs are transported from the cutting site to a landing.
A clam-bunk skidder has top-opening hydraulic jaws to hold a load of trees for extraction. The advantage over a grapple skidder is typically a larger payload that is located above the rear axle for improved traction. The disadvantage is that it must be loaded.
On a cable skidder, the cable is reeled out and attached to a pull of cut timber, then the winch pulls the load toward the skidder. The winch or grapple holds the trees while the skidder drags them to a landing area. Cable skidders are less popular than in the past. They are more labor intensive than grapple skidders because someone (the operator or a second person) must drag the winch line out to the logs and hook them up. This is helpful where it is not possible to drive the machine close to the log (such as in steep hills).
Alternatively, some skidders have a hydraulic grapple bucket instead of a winch, and the bucket- attached to the skidder by a boom- grabs and lifts the timber.
There are three types of ‘fixed boom’ grapple skidders: a single function boom type with two hydraulic cylinders, only allowing the boom to lower in one position. The dual function booms has four cylinders, which allows for adjusting the boom in two different places. The third type that permits the grapple boom to be swung from side to side allowing spread out trees to be grabbed at once.