Skidder
From Free net encyclopedia
Image:Old log skidder.jpg A skidder is a type of heavy vehicle used in forestry for pulling cut trees (timber) out of a forest as part of a logging project. Modern forms are generally categorized as either cable/winch skidders or grapple skidders.
Early skidders were pulled by a team of horses or mules. The driver would straddle the cart over felled logs, where dangling tongs would be positioned to raise the end of the log off the ground. The team pulled the tongue forward, allowing the log to "skid" along between the rolling wheels. Starting in the early 1920s, animals were gradually replaced by gasoline-powered engines, although some small operations continue to use them.
Contemporary skidders are tracked or four-wheel-drive tractors with a turbocharged diesel engine, winch and steel, funnel-shaped guards on the rear to protect the wheels. They have articulated steering and usually a small, adjustable, push-blade on the front. The operator/logger is protected from falling or flying debris (or parted cables) by a steel enclosure.
Alternatively, some skidders have a hydraulic grapple claw instead of a winch, and the claw (on a boom) grips and lifts the timber. Most grapple booms are fixed in place (to lift only), but some earlier models permitted the grapple boom to be swung to the side, resulting in instability. Furthermore, some Canadian loggers have created a hybrid by adding a grapple claw to the push-blade of their grapple skidders. This permits hauling back bark and tops when returning from a "landing" to a cut block.
On a cable skidder, the cable is reeled out and attached to a load of cut timber, then the powerful winch pulls the load toward the skidder. The winch or grapple holds the trees while the skidder drags them to a landing area or other collection point for forwarding to a loading point near a road.
The skidder can also be used for pulling tree stumps, pushing over small trees, and preliminary grading of a logging path known as a "skid road." They are rarely used for moving marketable logs (trees with limbs already removed) anymore because of the damage to the wood from being dragged.
One disadvantage of skidder logging in thinning operations is the damage to remaining trees as branches and trunks are dragged against them, tearing away the protective bark of living trees. Another concern is the deep furrows sometimes made by skidders, especially when using tires with chains, which alter surface runoff patterns and increases the costs of forest rehabilitation.
See also
- Feller buncher machine
- Log forwarder machine