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Skidder
From Wikipedia, the free encyclopedia
A skidder is a type of heavy vehicle used in a logging operation for pulling cut trees out of a forest. Modern forms can pull trees with a cable/winch or a grapple or in a clam-bunk.
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.
The early mechanical skidders were steam powered. They traveled on railroads, known as "dummylines" and the felled trees were dragged or "skidded" to the railroad where they were later loaded onto rail cars. One popular brand was the Clyde Skidder, built by Clyde Ironworks in DeLuth, MN. The Clyde skidder illustrated was photographed at the Marathon Lumber Company logging operations near Newton, MS in the early 1920's. Although these machines appear to be large and cumbersome, they were true workhorses of their day. The Clyde was capable of retrieving logs from four different points at the same time. Each cable, or lead, was approximately 1000 feet in length. Once the logs were attached and a clearance signal was sent for retrieval, they could be skidded at a speed of 1000 feet per minute. Working conditions around these machines were very dangerous.
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, or rolling over) by a steel enclosure.
On a cable skidder, the cable is reeled out and attached to a pull 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.
Alternately, 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 models permit the grapple boom to be swung from side to side allowing spread out trees to be grabbed easier. 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.
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".
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 in the topsoil, especially when using tires with chains, which alter surface runoff patterns and increases the costs of forest rehabilitation and reforestation.