Modern skidders

Date: 2015-10-07; view: 458.

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 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. They are one of the few logging machines that is capable of thinning or selective logging in larger timber. Forwarders can haul small short pieces out, but if mature timber is to be thinned, a skidder is one of the few options for taking out some trees while leaving others. While selective logging can be done badly in a host of ways, taking some trees while leaving some may be a preferred alternative to taking all the trees.

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". A positive thing about the skidder is that while wood is being yarded (pulled), tree particles and seeds are cultivated into the soil.

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.

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).

Alternately, 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, (such as the one pictured) which 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.

In some areas, loggers have combined a hydraulic claw on the side the blade of their grapple skidders, making it possible to pile logs in some cases. (More commonly seen on cable skidders) This also permits hauling back bark and tops when returning from a "landing" to a cut block.

Caterpillar 528 cable skidder Modern dual function grapple skidder

6. Вместо точек вставьте слова из следующего списка:

single , contemporary , hydraulic grapple , articulated, engine, landing , vehicle, single , hydraulic , fixed, articulated, steep.

1……………………….. .hills

2. ……..... ……………....vehicle,

3. ……………………. …engine

4. ………………………..skidders

5. ………… …………….bucket

6. ……………………….stage

7. ………… …… ……… function

8. …………. …………… claw

9. ………. ……………… boom

10. ……………………… steering

7. Найдите в тексте причастия I, II.