1. Прочитайте текст и ответьте на вопросы

1. What different timber and wood/pulp harvesting systems were used in the forests of southern New England over the years?

2. What are the main advantages and disadvantages of horse/oxen skidding?

3. What gives excellent traction and maneuverability to crawler tractors?

4. What are the lowest-cost harvesting systems used in southern New England?

5. What other harvesting systems have become popular in southern New England?

2. Найдите необходимую информацию и подготовьте мини-доклад на одну из предложенных тем

• Timber harvesting systems in Europe

• Timber harvesting systems in Asia

• Timber harvesting systems in Russia

4. CABLE LOGGING

Cable logging is a logging method primarily used on the West Coast of North America with yarder, loaders and grapple yarders. The cables can be rigged in several configurations.

There are two classes:

1. High lead logging, in which a simple loop of cable runs from the yarder out through pulley blocks anchored to stumps at the far end of the cut.

2. Skyline, in which a carriage, pulled by hauling cables, runs along a skyline cable, providing vertical lift to the logs.

Into this there are varieties of loading systems.While skyline logging requires additional setup time, the vertical lift of the skyline allows faster yarding, which can outweigh the additional labor costs, especially on larger harvest units. Since the 1980’s Grapple Yarders have become popular.

Skyline and grapple yarding, however, require more complex and expensive equipment. A traditional highlead or gravity system will function with just two cables, a skidding line and a haulback line. As the names imply the skidding line is used to drag the logs in, and the haulback line is used to drag the skidding line back out for the next turn (or group of logs).

A skyline system will add a third line - the skyline whose function is to hold the skidding line and the haulback line off the ground or 'in the sky'.

The yarder itself is located on a landing, a flat area on top of the ridge that is being logged. After the trees are retrieved by the yarder, the limbs are bucked (removed) and the logs are then placed in piles awaiting transport.

Swing yarder. A swing yarder is a mobile piece of heavy duty forestry equipment used for pulling logs from the woods to a logging road with cables. The swing yarder is also known as a grapple yarder.

In any logging operation, it is necessary to transport the harvested tree from the stump to a landing for transport to market (usually on a truck). If the ground is relatively flat it may be possible to transport the tree or logs cut from the tree on a wheeled or tracked machine. However if the ground is too steep for the operation of such machinery, it is common practice to rig some sort of a cable system for moving the wood. The swing yarder is one of several varieties of machines that have been used for this purpose.

The swing yarder has several drums to pull in the cables. The cables run up an angled boom and then to the far side of a setting. By using two cables set up like a clothes line, the rigging can be pulled out and logs can be pulled across a logging setting where the trees have been previously felled. This machine is most suitable for steep ground where it is difficult to access the logs with other machinery. Swing yarders can also be used in flatter areas with lighter loads.

While there are various rigging options, the most common one uses a grapple that can be lowered onto a logs and closed via the cable system. Using a grapple avoids the need for people in the setting to attach chokers to the log. Choker setting as a profession is a very dangerous occupation.