Page 15 - Moving the Earth_ The Workbook of Excavation

LAND CLEARING AND CONTROLS

LAND CLEARING AND CONTROLS 1.15

When practical, cutting should be done so as to take advantage of natural factors, to drop the
tree in the direction that it tends to fall. This direction can be made positive, or altered moderately,
by appropriate notching and cutting.
For greater changes in direction, including tipping the tree oppositely from its normal inclina-
tion, wedging or line pull is needed.

Wedging. If there is the slightest question about the direction the tree will fall, a wedge of wood,
plastic, or magnesium should be driven lightly into the back of the cut, to prevent wrong-way
leaning. This protects the saw against binding, and may influence direction of fall. See Fig. 1.7.
A large tree that has a moderate tendency to fall in a wrong direction can be forced into the
right one by wedging. The wedge or wedges may have to be iron or steel, as other materials may
not withstand heavy driving. Saw manufacturers oppose any use of hard metal.
The moving saw chain must never touch a hard wedge, as it would suffer immediate and severe
damage. The wedge therefore cannot be inserted until the cut is deep enough to provide ample
working space for the saw, and the operator must exercise extreme care.
Wedging tends to overturn the tree to the side directly opposite. But the fall will be affected
by other factors, such as unbalance to the side, taper in the hingewood, or wind pressure. These
factors should be allowed for in placing the wedge.
Wedging may be started with a soft wedge, to keep the cut open until it is deep enough to use
the hard one.
One wedge may not be sufficient to tilt the tree. A similar wedge may be driven just above it,
Fig. 1.8A, or a thicker wedge driven beside it. Since a thin entering wedge is not needed now, a
made-on-the-job wood wedge, Fig. 1.8B, may be used.
The hingewood may be cut thinner to make wedging easier. But if this strip is made too thin
or cut through, or if it is weak because the wood is brittle or decayed, a badly unbalanced tree may
fall backward over the wedge.
If tree diameter is too small to safely accommodate a wedge and a chain saw, the chain may
be replaced by a hand crosscut, if one is available. Or the tree may be pulled by a line fastened
high up, or pushed by a pole or a loader.

Pull or Push. Direction of fall can usually be controlled by a rather light pull on a line fastened
high up, the higher the lighter. The first problem is placing the line, which could require either a
good climber or a tall ladder, and must be done before starting the cut.
The tree should not fall on the workers or machine doing the pulling. Heights of trees are dif-
ficult to estimate, so it is safer, and uses a shorter line, to use a pulley block or blocks and pull
from the side. See Fig. 1.9A.
The best machine for pushing a tree is a backhoe. It has a high reach in proportion to machine
size, and can stand back far enough not to interfere with the cutting.
Pull or push is usually light at first, and is increased as the cut deepens.

FIGURE 1.7 Use of saw and wedge.