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Felling
The felling stage in clear-fell harvesting influences the
whole operation.
The felling direction and stem presentation for extraction
requires careful attention, in order to reduce breakage
and to be able to present a well-delimbed stem for quick
extraction or further processing.
To reduce breakage, and provide a larger working
radius, it is preferable to fell trees against standing trees
to cushion the fall and reduce the amount of
undergrowth around the base of trees to be felled. This
is achieved by felling the tree just off-center to a
standing tree, preventing the falling tree becoming hung
up.
It is preferred an operator has manual felling
experience, allowing a better understanding of felling
techniques.
Felling Process
The direction of the fall is determined by the position of
the harvester head; the tree should fall in a direct line
with the tilt frame.
Position the harvester head on the tree as low as
possible while gaining the correct felling angle.
Consequently, the delimb arms and feed roller arms
should be fully opened and the harvester head in the tilt
Operation: Clear-cut Harvesting
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up position. Close the delimb arms and feed roller arms
once the selected tree is positioned in the opening.
A slight amount of pressure is then applied to the tree to
ensure the saw chain will not jam as the tree is being
cut.
When the saw chain is activated, both delimb and feed
arms circuits will operate at their highest setting to
ensure the tree does not move within the harvester
head while cutting is taking place. A stream of chips
leaving the saw chain box area provides a visual
indication of the cutting taking place. Keep the saw
chain activated until the tree can be felt to move
vertically. Stop the saw chain, which automatically
retracts, and apply force to the tree in the direction of the
fall.
At the full reach of the harvester head, tree control gets
reduced. Optimum felling is achieved using the
harvester head as close as possible to 3/4 of maximum
reach. During these manoeuvres, the base unit should
remain firm at all times. A reduction in reach will need to
be immediately applied if the base unit becomes
unstable. Ensure the tracks are on a firm footing at all
times, avoiding locating one or both tracks on stumps
which could allow the carrier to move unexpectedly
during manoeuvres.
Higher production is achieved through maximum ground
coverage with minimal track movement. This also
reduces environmental impact.
Delimbing
At this point, the tree is ready to be delimbed. This
involves rotating the base and feeding the stem through
the harvester head, while obtaining the correct direction
of the butt. Once the butt has been positioned, the
remainder of the tree can be delimbed, using the
momentum of the harvester head to assist the delimbing
effort.
Care must be exercised when swinging stems around,
so as not to allow contact with the operator's structure,
and to be aware of tail swing which could damage other
trees or stems.
● Ensure the delimb arms are kept sharp, and in form,
to reduce the effort required to remove limbs.
● The delimbing procedure is about balance and stem
control, which, when perfected, gives excellent
results and increases production.
● Do not feed the stem through the harvester head
while the stem is facing the operator's structure.
It is recommended that during delimbing the harvester
head is only just high enough to position the butt and
clear objects. Operating the harvester head too high will
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