Skidding
damage happens during the extraction. It can be caused by the machine or the
skidded log.
Animals
seldom bump into trees, because they fear to be wounded. Machines have no
sensors to protect from damage, only the driver should have. Therefore, in
dense stands the moving pattern of the machine has an influence to the likelihood
of a damage:
Curves can
be tricky, when the rear axle has a shorter turning radius than the front axle
as it is common with Ackerman steering. Conventional machines like farm
tractors and trucks have Ackerman steering.
Dedicated forestry
machines often have an articulated frame, where the two half-frames are
connected by a central hinge. In that case, the rear wheels follow exactly the
same track as the front wheels. The risk to damage trees is much lower.
Another cause
of damage is that the superstructure of a forest machine (like cabin, loading
boom and basket) bumps against neighboring trees because of uneven floor. If
the machine is fitted with bogies, the deflection of the chassis is only half
as high then without bogies, so the danger of accident decreases.
Damage to
the stand can be caused by long logs, too. The area of the danger zone depends
on the length of the log and the angle 𝛂 between log axis and strip road.
This
formula says that the length has the most important influence on the danger
zone. Thus, Systems that transport short logs make less damage to the forest stands.
