23
EN
Using the cobra
®
system
DYNAMIC BREAKAGE CABLING:
To prevent breakage caused by oscillation-induced
overstretching, install cobra with a shock absorber
as dynamic breakage cabling. The natural oscilla-
tions of the crown are not impeded, yet load peaks
from strong gusts are softly dampened. You should
dimension the tree cabling system so that it is rela-
tively slack. Because the higher the tensile strength,
the less flexible the system and the stronger the load
peaks when impact forces occur.
STATIC BREAKAGE CABLING:
If the branch is already damaged (i.e. cracks have
formed), we recommend that you install a cobra
tree cabling system without a shock absorber or
low-expansion cobra ultrastatic, which was devel-
oped specifically for this purpose, in order to install a
static breakage cabling system. This will immobilise
the critical point, preventing the crack from opening
further and preventing the branch from breaking off.
LOAD/SUPPORT CABLING:
To ensure that the broken branch will not fall to the
ground and endanger passing traffic, pedestrians
or cyclists, install a so-called static load/support ca-
bling system. Fit a cobra tree cabling system without
a shock absorber or cobra ultrastatic as vertically as
possible for this purpose. Immediately after it breaks,
the secured branch will then remain hanging in the
cable and will only fall as far as cable expansion
allows with little or no impact force. The cable and
anchor point must be able to bear the weight of the
branch.
Installation rules in accordance with "ZTV Baumpflege"
DYNAMIC BREAKAGE CABLING:
To optimally reduce the forces that occur, install a
dynamic cobra breakage cabling system at a point at
least 2/3 the length of the branch to be secured be-
cause this is more or less where the centre of gravity
of the load will be when there are strong winds.
This keeps the swaying forces that occur as low as
possible and ensures low loading of the cable. You
then achieve
optimal dynamic efficiency of the system with the
lowest possible tensile strength (see tensile strength
table on page 25), protecting the supported crown
parts from overstretching and breaking. Installa-
tion at a lower point requires higher dimensioning.
Install cobra cabling without tension and slack in the
summer. Install cobra with a slight amount of slack
in the winter (max. 10 % of its length) to prevent any
continuous load in the summer.
STATIC BREAKAGE CABLING:
Install a static breakage cabling system at a point at
least 2/3 the length of the branch to be braced for
the same reasons as outlined for dynamic break-
age cabling. In this case, however, you do not want
any elasticity because further movement can make
an existing crack even bigger. According to "ZTV
Baumpflege", twice the values specified in the tensile
strength table (see page 25) therefore apply to static
breakage cabling systems.
SERVICE LIFE:
Permanent risk minimisation is necessary in sensitive
areas, e.g. on main streets. If a tree is damaged,
e.g. a branch breaks, a temporary installation may
give you time to better assess the damage and the
reaction of the tree.
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