GMT 050
User manual
15
5.
Application
5.1
Application GMT050
The GMT 050 felling grapple is a timber grapple with a saw function, consisting of a tilt frame, a
grapple frame and a saw casing. The tilting grapple frame ensures that both horizontal and vertical
timber can be sawed
.
The following tasks can be carried out with the felling grapple
;
Maintenance to or felling of trees, cutting of firewood/residual wood, clearing of storm damage and
mechanized pruning of trees. When performing these tasks on any wood growing horizontal to the
ground (usually considered limbs rather than trunk wood) a maximum limb cutting diameter of 50
cm must be taken into account in all cases.
Tree trunks with a wider diameter than 50 centimeters often require a dual cut for removal. This
operation is possible with the grapple saw when taking into account these safety precautions.
Remove as many side branches as possible to ensure a predictable fall direction.
When possible use the remaining tree trunk as a base for the double cut piece until ready to
lower it to the ground.
Once the trunk piece has been double cut free, it becomes a hanging load that the carry
vehicle must support. This requires a correct weight estimation be made before starting the
cuts.
Using the proper techniques and understanding how to apply them to individual trees is the key to
felling any tree safely.
After the limb or branch has been cut free high up in the tree, it becomes a hanging load and will
slowly tilt down. The maximum length which may be cut is limited to 6 meter (20 feet) or shorter
when the maximal allowed weight has been reached first.
The maximal height of a tree which can be removed safely is limited to the diameter of the wood and
the maximum length of the hanging load. Below an example of a quick height estimation of a tree
that could be removed:
A crane has a reach of:
10 meter
|
32 ½ feet
The crane is placed on a column:
2 meter
|
6 ½ feet
Maximal length of the hanging load:
6 meter
|
20 feet
This results in a maximum height of the tree:
18 meter
|
59 feet
At all times the maximum load mentioned in the load chart of the crane is decisive!
A common used method to determine the maximum load that can be cut is:
Find the maximum load mentioned in the load chart of the crane and subtract
o
The weight of the felling grapple (± 395 kg) ≈ (± 870 lb)
o
The rotator (± 50 kg) ≈ (± 110 lb)
o
Sometimes a crane boom-end connection piece (± 80 kg) ≈ (± 176 lb)
o
Or a telehandler extension boom (± 300 kg) ≈ (± 661 lb)
then 50% of the weight that is left will be the maximum load of the limb or branch which is allowed
to be removed when the load becomes a hanging load for the crane after cutting.