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TESTING THE STABILITY
The formulas and examples included in these instruc-
tions are based on the SFS 4677 standard.
During the test, the vehicle is in normal working con-
dition without load, tilted 5
must withstand the maximum load applied by the
wheels or the other points of support.
•
The test is performed at the maximum reach
with 10% overload. All normal crane functions
are performed, but cautiously. The vehicle's 5
inclination is achieved by putting a suitable riser
under one of the rear wheels. Its height can be
calculated as follows:
h = riser height needed
z =vehicle width from wheel center to wheel
center
h = 0.087 x z
Example:
z =120 cm
h = 0.0887 x 120 cm = 15 cm
•
The vehicle is considered stable if no more than
one point of support rises off the ground during
the test. Increased stability when loading it from
the side can be achieved by widening the track
and/or adding rear axle load by using, for example,
wheel weights.
DETERMINING THE STAND-STABILITY BY CALCULATION
The crane is considered stable when the stability ratio
"n" calculated from formula below is equal or larger
than 1.
A = Normal distance from cranes turning center to
overturning edge.
B = Normal distance from booms end (load) to over-
turning edge.
C = Distance from vehicles rear axles center and over-
turning edge.
E = Normal distance from booms point of support to
overturning edge.
G = Maximum load at distance A + B
N = Cranes weight without booms
P = Booms weight (centroid)
M
= Rear axle weight without load
2
n = Stability factor
You can use the example for calculating the stand sta-
bility for any tractor by measuring "K" and "H" from the
tractor. With these measures you can calculate "C". See
the tractors manual for rear axle weight M
must be more than 1.
o
to the side. The ground
o
, "n" value
2
CR40
EXAMPLE 1
tractor Valtra T190 + FT9 + CR40
Formula
N = 530 kg
A = 180 cm
G = 430 kg
n=
EXAMPLE 2
tractor Valtra T190 + CR40
Formula
N = 530 kg
A = 140 cm
G = 430 kg
n=
Formula
21
N x A + M2 x C
n=
G x B + P x E
B = 490 cm
C= 120 cm
P = 340 kg
M
2
E = 70 cm
530 x 180 + 1250 x 120
430 x 490 + 340 x 70
N x A + M2 x C
n=
G x B + P x E
B = 530 cm
P = 340 kg
E = 110 cm
530 x 140 + 2190 x 100
430 x 530 + 340 x 110
H x A
C =
K + H
= 1250 kg
=1,05
C= 100 cm
M
= 2190 kg
2
=1,11
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