National Crane Published 10-30-2014 Control # 040-09 7-9
1400H OPERATOR AND SERVICE MANUAL INSTALLATION
TRUCK FRAME STRENGTH
In order for a truck frame to be suitable for accepting a
Series 1400H size crane, the truck frame must have a
requirement for rigidity so as not to allow excessive boom
movement due to truck frame deflection, and it must be
strong enough to resist the loading induced by the crane so
as not to permanently bend or deform. Section Modulus
(S.M.) is a measurement of the area of the truck frame and
determines the rigidity of the frame. Resistance to bending
moment (RBM) is a measurement of strength and is
determined by multiplying the section modulus of each frame
rail by the yield strength of the rail material.
For a standard mount, 180° stability, the Series 1400H
crane requires a minimum of 3,300,000 lb-in (372 850 Nm)
RBM and 30.0 in
3
(492 cm
3
) S.M. under the crane frame
between the front and rear springs with 1,980,000 lb-in (223
710 Nm) RBM and 18 in
3
(295 cm
3
) S.M. through
suspension to rear stabilizers on each truck frame rail. For
360° stability the truck frame must have a 30.0 in
3
(492 cm
3
)
section modulus [3,300,000 lb-in (372 850 Nm) RBM]
minimum under the crane frame, 18 in
3
(295 cm
3
) section
modulus [1,980,000 lb-in (223 710 Nm) RBM] at the front
spring rear hanger, 12 in
3
(197 cm
3
) section modulus
[1,320,000 lb-in (149 140 Nm) RBM] through the front spring
and 3 in
3
(49 cm
3
) section modulus [330,000 lb-in (37 284
Nm) RBM] at the stabilizer attachment point on each truck
frame rail. Listed below is a table showing the commonly
used truck frame and reinforcing materials and the section
modulus required for each material to ensure adequate
strength and rigidity. In all cases, the minimum requirements
for section modulus and RBM must be met.
Truck Frame or
Reinforcing
Material
Min. Section
Modulus Under
Crane
Min. Section
Modulus Thru
Rear Suspension
RBM Under
Crane
RBM Thru
Suspension
180°
Stability
110,000 psi
(758 MPa)
30.0 in
3
(492 cm
3
)
18.0 in
3
(295 cm
3
)
3,300,000 lb-in
(372 850 Nm)
1,980,000 lb-in
(223 710 Nm)
360°
Stability
110,000 psi
(758 MPa)
30.0 in
3
(492 cm
3
)
13.0 in
3
(295 cm
3
)
3,300,000 lb-in
(372 850 Nm)
1,980,000 lb-in
(223 710 Nm)
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