Jib Crane Cantilever Bending Moment Calculator

Overview

The jib crane cantilever bending moment calculator is a free online engineering tool for analyzing the structural loading of a jib crane’s cantilever beam. By entering key parameters such as beam length, rated capacity, beam self-weight, and maximum slewing radius, the calculator instantly computes the total bending moment acting on the cantilever, helping engineers identify and avoid the risk of beam fracture before it happens. It also makes it easy to compare how different lifting capacities and working radii affect the cantilever structure, verify whether the cross-sections of the cantilever beam and support column meet working strength requirements, and evaluate the overall rationality of a jib crane design — providing a reliable reference for further structural development.

Input Parameters

Parameter	Description	Unit
G-beam	Cantilever beam self-weight	N
L1	Total cantilever beam length	mm
G-hoist	Hoist (or winch) weight	N
G	Rated lifting capacity	N
L3	Maximum slewing radius	mm
L2	Length from rotation center to cantilever front end	mm
G-counterweight	Counterweight force	N
L4	Distance from counterweight to rotation center	mm

Calculation Formulas

Uniformly distributed load:

\[q_1 = \frac{G_{beam}}{L_1}\]

Moment from the hoist and rated load at the maximum slewing radius:

\[M_1 = (G_{hoist} + G) \times L_3\]

Moment caused by the self-weight of the cantilever beam:

\[M_2 = q_1 \times L_2 \times \frac{L_2}{2} - q_1 \times (L_1 - L_2) \times \frac{(L_1 - L_2)}{2}\]

Moment caused by the counterweight:

\[M_3 = G_{counterweight} \times L_4\]

Total bending moment:

\[M = M_1 + M_2 - M_3\]

Where:

• M — total cantilever bending moment of the jib crane (unit: N·mm)
• M1 — moment produced by the hoist and load at the maximum radius of gyration
• M2 — moment produced by the self-weight of the cantilever beam
• M3 — offsetting moment produced by the counterweight

Calculation Notes

Different structural types of jib cranes arrange the cantilever beam differently, so this calculator uses two separate length variables — L1 and L2 — to accommodate various designs:

• L1 = total length of the entire cantilever beam
• L2 = length from the center of rotation to the front end

If the cantilever beam has a rear overhang beyond the rotation center, the rear length is calculated as:

\[L_{rear} = L_1 - L_2\]

Only with this value can the moment M2 caused by the beam's self-weight be calculated accurately, ensuring the result reflects the real loading condition.

Applicable Jib Crane Types

• Free Standing Jib Cranes
• Wall Mounted Jib Cranes
• Wall Travelling Jib Cranes
• FEM Standard Jib Cranes
• Workstation Jib Cranes

Why Cantilever Bending Moment Calculation Matters

A jib crane is essentially a cantilever beam structure — fixed at one end to a column or wall while the free end carries the lifting load. Because there is no second support to balance the load, the bending moment accumulates toward the fixed end and the area near the rotation center, making these sections the most vulnerable to bending failure or fracture. Calculating the cantilever bending moment accurately at the design stage allows engineers to confirm whether the selected beam and column sections have adequate strength, reduce the risk of structural failure, and make informed, quantitative comparisons between different capacity and working-radius configurations before finalizing a jib crane design.