This page now limits the post-crane calculation to the applied static moment from declared vertical load and boom-weight forces at declared horizontal radii. It does not establish rated capacity, stability, foundation adequacy or permission to lift.
Declared Post-Crane Moment Explorer
Enter a declared vertical load force, horizontal load radius, boom self-weight and boom center-of-gravity fraction. The worksheet sums their ideal applied moments without rating any crane, support or lift.
Equation Used
- The declared load and boom-weight forces act vertically downward.
- Load radius R is the horizontal perpendicular distance from the post axis to the suspended-load line of action.
- Boom center of gravity lies at declared fraction lambda of the load radius, so R_cg=lambda R.
- The forces are treated as static and coplanar for this ledger.
- Swing phase is visual only and does not change either declared radius.
- Dynamic amplification, side pull, hoist and rigging weight, boom/mast/bearing/support reactions, strength, stiffness, buckling, fatigue, foundation and soil resistance, anchors, vehicle or outrigger stability, counterweights, wind, controls, brakes, clearances, inspection, rated capacity, load charts and safe operation are excluded.
Removes unsupported capacity, foundation and operating claims while retaining exact declared vertical-force moment arithmetic.
A rotating jib transfers applied forces to a fixed post
A conventional jib crane has a horizontal cantilever boom carried by a rotating head on a stationary vertical mast. A suspended load acts vertically through its hoist line, while the boom's self-weight acts through its center of gravity.
The animation keeps the post, rotating head, jib, hoist line, load and boom center of gravity connected. Swing is prescribed only to make the topology visible.
Use this page only to audit declared applied moment
The worksheet can check force-times-radius arithmetic for two declared vertical forces. It cannot select equipment, determine capacity, size a mast, bearing, base, anchor or foundation, or plan a lift.
Actual crane operation must follow the applicable manufacturer procedures and rated-capacity information.
Use perpendicular horizontal radius for each vertical force
Each term is force times the perpendicular distance from the post axis to that force's line of action. Terms acting in the same rotational sense add.
A transparent declared-force example
For an 8.0 kN vertical load at 3.00 m, load moment is 24.00 kN-m. A 1.2 kN boom self-weight with its center of gravity at 0.50R acts at 1.50 m and adds 1.80 kN-m, for 25.80 kN-m total applied moment. The suspended load contributes 93.0 percent of that sum.
This is not a capacity or stability result.
Applied moment is only one side of a crane assessment
A real assessment needs equipment-specific geometry, boom/mast/bearing/support reactions, strength and stiffness, hoist and rigging weights, dynamics, wind, side-load prohibition, counterweights, outriggers or anchors, foundation and soil data, inspection condition, manufacturer procedures and the applicable load chart.
The former universal capacities, foundation dimensions and costs, bearing clearances, failure diagnoses, deflections, brand deployments and operating rules are removed because they were not supported for one documented crane and configuration.
Post-crane ledger questions
Is total applied moment the crane's capacity?
No. It is the moment imposed by the two entered forces only.
Does swing angle change this ideal vertical-force moment?
No. At fixed radial distance, azimuth changes direction in plan but not the moment magnitude about the vertical post axis used in this simplified ledger.
Can this size a foundation or anchor?
No.
Can it replace a load chart?
No. Rated capacity and manufacturer procedures govern operation.
Post-crane references
- Engineering Statics: Moment of Force: M=F d_perpendicular and force-distance units.
- Engineering Statics: Varignon's Theorem: add the signed moments of multiple forces.
- US Patent 3,358,849: horizontal cantilever boom, rotating head, stationary mast and transferred overturning moment.
- OSHA 29 CFR 1926.1417: manufacturer procedures, rated capacity, load verification and operating requirements.
Building or designing a mechanism like this?
Explore the precision-engineered motion control hardware used by mechanical engineers, makers, and product designers.
