A swing bracket crane carries a load at an entered horizontal radius while a tie supports the boom at an entered attachment distance and angle. The calculator applies ideal static moment and force equilibrium. OSHA requires manufacturer-approved operating radii, boom angles and configurations to be reflected in crane load charts; this simplified model is not such a chart.
Swing Bracket Crane Interactive Calculator
Vary the entered suspended load, working radius, tie attachment distance and tie angle. Results use ideal static equilibrium and do not rate the boom, brackets, wall, anchors, hoist or crane.
Equation Used
- The boom is horizontal, rigid and weightless in the ideal side-elevation model.
- The load is static and vertical at the entered horizontal radius.
- The tie is a two-force member attached at distance A and angle theta above the boom.
- Boom self-weight, hoist and trolley weight, dynamics, side load, member strength, anchors, wall response and safety factors are omitted.
The animation shows the tie-supported boom swinging about two vertically aligned wall pivots. The entered load radius and tie attachment stay fixed along the boom. Pivot spacing follows A tan(theta). The sweep is prescribed; the calculator evaluates static equilibrium at each orientation and does not predict motion or acceleration forces.
Ideal Swing-bracket-crane Free Body
The entered suspended load creates a load moment W times L about the wall pivot. In the ideal side elevation, the tie's vertical component acts at attachment distance A. Static moment equilibrium gives T A sin(theta) = W L. The tie's horizontal component is T cos(theta).
This is deliberately a free-body calculation, not a crane design. NIST describes crane statics by applying force and moment equilibrium to free bodies and treating cables as tension members.
Using the Animation and Calculator
The calculator shows why load radius and tie geometry strongly affect ideal force demand. It can support conceptual checks and free-body-diagram education.
Actual use must follow the manufacturer's load chart and approved configuration. OSHA requires design and testing across manufacturer-approved operating radii, boom angles, work areas, boom lengths and configurations.
Ideal Static Equilibrium
Taking moments about the wall pivot:
The tie vertical component is T sin(theta), which equals W L/A in this ideal model. The horizontal component is T cos(theta). No allowable load is calculated.
Worked Example: Entered Load and Geometry
For W = 1000 lb, L = 8 ft, A = 8 ft and theta = 35 degrees, load moment is 8000 ft-lb. Ideal tie tension is 1743 lb, its vertical component is 1000 lb and its horizontal component is 1428 lb.
These are static scenario forces. They do not establish boom, tie, bracket, anchor, wall, hoist or crane capacity.
What the Calculator Includes
- Calculated: ideal load moment demand, tie tension and tie vertical/horizontal components.
- Strong sensitivity: tension increases as tie angle or attachment distance decreases.
- Not calculated: member self-weight, hoist and trolley weight, impact, acceleration, slewing, side load, deflection, buckling, fatigue, welds, pins, bearings, anchors, wall or foundation response, safety factors or code compliance.
Frequently Asked Questions
Is load moment a wall-capacity result?
No. It is W times L for the entered suspended load, before structural capacity or detailed reactions are evaluated.
Why does a shallow tie angle raise tension?
Only T sin(theta) contributes the vertical force needed for moment equilibrium, so smaller sine requires larger T.
Why can tie vertical force differ from W?
If the tie attaches at A different from load radius L, ideal moment equilibrium gives V tie = W L/A.
Does the model include boom weight?
No. Boom, trolley and hoist weights must be added separately in a real analysis.
Can equal W times L scenarios use the same crane?
Not from this model alone. Reach changes deflection, stability and structural demands omitted here.
Can this calculator establish safe working load?
No. Use the manufacturer's approved load chart and qualified engineering.
References
Gorbel wall-bracket jib crane: tie rod, boom and two wall-pivot assemblies, illustrated in the distributor-hosted manual. The animation is a generic schematic, not a manufacturer-sized assembly.
- NIST, crane mast statics model: free-body force and moment equilibrium with cables in tension.
- OSHA 1926.1433, Design, construction and testing: manufacturer-approved radii, boom angles, lengths and configurations in load-chart design and testing.
- OSHA Subpart CC Appendix C: using load charts with working height, boom length, load radius and configuration.
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