A swing-boom crane carries a hoist and suspended load at an entered trolley radius on a horizontal boom. This calculator adds the corresponding vertical-load moment to an ideal uniform-boom self-weight moment. OSHA defines rated load by manufacturer design and nameplate and requires rated-load markings; this arithmetic is not a rated load.
Swing-boom Crane Interactive Calculator
Vary entered load, hoist and trolley weight, boom weight, boom length and trolley radius. The calculator sums ideal vertical-load moment components without evaluating crane capacity.
Equation Used
- The boom is horizontal, rigid and has uniform weight, so its center of gravity is at L/2.
- The load and hoist act vertically at the entered trolley radius R.
- All inputs are static scalar weights and distances.
- Slew dynamics, side load, impact, deflection, local stresses, connection forces, mast and foundation response, brakes and safety factors are omitted.
Ideal Swing-boom-crane Moment Sum
The hoist and suspended load act at the entered trolley radius R, creating (W load + W hoist)R about the pivot. Treating the boom as uniform places its ideal center of gravity at half the entered length, giving W boom L/2.
OSHA defines a crane rated load as the maximum load for which the crane or hoist is designed and built by the manufacturer and shown on its nameplate. The moment sum here does not determine that rating.
What This Explanatory Model Is Useful For
The calculator separates two ideal vertical-load moment components and shows how trolley radius and boom length affect them. It can support preliminary free-body reasoning and input sensitivity checks.
Actual operation must remain within the manufacturer's rated load and equipment instructions. Stops, brakes, inspections and load handling requirements remain outside this model.
Ideal Entered Moment Components
The displayed entered R/L percentage is simply 100R/L. Values above 100 percent mean the entered radius exceeds the entered boom length; the calculator reports the inputs rather than certifying a possible configuration.
Worked Example: Entered Scenario
For a 2,000 lb load, 180 lb hoist and trolley, 340 lb uniform boom, 16 ft boom length and 11 ft radius, load-plus-hoist moment is 23,980 lb-ft and boom self-weight moment is 2,720 lb-ft. Their ideal sum is 26,700 lb-ft, and entered R/L is 68.8 percent.
Those values do not establish capacity, stability or an allowable structural moment.
Model Boundary
- Calculated: ideal vertical-load moment, uniform-boom self-weight moment, their sum and entered radius-to-length ratio.
- Regulatory boundary: rated load is set by manufacturer design and marking, not by this calculator.
- Not calculated: capacity, overturning resistance, boom or mast stress, deflection, buckling, trolley and hoist details, connections, bearings, slew dynamics, impact, side load, wind, brakes, foundation or safety factors.
Frequently Asked Questions
Is combined moment a tipping limit?
No. It is a sum of entered ideal vertical-load moments, without resistance or capacity.
Why is boom weight applied at L/2?
The model assumes a uniform horizontal boom, whose ideal center of gravity is at its midpoint.
What if entered R/L exceeds 100 percent?
That indicates inconsistent entered geometry for this simple horizontal boom; it is reported as an input ratio, not validated as a real crane arrangement.
Does the model include dynamic load?
No. Acceleration, braking, sway, impact and side load are omitted.
Can the result size the mast or foundation?
No. Structural and foundation design require a complete load set, resistance model and applicable factors.
Can it replace the crane nameplate or manual?
No. Use the manufacturer's rated load and instructions.
References
- OSHA 1910.179, Overhead and gantry cranes: crane, wall-crane and rated-load definitions; markings, trolley stops, brakes, testing and operation.
- OSHA interpretation, rated-load markings: rated loads are marked and cranes must not be loaded beyond rated load except for prescribed testing.
- OSHA 1919.71, crane proof tests and examination: rating charts and manufacturer capacity ratings over operating radii where applicable.
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