KEVOS® MAKEOS · Mechanics
Two-Point Lift with an Off-Centre Load (Centre of Gravity, Leg Loads, Angles)
Where is the centre of gravity of this combined load, how is the weight shared between the two lifting points, and what does each sling leg carry at its angle?
Planning check for lifting a load made of several items from two lifting points on a line: combined mass and centre of gravity along the line (as the combined centre of gravity tool), the share of weight at each lifting point by moments, the sling leg angles and tensions with the hook placed above the centre of gravity at a given height, leg lengths, and checks of leg load against the working load limit and leg angle against your limit (for a central load the leg tensions match the sling tension tool).
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Items (position along the lifting line) | ||
| Item 1 mass | kg | Mass of item 1 (0 if not used). |
| Item 1 centre position | mm | Position of item 1’s centre of gravity along the line of the lifting points. |
| Item 2 mass | kg | Mass of item 2 (0 if not used). |
| Item 2 centre position | mm | Position of item 2’s centre of gravity along the line of the lifting points. |
| Item 3 mass | kg | Mass of item 3 (0 if not used). |
| Item 3 centre position | mm | Position of item 3’s centre of gravity along the line of the lifting points. |
| Rigging | ||
| Lifting point A position | mm | Position of the first lifting point. |
| Lifting point B position | mm | Position of the second lifting point. |
| Hook height above the lifting points | mm | Height of the hook above the lifting points (sets the sling angles). |
| Working load limit per leg | kg | Working load limit of each sling leg at its rating (your value; reduce for the hitch type). |
| Largest leg angle from vertical | ° | Largest leg angle from vertical your lifting procedure allows. |
Method and formulas
- Centre of gravity X = Σ m x ÷ Σ m (as the combined centre of gravity tool).
- Point loads by moments: R_A = W (x_B − X) ÷ (x_B − x_A), R_B = W − R_A.
- With the hook vertically above X at height h: leg angle θ = tan⁻¹(|X − x| ÷ h); leg tension = R ÷ cos θ; leg length = √[(X − x)² + h²].
- Example: the centre of gravity is 615.38 mm along; leg A carries 1,459.2 kg at 22.306° and leg B 816.54 kg at 42.709°.
Limitations
- Rigid load and planar geometry; a third dimension or a flexible load needs a full lift plan.
- Dynamic factors for the crane and the load are not included.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Plan a lift of an assembly with an off-centre heavy part
- Choose sling lengths so the load hangs level
- Check each leg against its rating
Who it is for
- Rigging supervisors
- Lifting engineers
- Maintenance planners
What you get
- Combined mass and centre of gravity
- Weight at each lifting point
- Leg angles, tensions and lengths with checks
Interpreting the result
- The leg nearer the centre of gravity carries more and hangs more vertical; the far leg is longer and more inclined.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2613–2650, 221–227. Topic reference; no source tables or recommended settings are reproduced.
- AS 3775 and AS 1418 series, or your national lifting standards
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Two-Point Lift with an Off-Centre Load (Centre of Gravity, Leg Loads, Angles) calculator
