Selected-leg static vector equilibrium · controlled lift-plan inputs

Controlled Sling-Leg Static Force Worksheet

Resolve one documented sling leg’s assigned vertical load share and angle into ideal static tension and horizontal force components—without inventing an assembly WLL or assuming equal load sharing.

Force, not massNo automatic leg multiplierNo capacity verdict

Geometry only—not a sling-selection or lift-authorization tool. The worksheet does not establish WLL, choose a sling, assign load share, approve an angle, apply a design/dynamic factor, check the hitch or weakest component, or prove equilibrium of the complete lifting system. Use only values from a lift plan controlled by a qualified person, the leg/assembly markings, the manufacturer and the governing rules.

Selected leg and controlled load-share inputs

Total design vertical load force

Force after all load-plan additions; do not enter mass or a tagged WLL.

Selected leg’s assigned vertical share (%)Must come from the controlled load-distribution analysis; the worksheet does not divide by nominal leg count.

Selected leg angle from vertical (degrees)Mathematical domain 0° ≤ θ < 90°. This is not an allowed-angle range.

Lift plan / project ID

Selected leg / attachment-point ID

Sling material, construction and hitch

Manufacturer / assembly tag / certificate ID

Rated capacity at the exact hitch, angle and leg count

Weakest component / end-fitting check

Angle definition and measurement record

Load force / centre-of-gravity basis

Selected-leg load-share analysis

Dynamic, acceleration and shock basis

Temperature, edges, D/d and environment

Governing jurisdiction / site procedure

Controlled standard / manufacturer source and edition

Inspection / damage / suitability record

Qualified person / lift authorization

Record date

Notes and exclusions Optional: unequal geometry, elasticity, tolerances, CG uncertainty, below-hook hardware, side loading, persons/special loads

The entered value is total design erő, not mass, not a sling WLL and not an unmodified object weight; all controlled lift-plan additions are already included.
The selected leg’s vertical share and angle come from the documented load-distribution/geometry analysis; no equal-share or “four legs use three” assumption has been made by this worksheet.
The exact assembly marking, hitch, angle, leg count, weakest component, inspection state and manufacturer restrictions have been checked independently.
A qualified person controls the complete lift plan, jurisdictional requirements and authorization; these geometric results will not be used as a WLL or permission to lift.

Ideal static vector result

Selected-leg ideal tension

—

Assigned vertical component

—

Horizontal component magnitude

—

cos θ / tension amplification sec θ

—

Normalized total design load force

—

Assigned vertical share / angle

—

Equation, units and classification

For the selected leg only, let W be the controlled total vertical design force, s its assigned vertical share in percent and θ the leg angle from vertical:

V = (s / 100) W
T = V / cos(θ)
H = T sin(θ) = V tan(θ)
amplification = T / V = sec(θ)

This is a direct resolution of an ideal static tension vector, a general engineering equilibrium relation—not an ASME, ISO or OSHA rating formula. The dimensional check is force = dimensionless × force; outputs are in kN and N, with 1 kN = 1000 N exactly.

The share is not calculated here. Equal division can fail because of centre-of-gravity position, unequal geometry or reach, elastic/stiffness differences, tolerances, hitch behaviour, a slack leg, load rotation, acceleration and other effects. Horizontal components of the complete system must also balance; one selected-leg result cannot prove that.

Model boundary and removed unsafe logic

No generic assembly WLL multiplication. The former single-leg WLL × leg count × cos θ treated a component rating as a universal assembly rating. Actual rated capacity depends on the marked assembly, material/construction, hitch, angle convention, leg count, fittings, D/d and other controlled conditions.
No automatic four-leg-to-three-leg rule. A particular standard/table may rate a three- or four-leg configuration in a specified way; it is not a universal load-sharing proof for every sling and lift.
No invented equal sharing. The user supplies the selected leg’s controlled vertical share; nominal leg count is not an input.
No universal “safe angle”. The former hard 60°-from-vertical rule was presented across all sling types. OSHA wire-rope guidance uses configuration-specific tables and a manufacturer/qualified-person route; other materials and jurisdictions have their own controls. The domain θ<90° is mathematical only.
No mass–force ambiguity. “Tonnes” was used as though it were force. This worksheet accepts N or kN only and does not guess gravity or convert a mass/WLL label into design force.
No false tension display. The former “tension per leg” output merely echoed the entered single-leg WLL. Tension is now calculated from the documented force share and angle.
No defaults, presets or silent calculation. Inputs start blank, use strict point/comma parsing, require an explicit submit and cannot persist stale results after editing.

Source traceability

Claim	Osztályozás	Evidence
ASME B30.9 covers fabrication, attachment, use, inspection, testing and maintenance of listed sling types.	Official current standard card; scope/status only	ASME B30.9-2025 official page; 2025 edition displayed
Slings must not be loaded beyond rated capacity; wire-rope markings identify the safe working load for the hitch, angle and number of legs; attachments cannot exceed the weakest component.	Official US regulation; jurisdiction-specific	OSHA 29 CFR 1910.184(c)(4), (e)(2)(i), (f)(1)
Wire-rope sling selection uses configuration tables; nonsymmetrical multiple-leg loads require qualified-person analysis; other angles/configurations require the lower table value, manufacturer or qualified person.	Official OSHA guidance; wire rope scope	OSHA Guidance on Safe Sling Use—Wire Rope
ISO 4778:2019 rates/tests specified Grade 8 welded single-, double-, three- and four-leg chain slings and states that its slings are for symmetrically distributed loads only.	Official ISO public abstract/status; narrow material/construction scope	ISO 4778:2019, Edition 2; confirmed 2024
V=(s/100)W, T=V/cosθ and H=V tanθ	General analytic static-vector geometry; not a standard rating formula	Direct equilibrium derivation shown above

Accessed: 15 July 2026. Public sources support the cited status, scope and safety controls—not a universal WLL multiplier, leg-sharing factor, allowable angle, dynamic factor or lift authorization. Exact controlled clauses/tables and manufacturer data are NEEDS_LICENSED_SOURCE.

Arithmetic reference example

For W = 20 kN, selected-leg share s = 50% and θ = 30° from vertical: V = 10 kN, T = 10 / cos30° = 11.5470054 kN and H = 10 tan30° = 5.77350269 kN. This checks the vector arithmetic only; it does not say that any sling, hitch, angle or lift is acceptable.

Questions

Why can’t I enter a single-leg WLL and a leg count?

Because a marked component/vertical rating does not by itself establish the assembly rating in another hitch and angle. Use the exact marked/manufacturer/controlled rated capacity for the actual configuration.

Can I use 100 divided by the number of legs as the share?

Only if the controlled load-distribution analysis establishes equal sharing. The page deliberately does not make that assumption.

Does an angle below 60° from vertical mean the lift is safe?

No. The page contains no safe-angle rule. The applicable material, construction, hitch, marking, manufacturer, jurisdiction and lift plan control.

Why use force instead of tonnes?

Vector equilibrium is a force calculation. A tonne is a unit of mass; converting mass to a design load force requires a declared gravity and all lift-plan effects, which this worksheet does not guess.