1. Inputs

Load

Mass M [kg] Total weight of the load. Length L [m] Long axis — vertical at θ=90°. Width W [m] Depth into the page (not in calc). Height H [m] Short axis / side-view thickness.

Centre of gravity

defaults to geometric centre — load-local coords (load horizontal)

x_cog [m] auto Distance from LEFT end of horizontal load to COG, along L. y_cog [m] auto Above BASE. Uniform beam ≈ H/2.

Lift points

picks default to load ends on COG centerline → head above COG at θ=90°; tail at top corner

x_lp1 [m] — head auto Head pick — end that becomes TOP when vertical. y_lp1 [m] — head auto Keep = y_cog for exact head-above-COG. x_lp2 [m] — tail auto Tail pick — end that walks. y_lp2 [m] — tail auto Tail pick height above BASE.

Tail lug

perpendicular offset above the tail pick — default 0 (lug overlaps tail pick)

Y₁ [m] — lug offset Lug perpendicular above tail pick (load-local +y direction).

Note: one or both lift points are off the COG centerline (y_lp ≠ y_cog). The calc uses the full 2-D moment-balance formula — load share now changes with θ (not constant) because the tail pick's y-offset contributes a non-zero perpendicular arm. Natural hang for this geometry: θ_natural = 90.0°.

2. Geometry

Rotation θ

0° = horizontal start; 90° = upright (head above COG, tail at bottom)

θ [°]

Start θ = 0°

Current θ = 30°

End θ = 90°

3. Results

Angle `θ`	`F`_head [kg]	% of `M`	`F`_tail [kg]	% of `M`
0° — start — horizontal	2500	50%	2500	50%
76° — near-vertical	3613	72%	1387	28%
90° — end — upright	5000	100%	0	0%
`θ` = 30° (slider — interactive)	2759	55%	2241	45%
Governing	Head crane sized for full load at `θ` = 90° → `F`_head = `M` = 5000 kg

Three key angles: 0° (start) / 76° (near-vertical) / 90° (upright). AS 2550.1 §6.28: at upright (θ = 90°) the head crane carries the entire mass.

Per-crane load `F` vs `θ` (0–90°)

Vertical marker tracks current slider θ = 30°.

4. Method of calculation

Tailing geometry (head crane stationary, tail crane walks load upright)

The head crane stays fixed above its lift point; the tail crane walks horizontally so the load rotates about the head pick by angle θ. Taking moments about the head and tail lift points:

F_head = M · [ X₂ · cos θ + Y₁ · sin θ ] / ( X₁ + X₂ ) · cos θ + weight beyond head F_tail = M · X₁ · cos θ / [ ( X₁ + X₂ ) · cos θ + Y₁ · sin θ ]

Validated against 27 XLSX rows in tests/vectors/. See web/src/lib/calc/mode2.ts for the implementation form (algebraically equivalent).

Three-key-angle assessment

Assess load share at θ ∈ { 0°, 76°, 90° }

0° — start, lever-rule split (no Y₁ contribution).
76° — near-vertical, tail crane still actively engaged; captures the late-phase load state before final stand-up.
90° — upright; head crane carries entire mass M (per AS 2550.1 §6.28).

Symbol legend

M: total mass of load [kg]
X₁: horizontal distance from head lift point to COG along load axis [m]
X₂: horizontal distance from tail lift point to COG along load axis [m]
Y₁: perpendicular offset of tail lug from load axis [m] (must be > 0)
θ: rotation angle from horizontal [°]; 0° start, 90° upright

5. References

AS 2550.1-2011 Cranes, hoists and winches — Safe use — Part 1: General requirements §6.28 Multiple hoist or crane operation
ISO 12480-1:2024 Cranes — Safe use — Part 1: General §8.1 Lifting with multiple cranes or multiple hoists — esp. §8.1.1 a–f, §8.1.3 Supervision, §8.1.4 Coordination of crane motions
ICSA N002 (Apr 2016) Lifting a Load with Several Mobile Cranes (Multiple Crane Lifts) — FEM industry consensus Tailing operations are excluded from the FEM dynamic-allowance scope; this calc is purely geometric.