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Wire Rope Slings

Sling angles and influence on capacity.

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Slings angles affects ropes capacities.

Wire rope sling - load capacity

If angle - alpha - is measured between

  • the vertical line (as with gravity force), and
  • the rope or wire

the relative capacity compared to a vertical straight lifting is reduced with reduction factor as indicated below.

f = cos(α)                           (1)


f = reduction factor

α = angle between vertical line and rope (degrees)

- α -
Reduction Factor
- f -
0 1.000
10 0.985
20 0.940
30 0.866
40 0.766
50 0.643
60 0.500
70 0.342

Wire rope slings reduction factor

Example - Capacity of a Single Rope or Wire

The capacity of a single rope that follows a vertical line is 100% since the reduction factor is 1.

If the weight of a body is W - the load in the wire is

F = W                                     (2)


F = force in rope (N, lbf)

W = m g = weight of body (N, lbf)

m = mass of body (kg, slugs)

g = acceleration of gravity (9.81 m/s2, 32.17 ft/s2)

For a body with mass 100 kg the load in the rope can be calculated

F = (100 kg) (9.81 m/s2)

  = 981 N

  = 9.8 kN

Example - Capacity of Two Ropes (or Wires)

Two wires or ropes follows the vertical line

The capacity of two wires that follows the vertical line is 100% since the reduction factor is 1.

If the weight of a body is W - the load in each wire is

F = W / 2                                  (3)

For a body with weight 1000 N the load in each rope can be calculated as

F = (1000 N) / 2

   = 500 N

   = 0.5 kN

Two wires - or ropes - with angle 30o to the vertical line

The capacity of two wires with angle 30o to the vertical line is 86.6% since the reduction factor is 0.866.

If the weight of a body is W - the load in each wire is

F = (W / 2) / cos(30o)

   = (W / 2) / f

   = (W / 2) / 0.866

   = 0.577 W                                          (4)

For a body with weight 1000 N the loads in the ropes can be calculated

F = 0.577 (1000 N)

   = 577 N

   = 0.58 kN

Wire rope slings - wire angle versus wire force

Wire Rope Slings Calculators

The calculators below can be used to calculate wire rope forces. Note that mass (kg) and not weight (N) is used as input.

Wire rope slings with two, three or four ropes

Two Slings

mass (kg)

length - a (m)

height - h (m)

Three Slings

mass (kg)

length - a (m)

height - h (m)

Four Slings

mass (kg)

length - a (m)

length - b (m)

height - h (m)

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