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# Wire Rope Slings

Slings angles affects ropes capacities.

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)

where

f = reduction factor

α = angle between vertical line and rope (degrees)

.
Reduction Factor Compared to Vertical Straight Lifting
Angle
- α -
(degrees)
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

### 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)

where

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 Calculators

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

.

## Related Topics

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