Wire Rope Slings
Sling angles and influence on capacity.
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)
| 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.
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)
