# Wire Rope Slings

## Sling angle 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 rduction 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, lb _{f})*

*W = m g = weight of body (N, lb _{f})*

*m = mass of body (kg, slugs)*

*g = acceleration of gravity (9.81 m/s2, 32.17 ft/s^{2})*

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

*F = (100 kg) (9.81 m/s ^{2})*

* = 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 *30*^{o} to the vertical line

^{o}

The capacity of two wires with angle *30*^{o} 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(30 ^{o})*

* = (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 Calculator

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

#### Two Slings

*mass (kg)*

* lenght - a (m)*

* height - h (m)*

#### Three Slings

*mass (kg)*

* lenght - a (m)*

* height - h (m)*

#### Four Slings

*mass (kg)*

* lenght - a (m)*

* lenght - b (m)*

* height - h (m)*