Sling / Grommet Node#

A Sling / Grommet node (SlingGrommet) can be used to conveniently model slings or grommets from typical properties.

Slings / Grommets are created between circle nodes. Between the endpoints it can run over other circle or roundbar nodes.

To create a sling or grommet,

  1. select the circle nodes that will act as endpoints. Hold shift when selecting a node to add nodes to the selection.

  2. select image-20231106150947456from the quick-actions.

Hint: Sometimes it can be difficult to see the the circles. In that case switching to x-ray-mode can help.

Physical properties#

Once a sling or grommet node is created it is time to define its physical properties.

Property

Meaning

#ID and optional remarks

This is for reporting only. The part followed by # is the ID and the rest of the text is comments. For example #3.1.12 re-used will show up as 3.1.12 as ID and re-used as comment.

Type

Either Sling or Grommet

Material

The material that the item is made off. For Steel IWRC and Cable-laid the wire properties can be estimated. For other types this estimation is not available

Length

The length can be specified as Ultimate, Nominal or Circumferential length. Whatever is most convenient or available.
See Wire properties

Rope properties

Diameter, Weight per length, EA and MBL are all inter-related. For Steel IWRC and Cable laid wires DAVE can estimate these if at least one of the values is provided.
See Wire properties

Total properties

Weight per length and Stiffness can also be defined as “total” properties. These are “derived” properties and will change when the length of the item chages. Weight per length and EA are “leading”

Sling specific#

For slings the length of the eyes and splices have to be defined.

Routing and connections#

Adding intermediate connections to a sling or grommet is done in the same way as for cables. Refer to the cable node for details.

The SlingGrommet node can be used to model a Sling or Grommet and allows easy switching between the two types.

For slings the connections are as for Cable nodes.

image-20230914174213309

For grommets there are two ways in which the connections can be interpreted: Line mode and Circle mode. Both are illustrated below:

image-20230914174345793

For line mode (left) the grommet follows the same way back running over the intermediate connections in opposite (reversed) direction. For circle mode the grommet automatically routes back directly to the first connection.

Friction#

Friction between the rope and the connections can be defined by pressing the “advanced” button. Note that the friction that is defined here will be overwritten when running a Rigging Analysis Report.

For slings or grommets in “circle” mode the friction is defined in the same way as for a cable.

Line mode#

For grommets in “line” mode the definition is as follows:

  • Either the friction at end A or the friction at end B needs to be non-prescribed.

  • For all other connections the friction needs to be prescribed.

In line mode the friction on the intermediate connections (connection 2 in the figure) controls the friction for both times that the grommet passes this point. A positive friction factor means that the tension on the A (1) side is higher than on the B (3) side of the line:

image-20230914204921514