Create Tracks

The create tracks dialog is used to wrap a track, chain, or belt on the rolling systems. The figure below shows the create track dialog.
Figure 1. Create track dialog


Wrapping Type

The Track/Chain or Belt option are available to create different types of wrapping. The difference between the wrapping types relies on the contact applied. When the CAD/H3D graphics option is not used, the Track/Chain uses sphere-to-sphere contact between the sprocket and track and sphere-to-box contact for other entities and the track. The belt uses sphere-to-sphere contact between all entities and the belt.

Wrapping Rolling System

A minimum of two rolling systems is needed to create a track. The Total number of Entities option enables adding more rolling systems to the track. Once the number of entities is defined, the rolling systems must be selected following the clockwise direction (positive Y). The wrap type can be inside or outside the rolling system as shown in the figure below.
Figure 2. Wrapping track on rolling systems


The dialog automatically provides a preview of the wrap system as soon as enough input data has been provided. If a wrap fails, error messages are displayed in the bottom of preview area. Catenary sag is included if more links than the minimum required amount are present. Conversely, if the number of links are less than the minimum amount, the track will be open. In that case, a flexible stiffness entity is created to connect the first and last link to close the gap during simulation. This causes tension within the track as soon as the simulation starts and might be preferred by design.

To create a symmetric track pair containing the same properties for left and right tracks, select the Track symmetric pair option.
Figure 3.


Wrapping the track pair requires rolling system pairs. When defining the rolling systems, select the Symmetric pair option, this option creates the rolling parent system with the left and right subsystem underneath.
Figure 4.


In the Wrapping rolling systems dialog with the Symmetric pair option enabled, the rolling parent system must be selected. In the case where the rolling systems were created as pairs, but the wrap must be done individually, clear the Track symmetric pair option and select the left (LH) or right (RH) systems to create the individual wrap. It is important to be consistent in your choices, either selecting all right or all left rolling components when creating a single track.

Track Properties

Two track link options are available when using the Track/Chain type, the Single Pin and the Double Pin track link. In the single pin, the track links are connected to each other using a pin. In the double pin, the track links are pinned to a connector link. The figure below illustrates the single and double pin track links.
Figure 5. Track link options


By default, track and belt are represented by a combination of primitive geometries. The option Use CAD/H3D graphics for links enables the use CAD or H3D file of all entities for the track or belt. With this option, mass and inertia properties are calculated from the CAD graphics. The CAD or H3D file is positioned at the center of the link or connector body, it is therefore important to make sure the center of the CAD graphics is positioned at the global origin (0,0,0 in XYZ coordinate) before including in the track system.
Figure 6. CAD/H3D graphics positioning


Note: The dimensions specified in the Chain/Belt properties, for both a single and double pin track link, refer only to the link part used to represent the track chain or belt. In track links containing a track pad or grousers, as these parts do not contribute to the chain kinematics, their dimensions are not considered in the wrapping of the track. An example of a single pin track link containing a track pad is shown in the figure below, the link thickness is taken only from the gray part of the CAD even if it a single CAD part.
Figure 7. Link properties from a track link containing pads or grousers


The option Use CAD/H3D graphics for link to roller contacts enables the 3D rigid contact between the CAD or H3D file of the rolling systems. If the rolling components do not have CAD/H3D files, this option cannot be used and the message “Contact graphics not found” will be shown in the track preview window.

User-defined mass and inertia can be provided using the option User mass and inertia, in this case the track links properties can be edited in the wrap system dataset.

The links in the belt or track are constrained to each other to prevent lateral movement. The type of constraint can be changed using the Link DOF option based on the requirement of the application. The details of the connection between the link are tabulated below:
Link DOF (degree of freedom) Connection Lateral Constraint Geometry Option Supported
1 - Rotation free Revolute joint for all links and Inline joint between the first and last link. Planar Primitives and CAD
1 - Rotation and bending stiffness Revolute joint for all links and Inline joint between the first and last link. Rotational stiffness and bending preload are supported between all links. Planar Primitives and CAD
2 - Tensile and bending stiffness Planar joint and Inplane primitive for all links. Rotational stiffness and bending preload between all links are supported, as well as tensile stiffness and tensile preload. Planar Primitives and CAD
6 - All direction stiffness Tensile stiffness and Tensile preload between all links. This option supports rotational, lateral, shear, torsional, and lateral-bending stiffness, as well as bending preload between all links. None Only CAD
Based on the selection Link DOF option, the busing properties are enabled as shown in the figure below.
Figure 8. Bushing properties for Link DOF 6 - All direction stiffness


Road Contact Method

Two types of soil interaction are provided in the track builder:
  • Soft Soil
  • Rigid Contact
The soil interaction can be turned off when not required, for example in the case of chain drives or simulation with Altair EDEM where the soil is represented by discrete elements.
Soft Soil
The Altair Soft Soil model provides a way to simulate the dynamic behavior of a track system on a surface that is compressible such as clay, dry sand, regolith, and ice-covered snow. Refer to Soft Soil Track Model for more information.

In MotionView, a force entity is created at the center of each track link containing the track soil contact equations. The parameters defined in the track properties are used to compute the soil interaction. Depending on the shape of the track link it is required to update the track link geometry as shown in Update Link Geometries.

When soft soil interaction option is selected the Soil Terrain file and the Soil Reference Marker properties are displayed.
Figure 9. Road Contact Method dialog


The Soil Terrain file requires the soft soil road model containing the soft soil and track soil parameters. A soft soil road library containing ready-to-use road data files for a variety of soils are located in the installation <Installation>\hwdesktop\hw\mdl\autoentities\properties\Tires\ALTAIR_SOFTSOIL. For more information on how to build a soft soil road model see Road Modeling.

The Soil Reference Marker requires a marker entity where the soil origin will be positioned at.
Note: Load the soft soil road file .rdf in the Road Tools to create a graphic representation of the soft soil road in MotionView. For more information see Road Tools.
Rigid Contact
The rigid contact soil interaction uses MotionSolve 3D rigid contact method between the track geometry and a road geometry specified in Terrain Graphics Files to capture the track-road dynamics.
Figure 10. Rigid contact soil interaction dialog


The Terrain Graphics file requires a CAD or H3D graphics following MotionView’s and MotionSolve’s recommendation for modeling contact. See Contacts and Best Practices for Running 3D Contact Models in MotionSolve.

The contact friction parameters, Static and Dynamic friction, Stiction transient velocity, and Friction transition velocity can be modified in the Rigid Contact soil interaction option. The normal force contact parameters are specified in the Contact Properties section.

After creating the track system, all parameters can be modified in the wrap system datasets.

Contact Properties

The contact properties of the track system can be specified in the Belt contact properties (Impact) section. These parameters are applied for the contact between the track links and roller using primitive or CAD graphics, and the contact between track links and rigid contact soil interaction. For the rigid contact soil interaction the friction parameters considered are the ones specified in the soil interaction section.
Figure 11. Contact properties dialog


After creating the track system, all parameters can be modified in the wrap system datasets.

Outputs

Output requests are automatically created with the track system.
  • Track tension – output the tension force in the track by measuring the longitudinal force on track link connection joint or bushing in its local coordinate system.
  • Contact Forces – output the contact force of each link with each rolling component.