Using Traction and Belts for Layout Sketches

The Traction PM_Traction.gif relation and the Belt/Chain Tool_BeltChain_Assembly.gif tool (Blocks toolbar) enable you to use layout sketches to create these mechanisms:
  • Multiple gear sets
  • Cable and belt pulleys
  • Chain sprocket systems


The Traction relation creates relative rotation constraints between sketch entities by adding a tangent relation between blocks that represent pulleys or sprockets.

Video: Traction Relation with Multiple Arcs

Video: Traction Relation with an Arc and Linear Entities

Adding Traction Relations

To add traction relation:

  1. Sketch multiple circular or linear entities to represent gears, rack and pinion mechanisms, etc.
  2. Make each entity a separate block.
  3. Add relations and dimensions to eliminate motion not related to the mechanism.
    Limit the use of the Fix relation, for example to the center of one circle. Use horizontal and vertical relations, dimensions, or construction geometry to locate the centers of additional circles or sketch entities. Adding multiple fix relations potentially restricts the model's degrees of freedom.
  4. In the graphics area, select two sketch entities to which you want to add relative rotation constraints.

Using the Belt/Chain Tool

To use the belt chain tool:

  1. Sketch multiple circular entities to represent belt members.
  2. Make each sketch entity into a block.
  3. Click Belt/Chain Tool_BeltChain_Assembly.gif (Blocks toolbar) or Tools > Sketch Entities > Belt/Chain.
  4. Add relations and dimensions to eliminate motion not related to the mechanism.
  5. Add belt members and belt to create the mechanism.