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Assembly4 Tutorial 3

This tutorial is for advances users, and demonstrates the use of variant links.

Theo Jansen sandwalker

See the video:

https://strandbeest.com/api/uploads/Voorzeil_bewerkt_77dc78a7a4.mp4

https://youtu.be/LewVEF2B_pM

Principle

the principle of variant links is to insert into the assembly a link to a part, and setting some variables specific to that link. In other words, it allows to create a generic "part" and insert it multiple times, with each instance having some pre-defined variables set to that instance.

For example, you can create a generic extruded beam with a default length, and add it several times to an assembly by specifying the length of the beam:

Any variable of the type float in the Variables container can be set for each variant link.

Anothe possibility for variant links is to insert a sub-assembly mutliple times, with each sub-assembly having a specific variable. This is very handy if you want to insert a same sub-assembly many times, where the difference will be in some kinematics of the sub-assembly. This is the example that we will describe here. The same principle can be applied to variant links to parts.

Important Note: variant links are more expensive in ressources as regular links, therefore use with caution.

A single leg:

Crate a single leg for the Theo Janssen sandwalker:

The dimensions:

  • create a new document, call it Walker_Parts
  • create 6 Bodies
  • in each body, create a part according to the dimensions
  • create a new document, call it Walker_Leg
  • create an Asm4 Model
  • in there, create a variable called Angle_Handle
  • create a Sketch, call it Sketch_Handle
  • attach it to the LCS origin
  • draw a circle and a radius
  • set the AttachmentOffset of the sketch to make a rotation of Angle_Handle
  • create a sketch, call it Sketch_Leg
  • in there, import as external reference the end-point of the radius
  • draw the walker leg as shown above, and attach the rotation handle to the imported point

Now this leg-assembly can be imported several times

Multiple legs

  • create a new document, call it asm_Walker_8legs
  • create a variable, call it Assembly_Handle
  • insert a variantLink, choose the Walker_Leg

  • attach it the LCS origin, offset it length-wise
  • set the Variant Variable to Variables.Assembly_Handle + some offset
  • do this for each additional leg, adjusting the offset
  • now, when you change the variable Assembly_Handle, the positions (kinematics) of each leg will be recalculated

Animate