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Lower Legs

Description


Lower Legs - different versions

  • we have been using different lower leg versions for our quadruped robots
  • the lower leg length and the foot diameter is identical for all the versions
  • the distance between the center of the knee and the center of the foot is 160mm
  • the foot diameter including the bicycle tyre is 34mm
  • all the lower legs have the same mechanical interface and are interchangeable
  • the different lower leg versions are described below
  • the foot surface is lined with a piece of thin bicycle tire
  • the preparation of the lower legs is also described below


Lower Legs - dimensions in millimeters

Lower Leg v3


Lower Leg v3 - weight: 22g each

  • this version is intended for solid printing on a SLS or FDM printer
  • STL file Lower Leg v3
  • bicycle tire dimensions: 7mm x 75mm
  • bicycle tire weight: 2g

Lower Leg v2


Lower Leg v2 - weight: 22g each

  • this version is intended for printing on a Fortus FDM printer with "sparse double dense" printer setting
  • STL file Lower Leg v2
  • bicycle tire dimensions: 7mm x 75mm
  • bicycle tire weight: 2g


Lower Leg v2 - internal structure with "sparse double dense" printer setting

Lower Leg v1


Lower Leg v1 - weight: 32g each

  • this version is a placeholder for the lower leg with foot contact switch
  • it has the same outer dimensions as the lower leg with foot contact switch
  • it also has a similar weight when printed on a Fortus FDM printer with "sparse double dense" printer setting
  • STL file Lower Leg v1
  • bicycle tire dimensions: 10mm x 75mm
  • bicycle tire weight: 3g

Lower Leg with Foot Contact Switch


Lower Leg for Foot Contact Switch - weight with electronics: 35g

Preparing the Lower Legs


Increase the size of the mounting holes with a 3mm drill bit if required.


If the lower legs have been printed on a FDM printer there might be beads on the surfaces.
The bead on the rectangular interface can cause problems later when the lower leg is installed.
Remove the bead on the rectangular interface surface with a sharp tool.


Use scissors to cut the bicycle tire into rectangular segments.
We use the center part of a Schwalbe Lugano 28" 23-622 tire.


Clean the bonding surfaces with ethanol.


We use a pin to secure the tire during bonding.
Place the tire on the foot and line it up.
Push a pin through the tire into the 3d printed part.
Make sure that you can see a mark from the pin.


Heat the pin up with a lighter.
Push the pin 2mm or 3mm into the 3d printed lower leg.
Use the location that was marked before.


The lower leg is now prepared for bonding.


Apply a thin layer of Loctite 406 onto the surface of the tire.


Place the tire on the foot and secure it with an electrical tape.
Stretch the tape and wrap the foot tightly.
Wait for 30 minutes - remove the tape and the pin.


Cut off the ends of the tire horizontally.


The lower leg is now ready for installation.

More Information

Open Dynamic Robot Initiative - Webpage
Open Dynamic Robot Initiative - YouTube Channel
Open Dynamic Robot Initiative - Forum
Open Dynamic Robot Initiative - Paper
Hardware Overview
Software Overview

Authors

Felix Grimminger

License

BSD 3-Clause License

Copyright

Copyright (c) 2019-2021, Max Planck Gesellschaft and New York University