Clip-On-2DOF-Joint Experiment (no torsion)

Short video: https://www.youtube.com/shorts/4xGUdVfBQSs
A 2-DOF joint inspired by the Tracta-joint.

For infos about Tracta-joints see here:
– https://commons.wikimedia.org/wiki/File:Tracta_Constant_Velocity_Joint.jpg
– https://en.wikipedia.org/wiki/Constant-velocity_joint#Tracta_joints

Resistance against loads

This joint prevents torsional motion.
It is weak against tensile loads though due to it being clip-on.

Self-centering & Backlash

It features self centering principles and some clip tension,
thus (if clipping is strong and tight enough)
this joint should have zero wobble and backlash.

Friction and wear

This joint features plastic on plastic sliding.
Thus it is not suitable for high speed and or high load applications.
Moving it around a bit to break it in can help.
Printing it in self-lubricating plastic may be beneficial.
As long as sufficient clipping force remain preserved.

Symmetry

Just like in a Tracta joint the two rotations in mutually orthogonal planes
have colocated centers of rotation. => Simplifies math for kinematics.
Unlike a Tracta joint it is symmetric. Downsides of symmetry:
– reduced range of motion
– undefined state of disassembly when pulling it apart as both clips are ~equal in strength Upsides of symmetry:
– less part types

Customizatios

Depending on your filament you may want to use
adjust the variablesaglobal andtclipglobal
in order to get a better stronger clipping action

You may want to change the X shaped struts to match your needs.

Print Settings

Rafts: No
Supports: No
Resolution: default
Infill: 33% or higher
Filament: whatever ideally self lubricating but not too soft

Notes:

Depending on your filament you may want to use
adjust the variables *aglobal* and *tclipglobal*
in order to get a better stronger clipping action

Post-Printing

If the two center parts do not hold together by themselves due to tight tolerances and friction, then you may want to glue them together.

Category: Robotics