bones / creating movable axis

hello blenderartists,
i need a little help with my project: atm i am meshing an electrical hand prosthesis that i will build afterwards… the mesh is my way to plan and design the parts i will need to create.
to see whether the movement of the hand is “natural” or if parts intersect when fingers are moved i want to give the mesh bones (or something similar you might tell me…)

to make a long story short: attached is a little picture of a mesh of one of the servo motors i will be using. i need to give it an axis (red) that enables the head of the motor (in the picture everything above the blue line) to rotate around it for 180 degrees (not more). the head needs to be fixed in all other directions though and after 180 degrees of rotation it must only be able to rotate 180 degr back.

can you give me any hints how to do this? In the end each joint of the fingers will have one motor and i want to be able to e.g. move a fingertip and see how the whole finger follows.

Thanks for any help



I would use an armature for this, but depending upon how complex the hand is, the rigging may get a little deep. Everything below the blue line, I would make one mesh object, the wheel above the blue line would be another mesh object. I would create an armature and position the first bone so it’s root is where the 3d cursor is, the tip should be exactly at the center of the pivot point for the servo wheel, then extrude another bone horizontally for the control horn, with it’s tip ending where the control rod will connect to the bone/control horn. You can then lock down the loc/rot/scale as needed and use a limit rot constraint on the bone, although typically I don’t limit rot of bones, leave that up to the animator to not rot to far to break things. Parent the servo body to the 1st bone, parent the control horn to the 2nd bone.

Using bones can get a bit deep, as I said, but when it comes to animating, it allows you to use the action/nla editors which IMO is easier to use than IPO curves.


Edit: just looked at the pic again, and the first bone I would make perfectly vertical, with the tip at the pivot point of the control horn, the root ending someplace about the bottom of the servo…

hi randy thanks for your help!
i just tried some of the ideas… either i did not really get it right or it wont work with my purpose:
in the end i dont want to animate the hand but to “move” the parts in object mode to see whether everything fits (after rotation etc). which locrot do you mean? i only know the locrot keys for animation which will lock the objects to certain frames… did you mean something else?

i need the hand (made of some of those servos and static shell parts parented to each other) to restrict my object movement in object mode… so if i select one finger tip (object) and want to move it it should only be able to be moved in the directions that are allowed (which means in a half circle around the axis of the servo it is connected to - rotation of 180 degr.)… does your method work for this?

or does anybody have other ideas how to do this?

to make things a bit easier: attached is my works progress…
i need to move the fingers in object mode without accidentally moving a part in a direction that is not possible (restricted by the motors axes).