Thanks - the locked track was very useful!
Is there any soloution to animate something using locked-track in 3D -- I set up an animation for the strut which has two parts, with one parented to the other.
However, the result is twisted as you can see (ignoring all the other components, only the biggest one).
It looks right -- but if you actually look into the bay you can see that the result is twisted.
Obviously, I know you can specify the lock-axis and track-axis using a vector of <x>, <y>, <z>. I set it up getting coordinates / axis from Blender... it should have worked, and indeed it does work.
It seems the two parts (which are parented to eachother properly) are not animated in the plane of the lock-axis / track-axis!