Well, Here is a Cardanic Joint 2.3Mb DivX
It is fully cinematic. I mean, one of the two axis has a rotation IPO, the rest follows. Given that there are just three object meshes in the scene (two axis and the thingie in between)…
…how did I did it?
Stefano
Nicely done Stefano. As far as how you did it, I have no bloody clue! 
BgDM
[Jaw drops open]
Very well done! I’m looking forward to your explaination! (I hope you tell us how its done!) I’m interested in methods for constraining meshes in blender to accomplish mechanical animations.
Yes! Stunning!
Me, a Newbie, to tell you how you did it? NOT!
Your next challenge is a constant-velocity joint.
See http://encyclopedia.thefreedictionary.com/Constant+velocity+joint
I don’t know exactly how but I geussed you used some sort of linking (as in the icon that looks like chain)
Well, i don’t claim to know it all and i would still consider myself a newbie despite being a “Monkey” but I think this is how you did it:
From analyzing your video it appears that the bottom axle is the only part moving in a full circle thus this is the actuator in which the other two objects are pivoting around … yes pivoting! The movie creates the accurate effect of an axle joint but in reality that animation isn’t exactly correct. It would appear that you created an IPO for each of the “child” shafts and that the middle shaft’s (the joint’s) IPO is a simple arch which causes the mesh to pivot from side to side and the upper shaft (the second axle) is a inverted 90* out of whack IPO of the joint’s. The “child” axles have been constrained to the “parent” shaft that when the main shaft rotates a specified amount the “children” shafts toggle their IPOs respectfully.
I could create the same animation by just creating an IPO of continual rotation for the main axle and then create toggling IPOs for the others respectfully but i would know how to get the constraints!
Nice works! I sure hope that explanation was clear enough (and right)! If that isn’t it the only other way is by creating a python link like @ner said for a game but instead of using a key you use an IPO or perhaps an action key. So how did the great Houdini do it?
Well I havent a clue about anything to do with animation, but it looks good.
You animated it by hand (by keys) :))
:o
Whoa…
How DID you do it?!
if ipo is on axe1 then:
on the join object:
-a rotation constraint from axe1 to join
-a locked-track at 0,5 on the join pointing at axe1
-a locked-track at 0,5 on the join pointing at axe2
a scriptlink on framechange copying local rotation of pointing_up_axis on axe1 to pointing_up_axis on axe2
though i’m not sure about the scriptlink stuff. i could do all the rest like that. I’m just still looking how to copy local rotation of object.
My guess… Magic.
Well:
Thanx BgDM, mr_rob, mzungu, okchoir, sornen, lemmy, Jeeves
@ner No linking 
Prince Clever idea, but it would have been quite hard to set up with IPOS, you could have done that with framechange scriptlinks.
Anyway the animation is exactly correct, maybe you’ve been tricked by the camera movement, but both axis rotates in full circles. One with constant velocity, the other not. But that’s intrinsic in the cardanic joint.
ErufailonThat’s cheating… I said only 1 object has an IPO, and keys are a different way to define an IPO 
GabioAlmost right! It is made with 3 locked track constraints and one null constraint… no need for scriptlink or for ‘0.5’ influence, indeed.
Here is collage of screenshots:
Stefano[/img]
nice! i agree that my way was way crazy (meaning difficult) but wow! still blown away at the simplicity of it! you mind posting a .blend for and maybe add a text doc with it on a mini-tut or something for some of use who want to experiment with that kind of stuff?
Hi S68! Having fun, are we?
Quite fitting subject for an Italian
Very well done!
Arnaud
right, that was the missing trick to make the axe2 turn.
for pp interested, here is a blend file with both S68’s way and mine. not big difference, but it give you a clean look nevertheless.
actualy, it’s a bit of cheating because there is not only 3 mesh, but also some emptys.
Gabio: I like your stuff very much. It’s kind of you to share the file! 
Thanks.
Arnaud
An interesting excercise.
Your technique works only with a constant angle, right?
can be done with a track to and an animated empty. it work. i can show you if you want.
S68 & Gabio,
Very nice indeed!
Thanx