Ok, thanks to the (few) but warm replies to my previous wip, here is a second animation, four spider legs now (Ok, only 3 are moving, I know)
http://www.selleri.org/Blender/movies/robot3.avi (DivX 5.0.2, only 427k, you can download it 
)
Comments?
Iām mirroring them, building a body, etc. etc.
BTW: I got say 8/10 errors like
āclip overflow: clve clvl 41 22ā
at each frame. What is that?
Stefano
hey s86 looks awsome, but how do you confine pistons to move lioke that, i would love to know.
Want to write me a shot tutorial on how to make a hydraulic ram?
Looks good
wow, Iām impressed with the direction youāre taking. love the movement. they donāt all come out at once but in a strange sequence. coolski 
Roel
Yeah, what bothers me in other mecha models seen around here is the lack of pistons or other means to let mecha actually move 
75% of the effort in this model was devoted to piston modeling/moving 
You get it by placing object centers in smart places, parenting a lot and make things track each otherā¦ Iāll try to write down a tut if you like.
Stefano
Looks nice even though it doesnāt animate when I play it backā¦ looks like a still.
A little tip I like to use.
Create an empty and make that copy the location of all feet. Then that stays perfectly between all of themā¦ after thatā¦ make it the parent of the body youāre going to make. And parent the legs to the body.
that way you can just make the feet walk and the body will stay in a nice position above them and usually moves rather naturally along with them.
Works with anything with more than 2 legs.
Iāll echo what everone else is sayingā¦
I love to see the mechanisms working. It makes it look great.
DivX 5.02
Thanx for the tip, it makes sense
Actually I need another tip.
The Blender IK (inverse Kinematics) is not elaborate enought or itās me who donāt know to use it??? I would love to be able to move the LAST bone of the chain whrer I want it to be, with all the other bones following nicely (in pose mode) so to be able to place the feet exactly where I want, whereas il looks like that you are obliged to move all bones one by one from leg to foot. And is very difficult to get the foot where you want it.
Furthermore, is there a way to constrain a bone joint to bend on a plane and not in any direction?
Stefano
that is awesome!damn i wish i knew how to animate.
cant wait to see it finished!! :o
rixtr
The Blender IK (inverse Kinematics) is not elaborate enought or itās me who donāt know to use it??? I would love to be able to move the LAST bone of the chain whrer I want it to be, with all the other bones following nicely (in pose mode) so to be able to place the feet exactly where I want, whereas il looks like that you are obliged to move all bones one by one from leg to foot. And is very difficult to get the foot where you want it.
itās just you who doesnāt know how to use it 
so if you havenāt figured it out yet then hereās one way to do it:
you have to make an extra bone in the end of the bone-chain you want to move like that and an empty for example at the place where you want the leg to goā¦
then in pose-mode you add a constraint āik-solverā to that last bone of the chain and make it point to the emptyā¦
then get out of pose mode and now you can move the whole leg by grabbing the emptyā¦
perhaps my attempt at explaning it makes no sense but oh wellā¦ 8)
and to your second Qā¦ I donāt have a clueā¦ sry :-?
Thanx Kurppa, Iāll try 
For the constray I solved like this:
Placed a camera perpendicular to the plane where I want the constrain to be
made that camera orthoā¦
Then I move the leg in camera view,
not much confortable though.
Stefano