I've been playing with IK joints and stuff in maya, but as far as I know, it has it's limits...

As for now, there is a very spesific task I have been unable to do with bones.

I don't know the correct english term for the machine, but in norwegian it's kalled a "gravemaskin".
Lookups in a Norwegian->English dictionary gave me these words: "excavator", "mechanical navvy grab-dredger excavator", "digger", "navvy" and "shovel".

The idea is to build a joint chain with a IK handle that is animated with a motion path. The base is only able to rotate around the horisontal plane, and the other two joints can only rotate around a vertical plane (hinge-joints). The last joint in the chain should not be manipulated by the IK handle exept from the fact that it is connected to the rest of the joints.

The joint-chain consist of 5 joints, where joint1 is the base, wich only should rotate around the X axis. The IK handle is connected to joint4

I've tried to de-select the Y and Z boxes on "Degrees of Freedom" for joint1 but that screws up the entire IK solver, and the joints aren't following the IK handle any more.

I've also tried to switch on Y and Z rotation limit in the Limit->Rotate for joint1, but the same result still appears.

Disabling "Inherit Transform" for joint2 doesn't work either.
I've even tried to adjust the "Rotate order for each joint, still with the same results.

As shown in the image below, The bones should have no problem reaching the IK handle.
It's a straight-from-the-box joint chain and IK handle except from joint1 wich has only "X" enabled in "Degrees of Freedom"

This "Degrees of Freedom".. Is it possible to break the connection/inheritage to the other joints, or is there another, more straight-forward way that I have missed?