I have never actually had to rig one for use in a game ( catapult that is ) and have found this rather annoying. Any clue on how you guys might go about rigging one of these?

The movable parts are the front and back wheel base, the turn arm, and the catapult arm. Thanks for any suggestions in advance.

This should not be a problem. E.g. using a bone system:

origin
- front-axis 
-- bind both front wheels to it
- back-axis
-- bind both back wheels to it
- lever-pivot (ends at the pivot point of the lever)
-- lever bone 
--- bind lever to it

Constrains:

- axis: only rotation around the bone (e.g. local z axis) allowed

- lever, only (limited) rotation on two axis allowed (you need to disallow the rotation on e.g. the y axis).

There are really many ways to rig this and it should be too hard.

It is not that it is hard, it is that I have never done something mechanical and thus have no idea how to do it. The people over at polycount helped though and I figured it out. Thank you very much for the response.