Mechanical excavators

A mechanical excavator provided on a vehicle, the mechanical excavator comprising:

• a main boom, said main boom being pivotally connected at its lower end to a king post assembly for movement up and down in a vertical plane, a dipper arm pivotally connected to the outer end of the boom for movement in a vertical plane, the king post assembly providing for pivotal slewing movement of the main boom about a vertical axis so that the main boom can be rotated from one side to the other of a center line of the vehicle, the king post assembly being mounted upon a guide means extending transversely of the center line of the vehicle, the king post assembly being moveable along the guide means, fixing means for releasably fixing the king post assembly relative to the guide means, a fluid operated ram means connected between the king post assembly and an anchor means fixed relative to the guide means, the fluid operated ram means being connected between the king post assembly and the anchor means so that extension and contraction of the fluid operated ram means to a first extent causes movement of the king post assembly along the guide means to a greater extent than the first extent, the fluid operated ram means comprising a a piston rod means connected at one end to said anchor means and a cylinder means carrying first and second actuating parts at opposite ends of the cylinder means, a first flexible element extending between the king post assembly and an anchorage on the guide means, the first actuating part being in engagement with the first flexible element, a second flexible element extending between the king post assembly and an anchorage on the guide means, the second actuating part being in engagement with the second flexible element.