Modern road graders present a special challenge in Meccano.  Their many hydraulic actuators (the Caterpillar has ten rams and a rotary drive) have to be reproduced, but unlike bulldozers and diggers which have fewer rams and hollow frames in which pulleys and cables can be concealed, the rams are externally and prominently placed.

Originally, the 1:10 scale model had real hydraulics, using the short-lived Action Engineering system, too bulky to fit inside the model (the pump and valves were in a separate module linked by an umbilical cord), and designed for only 2 bar, they quickly failed in spectacular fashion, coating the ceiling with hydraulic fluid.  

The model was later refitted, successfully, with Somerville-Dennis simulated hydraulics.  With these, like on the prototype, the mouldboard could be swung out sideways into a vertical position for bank cutting.

The circle is rotated by a Minimotor concealed in sleeve piece.  All are operated by reversible micro switches and a battery concealed in the engine housing.  Wires to the actuators are fed through the original hydraulic tubing.  A Minimotor in the steering console is wired into the steering circuit, turning the steering wheel.  A larger 12V motor inside the dummy engine block drives the four rear wheels via a locking differential, with 3:1 hub reduction in the tandems.

A lever to the right of the driver's seat sets and releases the differential lock, and another retracts the locking pin of the circle side shift radius arm.