A motor grader has a chassis or frame made of steel that supports the engine, drive mechanisms, control compartment, the motor grader mouldboard, steering mechanism and any extra attachments. In many modern motor graders the chassis is hinged between the Cabin and the engine and is able to be articulated at this point by hydraulic rams.
The engine drives the rear wheels through an automatic preselecting gearbox. The drive is via a limited slip differential and or a locking differential. The two (tandem) wheels at each side are driven by chains in such a way that both wheels are linked and revolve at the exact same revolutions. This method gives maximum traction and driving forces.
The steering wheels are not only capable of turning left and right, but they can also be tilted vertically. This tilting is done to reduce the sideways forces causing slippage in the direction of travel. All modern motor graders use hydraulics to control the mouldboard and other equipment. Most also use constant flow hydraulics which mean that the speed of operation of the hydraulic rams is constant no matter at what speed the engine is running.
The ‘Mouldboard’ of a motor grader is from 6ft to 14ft in length (typically 12ft) and is of a curved cross section. It has a ‘skin’ of special high wearing steel on the surface with disposable ‘cutting edges’ on the base and disposable ‘end bits’ and ‘overlays’ at each end of the mouldboard.
The mouldboard is attached to ‘Circle’. The attachment to the circle allows the mouldboard to be tilted in the vertical direction and moved horizontally sideways. The Circle is able to rotate a full 360°. The Circle is attached to the frame of the grader by an ‘A’ frame. This frame is attached to the frame of the motor grader near the front wheels by a ball joint. The frame is suspended from the ‘saddle’ of the frame by two hydraulic rams that allow both sides the be moved in a vertical direction independently of each other. A third ram allows the frame to be moved sideways horizontally. The saddle is also movable which allows for further sideways movements .
All of this means that the mouldboard of motor grader can be positioned very precisely in many different positions and angles giving a grader many uses.