a stacker has three basic movements:

·         Luffing: This is vertical movement. Stackers use either a winch mechanism with metal wire, or hydraulic cylinders, generally two. Winch mechanisms are highly reliable compared to hydraulic actuators and remain widely used, particularly in large stackers.

·         Travelling: The stacker moves on a rail track, which may be broad or narrow gauge, enabling it to move around the stockyard as required. For this purpose, traction motors powered by direct current (DC) are connected bybevel gears to between 12 and 22 wheels. For manual control, all the controls are in a controller's cabin above the boom conveyor or boom. Modern stackers can be controlled remotely.

·         Slewing: This is rotation of the stacker around its central axis to align or place the stockpile where required. This works mostly by a slew pinion that rotates around a slew base. This type of gear assembly is called a sun and planet gear. The axles may be multiple and are driven by DC-powered axle motors which transmit the torque via bevel or helical gears.

The conveyor belts used in stackers may be made of fabric or metal wire, depending upon the material to be handled. They are driven by pulleys, which in turn are driven by DC motors. The motors and gear are coupled by fluid coupling.