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. Most stackers are electrically powered by way of a trailing cable. There are basically two types of cable trailing: power cord rotating drum (PCRD) and control cable rotating drum (CCRD). Pendulum adjustments are made to ensure the proper alignment of these cables while the stacker is travelling. See also Coal homogenization Reclaimer Spreader (mining) External links References Bulk material handling Engineering vehicles Mining equipment Articles containing video clips