... cranes usually use internal or external gear, 4 meters in diameter three rows roller slewing bearings to ... bearings or double-row ball, diameter not more than 2 meters (9). Radar antennaUsually use three-row roller slewing ... bearing, slow rotation (10). ShieldDiameter from 2.5 meters to 6 meters, some larger diameter, these bearings work in ... double-row ball, diameter not more than 2 meters.