Robotics for welding of columns

A portable robotic welding system, comprising:

• a slewing gear comprising a circular inner gear defining a central opening, the inner gear nested within a circular outer gear, wherein the inner gear and outer gear are independently rotatable about an axis, and the inner gear comprises a plurality of mounting holes positioned along a central arc of the gear, and wherein the outer gear and the inner gear are each separable into at least two releasably attached segments at a set of attachment points, the slewing gear configured to be assembled around a structure;
• a platform removably positioned on the slewing gear;
• a robotic welder removably positioned on the platform;
• a driving gear removably positioned on the slewing gear;
• a channel extending around the axis, bounded by the inner gear and the outer gear;
• a plurality of bearings positioned within the channel between the inner gear and the outer gear;
• and
• a slot positioned in each segment of the inner and outer gears, intersecting the channel at each attachment point, configured to accept an end plate which interrupts the movement of bearings within the channel when inserted.