The outer portions of the rods, which were never actually in the pile, passed through openings in a thick shielding wall to the outer rod room, or rack room, which housed the rod-driving mechanisms and supporting racks.
The two electrically-driven regulating rods were used for fine-tuning the reactivity of the pile and could therefore be inserted or removed in small increments. The operator could move just one rod at a time at two different speeds, such as 1 in. per second or 0.01 in. per second. The gearing could also be changed to provide different high and low ranges. These slow rates of travel show just how delicately the pile could be controlled. The seven shim rods were operated by a hydraulic drive mechanism, powered by an electrically driven oil pump.