A big machine used by the D'ni people when constructing tunnels. It resembles a skeletal insect or a spider surrounded by a translucent sheath. It has a sleek engine and a metalling spinning hoop, as well as a hydraulic arm. It cuts a giant ring from the rock surrounding the central borehole made by the excavator.
Its hoop is set up by two men. The operator blasts the siren twice before beginning the drilling. As it cuts, the excavated rock is collected in the sheath and channeled into a chute that fed straight into the central borehole; then it is collected with great suction hoses to the rock-gatherer. Its arm raises and moves toward the horizontal as the hoop bites deeper, carving a circle like the outer rim of an archery target.
The circular track is 1.25 spans deep. Then a metal brace 1/4 span deep enters the cut and a special sealant stone is poured and fills the space. When it sets, they chip out the remaining "collar" between the tunnel and the seal with curved spears with diamond tips, they spray it with a coating of nara.
Four people wheel the great metal hoop of the brace and push it into place. Other people remove the covering sheath and fit the brace.
The brace is removed, and the Cycler starts all over for the remainder of the tunnel.