Abstract: A conduit travelling apparatus is capable of crawling through a conduit for performing certain operation by a stepwise sequence of alternating sequences of expanding and contracting the length of the body while bracing each end alternately. The apparatus provides a self aligning element for correcting rotation of such apparatus due to powered operations it may perform, or any natural tendency to twist as it progresses. The self aligning element includes steering elements overseen by a control system which helps return the travelling apparatus to a preferred alignment during its forward or rearward travel.

Abstract: A vehicle for travel through a conduit includes a forward and a rearward member, each member being provided with a wall-engaging mechanism for selectively engaging a wall of the conduit to hold the respective member in a stationary position within the conduit. Extensible elements such as a hydraulic ram connect the members for relative movement of the forward member toward and away from the rearward member. Each wall-engaging mechanism includes a plurality of legs extendable outwardly from the respective member and a wall-engaging surface on or fixed to each leg, one actuator engages each of the legs for coordinated extension of the legs to bring each wall-engaging surface into contact with the wall of the conduit. Preferably a rotary cuter is mounted at the front of the vehicle for clearing obstructions in the conduit.