Patent ID: 7779940

Claim:
A vehicle comprising: a principal frame; a first track frame rotatably coupled to the principal frame, to rotate about a first axis; a first member coupled to the first track frame, the first member being arranged about the first axis, the first member having a first engagement structure and a second engagement structure; a retractable member configured to operate in a first position engaged with the first or second engagement structure to oppose rotation of the first track frame in a first direction about the first axis, and oppose rotation of the first track frame in a direction opposite the first direction, and a second position allowing the first track frame to rotate about the first axis; a first roller rotatably coupled to the first track frame, to rotate about a second axis; a second roller rotatably coupled to the first track frame; and a first belt entrained around the first and second rollers, wherein the first member defines a first recess that constitutes the first engagement structure, and a second recess that constitutes the second engagement structure.