A vascular intervention device delivery system includes a handle comprised of a first shell connected to a second shell. A thumbwheel, which includes a radially outward thumb surface and a spool, is rotatably mounted in the handle. A catheter has a proximal end attached to the handle and a distal carrier segment for mounting a vascular intervention device thereon. A retractable sheath is movable from a first position covering the distal carrier segment to a second position retracted proximally uncovering the distal carrier segment. A pull extends between the thumbwheel and the retractable sheath. A rim of the pull and an internal surface of the first shell define a pull avoidance volume. The first shell includes a plurality of ribs positioned in the pull avoidance volume and oriented transverse to a pull pathway around an idler wheel, and the ribs block entry of the pull into the pull avoidance volume. The retractable sheath moves toward the second position responsive to rotation of the thumbwheel in a first direction.