On August 27, 2005, at approximately 1230 Pacific daylight time, a Bellanca 7KCAB, N11661, was substantially damaged when the left chain to the tailwheel steering assembly failed, which was followed by the pilot loosing directional control during landing roll at Chiloquin State Airport, Chiloquin, Oregon. The private pilot and his passenger were not injured. The pilot/owner was operating the airplane under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the cross-country personal flight that originated from Klamath Falls, Oregon, approximately 35 minutes before the accident. The pilot had not filed a flight plan. The pilot said immediately after touchdown on runway 35, the tailwheel started oscillating. It continued to oscillate on rollout until the airplane's speed dropped to about 20 mph when suddenly the airplane veered to the right. Subsequently the left main landing gear collapsed, bending the outboard 5 to 6 feet of the wing up.